Hey guys, what's up. So I just installed my 350 cylinder on my 2009 KLX250s. The build was fine, everything started up fine. I went for my first ride, and after about 25km, I noticed a sweet smell. Sure enough I was smelling coolant. I went to my buddies house, let the bike cool down, and topped up my rad with about 200ml of coolant. I noticed a little leak in my head gasket (I ordered a new one from Bill Blue), but I also noticed coolant out around my over flow tank. I then proceeded to go home. When I got home, I had coolant all over the rear of my bike (on the exhaust, on the rear wheel, swingarm, etc.) And my overflow tank had more coolant in it, than when I started. The bike ran fine, it did not overheat, but I'm wondering if anybody has any idea where the coolant is coming from. The bike is still hot, so I haven't been able to check the rad, but I'm sure it will be down some coolant.

 

You probably did not have the engine fully loaded with coolant, it overheated and expanded coolant into and out of the overflow. Think of an air bubble, when it gets hot it expands.
I would try topping everything off as per the shop manual. Reset teh overflow level and try it again.

 

or your head gasket has failed

 

I did check the head gasket. Looks like I had one tiny little leak down the side of the cylinder, it didn't even make it to the base gasket. I checked my oil level, no signs of coolant. How can I be certian it's my head gasket, and not just an air pocket in my cooling system? Thanks.

 

Get a small clear plastic bottle and fill with water. Poke a hole in the top and submerge a piece of plastic hose coming from the overflow fitting on the filler neck. Hang the bottle where you can see it and go for a ride. If you get bubbles then coolant start to fill the bottle, it's a compression leak...

 

Thanks, I will give that a try, but what exactly do you mean by a compression leak? Does that mean I have to replace the rings?

 

Compression from the motor is getting into the cooling system and pushing the coolant out.

 

And the only way this could happen is with a blown head gasket, right? I hope it's just a head gasket. Is there anything else I should look for? Could the thermostat also be a problem?

 

Check for coolant in the oil.

If you have coolant in the oil and the pump seals are good, most likely there is a head gasket problem (coolant leaking into the oil gallery) or a crack in the interior cylinder wall. Cylinders can crack during installation of the sleeve.

If there is no oil in the coolant, you can still have a head gasket (or sealing) problem with compression leaking into the coolant passages but without oil leaking into the oil galleries.

Of course, it goes without saying to check for leaks at all the hoses, radiator cap, etc. Any leaks will cause pressure loss in the cooling system and subsequently coolant loss.

Ron

 

I didn't see any coolant in the oil. I just ordered some new gaskets from Bill Blue. I'll be taking the head off in a few days. Hopefully it's just the gasket. I phoned Bill, he said (even though it's very rare) that it is possible that the sleeve may haved moved up a few thousands of an inch. If it has moved, I'll need to send the cylinder back, and he said he'd take care of it.