Evening All,
After more help please.....
I have been reading Don Daly's piece "Main Bearings" in the Heavyweight Twins Companion, and am confused by his statement: "I always put a heavy duty ball bearing on the timing side. This saves having to shim the crankshaft and a good quality bearing in this position will see you well past your own retirement...."
Having stripped my old engine down (and found no shims on the crankshaft), I am now in the process of rebuilding. Bought the roller (drive side) and ball bearings from Andover Norton. The crank needed a grind to 0.010", and it's now time to start to stick the engine together again. Wondering if I will need to check if shims are needed......and then go through the problems that calculating the shims obviously means.
Don't get how using "good quality bearings" may mean that shims are not required (Don's words).
Very interested in any thoughts or comments please.......
I always use a full…
I always use a full-complement ball-race on the timing side and a so-called 'Superblend' on the drive side.
It is not the quality but the type of bearings used which negates the requirement for swimming.
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The use of the ball bearing…
The use of the ball bearing removes the need for shimming as a ball bearing removes the side to side movement and has the load rating to cope with the forces.
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Crankshaft Shimming
The Bracebridge Factory machined the crankshaft and cases of the Dominator engines with the aim of around 12 thou lateral play in the crank. Which generally they achieved but between 8 and 20 is acceptable with DIY rebuilds. John Hudson did report that he once dismantled a Commando (under warranty) engine that had 40 thou of crankshaft side play. That must have given the conrods and oil pump worm a hard time.
If the original set-up of one ball and one roller main bearing are fitted to a Dominator engine then, as several members above have mentioned, there should be no need for any shims. Which will save an awful lot of messing about with assembling the motor. Also, unless the engine is going to be raced this bearing choice will almost last forever, if an oil filter is in the system and regular oil changes are done. My choice of main bearings again echoes above with an FAG roller on the Drive-side and an up-rated M306 on the Timing side.
Fitting twin roller bearings on any Dominator engine less than 600CC is usually a waste of time and money.
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Thank you all (as usual!)…
Thank you all (as usual!). Your comments are really interesting.
Now that I know a bit more about what I am talking about - the bearings from Andover appear to be FAG NJ306E roller (drive side) and an SKF 6/306 ball bearing for the timing side.
Very unlikely to go racing on my Dommie! At the moment it doesn't have an oil filter - but that's a good idea.
If someone could give me the thumbs up for the Andover bearings - I will get on and fit them.
Thanks again.
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As I understand it, with the Commando, the use of Superblend rollers both sides, allows lateral crank movement which has to be controlled by shimming. A ball bearing on the timing side prevents such lateral movement and obviates the need to shim.
An expert will be along soon to either confirm or rubbish this.