Motorcycle Repair: CL350 top end noise, honda cb350, cam chains

Question
Hi, Bill. Wonder if I can pick your brain again on my ‘71 CL350. The top end is uncomfortably noisy. VERY noisy. Noisier than any of the many 350s I have owned. It is NOT a tapping or knock, suggesting a valve problem, but I would describe the issue as a constant LOUD WHIRRING. A screwdriver to the motor and my ear reveals the sound to be loudest on the LEFT side of the motor.  I initially suspected vibration from a worn cam chain and tensioner, despite the fact the previous owner said these were recently replaced, and visually checked the top cam tensioner roller, which looks fine. I manually pressed in the tensioner and felt the chain tighten, apparently properly, so I am doubting the problem is a loose/worn cam chain, even though the sound is generally comparable to other Hondas I've owned that DID have worn cam chains, resulting in a loud top end. (I also have experienced NO slipping of the kick starter during a manual start, which invariably happens every so often with a worn cam chain.)

Could this issue trace itself to the points/tach housings the cam rotates in?

Oil is coming out of the check hole on the top of the case, so I presume oil flow is  ok.

If all else fails, can I replace the cam and/or cylinder head cam housing case with the motor IN the frame?

Thanks in advance for the great benefit of your experience with these machines. You’re a life-saver.


Answer
Vince, I don't think you can replace the camshaft housing case with the engine in place. It might be possible if you drop the motor down off the mounting bolts to gain some vertical clearance, though.

The camshaft needs to be shimmed up so there isn't excess sideplay at the thrust faces.

http://www.cmsnl.com/honda-cb350-super-sport-350-k0-usa_model430/partslist/E++03...  shows the camshaft spacers.

You really can't check the end play without dropping the motor out and pulling the top cover to look at the camshaft in place.

Have you looked at the end of the spark advancer while the engine is running to see if it is moving in and out? I think the end play needs to be down .008 to .024". If you see the end of the cam moving in and out more than that, at least the end play needs to be checked.

http://www.scribd.com/doc/15050635/Honda-CB-CL-SL350-Carb-Data-and-General-Info

You can loosen the valve adjustments, remove the camchain tensioner and rotate the engine over so that only one valve is partially open. That may lessen the load on the camshaft enough to allow you to push-pull it back and forth manually. If you are careful, you can remove the spark advancer, cylinder head cover/bearing from one end with the engine in place to inspect the bearing and/or change the end play. Just rotate the camshaft so there isn't too much download on the lobes.

The right way is to pull the motor and then the top cover to check the side play, then remove the end bearings to see if they are damaged.

CB350-450s have service bulletins on replacing the clutch cover and dyno cover gaskets, due to material failure and poor designs.

Bill Silver