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Discussion Starter · #1 ·
I bought a 1979 cm400 about a year ago and it recently started making a clacking noise in the lower engine. Checked the valves and cam chain and they seemed fine. Was going to adjust the balancer chain and found the punch mark on the balancer shaft was at the bottom, ie about 6 0'clock instead of around 12. The bike has 35,000 miles, so I assumed the chain was badly stretched and that someone had moved the plate and tried to keep adjusting past the 9/3 o'clock position, but upon inspection, think it was just put in rotated 180 degrees. I can turn the shaft clockwise and it seems to tighten the chain. Since the ecentric shaft only moves the balancer a small amount, can I just leave it like that and adjust it manually. Obviously, the spring is useless in this configuration. I'm new to the forum and will post something in the introduction section too.
 

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The adjusting of the shaft is when it turns counter clockwise normally, that's the direction the spring applies pressure in.
I think you can go ahead and rotate the shaft clockwise 1 turn or so. Yes, it's going to over stress the chain for the brief time it's at the high point of the eccentric shaft but it may rewind the spring. If you don't want to do that then doing it manually is fine.
 

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Discussion Starter · #3 ·
After taking off the right crankcase cover and removing the stopper plate, I was able to rotate the shaft counterclockwise to the proper position. Unfortunately, it did not cure by clacking problem, maybe worse. I also again took the valve cover off and retentioned the cam chain and checked the valves. Now, I am stumped. Just started this a few weeks back after riding about 100 miles when the oil was a little low. Seems a little louder when I let off the gas and decelerate, but pretty loud all the time.
 

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The 400 balancers were a multi piece assembly with the halves using rubber dampers to keep them quiet. Those harden and deteriorate over time, you'll find little bits of what looks/feels like hard black plastic in the oil. The permanent fix is to replace those with the 450 one piece balancers. In any case the engine has to come out and the lower case removed for access. Here's a couple of pictures of the black bits
201_4220.JPG 201_4221.JPG
 

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I am having a similar noise, also got worse after doing the manual adjustment (loosening the bolt and letting it auto-adjust then re-tightening). It's been about 100km so far and hasn't blown up. The sooner you do it the better but it'll probably be okay until winter (at your own risk).

Since mine were okay for a little before they started making noise I'm guessing they go when the bike sits for a while, they dry out and then you start running it again and the heat cycles cause them to fall apart
 
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