I recently bought replacement camshaft bushes from one of the big spares houses. I took my crankcases, the (new) camshaft and the new bushes to my local engineering company (who I have been using for engine work for several years) as I wanted the bushes to be installed and then line-reamed once fitted.
I received a phone call today from the engineer who said that he wasn't comfortable fitting and line-reaming the bushes I'd supplied. He said the reason for that is because the bushes I bought are supplied pre-sized and honed to give the final camshaft running clearance of 1.5 thou. Therefore, any slight misalignment between the installed bushes due to slight out of line bores in the crankcase halves or due to changes caused by heating the crankcases cannot be removed as the bushes will then either have oversize bores or unevenly sized bores.
Does anyone know if it's possible to purchase undersize camshaft bushes from any supplier?
hello now do try Rodger At RGM Motors will give you some guidance on bronze cam bushings. But how I fit new camshaft bushies is by heating the cases in the oven with two case half screws in the bottom and the 1/4 nut and bolt at the front for quick disassembly then when very hot you unscrew the two bottom case screws and the 1/4 nut and bolt at the front of the cases and on a wooden chopping block taps out the bronze bushies with a leather hammer with a couple of taps they fall out then back in the oven after a quick clean of the case then have ready the two new ones to fit back in the same way they came out but you need the camshaft with heavy grease on the end and fit the bush over this and tip back in place with you leather hammer no machining need all that needed is some valve past fine and rub in with the camshaft end to bed in the bushies then try fit the two case halves and 3 bolts and try his out for fit and free play if you have free play at each end then you next job is clean every thing down and oil up the bushies to reassemble the engine. the bushies should fit inline if the cases are matched correctly, And you may have these made, that a machine shop in bronze, And do make sure when fitting make the oil holes line up with the cases oil holes at each end. yours Anna J Dixon
Are you seriously advocating using valve grinding paste in bronze bushes? Bronze is relatively soft, and the paste will bed into the surface and no amount of washing will ever get the residual bits out of it, meaning that it sits in there wearing away your nice new cam.
Is this why you have so much experience changing bushes?
I would never let you near one of my engines!
I am rebuilding my MK3 commando and i assume the above method would also apply to mine as well. Sounds like a good plan to me, most helpful.
Kind regards, Ian
... grinding paste should never be let anywhere near bronze bushes.
hello well I think someone overreacting you get the bushies clean with no problems with you cleaning bath yours anna j
hello now what do you think bearing scrapers are for when we rebuild a Kelvin K4 we have to use a Bearing Scraper to scrap a bronze shell bearing to shape and then lap it in with valve grinding paste fine then wash off in clean diesel and Kelvin Large ends have shims at ether end of of the conrods side shims these sometimes are bigger than needed so we have to shape them to fit , you cannot get off a ship in the middle of the Atlantic you have to utilize what you have to hand and make it work some of you have not lived, I had to make shell bearing and bronze bushings from scratch In my time anna J
... grinding paste no. I'm sure you got away with it Anna but it's still the case that you'd never be able to get all the grit out of soft bearing metal.
Ian is absolutely right. Scrapers or reamers yes, abrasive compounds no.
There is a huge difference between a 120rpm ship diesel engine and a 7000rpm bike engine.
Anna, I wonder what your oft quoted craftsmen in Bracebridge Street would have made of your "grinding paste is ok" bodge?
I bet you would have been laughed out of the shop.
Thanks to all who have contributed opinions and advice. I wasn’t intending to start a heated discussion. I like Anna’s idea for inserting the bushes - that sounds achievable even with my limited experience. However, I’ll hold off using any grinding paste as the number of votes seem to advise against it. With any luck, the camshaft will fit well in the bushes without further metal removal.
hello You guys I think you all need to read practical machinist or Newman tools websites on lapping in hard bronze and you find the quick way of lapping in with fine valve paste silicon carbonate fine ground is the same as Clover fine lapping in paste and Norton Camshaft Bronze bushies are made in Hard Bronze if there were not they would not last very long So some of you are overreacting and need to read up on lapping in valves and bushings you only use a very small amount just to lap in and free up the bush then you can wash it all away with your paraffin gun at 40 psi with white spirt in, and you can clean up hard bronze with fine clover lapping and grinding paste which is used for valve lapping in too and other jobs,and you can also use chrome cleaner too for lapping in I done more engineering then some you has hot dinners in the last 50 years , A old bike and a Old bugger riding it, Yours Anna J
Do not allow any form of grinding paste near bronze bushes that have a shaft revolving in them. You will wear them or the cam out prematurely.
Plain bronze or white metal bearings are machined and then scraped to fit. (in the case of our cam bearings, being line bored after fitting)
In the course of my working career i have had to machine quite a few large and not so large white metal bearings for steam turbines, electric motors and pumps and the like. The use of grinding paste anywhere near these would have got you fired.
Grinding paste does have its uses but this is not one of them.
One does wonder, Anna, if all your 'engineering' is the reason why your bike isn't running?
Hello Peter both my bikes are in running order mate and you're wrong about lapping in paste on hard bronze engineering companies have been using it for years or they would not have bothered making lapping paste in the first place And try reading these threads first And do your research and try to learn something. Yours Anna j
When I did my apprenticeship toothpaste was recommended for easing tight fitting components.
Hello Too all there are reason, s why I have not ridden my bikes of late Has I have a number of health problems both my Norton will run when some fuel is added in the tank and oil turned on. And a good kick over they start and run. With no doubt. Yours Anna j
HAPPY CHRISTMAS to all you Norton enthusiasts. Keep going, Anna, always entertaining... Rolls Royce used jewellers' rouge to lap their timing gears until they were silent. Norton certainly did not, you can hear mine a mile away, above the clatter of the tappets! (1959 Dommi 99)