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Overheating problem

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My 2007 KTM 450 EXC started overheating, so I decided to bypass the thermostat in case that was the issue. At the same time I replaced the cap and flushed the system and refilled it with Engine Ice.

And it is still giving me problems..

The cover over the pump looks fine, ie I THINK the pump is good. But what else could be causing this?. There's not much else to the system.

Any feedback would be great!

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Are you able to verify that coolant is flowing?  How long does it take to overheat?

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If it's not thoroughly bled out, air can build up in the head causing a hot spot. 

When you're bleeding the bike, pull the RH radiator top-screw and lean the bike way over (like 45° over) with the bleeder screw up, crack it open and get all the air out of the head. 

 

Also check that the fins/pin on the water pump impeller is all intact and in good condition.  Probably going to need a replacement gasket, but they're not expensive.  Pull that cover off (4 bolts), clean the gasket and sealing surface on the cover, pull the circlip/impeller off.  Make sure it has fins, and the pin that locks the rotation of the impeller to the shaft is in place and engaged in the impeller body.  It's a cheap part to replace (like $5) if it is worn/damaged.

If the engine's running, the (cam)shaft is spinning.  If water's not being pumped, there's either a major blockage (unlikely) or the impeller isn't pumping or turning.

 

 

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could be running lean.  maybe jetts have gotten varnished over time. new set of jets is fairly cheap.  clutch slippage will lead to heat issues to.

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That's going to manifest itself in ways other than engine overheating first.  (It probably won't run well enough to even get to the point of boiling coolant.)

If the bike's running even reasonably close to correct, the problem's with the cooling system, not combustion heat.

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