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David Silver Pattern Cam chain Rollers/tensioner assemblies

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AshimotoK0:

--- Quote from: royhall on June 28, 2021, 06:54:37 AM ---That appears to be a lot of time trouble and risk to save a one time difference of £24 Ash. It's bad enough when Genuine parts are not available, but when you can get them it must be worth the cost. If a cam chain lets go at high revs it's goodbye engine.

--- End quote ---

24 quid is 24 quid to a tight Yorkshireman  ;D... Anyway Ben is considering fitting a Capellini style metal sprocket which the racing fraternity use (Graham Curtis does this on CB72/77's and it works really well).

AshimotoK0:
Ben, myself and another very young chap, where we all work, have formed WHAM ! ('Water Hydraulics Association of Motorcyclists') We meet every Tuesday evening and sometimes Saturday morning to work on or projects and it gives us all access to the bead blaster, parts washer, lathes, welder, mill etc.

Anyway, we couldn't meet tonight as Ben has been sent away on business and so I spent my time digging out the bits pictured  below from my 'stash' of CB250/350 bits.

The cam-chain tensioner is NOS, circa 1968/9 and came from Honda's UK Service Facility in Nottingham (one of about 5 that I have and was developed for the CYB350 race bike by Alf Briggs and his team ). Pictured also is a Honda Genuine cam chain sprocket from the DOHC 450'S ... it's used but I do have a couple of  brand new ones somewhere. I reckon the sprocket part can be pressed onto the CYB part to create a 'Capellini' style tensioner .  I am no sure about the CYB large steel idler. Ben has already bought a NOS Genuine Honda rubber one and I think I would use that still, to give a bit of compliance within the tensioning system. If you are reading this Ben the parts are yours for nowt if you want to have a bash.

Interested to see what other folks on here think, plus opinions on the pattern camchain tensioners out there for the CB750 and CB250/350K's, all of which use a similar tensioning system. Not sure about the David Silver ones but very bad  reports on the 4 into 1 and Cruzin rubber parts breaking  up after hardly any miles and I would personally stay clear of them.

Ben is a young guy on very tight budget, by the way, on his CB350K restoration. So I am trying to donate what I can to him.

Great to see chaps in their 20's joining our fraternity IMHO.... we need more!!

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CYB Parts List here:-

https://www.dropbox.com/s/jggut4r7j47fq60/Honda%20CB350%20info.pdf?dl=0

BenPowell:
Cheers Ash, really appreciate the help with the parts should be back at the club next week all being well so can take a look at the parts then and see what we can do.

It is a build on a tight budget, so being able to make the most of parts available and re-use what I can will leave money spare for other parts later, it actually makes the restoration more of a challenge but also quite enjoyable making and re-using old parts. So far the spend on the bike has been minimal hope to keep it that way to see what is achievable without throwing tons of money at it.

Bryanj:
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

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.

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