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Discussion Starter #1
I was just doing some bike maintenance and noticed at certain rpm's if I cover the end of the exhaust pipe with a piece of paper is seems like its intermittently sucking exhaust back into the muffler...Any ideas? Also smells like its running rich
 

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Discussion Starter #3
Seems like its running ok... I been trying to figure out how to post a video because its pretty bad....Rpm just off of idle it will suck a paper envelope tight to the end of the muffler....Then as i rev higher it will intermittently suck it up tight and push it away....I had a valve adjustment done about 6000 miles ago and it's definitely been much louder since then but I don't know if it's been doing this whole time because I just noticed it.....without knowing that much about small engines I'm afraid for some reason the exhaust valves are staying open too long and when the intake valves open its pulling a little exhaust back in....
 

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Discussion Starter #4
Im playing with it right now and between 2000 and 4000 rpm the exaust seems normal....Then at 5000 the amount of pressure coming out of the tailpipe goes wayyyyy down and the engine sounds buzzy....Like pretty serious vibration
 

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FORUM GODFATHER.....R.I.P. PAT
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Most likely it's a normal result of combining the two cylinders into one. Pressure waves combine or compete depending on the timing of cylinder firing. Nothing you have done can cause the cam timing to change.
 

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Discussion Starter #6
Thank you Greywolf......This has been stressing me out.....when I had my valves adjusted I had told my mechanic to put them all at the loose end of the spec...Like I said, it was noticeably louder but other than that seems to be running fine...Ive got about 27000 miles on it right now...
 

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Discussion Starter #7
Ive read with a car engine 1 of the ways the test for a burnt valve is to put a dollar bill against the end the tail pipe and see if it sucks back in occasionally, but I wasn't sure if that theory transferred over to a Vtwin motorcycle engine
 
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