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.

[3WW Star-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.