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David Silver Pattern Cam chain Rollers/tensioner assemblies

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AshimotoK0:

--- Quote from: Bryanj on June 29, 2021, 11:04:32 PM ---From my limited racing experience the steel idlers whilst last longer and probably keepin a more uniform chain tension are noisier and sound harsher.
Rebuilt a fair few "learner" 250 versions with shattered rings and a couple with siezed cams the lessons from these are
1 do not thrash the engine from cold
2 clea the cetrifugal filter regulary, i would say every other oil change and do inspect closely as the "sludge" looks just like its part  of the alloy casting
3 make sure the circular cover over the filter is refitted  correctly
4 be prepared to line the points cover with tape as the points can sort out on the cover.

Apart from that give yourself plenty of time to stop as whilst that front tls was good in the day its not realy, also make sure linings are not detaching

--- End quote ---

I take your point about the noise Bryan but I wasn't planning on recommending using the centre large idler in steel just the smaller tensioner wheel fitted with a sprocket. The sprocket is actually a CB450 Bomber part and there are about three of them whizzing around in the Bomber engine. Plus the CB250/350K is a notoriously noisy engine anyway, as was the G5. I sold a 250G5 with a pristine engine ..less than 2k miles and had perfect cam and rockers etc but it sounded surprisingly noisy. The 180° crank doesn't help.
My mate Graham Curtis has upgraded quite a few CB72/77 engines with cam chain tensioners he has fitted with the sprocket idler from a Kawasaki Z650 (very similar sprocket to the Bomber one) . I must ask him if he has noticed any significant increase in noise.

AshimotoK0:
A very well respected HondaTwins.net member has done almost exactly what I described. I found this in a post from 2015

I machined a xt500 lower cam chain sprocket and a insert to fit the honda needle roller bearings, it will replace the small rubber stock cam chain roller. I'm going to run the stock large rubber roller, I don't want any weird noise

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K2-K6:
The plain (round no teeth) look very different to conventional sprocket form but really do the same thing from a geometry point of view.

The teeth are only important to transmit torque and keep a precise timing relationship for each component,  which doesn't exist for the adjustment device.

Essentially the chain roller comes into contact at a tangent whichever it's approach route, then gets passed round the fulcrum (centre bearing) the same whether it has teeth or not, that distance from centre can't be variable for any of these arrangements else it would input it's own vibration/resonance.
The side plates obviously need to run clear of the centre support such that it only runs on the chain's bearing.

It may involve a very small increase in noise transmission,  but I can't see it making it's own noise.

The whole idea of splitting up chain run length is to brings spans that ordinarily can't be excited by latent system vibrations from crankshaft pulses and camshaft cadence.

If they are roller bearing cranks then they always tend to sound more like a lathe in comparison to plain bearing systems as there's just no mitigation for combustion percussion in preventing it from being amplified by the cases.

AshimotoK0:
Thanks for the informative reply Nigel.

I just found that the centre part of the Honda race tensioner and also a  Kawasaki Z650 one I have, have a section of rubber which should help with isolation and give bit of compliance.

I also found a spare Capellini  brand new rivet for the centre, which Ben can have. I also have the Capellini  tool for peening the rivet end over,  as pictured previously.

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