HELP! Piston, rod, cylinder (piston doesnt clear)

[beobe99]

Hey guys how's it going. So now that Im nearing the end of my build the sh** hits the fan with issues. heres the lastest and biggest so far.

Bought a piston for my (at least i was told) 89 bottom end/cylinder) had the cylinder bored/honed and Im set right??
Of course not. I got the piston on, put the cylinder on, and went to check to make sure the piston didn't rise above the cylinder you know. well it was about a 1/4 inch shy from hitting flush with the top of the cylinder and on its way back down it hit the crank and I couldn't turn it over anymore.. I had to reverse it..

Ok, so either the

1. rods to short
2. pistons to tall
3. or it's a diff. crank (which i doubt)
4. Cylinder is from an 86? (how could i tell anyway.. whats the measurement, could i just order the 86 piston I HOPE ha!)

Someone please tell me what i need to do.

-The piston I ordered is a Wiseco honda 250atc 87-9 prolite
0.0030 (0.076mm)

-The rod is a Hot Rods C.K 103 (I THINK this is the issue but dont know enough to move to the next step here)

The guy i got the engine off of had a 310 pro-x cylinder/piston on it. Do they requier a shorter rod?

If I can order a custom piston who/what do you recomend...

Thanks guys, all your help has been great so far with my other issues and I appreciate it alot!

Beobe

[Aceman]

The only combination that would yield those results is a short rod crank with an 87-89 piston. Buy a different piston.

[beobe99]

Originally posted by Aceman
The only combination that would yield those results is a short rod crank with an 87-89 piston. Buy a different piston.

Thanks bro. so just simply buy a 86 piston or let the supplier know my situation before ordering? What about with the piston not reaching the top flush with the cylinder? Im guessing I prob have to get an 86 cylinder? which if thats so it would prob be cheapest to just get the rod :/

Thanks

[wilkin250r]

The issue is the piston and crank combination.

In 87, Honda changed the length of the connecting rod to make it 5mm longer (about a quarter inch). Well, if all other things were equal, that would push the piston up about a 1/4 inch, wouldn't it? It would probably hit the head.

So, along with the rod change, they also changed the piston so the rod sits 5mm deeper, essentially bringing the piston back "down" to it's normal height. There are lots of reasons why they did this, but we won't go into them.

You have a mis-match, you have a short rod (86) used with a long-rod piston (87-89). The solution is to get an 86 piston.

The good news is, as long as you have the right combination of piston/crank, it will work in ANY year cylinder, so you can still keep whichever one you have now. The 86 piston sits taller, so it will bring it back up that 1/4 inch.

[beobe99]

Thank you VERY much for that info.. I was allready dwelling on getting a new cylinder, piston, or changing out the rod which would be a big pain concidering I just got the bottom end together and in the frame..

So I guess im just out $150 unless i sell this 87-89 piston.

Im guessingthe shorter rod rev higher safer and the long rod gives better low end?




Originally posted by wilkin250r
The issue is the piston and crank combination.

In 87, Honda changed the length of the connecting rod to make it 5mm longer (about a quarter inch). Well, if all other things were equal, that would push the piston up about a 1/4 inch, wouldn't it? It would probably hit the head.

So, along with the rod change, they also changed the piston so the rod sits 5mm deeper, essentially bringing the piston back "down" to it's normal height. There are lots of reasons why they did this, but we won't go into them.

You have a mis-match, you have a short rod (86) used with a long-rod piston (87-89). The solution is to get an 86 piston.

The good news is, as long as you have the right combination of piston/crank, it will work in ANY year cylinder, so you can still keep whichever one you have now. The 86 piston sits taller, so it will bring it back up that 1/4 inch.

[wilkin250r]

It's not really a "high rev vs low-end" issue. Yes, the short rod revs a little easier, and yes, it affects the power delivery.

But the REAL reason for the change is to alter the rod angles, and changes the sidewall pressures on the piston.

You could get really involved with the discussion, but the end result is that the longer rod has better reliability.

[beobe99]

Bump

was hoping someone could tell me what piston I should order.

Im guessing the same size but for 86?

This is the size i ordered for a 89 -

0.0030 (0.076mm)

[jon370r]

You can use any year cylinder but the rod and piston application need to match. If you have a short rod crank than you need a 1985-86 piston. If you have a long rod crank then you need 1987-89 piston or a 85-86 piston with a .190 thick base spacer. The .003 you listed is the cylinder to piston clearance not the piston size. You need to find out the actual bore diameter (such as 66.00mm) to order the correct piston.

[sk8ter0712]

get a spacer plate

[Aceman]

Originally posted by sk8ter0712
get a spacer plate

How about you try running a spacer plate with a short rod crank and let us know how it works out..........

[beobe99]

Originally posted by sk8ter0712
get a spacer plate

spacer plate would make my issue worse.. I think you misunderstood..

[sk8ter0712]

k your right I misunderstood
and aceman calm down I misunderstood

[Aceman]

Originally posted by sk8ter0712
aceman calm down I misunderstood

Yeah, I'm really riled up over this one.........:huh

[kit bazile]

same thing happen to me today putting my motor toghter my piston comes out the top of my head about the hight of maybe a quater amybe less but im about to sell all this crap and be done riding a 250r and if i caint fix the problem its gone but to make a long story short i have a 88 long rod and a 86 cylender on it and they gave me the piston so i guess that was right but it wasnet so now im stuck with a brand new wisco i caint use and i caint bring it back the rings have been cut to spect so i guess i just ate the 200 dollors

[Aceman]

Here ya go Kit:


Originally posted by jon370r
You can use any year cylinder but the rod and piston application need to match. If you have a short rod crank than you need a 1985-86 piston. If you have a long rod crank then you need 1987-89 piston or a 85-86 piston with a .190 thick base spacer.

[kit bazile]

i under stand that but listen tto this i have a 86 cylender and a 88 botom end long rod and i was asuming that what the piston was but undoughtley it aint and the spacer is in place its hits the head gasket

[Aceman]

Sounds like you need to talk to who ever gave you the piston. You need to find out exactly what you have going on with your motor. Is it a stroker, how thick is the spacer plate, what year piston, etc etc.

[kit bazile]

so what they saying that if i run a 86 jug witha long rod motor witha 86 piston i dont need the spacer in the motor are am i misunderstanding

[wilkin250r]

We can help you out, kit, but we need to understand your problem.

Your post said "my piston comes out the top of my head about the hight of maybe a quater amybe less "

Do you mean a quarter inch? Or do you mean about the thickness of a coin?

If it's a quarter inch, then Aceman has you pointed in the right direction. What you have is a long-rod motor, but you have a piston made for a short rod. It's no big deal (it's actually a very common setup), you just need a spacer plate to bring the cylinder up where it needs to be.

If it's the thickness of a coin, you have some major issues.

[kit bazile]

dude i dont wont to be agverting are nothing but let me tell you how it is i took this top end off and 86 atc 250r motor 2 weeks ago and it worked fine untill it leaned out ok then i took the clyender to the shop and had it reworked and put it back on the boke and the spacer plate is in there and now the piston is comming out of the head about half way in be tewin the top of the piston and the first ring and it is actually hitting the head gasket first and then the head so that is my problem the best way i can explain it to my knowledge i ama a desiel mechanic not a 4 wheeler mechanic so if im agvegating yall im sorry but i just wont my bike fixeed so i can ride this thing something i forgot to add is that the bottom end ive got i a 1988 bottom end long rod and the cylender came off a 1986 atc bottom end that is all i know please help

.

[kit bazile]

are if you wont to talk to me call 1-225-910-1748 and i will wxplain a little better i caint spell very good

[jon370r]

Do you know any history on this engine? Sounds like you might have a special setup like the ones some race shops would have that use a YZ250 piston. Has to be something odd like that. Measure your cylinders overall height. Should be about 4.920" or a little less than 4 15/16" and the space should be .190. If not then you have some hybrid setup and you need to get the piston numbers off the old piston dome if possible.

[mineralgrey01gt]

Originally posted by wilkin250r
We can help you out, kit, but we need to understand your problem.

Your post said "my piston comes out the top of my head about the hight of maybe a quater amybe less "

Do you mean a quarter inch? Or do you mean about the thickness of a coin?

If it's a quarter inch, then Aceman has you pointed in the right direction. What you have is a long-rod motor, but you have a piston made for a short rod. It's no big deal (it's actually a very common setup), you just need a spacer plate to bring the cylinder up where it needs to be.

If it's the thickness of a coin, you have some major issues.

kit is my brother and the piston goes out of the jug 1/4".

[jon370r]

Originally posted by mineralgrey01gt
kit is my brother and the piston goes out of the jug 1/4".

Then most likely you will need a 87-89 piston or a .190 base spacer, either will work.

[mineralgrey01gt]

he is on his way home now and is going to measure the spacer to see how thick the spacer he has now is.

That place that did the work doesnt know jack about 250r's obviously. Im not going back to them since the parts on the shelf have a STRONG possibility of being installed before (long story)

[my88r]

Originally posted by mineralgrey01gt
he is on his way home now and is going to measure the spacer to see how thick the spacer he has now is.

That place that did the work doesnt know jack about 250r's obviously. Im not going back to them since the parts on the shelf have a STRONG possibility of being installed before (long story)

whats the long story of the parts on the shelf

[mineralgrey01gt]

well my brother told him the problem he is having and the guy had an attitude which doesnt shock me since he caught one with me already. Well after my brother explained all of that the guy that owns the store asked him what kind of condition the piston was in. My brother told him that he filed down the rings for his application and the piston had been installed but never fired on. The owner said to bring it back and he would just wrap it back up and put it back on the shelf.

Also the owner admitted to hating fooling with this stuff, well I was thinking, if you hate it so much then why are you in the business?

Also shouldnt the owner of the store, the one that sold my brother the piston know that there are 2 different pistons?

That makes me wonder if the piston my brother has is the wrong piston for this application and if he said he was going to do that, what else did people (including myself and my brother) have bought that had been installed or used in some way. It may not seem like a big deal to some people but it is to me.

My brother will probably chime in and straighten the story up if i messed up on it any and sorry for the rant but I needed to vent

[my88r]

Originally posted by mineralgrey01gt
well my brother told him the problem he is having and the guy had an attitude which doesnt shock me since he caught one with me already. Well after my brother explained all of that the guy that owns the store asked him what kind of condition the piston was in. My brother told him that he filed down the rings for his application and the piston had been installed but never fired on. The owner said to bring it back and he would just wrap it back up and put it back on the shelf.

Also the owner admitted to hating fooling with this stuff, well I was thinking, if you hate it so much then why are you in the business?

Also shouldnt the owner of the store, the one that sold my brother the piston know that there are 2 different pistons?

That makes me wonder if the piston my brother has is the wrong piston for this application and if he said he was going to do that, what else did people (including myself and my brother) have bought that had been installed or used in some way. It may not seem like a big deal to some people but it is to me.

My brother will probably chime in and straighten the story up if i messed up on it any and sorry for the rant but I needed to vent

all of my local area places are like that around here.thats why im opening my own parts store tired of all these trouble shops.sorry for people like that i dont know how they stay in business

[kit bazile]

finley found the problem with the two thins iv been posting the wisco piston that i have is part number 640-526pb is for a short rod only motor you caint interchange the piston with a long rod even with a spacer in it. so the people i got it from and the little dude i got to do myboring said the diference is .020mm and from the center of a 87*89 pist where the pin goes throught from center of that to the top of piston is 0.20mm difference in them so if you are anybody ever runs in to this with a long rod motor get the piston for the long rod

thamks to everbody that help me i appraciated it thank yall

[skyhighatv]

dont know who told you that, you can run any year long rod motor (87-89)with the 86 piston-but as stated earlier in this post you must use a spacer plate,plain and simple.

[kit bazile]

i know but the piston i got for some odd reas you caint i have the spacer in it and it comes out the head dont know but i do know that the right piston is on the way it will be here friday or monday some time but i know it is puzzling to me to i dont know why this thing dont work but it dont but i solved the problem and all i care about now is getting my bike toghter

[mineralgrey01gt]

what i dont get is the jug and piston off of my 86 atc engine worked just fine on the 88 bottom end until it overheated but this one doesnt work. That just makes me believe that something else is wrong