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Gutless KX500

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Jan 18, 2019
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#1
I have a 1997 KX 500 that I just purchased, thinking it would be pretty kick ass. My 9 yr old's YZ-80 kicks it's ass. Never been on such a gutless KX. Compression is strong, fuel system has been cleaned. Running stock exhaust. I'm not a carb expert, so I had the shop I usually use go through the carb, check jetting, etc. Just runs completely flat, no power band, really no power at all. Engine sounds good. Power valve seems good. Any ideas? The guys at the shop say maybe reeds, but not sure that would cause it to be that bad. Not even exaggerating, it literally gets out-run by my 9 yr old's YZ-80.
 
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#2
Power valve SEEMS good? I know it seems obvious but when it comes to making power it's working correctly or it's not. NOT makes a huge difference. Do you have any idea if the porting is stock or not? Lots of great engines have been nutured by dimwits weilding porting tools.

If the carb and exhaust are stock and the compression is good then look for the obvious things that can really kill power, ignition timing, reeds and power valve timing and function . The Kawasaki service manual will be your best friend on this journey ;-)

It's worth the effort to chase it all down, the KX500 is a spectacular engine that's tough as an anvil when built correctly.
 
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#3
Thanks, the porting is stock, the power valve is timed correctly. Have ordered a new reed setup. Timing is correct. Not sure the reeds will make the kind of difference this motor needs. I'm pretty baffled. Hope the reeds will have more effect than I think. My first thought on the bike was that it had a flywheel weight on it. It doesn't, but has anybody ever heard of someone using a heavier aftermarket flywheel. Not sure that there would even be something like that that might be compatible.
 
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#4
Lots of guys stick heavy flywheels on open class bikes like this to try and tame them. For whatever an opinion is worth, it's a terrible approach. Once you get the stock setup sorted porting is the only real way to tailor the power to your needs.
 
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#5
I'm just trying to figure out what the previous owner has done to this bike to make it run like a kid's bike, and see what I need to do to get it to run like it should. How would I know if the flywheel is heavier than stock? I'm about to the point of just pulling the engine down and starting over. Might be easier than figuring out what they have done to it in the past. Then I'd know what is what.
 
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