Can someone tell me what happened???

[stever250r]

Well... yesterday was the test day for my engine on my R project and ... It didnt go so well at all.... Heres the story..

Im using a Pro-X 265 PV cylinder with an 89 long rod crank, spacer plate, and a 68.50mm cr250 piston...

Engine started on like the third kick... didnt want to idle but it was the first run... I held just enough throttle to keep it going. Everything sounded great. I quick bumped to 1/4 throttle like three times and then it went all to ****. PING PING PING LOCKED UP SOLID. It might have run a total of a 1-2 minutes tops.

When I pulled it apart... the piston was busted in two places above the upper ring groove... I've never seen this before. The top ring was pinched between the piston and cylinder on both sides. I like to never got the piston out of the cylinder.. thus the damage you see on top of piston is from me beating it out.

I paid over 700.00 for the setup and its destroyed. I could cry and my wife is ready to kill me.

Can anyone tell me what might have went wrong to cause this. Ive included pictures so you can get a better look.

[stever250r]

Needless to say ... Im in the market for a cylinder and piston.... Aftermarket.... ESR, CT, LRD, etc.... 265-310

If you have on for sell please let me know.

[250r4life]

why are you in the market for a new cylinder? your current one isnt junk. yah you will have to get it re-nikasealed and thats another $230, and another set of piston and rings, thats another 100... but other than that... did it chew up your dome?

i couldnt really tell from the pics, but what chewed everything up? did you assemble it with assembly lube? did your wristpin bearing break and chew up everything? you gotta give us a little bit more info- its hard to tell a whole lot from the pic...

[stever250r]

I dont think just nikasil will fix the cylinder.... I am sending it to LRD so they can take a look at it. The grooves in the cylinder ar very deep. It might be able to be bored and then a steel sleeve pressed in... Im not sure...

The dome did not really recieve any damage. Most of the damage was caused by the rings being pinched between the cylinder and piston... and then me trying to remove it.

The writpin bearing was not damaged..

Im just wondering what could have been wrong to cause this to happen under such low RPM within 2 minutes of startup.

[Jester]

a ring might have been overlapping the little notch in the ring grove just enough to let you put it in, but to much that it caught on the port and bent.

[stever250r]

Never considered that ... but one of the places on the piston where it is broken is located directly above the groove pin.

[matt250r21]

As long as the sleeve is not broken off you can get the grooves in the aluminum cylinder welded up, rebored, and replated. As for what caused it, I don't think you could get the cylinder on if one of the rings were not lined up if your bore size is correct. Are you sure your bore was 68.50 mm?

[zedicus00]

looks like a ring caught sumwhere and just went down hill from there... just to make sure you did have good premix in it and it wasnt lean or anything was it??

and why was u using a cr250 piston?

[beerock]

what cylidner is that and is it an aluminum sleeve i really cant tell? if its not aluminum just bore it out or if it cant be resleeve it.

why did you use a cr250 piston i believe the piston pins are not in the right location?

it does look like you didnt have the piston rings in right and you can get the rings in with the ring pin out of alignment.

either that or the cylinder was not shaved around the ports and it caught the ring

[stever250r]

THe cylinder is aluminum with a nikasil bore, no steel.

Hopefully it can be repaired.

I used a cr250r piston.. because that it what the guy sent me when I bought the cylinder. I assumed that was the correct one.

Someone else at my work had mentioned that I might have had the rings installed upside down.

I know that on most cars you have some marking on the ring..ie...(dot)...etc. but I didnt think there was an up or down side to the rings on these two strokes.

If there is ... I guess Ive been really lucky because Ive never paid attention to it for any others that Ive changed.

What about the spacer plate? I know they make different thicknesses. I imagine this is only to make changes in compression ratios.... but do you think that maybe the the upper ring could have gotten caught on the top of the cylinder ridge? Is that even possible??? I only ask because after looking again I notice some damage just around the ridge of my cylinder.

[zedicus00]

thas very possible. i think hes right, the CR piston is in a slightly different place. there are different thickneses of spacer plates for running different combination rod lengths piston combos.

first step might be get ahold of the guy u got the setup from and ask why he sent a cr piston

also does the gasket stick into the cylender anywhere?

usually the piston will hit the underside of the head before the top ring catches the cylender edge but it all depends on the setup yur running....

[dober250R]

sounds to me like whoever bored the cylinder didn't do a good job. It sounds like the bore was to close to the piston. Or the CR piston is what caused the problems....

[DezSled]

Where was the piston in the bore when it stuck? Right at the top of the exhaust port? Rings have markings at the gap for installation upwards. The stock piston ring positioning pin is offset ever so slightly upwards in the ring land. If you put them in upside down when things started to expand from the heat of combustion it may have caught the upper roof of the exhaust port.
Whats the rings look like, did they break apart? The diagonal damage in the bore looks like something harder than aluminum caused it. Possibly from extraction? Doesn't look like when a sieze happens (verticle scarring). Could something been inhaled thru the carb? What did the piston dome look like before you beat on it to remove it?

[DezSled]

1

[stever250r]

The piston was located in the top of the cylinder just above the exhaust port. The top ring had been broken in two places and was pinched in between the piston and cylinder wall. Most of the damage was done removing the piston.

I honestly have never paid attention to the the way I installed the rings , and this is the first time I"ve ever had a problem.

One thing is for sure...... I will be sure to check it before I put it back together.

Thank you for the information.!!!!!

[Mechanix311]

From what i remember wiseco pistons dont have to have a certain side of the rings up. I thought you can install them any way but that may not be a wiseco piston either. It looks like their is no bridge on your exhaust port either. I know alot of builders do this but it always looked like a ring could get caught with an opening that big in the cylinder. Sorry to hear about your misfortune it sucks when something so expensive and nice gets messed up.

[Eric_Winkworth]

Always always always check tolerances yourself, i've rebuilt a few sled motors and taking one back apart because you ordered some POS cast pistons that has a hurtin tolerance or someone sent you wrong one, that pisses you off.

BTW I hate wiseco pistons, a guy I know that has been rebuilding 2 strokes for 25 years calls them seizeco. Sometimes they have funny densities in them that make them expand more then they should. Really let her warm up good and follow break in procedures to the T.

Not saying it was the seizco, but a new motor sould never do that.

[beerock]

Originally posted by Eric_Winkworth
Always always always check tolerances yourself, i've rebuilt a few sled motors and taking one back apart because you ordered some POS cast pistons that has a hurtin tolerance or someone sent you wrong one, that pisses you off.

BTW I hate wiseco pistons, a guy I know that has been rebuilding 2 strokes for 25 years calls them seizeco. Sometimes they have funny densities in them that make them expand more then they should. Really let her warm up good and follow break in procedures to the T.

Not saying it was the seizco, but a new motor sould never do that.

honestly, cast pistons perform much better then forged pistons in certain situations ,but they cant handle high compression as well

weiscos do have a high rate of seizure but thats because people dont releive the exhaust ports as much as they should and proper warm up is not stressed by the builder. forged pistons are great but are like hand grenades if you dont work with them and not against them

[stever250r]

Well, I got a call back from LRD today... and as I suspected he said the cylinder and head were toast, and cant be repaired.

He said that someone had welded new studs in the cylinder and there were several things that could have caused my problem...

I was doomed from the get go...

Im looking for a new big bore cylinder....... Please get in touch with me if you have one.

Thanks

[b.lee]

i'd still want my cylinder back...if i was you..

for what? i dont know, but at least an expensive souviner.

[stever250r]

Yeah I considered that too... but didnt feel like paying the 20+ $$$ it was going to cost for return shipping...

They can have it.

[b.lee]

they are prolly fixing it and selling it..

i wouldnt doubt it one bit.

[matt250r21]

I would get that cylinder back if I were you. It can be fixed, I don't care what LRD says. They will most likely fix it and sell it to someone else.

[beerock]

yea get back the cylinder it can be fixed there totally screwing with you thats not cool either

[stever250r]

Well, if I get the cylinder back, would any of you be willing to buy it? I dont know of anyone that will fix it... and I dont want to take a chance on it.

Make me an offer. Sold as is.