watkins Posted October 24, 2005 Author Report Share Posted October 24, 2005 (edited) Yeah I know. Edited October 24, 2005 by watkins Quote Link to comment Share on other sites More sharing options...
Wallrat Posted October 24, 2005 Report Share Posted October 24, 2005 Well regardless it looks like you overheated it. The exhaust port gets the hottest out of the cyl so that's why ur piston is melted there. I would go over those exhaust ports really close cuz if there's chips, then it obviously made contact with the cyls. Take apart your water pump and take a look there, make sure the bearing isn't flowered and the impeller is still intact. Might as well replace it with a billet one while ur in there. Also you should install a temp sensor before you ride again. I'd also check out the crank really well in case it got damaged. Actually if it was me I'd split the cases just to make sure that nothing went down inside and to visually inspect the crank bearings...but then I'm kinda anal that way. Plus you can split the cases and have it back together in a few days if nothing is damaged. Quote Link to comment Share on other sites More sharing options...
watkins Posted October 24, 2005 Author Report Share Posted October 24, 2005 (edited) Well regardless it looks like you overheated it. Edited October 24, 2005 by watkins Quote Link to comment Share on other sites More sharing options...
Justintoxicated Posted October 24, 2005 Report Share Posted October 24, 2005 (edited) Hmm, that really blows man sorry to hear about your trouble. Definately looks like you overheated. If you can do a leak down check make sure you don't have any air/coolant leaks after you next rebuild. also check to make sure your cylinders were bored and honed correctly (proper specs and gaps). When you checked the compression you warmed up the bike first shut it down and kicked it over with the throttle wide open right? Was the gauge reliable? Not all gauges will read the same... Also check your timing as sugested, but it does sound like you should have been fine on premium pump gas / race gas mix...sounds more like the bore/hone or new pistons were not mached up or possibly an air leak or something. When you loose pieces of the pistons and plugs it's best to split the cases, but definately check the crank to see if it is within spec..If it was a stock crank and especialy a non welded stock crank that could be your problem. Edited October 24, 2005 by Justintoxicated Quote Link to comment Share on other sites More sharing options...
Wallrat Posted October 24, 2005 Report Share Posted October 24, 2005 ...And a blown crank is a perfect excuse for an H129! Quote Link to comment Share on other sites More sharing options...
watkins Posted October 29, 2005 Author Report Share Posted October 29, 2005 Well.. going to be splitting the cases tonight, but I pulled the impeller out and it looks fine, I replaced it anyways so I dont have to worry about it again. So I dont really see how the bike could have overheated, I was running straight engine ice and the impeller seems to work fine. So I am leaning towards detonation, but the cause is driving me nuts. I guess I will get it put all back together and run 50/50 race gas with way rich jetting just to see what happens. Only mods I did before this trip was a coolhead and replaced the needles with dynojet needles and put them on the 4th clip from the blunt end (which is richer than I had the stockers on). So I dont think its a jetting issue. Quote Link to comment Share on other sites More sharing options...
trail rider Posted October 29, 2005 Report Share Posted October 29, 2005 I had the exact same thing happen to me on my cr 125 the other day. I was goin wide open and it started losin power and missin, i thought it was a fouled plug at first. then it quit on me, i had a spare plug with me and changed it, and it still would'nt start. Then i noticed that i had no compression at all. So i pull the head and the piston has a nice, neat little chunk missing from the exhaust side, and you could see the ring. But i didnt have not even a scratch or anything in the cylinder or head, nothing at all. I read on the eric gorr site that it was a head gasket leak that cause'd the piston to break like that. the coolant that enter'd the combustion chamber hits the piston and makes it weak and brittle untill it breaks off. I did notice that i was low on coolant after some rides earlier and seen some black on the head gasket where the piston chunk broke off at. I guess i was pretty damn lucky though, could have been alot worse. Quote Link to comment Share on other sites More sharing options...
watkins Posted October 30, 2005 Author Report Share Posted October 30, 2005 Well.. buddy of mine who thinks he is the all knowing banshee god is saying that +4 timing is way too much for a non-ported bike. I told him to suck it and that he didnt know what he is talking about... any thoughts, I know a lot of you run +4 with no porting.. just want to be safe is all. Quote Link to comment Share on other sites More sharing options...
cb67rs1 Posted October 30, 2005 Report Share Posted October 30, 2005 you have a air leak pretty bad some where, are you plugs good and tight? from the looks of it it ran way too lean, not enough gas plus too much air will = a burnt piston really fast, you need to check for air leaks ,whats your jetting? Quote Link to comment Share on other sites More sharing options...
sand rocket Posted October 31, 2005 Report Share Posted October 31, 2005 my pistons looked simalar to those when my crank twisted and broke the crank seals. Quote Link to comment Share on other sites More sharing options...
Fireman-hott Posted October 31, 2005 Report Share Posted October 31, 2005 Ah I lost the website with the piston diagnostics after the recent HD death. Hole in the center is A) Detonation or Overheating. If your fuel was fine than any overheating would be a bad gasket. Reed gasket, head gasket, carb boots not tightened fully. Secondly the first set I also experienced something like that, but mine blew in less than an hour, hell I think in 10-20minutes. I put the pistons in backwards major oversight in the rush to rebuild and ride that afternoon. Good luck with it, but definately checkout the air leak/overheating suggestions. Quote Link to comment Share on other sites More sharing options...
Hulio-mv Posted October 31, 2005 Report Share Posted October 31, 2005 this is sort of basic but did you make sure the dowell sleves at the base of the cylinder were still there and didnt fall out has hapened before Quote Link to comment Share on other sites More sharing options...
trex banshee Posted October 31, 2005 Report Share Posted October 31, 2005 most definitly lean same thing happened tome in LS my left carb got pluged up and burnt a hole right throught the piston. and all the black marks on the sides of your pistons is alsoa good sign of overheating. have you ran it out of gas or maybe your screans in your tanks are clogged up and it isn't getting enough fuel. since you said you eliminated the air leak issue when you had the cylinders bored did you take them the pistons as well? there is a specific clearence between the piston and cylinder wall and they may be too tight? just a thought. but if i were you i would do a complete tear down replace every gasket and seal, get your cylinders checked, clean your carbs and tank(take the valve off and clean the screans or better yet take them out) and go from there and another thing did you happen to take the flywheel off? if so did you make sure you got it on the woodruff key, if not the flywheel will spin some resulting in timing change.(i have seen this happen before, and believe it or not they will start and run, but not for long) Quote Link to comment Share on other sites More sharing options...
sheefreak Posted October 31, 2005 Report Share Posted October 31, 2005 This may help. http://www.mztech.fsnet.co.uk/workshop/wrk_piston.html Quote Link to comment Share on other sites More sharing options...
2003LimitedBanshee Posted November 1, 2005 Report Share Posted November 1, 2005 Well.. buddy of mine who thinks he is the all knowing banshee god is saying that +4 timing is way too much for a non-ported bike. I told him to suck it and that he didnt know what he is talking about... any thoughts, I know a lot of you run +4 with no porting.. just want to be safe is all. 431308[/snapback] I've been running +4 on my timing for a while now, and have had no ill effects. Anywhere in the 3-4 range seems to be pretty common. I've heard of people running as much as +7 on ported bikes. Quote Link to comment Share on other sites More sharing options...
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