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Knock in rear cyclinder

Old Jul 17, 2009 | 05:35 PM
  #1  
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Knock in rear cyclinder

I see there is another new topic regarding this issue but did not want to hijack the thread. I have a real lack of power in my bike. I don't care how aggressive you are with the throttle, this thing does not want to come up unless you're coming from a stop and dumping the clutch. I have only owned it for 1200 or so miles but it is becoming progressively worse. It now has just over 19k on it.

The idle is fluctuation a couple hundred rpm and stalling when coming to a stop. Not every time but often enough. From 3-4k rpm, the bike feels as though it is missfiring. If you put it in a higher gear to increase the load on the motor, it becomes even worse. I replaced both the plugs even though the old ones looked great. I ran carb cleaner through a couple tanks of gas. I just checked the air cleaner and it has a pretty clean K&N in it. I was checking to see if there was a vacuum leak and can hear a steady knock in the rear cyclinder that speeds up as the rpms increase. I was thinking I had a fuel problem, but now that I hear the noise in the rear cyclinder, I'm assuming it's something worse. What is the chances I just need a valve adjustment and not something more serious?
Old Jul 17, 2009 | 06:59 PM
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Carb problems maybe.
when one of the cylinders arent firing, it will make all kinds of piston slap.
Ignition failure on a cylinder does that too.
Im being optomistic for you ,of course.
Check these two items off before worrying about hard parts failure or skipped cam timing.
Old Jul 18, 2009 | 08:22 AM
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I checked it with the motor cold and the noise is definitely in the top of the cyclinder. I'm assuming it's the cam chain/gears. I wonder if this is something relatively easy that I can tackle myself?
Old Jul 18, 2009 | 09:49 AM
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Originally Posted by Paradisd
...I just checked the air cleaner and it has a pretty clean K&N in it.
You named it right there! I had the exact same 4K RPM hole with the K&N. See how I had to "fix" the a/f to eliminate this side effect
https://www.superhawkforum.com/forum...hp?albumid=100

To test my theory, install an OEM papaer a/f and test away.
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