Ariel Owners Motorcycle Club

My engine is being refurb at T & L near Bedford and they offered to dynamically balance the crankshaft assembly for me and want to know what balance factor to use. I've seen some old posts on this subject where 65% was mentioned. Anyone know any better?

Also struggling to get an oil pressure gauge and head race bearings, Drags are out of stock at present, are their any other suppliers of these?
Cheers
Les

hi,Les try the clubs spares or peter kemp he may be able to help you

When I rebuilt my KH I had it dynamically balanced, it made little if any difference. I tried various balance factors between 60 and 80% without any noticeable effect until 80% when the vibration became worse. If it is vibration you want to reduce the best means is to ensure that the sparks are exactly 180 degrees apart for even firing, easiest to achieve with electronic ignition and reduce reciprocating weight as much as possible. Many modern pistons, for reasons of economy, have parallel bored gudgeon pins, which is where most of the extra weight comes from. Either modify them, not easy, or use good used ones.

Prior to refurbishing the crank assy. on my KH500 ie new pistons and crank pins reground, I checked the Balance Factor (BF) as near as possible doing it statically, see attached, the BF result was 64%, the bike had previously been running OK, ie low vibration.
After refurbishment I reset the BF at 64%, again doing it statically, the bike still runs ok with low vibration.
Obviously dynamic balancing would be much better than static balancing.

Hope this will help,
John P.

I'd leave it where it is. Mines not smooth and was original pistons in original bores. Haven't checked the factor as the bottom is not dismantled. Making the thing s that go up and down as light as possible helps and tapered bore gudgeon pins are helpful there. The best factor is usually derived by trial and error as things like the frame and handlebars affect it.. 65% is not hard on anything and is a very common start figure for singles and vertical twins. Nev

Thanks for all your help on this it seems 64% - 65% is what I will ask them to set into the balancing machine.

The dynamic balance can help significantly when there is significant difference
between the weights on the two sides of the crankshaft. T and L's dynamic
balancing made a significant difference to my friends early A10.