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After reassembling the motor from a complete gasket kit install I just snugged up the cam chain adjuster nut. The bike seemed unreasonably loud since then, although this is the only CM400 I've ever heard run. Yesterday out of curiosity I loosened the adjuster locnut per the Clymer manual, while the bike was running and I expected to see the shaft move in toward the engine as the slack was taken out. This did not happen, nor did it quiet the motor. As I started to tighten it back down I ended up pulling a little to the side as there is limited room for a ratchet in there, and it got really quiet, but as soon as I let go it was just as loud and rattley.

Any ideas?
 

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I don't know anything about the CM400's but when your reassembled the motor do you recall the condition of the cam chain roller inside the motor? On the 350's that wear quickly and get pretty ugly.

I was thinking that when you "pushed it to the side" while tightening, you might have pushed the chain a little off the roller on to a part that wasn't so worn.

Just a thought.
 

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Sensei
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Sometimes the "adjuster" gets "stuck"....Try again backing the nut off at least two full turns (and loosening the bolt it attaches to...wiggle it, tap it, whatever)... Another common "noise problem" with this engine is the counterbalancer chain adjustment... The "balancer" can get so far off it makes the engine seem to "knock".
 

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66Sprint said:
Another common "noise problem" with this engine is the counterbalancer chain adjustment... The "balancer" can get so far off it makes the engine seem to "knock".
What kind of knock would result from a balancer that was setup incorrectly or not adjusted correctly? The reason I ask is that my CB400T I just bought has an engine knock and I know the person I bought it of was doing some work in the engine and had a difficult time with the balancer. Where would the knock sound seem like its coming from?

Thanks.
 

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Sensei
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The balancer is near the crankshaft, so it could sound/feel/vibrate like a bad crank or bad lower rod bearings.......You would have to ASSUME that the balancer was "timed-in" correctly to be able to "cure" the problem by resetting the balancer chain adjustment...... Also, the slotted adjustment plate on the end of the shaft could have been installed a spline or two "off"....
 
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