Holy piston!

[pickleweasel_00]

Doh! Was out riding my Tri-Z today. I noticed it started to lug down a little bit and lose power. About 30 seconds later i hear a loud pop and it dies. Needless to say I was 1/2 mile from home so had to walk back, get the trailer and haul it back. Started looking things over and noticed it had no compression at all whatsoever. So I took the head off and sure enough, right in the center of my new $120 wiseco piston was a quarter inch hole.

Now the questions... I'm positive the carburetor was set too rich (it smoked a litle and ran better as I leaned it out) but the plug was grey in color. Running them lean will put a hole in a piston, right? What about the timing? If the timing is off, will that do it too? It ran pretty good... Guess I wanna find out what caused it so it doesn't happen again. But I think I might look into getting a 310 kit for it now since it's apart. If not that, go for a phase 2 cylinder set-up.

Any comments, suggestions, insight? Oh, and I finally took a pic the other day so I thought I'd share that while I'm at it :beer

http://a790.ac-images.myspacecdn.com/images01/82/l_04e18556d0196ae6137c6d87e2c7f8cd.jpg

[Erics350x]

lean or the timing was way to advanced, but most likely jetting.

[viper]

sounds like it was lean to me jessie but thats hard to believe .....you didnt jet it down from when i sent it to you did you ? detination could have done it also but the plug wouldnt be grey unless it was lean ..how was it running before the piston failed ?

[viper]

and i would def buy the sprock big bore if you are going to do more work than just a rebuild .........best bang for your buck since you will have to bore and get a new piston also .....that kit from sprock is a very good price .......sorry about your bad luck with it .

[pickleweasel_00]

well i know almost for a fact that the jetting was to rich. The plug was medium to dark grey in color. So I'm leaning to the timing being off, but it still seemed to run good. Is there any way to tell foe sure if the ignition is off (besides actually checking it) I mean, audible pinging coming from the engine like in a car? Oh well, crap happens. Hey shannon, any idea on whether or not there will be any kits left after all the orders are taken care of? And I'll need a different dome for the head, right?

[pickleweasel_00]

and no, didn't change the jets on that carb yet, just played with the clip position on the needle, but it was still too rich

[ceaserthethird]

Black & Oily is Rich To me , Gray is LEAN

Light Brown is perfect - checking Jetting 101

[Erics350x]

sounds like you where mixing your fuel to rich and your jetting was way lean.
you also could have and air leak.
if the timing was that high you would have heard pinging.

[200x350xtriz250]

Now the questions... I'm positive the carburetor was set too rich (it smoked a litle and ran better as I leaned it out)...

not trying to treat you like an idiot, but you do know it's a 2 stroke right? what ratio of oil to gasoline are you running? I only say this because in my experience 2 strokes smoke regardless of jetting unless there is no oil in the mix:eek:

[pickleweasel_00]

i was running 32:1 with the yamalube 2R oil and 93 octane gas. Guess I should have paid more attention to the plug, but like I said the richer I set the carb, the crappier it ran and semed to run better as I leaned it out. And the carb came off a ported drag bike so i was sure it was going to be too rich to start, but better to rich than to lean. Chalk it up to another learning experience the hard way :rolleyes: And this is my first two-stroke, so that may have something to do with the slow learning curve :wondering I will chack out the cylinder and if it's ok, I might hone it and throw in a new piston and rings for awhile to see how it does. Or I might go for the big bore...

Is there any change that the piston could be welded or is that going to be as big of a waste of time as I think it is???

[pickleweasel_00]

also, as Erics350x said, it could have been an air leak. The idle seemed to be a little erratic at times, sometimes it was a little high and sometimes a little low. And the carb fit in the boot somewhat loosely... probably makes the most sense, not much else that could be at fault

[pickleweasel_00]

one more real quick update... I went out and looke things over and found a couple small cracks in the outer layer of the boot. Not where the carb slides in but on the flat part closest to the engine (sorry no pics yet). The more I think about it the more it makes sense. It would smoke pretty good when I first started it and as I ran it and it got warmer it seemed to smoke a little less (the rubber expanding letting air leak through the cracks?). And to top it off, there was a slight trace of oil in/around the cracks. Doesn't look like they go through to the engine side but i think it's more or less a two piece part so I'm sure the air found a way through. Sound like a likely suspect? Makes perfect sense anyways. So, where's a good source for a new boot? :)

[jason 32]

what plug was in it ? sounds like too hot of a plug

[viper]

yamaha dealer ..........i would shitcan the yamalube oil and use maxima castor or klotz benoil .....if the idle was iregular like you are saying i bet it had a air leak......toss that piston in trash and get a new one ........will ask sprock if he is going to have any more cyl,s left for ya