Cluttering sound in engine over 3500k

[ty998]

Hey All,

I went back and rebuilt/cleaned the carburetor the right way.
I am still having the same problem:
Bike sounds great till 3500 rpm. Then it starts to make a terrible cluttering sound. At idle and any speed up to 3500 it sounds perfect. No valve chatter. Sounds great. However, I am also still seeing a intermittent flash from the vacuum line as well. I am guessing it is an issue with the timing chain. I might be going to the pros on this one. Any recommendations on what to begin looking at?

Thanks.

Bike is a '81 GS650 GX

[tom203]

Make sure you grasp how cam chain tensioner works- it must be allowed to slide out and take up slack. Many times folks misunderstand the correct use of the locking screw and lock nut.
"flash from vacuum line" ???? say what?

[ty998]

About every 20-30 seconds I see a flash in the vacuum line. No idea. That is why I am here

[ty998]

Make sure you grasp how cam chain tensioner works- it must be allowed to slide out and take up slack. Many times folks misunderstand the correct use of the locking screw and lock nut.
"flash from vacuum line" ???? say what?

I will research cam chain tensioner settings/adjustment in my maintenance manual tonight

[tom203]

About every 20-30 seconds I see a flash in the vacuum line. No idea. That is why I am here

Might be a shot of gas being sucked down vac line- remove line from petcock, get yourself some clear vinyl tubing, put on petcock nipple, and suck on it- no gas allowed!
Unfortunately, the tensioner on 650 can't be pulled to inspect without removing carbs first- at least that's what it looks like. Someone might have installed it wrong either by not loosening the lock screw after reinstalling ( so it can't slide), or by not winding the spring gizmo back (so it doesn't have any umph to make it slide ). Needs more thought, but I'd pull cam cover off and see if cam chain has too much slack. You might have to do this anyways, to make sure chain didn't jump on the camshafts- a couple teeth off and you got big problems!

[ty998]

Thanks tom203. Gives me somewhere to start.