Thumper Club Forum
Technical => Bike Problems/Questions => Topic started by: xbally on December 15, 2024, 05:46:13 PM
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I've owned my current RS for over 10 years now and I can't recall checking the valve clearances although I'm pretty sure they would have been done in that time.
Anyway today I decided to whip off the seat and tank to do them.
I must be getting old because it took me the best part of the day to complete the job.
I had to do it outside as my close up eyesight with or without glasses is not great and even using a torch I struggled.
I thought it would be an easy enough job to do but......not so easy nowadays...Couldn't manipulate the feeler gauges in the tiny space under the removable covers of the cam box. There didn't seem to be any clearances that I could feel or measure with my smallest feeler gauge. Then I couldn't get the round engine case cover off the turn the engine over so I had to put the plot in top gear and turn the back wheel. Then I couldn't see the "T" mark in the other smaller hole......
Eventually I managed to get the crank bolt cover off using an impact driver and a succession of slotted screwdrivers.
All 4 valves needed opening up and it was then the usual fiddle to turn the square on the adjuster and nip up the lock nut in the available space. Mr. Honda makes a special tool but I don't recall needing on the the other SOHC Hondas I've owned over the years.
I managed to get it all done but my back is in a few pieces ( and my knees) as I don't have room for a hydraulic work bench unfortunately.
Took the bike out before dark and it does appear to be running better but that could be psychological?
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I think when I did mine I used the fact that the thread on the adjuster was 0.8mm pitch (this may be wrong but is what I remember). Hence a full turn of the adjuster equated to .8mm and fractional turns could be calculated. In fact I may be thinking of the Triumph engine which had similar awkward access.....
I did make a little tool to make turning the adjuster easier - a bit of 1/2" round soft alloy with a centre bore hammered over a tapered square section drift (barbarians may use a file tang) to create an internal square. In fact here it is. I may still have it somewhere.....
(https://www.iansoady.org.uk/CB250RSA/images/tappet%20tool.jpg)
The Norton Electra has very easy unhindered access to the rockers and a nifty adjustment system using an eccentric rocker shaft. Unfortunately the locking mechanism is a bit iffy.
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I always found that a short piece of flexible plastic tube that fitted snugly over the 'square' of the adjuster screws enabled me to easily adjust the clearances and 'hold' the screw firmly enough to tighten the nut without having to repeat checking..