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15 YZ250f Valves at 15 hours??

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Ok so I picked up a 15 yz250f on my local craigslist. It was brand new spotless had 8 hours on it. I had a tuner I scanned it with and everything. I rode it once quick and changed the oil. I put what I normally run shell rotella. Rode it again and was riding it. wasn't beating the crap out of it but was going good. Started smelling like a burning oil coming from it. Then noticed it was really hard to start. Also noticed when I would kick it smoke would pull out of the breather hose going to the top of the head. I figured maybe I put to much oil so I went home next day changed the oil and filter changed the oil with the recommended Yamaha oil. measured it all out and rode it again and same thing. Bike is fine when its cold. Easy to start no burning or anything. once it gets hot you can smell it burning. its impossible to start and when you kick it, it puffs smoke.

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something is definitely off in there, yamaha valves from what i have heard are pretty resilient, about 35 hours on my 15 and never had to even check them.

if i was you i would have that valve cover off and have a peek at the valves. 

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ok so upon further investigation. I found today that the bike has been low on coolant? I never check it like a dumb ass and I checked it today and took about half a quart of coolant. I changed the oil fired right up let it sit and idle for a while. Im still getting the oil coming up from the breather tube on the head. Its just dripping out forms a little puddle of it.

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check the valves and see if they are in spec. If I was you, and the valves were in spec, I would be doing a tear down and rebuild. $300 in parts now is worth the peace of mind knowing that the motor is going to go down on me while riding. If the valves aren't in spec, obviously get them shimed correctly and run the motor while watching the fluids as you've been.

Edited by motox331

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Do you have a lot of micro-bubbles in the coolant when you remove cap and look?  Sounds like head gasket has failed.

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55 minutes ago, motox331 said:

check the valves and see if they are in spec. If I was you, and the valves were in spec, I would be doing a tear down and rebuild. $300 in parts now is worth the peace of mind knowing that the motor is going to go down on me while riding. If the valves aren't in spec, obviously get them shimed correctly and run the motor while watching the fluids as you've been.

yeah that's how I think im going to proceed. Im afraid after running for a unknown amount of time with no coolant I could have hurt something inside. Im going to pull it apart and check the valves and replace the top end. I think this is the only safe way to continue on.

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28 minutes ago, freebird65 said:

Do you have a lot of micro-bubbles in the coolant when you remove cap and look?  Sounds like head gasket has failed.

don't see any micro bubbles. I don't think its a head gasket I the bike isn't burning anything out of the exhaust. The bike has GYTR radiator braces on it. the previous owner had to drain coolant and remove radiators to put the braces on. He swears he re-filled them, but I don't think he ever recheck the coolant level. SO as far as I know the bike has been low on coolant for 15 hours of run time.

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you may not see coolant out the exhaust - in my case I just had bubbles in the coolant and signs of coolant loss.  How much oil are you loosing out the breather tube?

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Tear it down and have a look, bare minimum it'll give you an idea if anyone else has been in there. Plus, you'll know exactly what you're dealing with instead of speculating.

 I wouldn't trust the hours that the tuner says are on the bike since that can be reset. Not saying it was, but you never know. 

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Bike was defiantly had the hours the tuner said. It was legit brand new. Not a scratch on anything at all. Looked like it just came from the dealer floor.

 I will check for bubbles in it when I get home and after the bike was sitting idling for say 8 mins ish there was a puddle of oil maybe the size of 3 quarters.

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You probably overheated the engine and cooked the rings. So now it has a crazy amount of blow by.

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11 hours ago, jyamaharider713 said:

Bike was defiantly had the hours the tuner said. It was legit brand new. Not a scratch on anything at all. Looked like it just came from the dealer floor.

 I will check for bubbles in it when I get home and after the bike was sitting idling for say 8 mins ish there was a puddle of oil maybe the size of 3 quarters.

You do know that you can reset and zero out the run hour meter in the ECU, right? Just saying. Everything expands when it heats up. Sounds like rings at the least. I would replace the valves as well knowing the heat its been put through. Lets  hope the valve guides are still good.

Edited by Enduro R Rider

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Letting the bike idle for 8 minutes with no airflow over the radiators will overheat it. You need to tear down and inspect. Best case everything is ok and you replace gasket and rings. Doubt if it is worse than that if you never noticed extreme signs of overheating.

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rings could be blow by oil out the vent.also hard to start is a sign of valves being out. I put braces on my 15.never removed the radiators or drained them. never let it sit and idle . 2 minutes tops.double check all his connections. if he did fill it up. could be a drip. keep us posted on that inspection. if you do need a top end. go with 16' piston,oil sprayer,wrist pin etc. good luck.

Edited by bring the rain
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