I've previosuly restored an A50 and an A65, both in vanilla 'Star' configuration. On both of these I had the T/S bush replaced and the cases line bored.
I'm shortly about to start on a complete restoration of a U.S. A50CC road model in original factory spec with 10.5:1 pistons.
The plan is to rebuild to original spec and for road use.
What are the thoughts about the bush/roller bearing options for this project please - and any other recommendations for an engine that will be more highly stressed than my previous two?
Thanks,
Bernie
Hi Bernie,
As it was almost certainly originally a development to increase reliability for tuned racing engines the needle roller end feed conversion is the best choice. The end feed of the oil in to the crank ensures the best possible oil feed to the big ends and the needle roller/thrust race bearing can more than take the load that you will put on it.
Dave.
The A50 sports models are a great bike, especially when coupled with the 473 (spitfire cam which they would have been fitted with at the factory)
The motor won't be as stressed as an A65 even with the high compression but for the small difference in cost I would go down the needle roller route, especially if you choose the ride the bike spiritedly.
Hi Bernie,
I prefer the roller conversion its a trustworthy solution to the timing bush shortcomings. However in my case it has come down to cost, I couldn't afford to have the work done on the A65's but had the money when I built the A10.
Many owners of standard tuned engines who carry out regular oil changes and pay attention to the service schedule have never had an issue with the bush.
The benefits of the roller conversion are it locks the crankshaft so eliminates the end float issue, no messing with shims. The oil is fed directly to the crank, this eliminates loss of system pressure and subsequent reduced oil flow to the big end journals when the timing bush wears.
Best wishes...
Thanks all - I think that I would like to go with the conversion if the cost isn't prohibitive.
I'm familiar with the services offered by SRM - any votes for alternative companies offering a similar service?
I usually do most of the work myself and just use specialised machining services for regrinds and rebores etc.
Thanks,
Bernie
Hi,
I know some people have done their own but SRM are the benchmark as they took over the original set up from Devimede.
On their web site I think there is a cut away engine showing what is involved. If the price is no too prohibitive then it is worth getting them to set up the crank in your cases with the bearings. Have the crank dynamically balanced at the same time.
Their work will come with a guarantee.
Dave.
Contact Steve Macfarlane.
Steve was originally SRM but is now independent. I know he is incredibly busy with the electric starter for A10s but it is worth a try.
Dave.
:) :) :)
Recent quote from SRM :) to "do" my bottom end and reassemble with SRM conrods and some other bits. About £1800. That's with end feed etc.
To fit roller bearing conversion with standard type timing side bush, I assume with thrust washer, and do a small weld job on casing £580.
So its really a matter of what you want. For the miles mine will do £1800 is way over the top. I had a conversation with Geoff at SRM and this is the compromise that we reached. He is a listener and advisor and certainly does not push any particular "product".
Mike 8) 8) 8)
Hi,
I suppose if you take the cost of the rods off and something for assembly then it may get down below £1000 but as Mike says will the use justify the cost.
If you spend the £1000 and cover 10,000 miles I think that works out to 10p per mile. It is the upfront cost that looks daunting.
Dave.
:) :) :)
Dave I think you are right. It is the upfront sum that is a bit scary. Even if I could realistically afford it, I should still have to justify it to myself. Yes if I could do it at 10p per mile that would be a goer. However-----dream on.
Seriously---having the bottom properly done to original spec (plus the roller bearings) should certainly last 25,000+ which I reckon is probably 10years or more for a high percentage of our bikes.
Mike 8) 8) 8) 8)
Hi Mike,
I agree. A well done bush etc. will probably be as good as anything for most of us. Thinking of mine and my wife's experience, we had her '51 A10 done back in 1997 and according to the Smiths speedo it has exceeded 100.000 miles on that bottom end so excellent miles per £ pound spent. My A65 had about 25,000 on a rebuilt end fed engine when I got it and we have ridden the same mileage so even better miles per £. I doubt that we would do that sort of mileage again but we like to think that we will.
Dave.
I've just remembered that as both my A50 and A65 were very early models - the A65 was first week of production - both had the early crankcase with single rear mounting bolt and a ball bearing on the drive side crankshaft. I believe that early configuration suffered less from end float and that was a factor (apart from cost) in my deciding to stay with the T/S bush.
I haven't dismantled the A50CC yet but assume that will have a roller?
Thanks for the continuing thoughts on the options, this will likely be a project for next winter so plenty of time to mull it over.
Cheers,
Bernie
Regardless of the bearing type the endfloat will still need to be set if nothing else but to centralise the crank. The ball bearing is supposed to suffer with radial load capacity but after having one in my
High compression A65 it doesn't cause an issue. I do have a needle roller on the timing side on this bike but not using the combination roller unlike the Devimead SRM setup.
:) :) :)
One of my "areas of thought" on this is that we are used to 2020 standards and trying to apply them to 1950/70s machines; standards that weren't applicable or available at the time these machines were made. In use metals are of a much higher grade?? and the fabrication/machining is likewise.
This does not mean to suggest that we should not strive to attain such standards but that within sensible financial limits, they are possibly unattainable. Neither do I suggest that no-one should try for such, but thinking back to the days of regular "de-cokes" etc even with our old machinery we have come a long way forward.
Neither do I wish to sound to be preaching.
Does it justify the cost??that will always be an individual choice.
Mike 8) 8) 8)
Yes, cost is always a major consideration - especially as I am still recovering from some years of recent austerity (nothing to do with the financial crash but three years restoring a basket case SQ4!!). Also, having a few bikes and using them only for 'bimbling' each one doesn't get used that much - maybe 100-200 miles each year after running in.
I guess I should strip the bottom end and see what's in there - you never know what you might find!
Cheers,
Bernie