I bought a 2001 YZ250 last week. Took it home rode it 45 minets and it ran great. Stoped to rest and it would not start. Found it had coolant in the cylinder. I tore it down and found ablown inner o ring. I had the head resurfaced and installed new o rings. I also pulled the cylinder and visually checked for cracks and could not see any. I put it all back together and with a new plug it will run for a few seconds and then die. When I pull the plug it has water on it. I clean the plug and it will start and run a few seconds again. I also changed the lower end oil. Where is the water comming from??
YZ250 water in cylinder
- Thread starter sdkinion
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I bought a 2001 YZ250 last week. Took it home rode it 45 minets and it ran great. Stoped to rest and it would not start. Found it had coolant in the cylinder. I tore it down and found ablown inner o ring. I had the head resurfaced and installed new o rings. I also pulled the cylinder and visually checked for cracks and could not see any. I put it all back together and with a new plug it will run for a few seconds and then die. When I pull the plug it has water on it. I clean the plug and it will start and run a few seconds again. I also changed the lower end oil. Where is the water comming from??
- Thread starter
- #3
I bought a 2001 YZ250 last week. Took it home rode it 45 minets and it ran great. Stoped to rest and it would not start. Found it had coolant in the cylinder. I tore it down and found ablown inner o ring. I had the head resurfaced and installed new o rings. I also pulled the cylinder and visually checked for cracks and could not see any. I put it all back together and with a new plug it will run for a few seconds and then die. When I pull the plug it has water on it. I clean the plug and it will start and run a few seconds again. I also changed the lower end oil. Where is the water comming from??
If the new o ring is holding that would eliminate water from that area. Water coudl still be in the lower end. The oil you changed was for the transmission. It would not get rid of any water that was around the crankshaft. That area is lubricated by the oil in your premix.
Dont overlook the airfilter. If you washed your bike during theis time, it could be possible. The rear fender dumps water right square on the airfilter on this bike during washing.
Dont overlook the airfilter. If you washed your bike during theis time, it could be possible. The rear fender dumps water right square on the airfilter on this bike during washing.
Eric Gorr
Engine Builder
- Jun 29, 1999
- 384
- 12
Resurfacing the top of the cylinder is difficult because in order to remove the scale and warpness you have to remove a significant amount of material that warrants remachining the o-ring grooves. Sometimes the damage is so bad that the cylinder needs to be stripped, TIG welded, bored, faced, and re-grooved. The head suffers the same degree of damage and most times they need to be replaced. On some 125s its possible to turndown the cylinder enough to repair the damage if the head is being converted from a domed piston to a flat top design.
B
biglou
Please post your questions in one forum only, not three! Thanks.
