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Comet Timing Side Noise

chankly bore

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Non-VOC Member
As someone once said: "The variety of percussive instruments" make it impossible to isolate a single culprit, but here is a list of known criminals. Alloy large and small idlers, dynamo pinion meshing too deep, worn and/or loose spindles- particularly the Series B/C large idler boss, worn camshafts and followers, tightly meshing (usually nylon) magneto pinion, loose rocker bearings. These are a good start. Piston slap may be heard more clearly once you have solved the foregoing problems. Does the motor burn or blow much oil? Is there evidence of high crankcase pressure i.e. leaks at jointing faces.I hate to say it, but better have a thorough examination of the timing chest, then go further if required. Please let us all know what you find. Steel idlers and one piece Series D large idler boss are prerequisites for a good timing chest.


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VOC Member
Ola Enrico. Please do as Chankly Bore says above and take off the timing cover before you use the bike. It sounds to me like something is broken and rubbing. Continued use of the bike will probably make the final repair bill larger.


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VOC Member
Sounds ok to me. :)

Try the screwdriver trick to see if you can get a better idea of where the noise is coming from....... Big screwdriver, handle pressed to ear, then touch the metal end to various parts of the engine to listen where the noise is loudest - like stethascope.

If that's an Alton generator, I've heard similar strange rattles from one.

Safest option is to remove the timing cover as per Chankly and TT suggestions.

Buena suerte



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VOC Member
Sounds like the dynamo/alternator/generator nut maybe rubbing the timing cover. maybe it backed off, Or other gear wheels are rubbing due to missing or inproper spacer washers.
Simply pull the oil quill, banjo bolt, cover screws and cover and have a look.

Tug Wilson

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Non-VOC Member
Switch it off! Sounds like loose spindles/nuts, therefore gears out of sync. Agree with previous re serious damage. May be visually correct! But loosen nuts if tight and check for spindle wear is my first thought.


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Non-VOC Member
Hi all.
Thanks for your helpful comments.
I do not know how to find the reason for the noise.
Send the Comet to the mechanic.
The problem seems to have been excessive wear of the piston and connecting rod bearings.

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