Well I really did it this time

[TheFontMaster]

Blew the top end in the 250r thisafternoon. I was ridin along a really fast pace, I wanted to test myself and see how fast I can go, and goin though part of a trail I hear the 250r start knocking really bad, and it looses alot of power. So I shut it off, and I hear the water in the radiator boiling a little, then some starts flowing into the overflow rezzie. I had the R overheating bad the last time I went out, but after I let it cool down and added more coolant it was running just fine so I didn't think anything of it. I try kicking it over, and I hear a scraping sound, nothing really bad, but bad enough to know something is wrong. So I took it home, and took the top end apart. Looks like I will need a new piston, rings, and a dome.

I will get pics tomorow, but the piston is pitted really bad, but it is only along the outside, the middle is fine. The dome looks just like the piston pretty much. Looking at the cylinder, there aren't and scratches in it really, a hone should be enough for that. Everything came apart really nice, I didn't have to fight with anything.

Now that I said how it blew, I am wondering exactly what caused it to blow. Are those typical charateristics of overheating? Did something get into my motor? When it first blew I thought it was mainly the rings from what it sounded like, but the rings looked fine, and so did the cylinder.

Last question, how much play is there suposed to be in the crank rod?

[250r4life]

what do you mean by pitted? and why would you need a new dome? im not understanding exaclty what happened with it, but unless something came apart....


the rod shouldnt have very much play in it... you can look and see if you are missing some rod bearings...

did something chew up your piston and your dome?
if so you need to find out what?


more info man...
and i dont know what the heck would cause scraping noises...

[250r4life]

ps... how would your rings look fine, but your dome be messed up? whatever is in there had to pass through your rings to get to your dome...

and stuff doesnt just "get" into your cylinder... if there is stuff in your cylinder it probably came apart and left where it is supposed to be... i've had wrist pin bearings shatter, and ive had rod bearings go out, and....

[GPracer2500]

I'm guessing nothing actually got into your cylinder that wasn't allready there. "...pitted really bad, but it is only along the outside, the middle is fine..." sounds like it could be deto damage. I'm sure pictures will tell the tail of what happened....

I bet your damage looks something like this, but maybe not quite as bad:

http://www.accurateis.com/images/piston.jpg

[TheFontMaster]

Originally posted by GPracer2500
I'm guessing nothing actually got into your cylinder that wasn't allready there. "...pitted really bad, but it is only along the outside, the middle is fine..." sounds like it could be deto damage. I'm sure pictures will tell the tail of what happened....

I bet your damage looks something like this, but maybe not quite as bad:

http://www.accurateis.com/images/piston.jpg


That is really close to what it looks like. I'm gonna try to get the pics up in a couple minutes.

[TheFontMaster]

Well here's the pics.

Dome.
http://img.photobucket.com/albums/v602/fonty/Picture001.jpg

Piston.
http://img.photobucket.com/albums/v602/fonty/Picture003.jpg

Couple of the cylinder.
http://img.photobucket.com/albums/v602/fonty/Picture006.jpg
http://img.photobucket.com/albums/v602/fonty/Picture009.jpg

Rod.
http://img.photobucket.com/albums/v602/fonty/Picture012.jpg

[zedicus00]

yup, definatly deto damage. looks like yur running a cr gasket and maybe a shaved head too. try using an ATC gasket. they aare a little thicker then the cr but not as thick as a trx gasket. also do yurself a favor and get rid of the green coolant.

[TheFontMaster]

Originally posted by zedicus00
yup, definatly deto damage. looks like yur running a cr gasket and maybe a shaved head too. try using an ATC gasket. they aare a little thicker then the cr but not as thick as a trx gasket. also do yurself a favor and get rid of the green coolant.


Yea I think it is a shaved head, the mount on the cool head for the headstay was a little lower than the holes in the headstay itself.

I have a question on that CR head gasket. If you look at the picture with the piston, it looks like not all the holes for the coolant are cut out all the way, or aren't lined up with the holes in the cylinder. I haven't had a 250r top end apart before, so I don't know if they are suposed to be like that. But I was having problems with it overheating, could that be part of my problem?

My last question for now, is how do I figure out what size dome I have. It is a cool head. I looked on it, but I didn't see any markings. I been running 93 in it since I got the motor, I thought that would have been enough, so I'm guessing the motor had to have atleast 200PSI. I would like to get that down to about 180 with this next rebuild, what size dome should I buy to go with the ATC head gasket to get around 180PSI?

[250r4life]

you should be able to knock the dome out of the head, and it should be written on the back side... that is how my duncan (made by cool design) head it... stick a spark plug in it and tap the dome out with a mallet....


so did you find out what came apart and chewed everything up?
by deto damage im assuming you mean detonation? is that correct? how would that chew up his piston and dome?

[250r4life]

i took another look at your pics, and yah that dome should pop out just like i said...

and yes, i would definately do something to make sure all the coolant holes were not blocked by the head gasket... that for sure couldnt have helped your over heating situation...

[TheFontMaster]

250r4life, I got the dome out yesterday when I was taking the whole thing apart. I just looked it over again, and I still see no marking anywhere on the done to say what size it is.

I still wanna know if that is how the head gasket is suposed to be, or if the last owner of this motor just put it together wrong. Also what size dome should I be looking to buy to run 93 pump gas with a ATC head gasket.

[250r4life]

thats weird that the dome has no marking of identification... that sux.... yah, i would say that gasket isnt on there right or something is wrong- it shoulding be blocking the holes...

i dont know exactly what dome you should be running... i have a 265, but mine is o-ringed, and i was at like 210-215 with a 19cc dome... i want to drop that, so i just ordered a 21cc and wanna see where that will get me... i couldnt tell you exactly on that...
you may want to contact coolhead for that...

[jon370r]

That sure doesn't look like detonationation to me . Looks like somethine bounced around in the topend, like a piece of bearing or ring. Detination wouldn't make pits that deep in both the piston and the haed. Something solid bounced around in there and I would want to know what it was before I put it back together agian. Looks like your lower rod bearing got hot by the discoloration(blue rod bottom).

[250r4life]

Originally posted by jon370r
That sure doesn't look like detonationation to me . Looks like somethine bounced around in the topend, like a piece of bearing or ring. Detination wouldn't make pits that deep in both the piston and the haed. Something solid bounced around in there and I would want to know what it was before I put it back together agian. Looks like your lower rod bearing got hot by the discoloration(blue rod bottom).

i was just about to write that... i replied to his other stuff and forgot to ask again if he had found out what had caused it...
i have chewed up two pistons and domes way worse than that- 1 was a wrist pin bearing that shattered, and the other were the rod bearings...
i fear that he may have blew his rod bearings since obvioulsy something chewed up everything, and he asked how much play it shuold have in it, and it looks like it got hot....

i would hope not- cuz then the rebuild just got a whole lot pricier...

[250r4life]

ps... when you are tearing down something, you really want to pay a lot of attention to everything, as stuff doenst burn up for no reason, and you want to know why it burned up before you put it back together so you dont do it again...

[zedicus00]

hold yur hoerses guys, if its a cool head get around a 20 or 21cc dome and keep using the cr gasket. also i still think its detonation damage otherwise the entire dome would be chewed up.. AND yes the gasket is supposed to block the coolant holes. if you R was overheating make sure the LITTLE hole is on the intake side and the BIG hole is on the exhaust side. the dome should say the size on the edge. you can get a replacememnt fairly easy, i use to get domes from noss machine they were the cheepest.

[TheFontMaster]

Yea I really don't think there was anything bouncing around in the cylinder. The pitts were only on the outside of the piston, and mostly the outside of the dome. And if something was bouncing around in there, there would be marks on the cylinder walls, and there isn't. They cylinder made out ok, it will just need a honing.


Ok so I think I got all my top end questions answered for now. So to the rod, you think I may have cooked the rod berrings? I know a little play is normal in the rod, but just how much is normal? There is some play in the rod, both side to side and up and down.

[xlr810]

Your head gasket was in there the correct way. Have you checked out the size of your dome yet?

As for the crank. Bad news, Guy. There should not be any up and down play. Side to side measure with a feeler guage. It needs to be less than 40 thousandths.

[BLACKeR]

you can get material on top of your piston withought damaging the cylinder walls, i sucked a frag of a rod bearing through my transfers and never damaged the cylinder walls but i did have steel chunks in my piston and dome. yours does look like pre detination since theres nothing in the middle. and xlr810 is right you shouldnt have any up and down. i bet if you look at it youll see the bearings are damaged.

[250r4life]

now how exactly does predetonation chew up the piston and dome?

[GPracer2500]

Originally posted by 250r4life
now how exactly does predetonation chew up the piston and dome?

By melting and blasting away material. Detonation is the explosion (verses the normal burn called deflagration) of "end-gases" that are formed from the extreme pressures created after the spark plug fires. That strange knock or ping you hear signals that deto is taking place. What you're hearing is the pressure wave from abnormal combustion (deto) smacking into the piston/head like a sledge hammer. The pressure waves from normal combustion are much slower because the mixture is burning not exploding. The explosions from detonation are many times faster and the engine struggles to absorb the blows--it just can't relieve those pressure waves fast enough. The result is excessive heat that combines with the pressure waves to errode metal away.

End gases are just regular fuel vapors that have been decomposed by heat and pressure into very unstable chemicals. They are so unstable they can ignite spontainiously instead of waiting for the normal flame front to get there and comsume it through deflagration. In a nutshell, that's what detonation is.

That's why compression ratios (pressure), octane rating (the fuels resistance to forming into end gases), and igntion timing (the sooner the normal deflagration process begins the more time there is for end gases to form) are the three primary variables that contribute to detonation.

Detonation damage is often seen only around the edges of the combustion chamber. It takes time and increasing pressure for end gases to form. That makes the edges of the combustion chamber the only place the deto prone end gases are likely to be. Many times deto damage will be localized on one edge of a piston--not all the way around. Sometimes you'll have deto damage around the edges AND other damage everywhere on the piston and head. That's often from pieces of the cylinder breaking off from the original deto damage and bouncing around.


BTW: "Predetonation" isn't really a term. It's just called detonation. The other abnormal combustion phenomenon is pre-ignition. The two words get erroniously intermingled fairly often.

[jon370r]

There is no way the damage to that piston happened from detonation. You just said it, detontion is the preignition of the gasses and it creates mini explosions where there shouldn't be. It eats away the material in small amounts and looks like it has been sand blasted not dented and raised like this piston looks.
The piston is only beat up around the outer edge because that is where the squish band traps and compresses the pieces in an area where there is only .030 to .050 of an inch clearance between the piston top and the edge of the dome. That is the thickness of aprox. 10-20 human hairs. Not much room there when you have stuff bouncing around in there.

[GPracer2500]

Originally posted by jon370r
There is no way the damage to that piston happened from detonation. You just said it, detontion is the preignition of the gasses and it creates mini explosions where there shouldn't be. It eats away the material in small amounts and looks like it has been sand blasted not dented and raised like this piston looks.
The piston is only beat up around the outer edge because that is where the squish band traps and compresses the pieces in an area where there is only .030 to .050 of an inch clearance between the piston top and the edge of the dome. That is the thickness of aprox. 10-20 human hairs. Not much room there when you have stuff bouncing around in there.

Good point. We need better pics of the piston. A close up of the marks should show whether it's impact damage or deto damage.

ETA: Plus, your idea explains why the damage is so even around the edges when deto damage is so often localized around only 1/4 or 1/3 of the piston.

Another thing that would almost certainly rule out deto would be to look at the sides of the top ring land. That's one of the first places deto damage normally shows up. If the sides of the lands look normal than you'd have to think something was bouncing in there.

Here's a pic of what deto does to the sides of the lands.

http://www.mr2.net/images/d796env/DSCF0795.jpg

[GPracer2500]

When that land wears down enough it just gives way...

http://img206.imageshack.us/img206/2474/p70900216le.jpg

[TheFontMaster]

Ok I got some better pics of the piston. They aren't the greatest, my camera don't take good close up pics I gues, but here ya go.

http://img.photobucket.com/albums/v602/fonty/Picture015.jpg
http://img.photobucket.com/albums/v602/fonty/Picture014.jpg
http://img.photobucket.com/albums/v602/fonty/Picture013.jpg

[Scott-300ex]

Yes, your gasket is the right way, My tope end is off now and thats how it is.

2. I have a Cool Head and want to run a CR gasket, mine is 22 or 23cc I want to have enough piston to head clearence, so will a CR Gasket with Pro Design Cool Head work good?

I thought that head looked like mine. LoL

Don't want to steel your thread but I wanna know if I can run a CR with my head.

Here's my gasket.

[novaracr70]

if i remember the gaskets will only fit 1 way

[GPracer2500]

Dude, your pictures suck! ;) Just kidding--but try the macro function on your camera.

From what I can see though, those marks do look more like something was bouncing around in there then pure deto damage.

I wonder what though? :confused:

[TheFontMaster]

Originally posted by GPracer2500
Dude, your pictures suck! ;) Just kidding--but try the macro function on your camera.

From what I can see though, those marks do look more like something was bouncing around in there then pure deto damage.

I wonder what though? :confused:


When I took it apart there was nothing in the cylinder. I'm going to try and take apart the bottom end tonight. The rod berrings are bad, so my gues right now would be it was part of the rod berring.


Scott-300ex, I had the cool head with the CR gasket on my R as you can see, and it ran great with it. I would just run a compression check on the motor once you put it on to make shure you don't need to run race gas.

[250r4life]

my bad on the mis info about the gasket- its been too long since ive had a head gasket on mine- just o rings now... sorry man, my bad

[250r4life]

those pics sure do look like something was bouncing around in there to me...

and im not surprised you didnt find anything in the cylinder- parts will melt down and stick in the top of your piston like it looks like, and they'll blow out, and...

and if your rod bearings are out, it wasnt just a coincidence that it blew up cuz of detonation and rod bearings going out... im not sure about your compression and fuel situation, but i would bet your piston looks like it does from a bearing hopping up in there... now if detonation is happening, i would think that would cause more stress on your bottom end, from explosions happening at times they are not supposed to, so that extra stress could certainly contribute to your rod bearings going out...

[matt250r21]

I think your bigend rod bearing is shot. I've blown cranks before and the top of my pistons have looked very similar. All the junk gose up the transfers and pounds into the head and piston, missing the cylinder walls and blows out the exhaust.

[TheFontMaster]

Now if I can just figure out why the rod berrings went. If it was because of detoonation, I never noticed the motor detonation. There was no abnormal noises at all while it was running that would hint at detonation. Is that normal. And also the pinging that I heard started right away, there was slow noise getting louder, it was just running great, then the next secong the pinging. So to me sounds like thats when the rod berring went.

[250r4life]

those bearings wear out eventually...

i have an 89 that the bottom end was all original... i was at the dunes and racing the hill and the bike was screaming... had it pinned in 4th over and over... was fine...

my motor blew as we were on the flats just cruising back to camp... they just go...

[BLACKeR]

the same thing happened to me earlier this year, rod bearings just went. i bet if you look close at the dome and the piston you might be able to find chunks of steel burried in them. it does look too jagged to be detonation...

[86 Quad R]

>shruggz< sure looks like detonation.

[beerock]

that is NOT detonation, that is a rod bearing.

if you examine your lower rod closer and spin the crank i garauntee that you will notice the needle bearings are not STRAIGHT and are angled due to one of them taking a crap.


the pinging was a combo of the motor spitting out fragments of the needle bearing onto the pipe AND detonation from overheating the internals(bad rod bearing) but detonation was not the reason.

the reason your motor ran again is because the first time you thought it overheated, it really was the start of the main rod bearings taking a crap, then it did it again..

I had the same thing happen a long time ago, my needle bearings that **** the bed were hitting my sparkplug and killing the motor, so i would replace the plug and it would run again. until the bearings were completely shot(I had to ride it home)

the R motor maybe finicky but if the needle bearings blow it WILL still run... how long is dependent on the operators stupidity to keeep riding it and not taking it apart at the first sign....(thats why the rods blow on these bikes)- cuz they will run with bad needle bearings until its to late..

[86 Quad R]

the rod bearings may very well have put the final nail into the coffin BUT detonation is what put the engine in the coffin to begin with. ;)

its been stated that the head is possibly shaved(pics seem to indicate this) and a cr250 gasket is being used. he also stated that 93 pump gas was run. you mix all this up and you have a NICE recipe for detonation.

what cornfuses me is why did the foriegn material only saw fit to damage a uniform ring to the outside edges of the piston and chamber?

[GPracer2500]

Originally posted by 86 Quad R
...what cornfuses me is why did the foriegn material only saw fit to damage a uniform ring to the outside edges of the piston and chamber?

The explination offered in a previous post was that the offending shrapnel was too small to get smashed anywhere but in the very tight clearences around the edges (squish band).

[fireburns99]

seeing as how i might be in the same boat as fontmaster, where is the best place to find a new rod and bearings? I'll be pulling ym engine apart this week or next.

[250r4life]

i had the same thing happen a couple months ago, and i just went ahead and bought a whole new rod and crank assembly from calatv... i figure my bottom end was 17 years old, so i went ahead and put a new crank, rod, seals, bearings, etc... so i wouldnt have to worry about it later...

[86 Quad R]

honestly! unless you know of a reputable engine builder i would get an OEM crank. otherwise i'd go with a pro-X rod. i've used em for years with great results.

[norcalduner]

Originally posted by beerock
that is NOT detonation, that is a rod bearing.

if you examine your lower rod closer and spin the crank i garauntee that you will notice the needle bearings are not STRAIGHT and are angled due to one of them taking a crap.


the pinging was a combo of the motor spitting out fragments of the needle bearing onto the pipe AND detonation from overheating the internals(bad rod bearing) but detonation was not the reason.

the reason your motor ran again is because the first time you thought it overheated, it really was the start of the main rod bearings taking a crap, then it did it again..

I had the same thing happen a long time ago, my needle bearings that **** the bed were hitting my sparkplug and killing the motor, so i would replace the plug and it would run again. until the bearings were completely shot(I had to ride it home)

the R motor maybe finicky but if the needle bearings blow it WILL still run... how long is dependent on the operators stupidity to keeep riding it and not taking it apart at the first sign....(thats why the rods blow on these bikes)- cuz they will run with bad needle bearings until its to late..

when you say rod bearings, do you refer to the piston pin side or the crank end side of the rod ? just curious.

[fireburns99]

250r4life when you bought the crank from cal atv did the crank come with the rod, and ready to put in, or did you have to buy them separately and put it together yourself? And how was the customer service with cal atv?

[250r4life]

yah, its a whole crank and rod assembly... its like $250 for a brand new OEM honda crank assembly... comes ready to slap in the cases... you'll want to get new bearings and what not while you are in there, the main bearings, and bew seals, but yah get the crank assembly...

[250r4life]

Originally posted by norcalduner
when you say rod bearings, do you refer to the piston pin side or the crank end side of the rod ? just curious.

im pretty sure he means the crank end side of the rod...
either would do it, although he was saying he had play in his rod... which would be caused by the rod bearings...

i have had both sides go out- my rod bearings and my wrist pin bearings go out and chew up my cylinder, piston, and dome... and it looked just like his pics... all chewed up around the outside but fine in the middle... that piston has definately been chewed up and is NOT DETONATION!!! i'll try and post pics of my pistons and domes later...

[fireburns99]

alright thanks for the help 250r4life

[86 Quad R]

Originally posted by GPracer2500
The explination offered in a previous post was that the offending shrapnel was too small to get smashed anywhere but in the very tight clearences around the edges (squish band).


the material regardless of size doesnt have to get "smashed" in the confines of a area tighter than the peice itself to do structural damage. i've had a peice as small as a ring end break off and get tossed around ontop of the piston and in a matter of seconds, destroy the piston top and the chamber. the damage was of no pattern as pictured. it was scattered about in the low and hi spots of the chamber.

[TheFontMaster]

I am deffinatly going with a OEM honda rod. While I'm tearing the bottom end apart I'm replacing every seal, gasket, and berring. I was just amazed that the OEM ATC gasket kit was 455 dollars. I'll be looking for a pro-x piston. I hope to be able to aford to put in a L.A. Sleeve 300cc re sleeve kit on it.

[86 Quad R]

Originally posted by TheFontMaster
I am deffinatly going with a OEM honda rod. While I'm tearing the bottom end apart I'm replacing every seal, gasket, and berring. I'll be looking for a pro-x piston.

good deal en good luck with it. :)

a peice of advice..... when ya get things back together and all(regardless of what cc you choose). be sure that you determine what compression that you have and run the corrisponding octane rated fuel. it'll save ya lots o hassel in the future.

[TheFontMaster]

Originally posted by 86 Quad R
good deal en good luck with it. :)

a peice of advice..... when ya get things back together and all(regardless of what cc you choose). be sure that you determine what compression that you have and run the corrisponding octane rated fuel. it'll save ya lots o hassel in the future.


Yea that is deffinatly one of the first things I plan on doing. Can I run a compression check on it before I even get it running just as long as everything is together? As of now if I do stay with the stock cylinder, I will be going with a ATC head gasket, and 20cc dome. If I do go with the L.A. sleeve kit, I'll just run what they sugest to get my compression where I want it. I want to try to get between 175, and 180 psi so I can still run the 93 pump gas.


And does anyone have the website for L.A. Sleeve?

[86 Quad R]

yea you can do a compression check prior to the breakin but ya should plan to add about 10-12% to that number after the engine is fully broken in.

what i do is coat the cylinder with the mix i normally run. after engine is installed and everything is hooked up i do a check, make note of it then i do another after the heat cycles(usually 3 or 4) then take another reading. once the engine is completely broken in i take a final reading. some may think it's overkill but, it's my procedure. every so often i take a reading and compare it to the one i got after the breakin and when it drops 10% below i refresh the rings.


LA Sleeve (http://www.lasleeve.com/master.html) web site

[beerock]

Originally posted by norcalduner
when you say rod bearings, do you refer to the piston pin side or the crank end side of the rod ? just curious.

crank side

could be piston side also, but the dents in the piston would be smaller

[beerock]

and btw, if the cause of failure was detonation, then where is the melted area of the piston??????????????????????????


there is none..... its not from detonation...

case closed....


p.s.

detonation is usually located in the center of the dome and burns holes in the pistons. exhaust side detonation is a combination of detonation BECAUSE of the exhaust side of the piston not being relived properly, or not being warmed up properly...


you heard it here first folks...

[250r4life]

Originally posted by beerock


you heard it here first folks...

:D

[TheFontMaster]

Originally posted by beerock
and btw, if the cause of failure was detonation, then where is the melted area of the piston??????????????????????????


there is none..... its not from detonation...

case closed....


p.s.

detonation is usually located in the center of the dome and burns holes in the pistons. exhaust side detonation is a combination of detonation BECAUSE of the exhaust side of the piston not being relived properly, or not being warmed up properly...


you heard it here first folks...


So are you saying that even with the compression I had there was no detonation occurring?

[250r4life]

we dont know that for sure, but we know what happened to your cylinder was not caused by detonation...

[jon370r]

So after much debate my origional diagnosis that was posed on the fist page is found to be correct. Just goes to show you that just because someone says "that looks like what mine did, must me the same thing" doesn't always ring true. As stated before in this thread. If something goes wrong alway inspect everything as you take it apart because the end result (blown topend) may not be the root cause of the problem and if the root cause isn't found you have just waisted you money on a new topend just to blow it up again. Just my 2 cents

[250r4life]

Originally posted by jon370r
So after much debate my origional diagnosis that was posed on the fist page is found to be correct. Just goes to show you that just because someone says "that looks like what mine did, must me the same thing" doesn't always ring true. As stated before in this thread. If something goes wrong alway inspect everything as you take it apart because the end result (blown topend) may not be the root cause of the problem and if the root cause isn't found you have just waisted you money on a new topend just to blow it up again. Just my 2 cents

dont worry jon- you and i were on the same page the whole time :D

like beerock said- remeber ya'll heard it here 1st :D

[beerock]

i know some of ya may think im really anal with my posts but what you dont know is that i have done things wrong in the past and have learned the hard way..

for example....

I raced in a harescramble one year and hole shotted 3rd after three turns we went through a huge mudhole and i suclked in alot of water and my motor crapped out.

there were 13 competitors in my class 2stroke A they all went by me, along with every other class, 4 stroke pro,A,B and utility.

i sat on the side line trying to get my motor started again, i finally got all the water out and cleaned my plug for the 3rd time(since i was dumb and had no spares on me) ANDF FINALLY STARTED UP...

I finished the race DEAD last in my class BUT 7 people dnf'd and i ended up with a 6th place finish not bad......


SO(heres my screw up) i put a fresh top end on after checking my rod play which was right at the limit (.020) i broke in my new motor and then 10 hours into riding it BOOM i blew it up(just like the motor in this thread did) BUT I NEVER SAID IT LOOKS LIKE HOW MINE BLEW UP....


what happened was, the water wore out my con rod bearings on crank side and decided to blow after I did my top end..... OOOPSS, at least i can say i checked my rod for tolerance and it was barely in.

so i ate it big time for that and had to bore my cylinder again and buy a crank....


you live and ya learn!!!!:scary:

[250r4life]

i dont think you are anal man... if anything considerate...

there are only two ways to learn- by experiencing it yourself, or sometimes you are lucky and can learn from other people's experiences...

obviously you have experience, so you post what you have found to be true, and some people may learn from it and benefit, some wont...

if stuff is gunna be posted on what to do, it should be anal and correct postings... not nigga-riggings (excuse the term)

[xlr810]

Originally posted by TheFontMaster
I am deffinatly going with a OEM honda rod. While I'm tearing the bottom end apart I'm replacing every seal, gasket, and berring. I was just amazed that the OEM ATC gasket kit was 455 dollars. I'll be looking for a pro-x piston. I hope to be able to aford to put in a L.A. Sleeve 300cc re sleeve kit on it.

$455 gasket kit? That has to be a typo on someone's part. 45 or 55 would be believable.

As for the rod-- I think you are trying to ask if the rod alone can be purchased from Honda. The answer is NO. If your journals and cans are good on your existing crank, then any reputable shop could put an aftermarket rod on there for you to save you some dough, but even the best rebuilt crank isn't going to be as good as a new OEM crank.

Btw. I am personally not a huge fan of the ProX pistons. If they fail, they often become shrapnel that is capable of taking out the crank and the cases. For cast pistons OEM (made by ART) is the only thing I'd consider. Wisecos have their own set of issues, but are a better alternative in most situations.

[beerock]

Originally posted by xlr810
$455 gasket kit? That has to be a typo on someone's part. 45 or 55 would be believable.

As for the rod-- I think you are trying to ask if the rod alone can be purchased from Honda. The answer is NO. If your journals and cans are good on your existing crank, then any reputable shop could put an aftermarket rod on there for you to save you some dough, but even the best rebuilt crank isn't going to be as good as a new OEM crank.

Btw. I am personally not a huge fan of the ProX pistons. If they fail, they often become shrapnel that is capable of taking out the crank and the cases. For cast pistons OEM (made by ART) is the only thing I'd consider. Wisecos have their own set of issues, but are a better alternative in most situations.


umm pro x pistons and honda pistons are BOTH made by art

also pro x connecting rods are pretty much oem honda rods but your right nothing like an oem crank

[jon370r]

In no way was my little observation directed toward you Beerock, and I'm sorry if it sounded that way. I was just saying that people tend to think because something happened to them a certain way and they see something that looks similar it must be the same problem. When in actuality there are many answers to the same resulting breakdown of machanical equipment and all areas must be examined before the true base issue is found.

[beerock]

Originally posted by jon370r
In no way was my little observation directed toward you Beerock, and I'm sorry if it sounded that way. I was just saying that people tend to think because something happened to them a certain way and they see something that looks similar it must be the same problem. When in actuality there are many answers to the same resulting breakdown of machanical equipment and all areas mut be examined before the true base issue is found.

jon dont worry i know it was not directed at me AT ALL(no sarcasm) im just saying to others that i may not say everything i have messed up on or how i know or why I know what a cause of some sort of condition could be. (but the marks on that piston are con rod needles which ive seen first hand plenty of times)

in other words if I say thats not detonation, maybe other people should take note instead of continuing on, and inadvertantly saying im wrong when i can pretty much determine the problem of an engine failure in my sleep, not just because im the know all(which i am no where near it) but because i have done lots of R motors and seen all sorts of blown motors. and have screwed up myself a few times.

its like arguing with a math professor that 2+2 isnt 4 all you do is piss off the professor

I do understand there are some younger boys floating around here so its not a big deal if they argue against my point because THERE ON THE RIGHT TRACK, heck i used to be one of those boys. then I realized i didnt know ****, and kept busy learning... hehehe

[xlr810]

Originally posted by beerock
umm pro x pistons and honda pistons are BOTH made by art

also pro x connecting rods are pretty much oem honda rods but your right nothing like an oem crank

I know that OEM pistons are ART, but this is news to me if ART is making ProX pistons... I need a little convincing to buy into that...

There are a number of little differences between a ProX and an OEM (The rings are the most obvious difference), but an ART branded one is identical to the piston straight from Honda.

[beerock]

Originally posted by xlr810
I know that OEM pistons are ART, but this is news to me if ART is making ProX pistons... I need a little convincing to buy into that...

There are a number of little differences between a ProX and an OEM (The rings are the most obvious difference), but an ART branded one is identical to the piston straight from Honda.

lol, ok art makes kawasakis pistons too, does that help convince you? rofl

[TheFontMaster]

Originally posted by xlr810
$455 gasket kit? That has to be a typo on someone's part. 45 or 55 would be believable.

Yea it was a mistake, it costs 55 dollars.

And thanks everyone for your help. I have decided to get a new OEM crank and rod assembly, new OEM berrings and seals for the whole bottom end, and transmission, new OEM ATC gaskets, bore the cylinder another .010 over, so it's .020 over from stock, get a 20cc dome, maybe send the cylinder out to Cliegh racing to get a re-port and polish, and maybe a 39mm kehien carb.

[250r4life]

Originally posted by TheFontMaster
Yea it was a mistake, it costs 55 dollars.

And thanks everyone for your help. I have decided to get a new OEM crank and rod assembly, new OEM berrings and seals for the whole bottom end, and transmission, new OEM ATC gaskets, bore the cylinder another .010 over, so it's .020 over from stock, get a 20cc dome, maybe send the cylinder out to Cliegh racing to get a re-port and polish, and maybe a 39mm kehien carb.

now were talking... :D

[Scott-300ex]

Originally posted by TheFontMaster


Scott-300ex, I had the cool head with the CR gasket on my R as you can see, and it ran great with it. I would just run a compression check on the motor once you put it on to make shure you don't need to run race gas.

Thanks man, I got a CR250 Head Gasket for it. I did check compression before and after as well, it stayed about the same, little increase, and I measured the old and new gaskets with a dial calipers and they were the same so he must have had one on before.

BUT, My compression was 90 pounds. And I think they are supposed to be more than that stock, unless I didn't hook the compression gauge up right, cuz I only tightened a connection with my hand, and don' t know if I had the other one fully in the spark plug hole enough, about 6.2:1 and stock said 7.7:1 :eek:


But it runs the same, but if I could get more power out of it I would do it. Unless its supposed to be like that.

I beat a modified 450r yesterday!:D

[TheFontMaster]

Originally posted by Scott-300ex
BUT, My compression was 90 pounds. And I think they are supposed to be more than that stock, unless I didn't hook the compression gauge up right, cuz I only tightened a connection with my hand, and don' t know if I had the other one fully in the spark plug hole enough, about 6.2:1 and stock said 7.7:1 :eek:



90 pounds!! That is way too low. I would re-check the compression, and this time tighten the compression tester down more with a wrench, not just hand tight. If it is still reading anything under 140 or so I would replace the rings, and check to see if you need a new piston too.

[86 Quad R]

............... and how many times are ya kicking it over? are ya holding the throttle wide open when ya kik it over?

90#'s is aweful low.:huh

[GPracer2500]

Originally posted by beerock


p.s.

detonation is usually located in the center of the dome and burns holes in the pistons. exhaust side detonation is a combination of detonation BECAUSE of the exhaust side of the piston not being relived properly, or not being warmed up properly...


you heard it here first folks...

Beerock, I think your comments are right-on. Except for that part, though. ;) I'm a little (ok, maybe a lot) anal on the subject of abnormal combustion.

Holes burned in the center of a piston is usually pre-ignition, not detonation. They are two separate phenomenons although they can both happen simultainiously. Detonation damage usually occurs around part of the edge of a piston because that's where detonation actully takes place--the edges. The protective boundry layer of gas gets blasted away here first because; 1) the source of deto is local to those areas and 2) the angle of the piston surfaces and the cylinder wall create spaces in which the shock waves are amplified. That's why the top ring land takes such a beating from deto. The shock waves from deto get between the land and the cylinder and scour the protective boundry layer away. That lets the heat get right on the piston and burns it away.

Pre-ignition burns holes in the centers of pistons because of the tremendous heat created when the piston trys to compress an already burning and expanding (pre-ignited) charge. The piston becomes overwhelmed with heat and the middle gives way because that part of the piston is the least able to handle the excessive heat.

[beerock]

Originally posted by GPracer2500
Beerock, I think your comments are right-on. Except for that part, though. ;) I'm a little (ok, maybe a lot) anal on the subject of abnormal combustion.

Holes burned in the center of a piston is usually pre-ignition, not detonation. They are two separate phenomenons although they can both happen simultainiously. Detonation damage usually occurs around part of the edge of a piston because that's where detonation actully takes place--the edges. The protective boundry layer of gas gets blasted away here first because; 1) the source of deto is local to those areas and 2) the angle of the piston surfaces and the cylinder wall create spaces in which the shock waves are amplified. That's why the top ring land takes such a beating from deto. The shock waves from deto get between the land and the cylinder and scour the protective boundry layer away. That lets the heat get right on the piston and burns it away.

Pre-ignition burns holes in the centers of pistons because of the tremendous heat created when the piston trys to compress an already burning and expanding (pre-ignited) charge. The piston becomes overwhelmed with heat and the middle gives way because that part of the piston is the least able to handle the excessive heat.

yea it was an educated guess i wasnt positive(like70%), I keep forgettng the reason is for preignition(holes in center) my bad.
on both my quad and boat i have my timing maxed out and jetting spot on so i wory about being to lean and to much timing so i confuse em sometimes

[GPracer2500]

Originally posted by beerock
yea it was an educated guess i wasnt positive(like70%), I keep forgettng the reason is for preignition(holes in center) my bad.
on both my quad and boat i have my timing maxed out and jetting spot on so i wory about being to lean and to much timing so i confuse em sometimes

I hear ya. Pushing the limits of timing advance can start to do the same thing as pre-ign (i.e. build up too much heat in the piston). AND, timing advance has a lot to do with the onset of deto.

The sequence of events (both normal and abnormal) that happen inside a combustion chamber are all so closely related it's hard to keep track of what's doing what. :)

[Meat]

Font-man sorry to hear bout your loss. have you thought about strokin' that puppy ??

[TheFontMaster]

Originally posted by Meat
Font-man sorry to hear bout your loss. have you thought about strokin' that puppy ??


No stroker for this quad. It's just gettin a basic rebuild this time. I can barley aford this rebuild let alone doing some crazy motor. Besiedes for how much I ride I would never get a stroker motor. I hear that they aren't the best set up in a 250r.

[wilkin250r]

Originally posted by TheFontMaster
I hear that they aren't the best set up in a 250r.

Who told you this? I believe, back in the glory days of the 250r, a lot of pros actually kept the bore the same as stock, and stroked it to get to the max 265cc.

I'm not trying to convince you to get a stroker, but don't ever rule them out because "they aren't the best set up in a 250r". When properly designed, they are very potent motors.

[beerock]

your right wilkin they are potent but they ar eno where enar as reliable as a stock crank..... to stroke the crank they machine a offset crankpin which is actually smaller then the original crank pin which there fore cause more rotational wear and thus will blow faster....

for pros though, they rebuild them all the time. so that a non issue