The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: spottycat on 28.06. 2024 09:19
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Hi, Being quite new to the A10 I am still learning about its specific foibles. The bearing conversion at the timing side seems like a good idea. I know SRM offer a service but I have read articles that say there are other options, some of which are simpler (and maybe, therefore, cheaper) I spoke to SRM and as well as the cost, which would push my budget, they have an 8 to 10 week turn around. I want to move on with my rebuild but am having trouble deciding which way to go on this. Can anyone recommend another engineering firm experienced at carrying out this procedure even if there system is slightly different please. I do not thrash the bike but intend to cover a lot of miles. I may end up sticking with the standard bush but all the shimming sounds like a pain. Cheers, Chris
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I've just rebuilt my engine with the standard bush. Over the years I've had a number of A10s and an A65 (with the bush) and its not been a problem. There are still huge numbers of BSA twins running after 60 years on plain timing side bushes. What is a problem is oil, use the right grade, the sludge trap which is what kills most T/S bushes and setting it up right. I did the end float and is was not a bad job, there's some tricks - use an old bearing to pull on and of, but its straight forward. The ball/roller conversion is a big job. If you follow Paul Henshaw on YT he recently rebuilt an A65 with a full TS roller conversion that had been seized because it had an anti wet sump tap and the owner forgot to turn it on. There's a lot to be said for keeping things simple.
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SRM converted my A10 in winter 1984/85. Done very many miles, including commuting to work, since then. Several new end feed oil seals, one new conversion bearing, one new roller bearing and one big end regrind since then. No shimming worries. No issues. I certainly got my money worth.
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I'm another who chose SRM conversion 1981/2 no trouble since so they still get my vote, however, of my 3 previous A10's all bushed only one seized and that was my first bike and I hadn't noticed no oil return so my fault the others went well .
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Ain't that the truth👍
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When I had my GF engine rebuilt, the engineer warned me off the change of the timing side bush if the engine was not going to be highly stressed. He claimed the bush absorbs the vibration a little better than a bearing. No idea about the truth of this but this guy knows more about BSAs than I ever could imagine.
I would look at it as a cost benefit analysis. Not a massive benefit but a fair bit of cost.
John
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I think the T/S bush and BSA have an unfair reputation. l've recently got hold of a '53 Matchless single, now these have a reputation of going on forever so I was surprised to find it has a plain T/S bush. Its actually a smaller dia than the A10 one but longer. Either way its a plain main bearing.
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Cost benefit analysis is a very good point. How many billions of miles in total have these old girls done with a bush bearing on the timing side?
More than enough to prove their reliability I would think.
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I was trying to recall when a TS bearing conversion became a thing for A10s. I think it all started with the Devimeed 750 conversions for A65s and the tuned A65s for sidecar racing. My modestly tuned (10 1/2:1, bell mouths, exhaust RITA ign) A65 was pushing 60hp on a TS bush and when the bush failed it was, yet again the sludge trap that did for it. I don't ever recall anyone suggesting this conversion for an A10 but I could be wrong. That engine was rebuilt with a new TS bush and an external oil filter and was going strong 20,000 miles later when I sold it. Bear in mind also that an A65 is revving to 7500 and having just caught the last of the A65 outfits in the TT (in the mid 70's) I'm sure they were getting another 1000 rpm at least.
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Thanks to all those that responded. I have decided that a decent bush, oil filter and clean sludge trap is the way to go. Cheers
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I had the SRM conversion done on my RGS with Carillo rods on the basis that a thrown rod would take out the crankcase destroying the RGS originality. The way I ride now that was overkill but was good insurance originally.
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Haven't you now destroyed the originality? *smile*
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Haven't you now destroyed the originality? *smile*
Yes, but is any bike "original" in the sense of exactly how it left the factory. Generally RGS originality is based on the frame and engine, most other parts are available as repro parts or off other BSA bikes, hence the plethora of look a likes.