Over heating?

rushy08

Member
Jul 17, 2006
235
0
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
 

yamarider88

Member
Jun 24, 2007
153
0
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
N. Texas SP
Nov 25, 1999
7,915
33
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.
 

rushy08

Member
Jul 17, 2006
235
0
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?
 

whenfoxforks-ruled

Old MX Racer
Sponsor
Oct 19, 2006
8,130
2
Merrillville,Indiana
If your engine is slowing or stopping on its own,and overheating,it is seizing! Should be torn down and inspected,yes!
 

rushy08

Member
Jul 17, 2006
235
0
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.
 

rushy08

Member
Jul 17, 2006
235
0
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.
 
Apr 18, 2006
1,534
8
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
 

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