Pics of fryed piston. I think it was to lean?.(picture of top of piston)

[bushwacker51]

I enclosed a picture of the piston from my honda 350 pv motor. I was breaking it in and it was running great through about half throttle then I opened it up all the way and it just quit pulling and acted like it had no power then it just quit. Checked compression and it had 100 psi. I tore it down and this is what I found . There is no hole on top of the piston. I assume I ran the motor to lean and I smoked the rings?. Oh well guess its time for a new bore and piston. Glenn ps. I guess I need carb jetting class 101 lol.

[nd4speed]

I did one top end rebuild on my LT250R and I had to line up the ring gaps properly with the tabs on the piston. Looks like the rings caught on the ports. But I have never seen a meltdown firsthand.

They always run like a champ until they seize.

Wish I had that motor. Well, live and learn.

[Somekindofjerk]

[QUOTE=nd4speed]I did one top end rebuild on my LT250R and I had to line up the ring gaps properly with the tabs on the piston. Looks like the rings caught on the ports. But I have never seen a meltdown firsthand.

Hes right when installing new rings on any engine try to get good instructions or pay a bit of money and get it done pro. ;)

[TimSr]

I agree with the other posts. I can tell for sure if you post a picture of the top of the piston. When a piston begins to melt, it looks like it was sandblasted away.

My first question would be about who did your boring? Ive seen this a million times when budget boring outfits drill it out, but dont do the proper portwork.

[BigGreenMachine]

So what is the blame for this? Ring gap or was it a lean condition?

[MTS]

You did run mixed gas in it right? was the bike nice and warm before you took it WOT? im thinking you either didnt like the pins up in the piston, the end gaps where not filed to proper spec the Outer ride AND the inner ridge that sits against the pin on the piston, i have seen a bike size 3 times becuse the guy didnt file the inner grove of the ring to properspec...and last but not least inncorect bore size, not enought clearence, or a cold sizeure..

[bushwacker51]

Here is a couple more pictures. The one picture is of the top of the piston and the other one is the other side of the piston. I do mix my gas with oil. If you think it was bad ring gap how come it ran fine for several hours then all of a sudden it siezed. When it siezed it was not the first time I had it out all though it was the first time I gave it full throtle. It was also warmed up before I got into it. Thanks for all your comments

[oddball3]

Check your ring gap and piston clearance. is that a wiseco piston? Forged pistons you need a little more clearance, on ring gap and piston clearances.

[CoeShow]

What you experienced is a common mild seizure from running the engine to hard before completely up to temp (cold seizure) and or not enough piston to cylinder wall clearance.

Wiseco and all forged pistons need additional clearance over cast OEM pistons.

I would have the cylinder re-honed to remove the small scoring (from what I can see) and purchase another piston and ring set. The extra clearance obtained by re-honing should allow for proper clearance.

Good luck!

[max]

Coe Is Right. I Did The Same Thing On My 84r. The Piston Heats Up Quicker Then The Jug And Swells. Thats What All The Scaring On The Skirts Is From. You Have To Let These Bikes Warm Up A Little Bit.

[Blown 331]

My 250R blows up all the time.

[86250RZ]

My 250R blows up all the time.

If thats the case I would let someone else that knows what they are doing tune your carb for you next time. I have over 50 hours on the piston in my R

[Blown 331]

If thats the case I would let someone else that knows what they are doing tune your carb for you next time. I have over 50 hours on the piston in my R

It has nothing to do with tuning, it's nothing I'm doing to them. I'll will pm you so I'm not whoring the thread.

[gasmask]

here's my blown piston...next time i will use a way bigger main jet then work my way down...$125.00 plus shipping per piston

[nd4speed]

When I had my cylinder bored I ordered the piston first then the experienced moto-x guy I paid to do the machining ($60) measured the Wiseco piston and programmed the CNC off its specs. I installed it and did some warm up/ cool down sessions to set the gaskets. But after that I just kick 'er over then let 'er rip. These pics of "cold seizer" are causing me to rethink my behaviour.

[bushwacker51]

Guys,
Thanks for all your help. I swear I had the trike hot before I cracked the throttle open all the way. But the guy that ported the cylinder had some machinest bore the cylinder for me and I dont know who he was so......... I dont think I can just hone it there are some deep scraring marks on the cylinder walls. If it was my torro lawn mower engine I would hone it slap new rings and piston in it and go on but dont want take a chance with my baby. Once again thanks for all your help makes me feel a little better I did not lean it out and fry a piston. Glenn O.

[oddball3]

If you got a good ring slide it down in the bore and measure your ring gap, if your below specs you might just be able to hone out the marks and just use a new piston and rings.

[DIGGER DOG]

were the ports chamfered?? when you got yhe cylinder back did the ports have sharp edges or were they rounded off ?? if the ports were sharp when you got the cylinder back the machine shop owes you a bore job because your piston rings caught on the ports and bridges of the cylinder, also definately check the ring end gap to see if they are to spec. you may have had improper ring to cyl. or piston to cyl. clearance. or it could be cold seize but i would be willing to bet the machine shop screwed up and didnt chamfer the ports .
i am by far not an expert or a professional but I am attending motorcycle mechanics institute (MMI) Im in machine shop now where we bore,rigid hone,and flex hone the cross hatch in the cylinders as well as cut valve seats,press valve guides,reface valves,and true crank shafts etc.. etc...... like i said im not an expert just my 2 cents.

[crackshot]

You people and your 2 strokes. I have had countless 2 strokes through the year.
After a rebuild, RUN YOUR PREMIX RICH during break in and I mean where you see smoke coming out pipe. Cheaper to replace fouled plugs than to tear down again and again.
Ya wanna know another secret? Don't baby them during break in. You want it to go fast? Run it hard during break in for 15 minutes at a time then let cool down 30 minutes.

[Blown 331]

Ya wanna know another secret? Don't baby them during break in. You want it to go fast? Run it hard during break in for 15 minutes at a time then let cool down 30 minutes.

This should probably be split into another thread, acutally I'm sure it has been discussed in the passed. I highly disagree and I don't know how anyone can think that is a good idea. An engine is an engine and I have lots of automotive credentials. Let take an 2003 Cobra for example. You can have 2 identical cars. Break one in like you say, break one in easy. The one that was broken in easily will have an easy 20 more rear wheel horse power on the dyno, seen this quite a few times and other examples just like it.

[denn]

ok, wiesco pistons expand a bunch more than a stock cast piston. This is due to being forged aluminum. This is no different than any other aluminum item. You would not normally run aluminum connecting rods in your 350 chevy engine if you were using it on the street all the time would you. No, It wouldn't be practical. The aluminum rods expand upwards more than steel so you would have to leave more deck clearance between the top of the block and the head. You could do it no problem but you would have to take your time and make sure all clearances are correct. Meaning really blueprint your engine. Steel would just be eaiser and less precise. Well when you get a wiesco piston the best way to install it is to have the piston in hand and take it and your cylinder to the boring place. They should measure up the piston and then bore your cylinder to the piston leaving the extra clearance for expansion. Of course, the cold seizure thing is still true and will happen but if the cylinder is bored to the piston it will be running it is less likley. I know that when I change pistons if it is a new piston I will start it up and take it easy letting the bike get hot and cold a few times after that I beat the hell out of it. Letting it get hot and cold makes the piston expand and contract a few times. So eventually it wont expand and contract as much. After that you should be able to get on the bike start it up and go. I don't let it warm up to much after that. How many people here have blown up a stock piston on a stock bike. I'm sure it isn't to many. Most of the problems is when you change pistons it is machinest error or jetting problems that are caused by another aftermarket part. Anyway, hope this helps.