Twin Crankshaft end float.

bruv · Post by **bruv** » Wed Feb 15, 2012 9:05 pm

Some advice please. Can anybody tell me what governs the amount of crankshaft end-float on a 1959 mag/dyno 650cc twin engine. I suspect that it's the centre bearing in the crankcase. I'm about to strip down the engine and I've noticed about 2mm of end float at the engine drive sprocket. Tightening up the sprocket on the crankshaft has no effect on the end float, so it's not the same as my G2CSR. I can't find any figures for any permissable end-float, but to my mind it spells real trouble ahead. The engine was running when I bought it, but it sounded like a bag of nails. Any advice would be most welcome. Many thanks, Bruv.

wilko · Post by **wilko** » Wed Feb 15, 2012 10:26 pm

New centre main thrust bearing will fix that.

cf160 · Post by **cf160** » Wed Mar 07, 2012 2:36 am

I did a complete crank regrind and fitted all new shell bearings many years ago and looking at an extra centre
main web with old shells in it(which I saved), there are
a set of four thrust type washer half circles with small tabs on them to locate them . These are the thrust washers which I believe locate the crank and adjust the end float . There are four , two on each side of the web one above and one below the main journal on each side of the web.
It was so long ago, I may be wrong in some way,but some things stay in the memory , and this one did.
Dave(cf160)

bruv · Post by **bruv** » Thu Mar 08, 2012 9:44 am

quote:
I did a complete crank regrind and fitted all new shell bearings many years ago and looking at an extra centre
main web with old shells in it(which I saved), there are
a set of four thrust type washer half circles with small tabs on them to locate them . These are the thrust washers which I believe locate the crank and adjust the end float . There are four , two on each side of the web one above and one below the main journal on each side of the web.
It was so long ago, I may be wrong in some way,but some things stay in the memory , and this one did.
Dave(cf160)

bruv · Post by **bruv** » Thu Mar 08, 2012 9:54 am

Thanks for your help, Dave and Wilko. I'll be stripping the motor down pretty soon and I'll be able to look in all the right places for the trouble. It's in a terrible state, so it may be that the thrust washers have been left out completely. Thanks once again for your help. Regards, Bruv.

Groily · Post by **Groily** » Wed Sep 28, 2022 8:58 am

I'm reactivating this old thread because the question has come up again via a member in France with a basket case Model 30 rebuild.
I have foolishly promised to see what I can find out.

However, I can't find any data on the permissible float today, any more than I could ten years ago! Is there a figure, anyone? Or is it a non-question because the design is good and the problem of excess float simply can't arise?

And a) are thrust washers 016648 still available from anywhere (no stock at Kettering), b) do/did they come in different thicknesses? Did someone once say 'Fiat' for parts that can be modded to suit - I seem faintly to recall something . . .

In my own experience, replacing undamaged original thrust washers seems always to have resulted in a solid job with no obvious lateral slop and I've left things at that as long as the cranks turn freely, etc etc. But what do people do if things don't come out as hoped (if it ever happens)??

g80csp11 · Post by **g80csp11** » Wed Sep 28, 2022 9:06 am

New thrust washers are expected 'soon' at Kettering in standard and oversize to reduce end float on worn engines. they control the end float
new thrust washers have not been available for years
I did read that oversize were originally manufactured and listed in some parts catalogs but I have never seen any .

Joker_Bones · Post by **Joker_Bones** » Wed Sep 28, 2022 9:29 am

There are a set on Ebay at £75

https://www.ebay.co.uk/itm/255743620969

Groily · Post by **Groily** » Wed Sep 28, 2022 9:46 am

g80csp11 wrote: ↑Wed Sep 28, 2022 9:06 am New thrust washers are expected 'soon' at Kettering in standard and oversize to reduce end float on worn engines. they control the end float
new thrust washers have not been available for years
I did read that oversize were originally manufactured and listed in some parts catalogs but I have never seen any .

Thanks muchly Peter (and JB for that link). 'Soon' is good, but we know how hard it is to get small batch parts made these days . . . Oversize is good too, if and when.

Do you have a figure in your own mind for max float when you're assembling these things? That's the nub of the question from our friend over here, and I couldn't give a good answer. Couple of thou? 4? Aim for zero if you had a choice of bits? What do you think? I've always just had 'minimal', by luck or happenstance whenever I've done my various twin motors, even at high mileages. Even using a complete thin gasket between the cases, 'Biscuit' / Alan Jacobs style. But I imagine with mixed and matched parts things could be a bit trickier.

g80csp11 · Post by **g80csp11** » Wed Sep 28, 2022 10:00 am

norton end float is 0.012" max , so im guessing that is approx what we would expect . enough to give clearance , certainly not much more
also the oversize will be 0.010" , so makes sense somewhere around 6-10 thou as standard at a guess

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