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Discussion Starter · #1 ·
1990 KLR 650 36k miles

So I get this kinda scary sounding banging noise from the motor. It happens at low RPM under load, like taking off from a stop in first gear (or second gear even worse). Or I can get it to do it momentarily by stabbing the throttle in neutral. It coincides with ignition / power stroke.

It sounds similar to a rod or main bearing going out.. but I don't believe that is the problem. I recently had the motor apart, cylinder off, and everything looked really good. Rod, main, piston, no play at all. Cylinder walls looked great and measured to spec. Put everything back together, new spark plug, valves re-shimed, and more.. Still doing the banging though. I'm thinking it is a carb or timing problem? Any ideas?

Here is a video I put up, you can hear it when I stab the throttle. Its much louder in person though.
https://youtu.be/rcQMb_MpLGs
 

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rhubic90,
Does your doo hickey use the New Torsion spring or the old style extension spring?
Does your 1990 engine balancer shafts still have the spring damped sprockets?

I didn't get the youtube keyed in correctly, but I'll guess that your engine may sound like mine 'down-low'. "CLACK, CLACk, CLAck, Clack, clack" as it accelerates.

I think it may be the combined slack of the spring 'pull lever' and the springs in the sprockets to allow balancer chain whip.

Lots of people advise installing 1996 up 'solid balancer sprockets'. I still haven't done it on my 1987.
 

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Discussion Starter · #3 ·
rhubic90,
Does your doo hickey use the New Torsion spring or the old style extension spring?
Does your 1990 engine balancer shafts still have the spring damped sprockets?

I didn't get the youtube keyed in correctly, but I'll guess that your engine may sound like mine 'down-low'. "CLACK, CLACk, CLAck, Clack, clack" as it accelerates.

I think it may be the combined slack of the spring 'pull lever' and the springs in the sprockets to allow balancer chain whip.

Lots of people advise installing 1996 up 'solid balancer sprockets'. I still haven't done it on my 1987.
Yes I did the eagle mike torsion spring.
Yes I have the spring sprockets.
Yes, that is a good way to describe the noise.

Sounds like a really good guess to me. I'm going to see how much those sprockets cost. thanks
 

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Sounds like detonation, or pinging, to me ( by the description- I couldn't get the vid to load). Try high octane gas on the next tank full and see if it goes away.

My bike will ping under load when it's warm outside unless I run 93 octane. I can get away with 87 octane in the winter, but if the bike gets good and hit it will still occasionally ping.
 

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rhubic90,
Here are the part#'s. Suggest ebay used parts.

12046-1165 sprocket,upper/rear
92022-1880 thurst washer, goes behind upper rear sprocket
13164-1007 front lower sprocket/weight assy
qty2 480J2000 Circlips
 

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Discussion Starter · #6 ·
rhubic90,
Here are the part#'s. Suggest ebay used parts.

12046-1165 sprocket,upper/rear
92022-1880 thurst washer, goes behind upper rear sprocket
13164-1007 front lower sprocket/weight assy
qty2 480J2000 Circlips
Thanks.
Well I found *A* problem. I had timed the cams wrong when I put it back together. I timed it to the 'blank' mark instead of the 'T' mark. (my rotor has 3 marks, I guess that is only on early models??)

So now it sounds better but it is still doing the noise. I think its better just because it has proper timing now and it doesn't bog down so easily. I'm going to ride it for a bit and see if things change at all. I'll try the high octane gas also. If no improvement then I'll plan to do the sprocket swap.
 

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Mine makes that same "knock" sound when blipping the throttle like you did in the video. Mine with less that 2000 miles on it I'd say is normal.
 
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