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Help diagnose top end noise

798 views 5 replies 5 participants last post by  Ecosta777 
#1 ·
Just fired up my 78 cb400A for the first time since I bought it and have been rebuilding it. I haven't done any work to the engine, only mostly cosmetic and mechanical stuff like cables and brakes etc... Also rebuilt the carb.

It runs fine but still needs to be tuned. I did however notice this disturbing clunking noise on the top end at lower throttle speeds. I'm afraid I'm going to have to rebuild the top end just by the sound. But can anyone help me by trying to pin point it? Sounds more like rocker or valve noise than piston noise, seems to be right under the rocker cover.

Can't seem to upload the video from my phone here so I've attached a YouTube link of it. (Which hopefully works)
Thanks
Eric



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#2 ·
You might try adjusting the timing chain and or the valves . The As not that hard to work on and you can rebuild the top end without removing the motor.

You will need a FSM. If you remove the valve cover I find it helps to move the coils out of the way. Just a thought.

Bill
 
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