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YZ250 overheating

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I have a 2006 YZ250 that I got in 07. I ride lots of hard, tight and rocky single and 2 track. My bike has never overheated or boiled over before until now. I installed a Rekluse EXP 2.0 about 7 months ago. About 7 rides or so ago I was going up a long steep slick switch backed rocky hill and when I got to the top steam was coming out of my overflow. Let the bike cool down and then I put about 8 oz. of water to fill it up. I rode the rest of the day and had no problems. I pressure tested the cooling system and seen the water pump licking out of the weep hole. So I put in a new shaft (it had a grove in it) 2 new seals and a new bearing. Rode the bike for several more weekends and bike was fine. Then last Saturday the bike boiled over 2 more times again up 2 nasty hills. I needed to do a top end anyway so I took the head off and found a bad inner O-ring and my piston was very clean so I know I was burning coolant. I spoke to Rekluse and he said the EXP can make the bike run hot but it should not overheat the bike. So maybe the O-ring was slowly going. I am thinking of putting on a higher pressure radiator cap. Stock is 1.1 BAR (16 PSI). I could get a CV4 20 PSI or 30 PSI or a Tuck 1.6 BAR (23 PSI). Witch one would be safe to use or is it a bad idea to go higher than the stock 1.1 BAR?

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cv4 with fesh 50/50 mix would do the trick. Flussh the system at full temp with 50/50 water and white vinger, it cleans out the system on a chemical level.

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I would start with what that other guy with the stunningly handsome name suggested, a viniger flush to remove scale/deposits in the system. You can even remove the radiators and fill them up with it.

Personally I wouldn't go over the 20 psi cap, I'd think you'd be stressing the system with 30 psi. You may want to look into things like your clutch engagement setup and gearing and see if you could get away with something a little less stressful to the engine.

I ran a Rekluse Z-start when I lived in AZ, never had an overheat issue, just running std "All makes all models" coolant. But, my clutch setup was to engage just off idle and be fully engaged very quickly, not much slip. Even with 15/51 gearing it did well, although I'd drop a tooth or two on the front for really nasty "hike-a-bike" stuff. 15 tooth for most trails, and all the AMRA races.

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cv4 with fesh 50/50 mix would do the trick. Flussh the system at full temp with 50/50 water and white vinger, it cleans out the system on a chemical level.

That’s a good idea. Since I have the bike all apart could I heat up the 50/50 mix and then just cap off the rads. and let it sit in there for a little while and do the same with the head and cylinder?

I would start with what that other guy with the stunningly handsome name suggested, a viniger flush to remove scale/deposits in the system. You can even remove the radiators and fill them up with it.

Personally I wouldn't go over the 20 psi cap, I'd think you'd be stressing the system with 30 psi. You may want to look into things like your clutch engagement setup and gearing and see if you could get away with something a little less stressful to the engine.

I ran a Rekluse Z-start when I lived in AZ, never had an overheat issue, just running std "All makes all models" coolant. But, my clutch setup was to engage just off idle and be fully engaged very quickly, not much slip. Even with 15/51 gearing it did well, although I'd drop a tooth or two on the front for really nasty "hike-a-bike" stuff. 15 tooth for most trails, and all the AMRA races.

That’s what I was thinking going to the 20 PSI. My rad. hoses are the original ones from 06. They have no cracks and are in great shape. Do you think going to the 20 PSI might cause them to leak? As for the Rekluse they wanted me to take it apart and send them pictures of the inside where the ramps are. He said they do not look too good and the clutch overheated at some point and that might of caused the bike to run hot. They are sending me new half’s under warranty.

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You could do it off the bike but it makes more sense and works better todo it on the bike.

Fill the rads with 50/50 white vingar and water and run the bike on the stand, let it get hot almost to the point of overheating. let it cool and drain drain, refill with water, run the bike a few minutes, drain and repeat with water once more.

then fresh 50/50 mix of green antifreeze and water. cv4 cap, doubt it would overheat after that but if it does, take the time and drill the radiator louvers with 1/8th inch holes. this was super popular on the early kcf/rmz bikes that would overheat easily at low speeds.

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You could do it off the bike but it makes more sense and works better todo it on the bike.

Fill the rads with 50/50 white vingar and water and run the bike on the stand, let it get hot almost to the point of overheating. let it cool and drain drain, refill with water, run the bike a few minutes, drain and repeat with water once more.

then fresh 50/50 mix of green antifreeze and water. cv4 cap, doubt it would overheat after that but if it does, take the time and drill the radiator louvers with 1/8th inch holes. this was super popular on the early kcf/rmz bikes that would overheat easily at low speeds.

Do you think that would be ok running it that hot on a fresh topend? Thats whay i was thinking of do it with the parts off the bike.

Are you sure that your water pump is running ?

Good question, im sure it is since the bike did not over heat when i was on the bike all day and it only overheated up 2 nasty hills. Also we did about 5+ miles on highway at about 55 to 60 MPH and it did not overheat once. But i will check since i have the bike apart.

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up to temp would be fine. forgot about the fresh piston. a heat cycle or two and break in.

So do you think 1 heat cycle with the vingar/water, then another with water, drain one more heat cucle with water, drain and my coolent and go ride would be fine?

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So do you think 1 heat cycle with the vingar/water, then another with water, drain one more heat cucle with water, drain and my coolent and go ride would be fine?

everyone has there own "best way" to break in a motor, that would work fine, on the 3rd heat cycle i would take the bike for a ride IMO its best to put the piston rings under a bit of a load, half throttle max type situations.

but yes, the heat cycles work also work just fine and dandy. and the flush can be done during break in or after, what matters is it has time to heat up and clean out the system. (i went for a short ride when i did mine, bike smelt a bit like fish n chips)

Edited by adam8781

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everyone has there own "best way" to break in a motor, that would work fine, on the 3rd heat cycle i would take the bike for a ride IMO its best to put the piston rings under a bit of a load, half throttle max type situations.

but yes, the heat cycles work also work just fine and dandy. and the flush can be done during break in or after, what matters is it has time to heat up and clean out the system. (i went for a short ride when i did mine, bike smelt a bit like fish n chips)

That’s what i normally do is on the 3rd heat cycle i ride the bike pretty much like you described. I just was not sure it was ok to ride it with the vinegar and water

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