Over heating?

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Jul 17, 2006
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#1
OK, i was at the local track yesterday and cut about 10 laps and then the problem started. I would be going along the track when suddenly the bike would sort of bog down and wouldnt reach higher revs. I took it back to the ute to sit while we had some lunch.
An hour later we started the bikes back up and it ran fine for about 2 or 3 laps then the problem occured again. I pushed the bike back to the ute because this time the bike stalled on me halfway back.
10 minutes i left it for before i geared back up and went to leave again. It started up and revved well in neutral and off i went. Got about 20 meters and it happened again.
So i left it for about half an hour and started up, did a few laps and it sort of tried to do it, but only did it for about 10 seconds. So a few more laps around then went home.

Anyone have this problem or know what i can do to fix it?
The bike has good compression and is a yz125.
Cheers
 
Joined
Jun 24, 2007
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#2
check your coolant my 95 yz250 boiled over on me at the dunes once and ran like crap cooled it down ran good for a little while then over heated. finally i checked the coolant and there was none so i filled it up and it's ran like a champ ever since
 

BSWIFT

Sponsoring Member<BR>Club Moderator
N. Texas SP
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#3
It sounds like you have seized up. Pull the top end and inspect. Either you have run low on coolant or run lean. I wouldn't ride it again until you inspect the top end.
 
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#4
top end is fresh on it, about 4 hours old. i went out riding yesterday and it went well for a while then started again, but figured that it is only occuring when i move to low revs. If it happens and i pop the clutch to get it back to higher revs, it rides like normal until it decides to stuff up again. Im thinking a pilot jet problem?
 
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#6
well ill take the head off tomorrow and have a look. What are the signs that it is seizing when i look at it?
Will the piston be 'melted'? Will i be able to notice it?
Also, i shouldnt need to replate/bore the cylinder should i, because it seems to be running as normal at higher revs without any power loss.
 
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#10
Ahhh true well this is gonna be a prick of a job, lots of gaskets to buy, no more riding on the holidays, oh well gotta get done i guess.
 
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Apr 18, 2006
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#11
It could be several things. If you were actually overheating I would expect you would have other signs, such as puking water, blowing steam, detonation, etc.

It could be a fuel delivery problem. If you have a fuel filter change it. Inspect the gas hose between the tank and the carburetor to make sure it doesn't have a kink in it. Try taking the fuel line off at the carburetor and then opening the gas valve at the tank (be ready to catch gas in a jar or something). You should get a good steady flow of gas. If the gas dribbles out then it probably isn't flowing enough gas. The float bowl will fill up when you are idle, but after a few laps the reservoir in the float bowl gets used up.

Another thing you might want to try is to re-torque the head down. It is possible that the head is a little too loose and when it heats up the head gasket leaks.

Rod