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Post by ThomasTPFL on Mar 4, 2017 12:38:26 GMT -5
 Anyone have an idea on this being too much air vs. too little oil? |
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Post by gsx600racer on Mar 4, 2017 13:14:23 GMT -5
I'd say lack of oil(per pic supplied)
What does the top & and underside of the piston look like?
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Post by 190mech on Mar 4, 2017 13:16:55 GMT -5
Neither!It got hot and melted!!(just kidding)..Could be several problems,as you said,lack of oil or lean mixture,also ignition timing too far advanced,cooling system failure..Oil injected?Miles on the top end?Was it WFO or part throttle when it fried??
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Post by ThomasTPFL on Mar 4, 2017 13:28:56 GMT -5
The top has a small divot, but no signs of aluminum blowing out the exhaust. I'd venture a guess the divot is from a prior lean condition as there is a consistent layer of carbon on everything.
I didn't have a temp gauge on the bike. All the shrouds, fan, etc... are in place.
Was running wide open when it happened.
I'm leaning towards oil myself as the day before this happened I fixed airleaks and made the oil pump valve stop sticking in the wide open position. I have a feeling that may have something to do with it.
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Post by 190mech on Mar 4, 2017 14:11:48 GMT -5
Cant break PREMIX!!!!
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Post by eclark5483 on Mar 4, 2017 14:18:48 GMT -5
What does the crown look like? Pics?
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Post by ryan_ott on Mar 4, 2017 21:05:41 GMT -5
Is it scored all the way around or just the exhaust side? Lack of lube and lean mixture kind of have the same effect on a 2T. If the crown is caved in I say high EGT - lean, but the scoring says lube. Likely a combo of both.
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Post by stepthrutuner on Mar 4, 2017 22:40:16 GMT -5
My idea is mostly lack of oil since since less oil richens the mixture. Provided you found and fixed all the air leaks. The divot could have happened in an earlier episode. Regardless, a new piston w/rings is in order followed by a retune and monitoring. Premixing is advised per 190mech.
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Post by ThomasTPFL on Mar 5, 2017 0:09:41 GMT -5
 The divot is there above my thumb. Its directly above the exhaust side. The even layer of carbon covering everything leads me to believe it happened some time in the past. Probably before I sealed up the intake tract. Possibly the day my idle air screw fell out. May have happened at Suches when I got the engine hot enough to cause my spark plug cap to come apart. The clean looking spot is lined up with an intake port. It'll probably get a whole new cylinder kit. There's a whole lot of aluminum stuck to the cylinder wall. |
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Post by ThomasTPFL on Mar 5, 2017 0:18:23 GMT -5
 Not as bad but the intake side smeared a good bit too. |
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sanec
Scoot Member
Posts: 69 
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Post by sanec on Mar 5, 2017 4:27:37 GMT -5
It is lack of oil. I've had the same problem- lack of oil leading to one of the bearings to play a lot and piston that looks the same as yours
You should check your bearings too
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Post by ThomasTPFL on Mar 7, 2017 22:58:42 GMT -5
The bearings seem fine. No excessive play on the conrod or anything. It'll be going back together with a fresh topend and no oil injection.
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Post by gsx600racer on Mar 7, 2017 23:16:34 GMT -5
The divot is there above my thumb. Its directly above the exhaust side. The even layer of carbon covering everything leads me to believe it happened some time in the past. Probably before I sealed up the intake tract. Possibly the day my idle air screw fell out. May have happened at Suches when I got the engine hot enough to cause my spark plug cap to come apart. The clean looking spot is lined up with an intake port. It'll probably get a whole new cylinder kit. There's a whole lot of aluminum stuck to the cylinder wall. If your bored while waiting for parts and the cylinder didn't get dug up by the rings and its just aluminum on the cylinder, you can get some muriatic acid and brush it on the bore to dissolve the aluminum. This is a messy and nasty(fumes) procedure and once done rinse in a bucket of soapy water and dry immediately and coat with oil or it will rust almost instantly. Then hit it with a hone and you will be good to go again for a new piston. |
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Post by ThomasTPFL on Mar 7, 2017 23:26:09 GMT -5
I'm sort of tempted to modify the topend that came off my Derbi to go on there.... I'd have to bore a hole into the water jacket for a hose fitting.... but it looks like I'm buying O'verse's Minarelli to drop in this bike so playing around with a budget LC build on the TGB engine may be fun. I still have a TGB frame with no engine.
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Post by ThaiGyro on Mar 8, 2017 6:13:08 GMT -5
The scoot masters and others have detailed many threads that can lead to this condition...seizure! If you are running a stock pump...dump the pump! You will never be sorry, unless you cannot fill a "ratio-rite' for 5 gallons consistently. There were just new threads regarding pre-mix and pump removal and crankcase displacement plugs...
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