98 vmax 500 - poor running between 5000 - 6000 rpms - Why?

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rkkoeb

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Green Bay
I have a 98 vmax 500 and last weekend it ran great. Took it out again today for about 90 miles and notice an issues. After about 40 miles we stopped for something to eat and after when I was riding the sled I notice between 5000-6000 RPM it seems to have very poor response, once over 6000 it takes off and runs outstanding. You can feel it almost bogging or missing and the exhaust sound seams different. Any idea what could cause this issue? Fuel issue? Spark issues, can a plug not be firing correctly around this RPM range? Any help would be great.
 
Carbs had been clean in the beginning of the year. Only have three rides on them. Will still check them out
 
Not sure when I will be able to get back out on the trail to try this out but what will this tell me if they are dry or wet?
 
One other thing it was about 35 degrees out when we were riding so not sure if this is something that is important or not
 
35 F would not cause such issues


If the problem happens and your plugs are wet it's an ignition problem, if the plugs are dry as a bone, it's a fuel problem.
 
I had a simular problem a few years back. Motor ran fine from idle to 6000rpms, and from 7500 to 8500rpms.
But I had a huge hesitation / miss fire from 6000 to 7500 rpms. In my case it was wiring harness rub threw that was grounding out my ignition at those specific frequencies
 
I will try to put he sled up on a stand and run it at 5-6000 RPM and see if I get the same issue and if so I will pull a plug and see what they look like. Not sure if I will get the same results as if I was riding or not. Could I have a bad spark plug that will cause issues at the RPM range?
 
i would leave the coil alone for now.

clean the primary clutch out as it is probably full of belt dust and binding.

try turning the carb heaters off if equipped.
 
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Took the primary clutch apart and it was pretty clean looking. I did notice a little rust on the shaft that I cleaned off. How do you test the coil? What does the carb heaters do
 
Carb heater prevent your carbs from freezing up and causing sticking throttle problems and blocking certain vulnerable small passages at the mouth of your carburetor...

I generally only use them in - 20c or colder situations
 
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I have seen some BAD ones in my day on Grandpappy type sleds that never get over 30 mph...
Luckily, its never been a problem for me..lol
 
Weights look good no marks on them. Clutch was a little dirty so I clean it up. Installed new plugs and turn off antifreeze to carbs. Will have to run it again and see what happens. On a jack stand seams to sound good but until it is under load will not know for sure
 
Vincent said:
I had a simular problem a few years back. Motor ran fine from idle to 6000rpms, and from 7500 to 8500rpms.
But I had a huge hesitation / miss fire from 6000 to 7500 rpms. In my case it was wiring harness rub threw that was grounding out my ignition at those specific frequencies
Click to expand...

If I were a betting man, this is where I'd place my money on being the culprit. It makes the most sense for this issue.
 
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