Honda-SOHC
SOHC.co.uk Forums => Recommended Sources for Parts and Services => Topic started by: Laverda Dave on November 10, 2018, 11:13:34 AM
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J D Autoworx in Wallington, Surrey are developing a camshaft bearing repair using phosopher bronze shells. They measure the damaged bearing face and the camshaft bearing and make a ring sleeve to suit. The damaged bearing face is them machined to allow the new bronze shell to be cut into two halves to sit in the machined bearing faces in the head and rocker cover. The new bronze bearings are pegged into the head to stop it spinning.
I don't know how much this conversion will cost as every head is different in terms of number of bearing faces etc. When I collected my CB250RSA barrel Russell was just completing a conversion on a Yamaha XT350 head.
The conversion is in its early stages of development but good to see someone is actively trying to overcome the common problem of how to reclaim damaged heads.
Might be a worthwhile conversion on our bikes if the bearings are badly worn?
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Interesting....
I suppose the same approach would work on a set of 750 cam carriers too. Plenty of ruined ones out there which could be reclaimed and made servicable.
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I could be wrong and talking out of my backside but, i'm sure Graham has done this or tried this in the past. We have so many CB750 engines in with very worn cam carriers and had a problem sourcing replacements and i remember him trying to achieve the same as you are talking about. If he still does it or not, i wouldn't know, i don't look or listen very intently all the time ::) ::) ::)
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I suppose part of the limitation is the amount of material around and between the various elements of the construction, with little need for the original designer to plan in space for adaption.
Interestingly, most things like this appear to be clouded by "round" thinking as most solutions head towards something like plain bearing shells to offer a solution.
If there's enough meat in the supporting casting you could consider milling out the originals to square form, then making phosphor bronze blocks that wouldn't rotate anyway. If you made the bottom one wider (length along cam journals) than the top, then you'd get a staggered joint that would be pinched by normal assembly. Pairing the half blocks and line boring them would give you cam clearance dimension. Close, not interference, would produce head casting fit.
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We had a man who subbed for Dowty Rotol back in the 70's who did this when carriers and cams were in short supply
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I think Dixon racing used to fit Villiers shells to 400/4 heads years ago. The project bike that one of the magazines did a while ago was fitted with them when they bought it. When they cross referenced the bearing shells I think they were off something like a lawnmower and possibly made by Glacier.
UPDATE: this was the post:-
http://www.sohc.co.uk/index.php/topic,7175.msg43066.html#msg43066
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I have a cb550 head that had been converted to needle roller bearings in the head, I basically bought that to see how on earth they did it. Still sat in the loft someplace.