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Motorcycle Repair/CL100 Whirring Noise


Hello, I have a 1971 CL100 K1 which I restored about seven years ago. It ran fine until last year when it started making a loud whirring noise which seems to be coming from the bottom end and is slightly more noticeable on the right side, though I can't pinpoint exactly where the sound comes from. The noise is consistent with engine RPM in all gears including idle, with the clutch pulled in or released.

My father and I recently changed the can chain tensioner but it didn't fix the whirring noise. My next thought (hope) is the clutch, which I've never had apart. The clutch plates stick when the bike has been sitting for any period of time and after the restoration, years ago, I found some small thin metal pieces in the oil screen that I suspect are clutch parts. The bike ran and sounded normal for over 1000 miles after I found the parts in the oil screen.

The bike has about 2,000 miles total and sat for most of it's life until I restored it.

John, well the right side of the engine is a busy place..  clutch, kickstarter ratchet parts, oil filter, etc.

If you found metal shavings in the little filter screen on the left, I'll assume you didn't pull the cover off the oil filter on the right end of the crankshaft. I would certainly drain the oil into a clean pan and look for signs of metal flakes in the oil or larger pieces that might get flushed out.

I think pulling the clutch cover is probably your next best move. See if there is more debris in the bottom of the clutch cover and inside the oil filter. Hopefully, the centrifugal filter hasn't loosened from the end of the crankshaft. If some debris has been floating around in the oil, it may have gotten caught up in one of the crankshaft main bearings and is creating the sound you are hearing, especially if it is rpm related. BTW You do need a special 4 pronged tool to remove the locking nut from the end of the crankshaft, deep down inside the filter housing.

If you over-tighten the camchain tensioner, it will setup a whining noise.

There was an update to the kickstarter gears on the early 100-125 singles to help them disengage more readily and to engage more easily when kickstarting.

Bill Silver

Motorcycle Repair

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Bill Silver


Need help with vintage Hondas from the 1960s? I am an expert with 250-305cc bikes in particular and most all of the other pre-91 models, in general. I do NOT claim to have a great deal of experience on Gold Wings, Cruisers, ATC/ATVs and dirt bikes.


I have owned/ridden/maintained Honda motorcycles for 35 years. I have written five books on Honda repairs and collecting. I was a service manager for two Honda shops back in the 1980s.

VJMC (Vintage Japanese Motorcycle Club) of North America

VJMC newsletter, as editor for two years and as contributing editor currently.

3 years auto shop in high school, teacher's aide in Automotive Technology in Jr. College, Diesel mechanic course in college, self-taught mechanic and automotive writer.

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