200x meltdown pictures

[michaelwbrenner]

Hey guys. Check out my pics of the engine disassembly. I guess it could be worse. The 20 year old piston that I replaced looked better than this one and was so loose (low compression) that the bike would barely start anymore and burned about 200cc of oil every 2 hours of running. I posted earlier in the week and many of you suggested that my camshaft chain could have slipped and jumped a tooth on the cam sprocket. My bike seemed to be running stronger than ever and then after about 10 minutes on the new topend with a fresh bore job the motor lost compression and came to a stop. I think the gas I was using was suspect. Also. I am running the stock 108 main jet with the needle clip one notch richer, and have since heard that I should be running a 113? I have a cobra exhaust and a k&n with a modified airbox. I think this time around I'll jet up to 113 and run the needle clip 1 notch richer. There are 5 regions of scratching on the piston/cylinder. I think that is the 5 ring endgaps. TOP, SECOND, 2x Oil Rings, and the Oil rings retainer. My question is.... Is this detonation? The top of the piston is a very light grey color and so is the combustion chamber/both were polished aluminum color before. The top of the piston and the chamber also have a rough texture to them now. The rings are shot. They look like they've worn out a lot. I haven't checked the end gap on the rings since I tore down the engine. Any advise? The motor ran well then started loosing power and then lost all power and cycled to a stop. No sieze. Then it would turn over freely and wouldn't start. Any advise? I've rebuilt motors before but never seen a failure like this so quickly.

[samster143]

Is this a 12:1 piston? what fuel are you using? Hoow did the cam and rocker arms look?

[speed20]

The piston makes it look like a jetting problem (to me anyway) too much air and not enough gas....if it wasnt getting oil, your cam would be trashed, and it most likely would have seized up. whats the plug look like? if its a brownish color like the piston, id say it was jetting. ive never had anything like that happen to my 200x's. If it was pre-detonation, wouldnt there be a hole in the piston? If it was out of time, you would know it (the kickstarter would jump back up when you kicked it....almost like a backfire.

[michaelwbrenner]

Does anyone know. Is this a 12:1 piston for a 83-85 200x? I ordered the 10.25:1 and that's what the box the piston came in said it was. Is it really 12:1?

[speed20]

thats a 10.25:1 piston....the 12.25:1 has a larger "rise" on the top of the piston (looks small in the picture).

[EvilMooseofDoom]

The piston makes it look like a jetting problem (to me anyway) too much air and not enough gas....if it wasnt getting oil, your cam would be trashed, and it most likely would have seized up. whats the plug look like? if its a brownish color like the piston, id say it was jetting. ive never had anything like that happen to my 200x's. If it was pre-detonation, wouldnt there be a hole in the piston? If it was out of time, you would know it (the kickstarter would jump back up when you kicked it....almost like a backfire.

I have seen several burned pistons....this bike simply ran lean. Detonation usually punches holes in the center, a general lean condition (as richer A/F ratios tend to cool the combustion chamber vs. a lean ratio) will burn the edges, rings, ring lands, cylinder wall, etc...lol...

Next time, maybe you should toss a Holley 1150 dominator on there, just for giggles...hey, it may never run, period, but at least you will never run lean, lol...

[michaelwbrenner]

I guess it just ran lean then. With the mods I have: I forgot to mention that I smoothed the ports quite well. I radiused the inside radius of both ports very well while it was apart. I guess that along with a new piston, pipe, and airbox modded with the kandn filter and stock main jet equals lean condition. Thanks for the difinitive statement. " This engine ran lean " Thats what i needed to hear. Where should I start next time on main jetting.. Jet go 108(stock), 110, 112.5?, 115? I was thinking of starting out 4-5 sizes larger than stock and jetting down from there. Your thoughts? Ballpark. By the way. Changing main jets in Glamis after my girlfriend has been riding it all day is my favorite thing in the world to do!!!! lol.

[clong]

Hey,
I sounds like you feel you got an answer but I would be cautious as to a small jet being the cause of all this. I definatley am not a bike mechanic, but your engine only ran for what sounds like a few minutes. I'm sorry but no jetting issue would ever casue that in such a short time period. Even if you were running it hard in 100+ degree weather, would jetting blow a motor that fast. Its also not like these are 2 strokes with oil in the gas lubricates the motor. The difference from a a 109 to a 113 main jet is only a 4% difference which means if your motor stopped that fast from a 4% difference, then it was something more that caused it. I'm not saying I have an answer but before you go through all the work again do some more research.