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flywheel

Hello All
Can some one please tell me the difference in B.S.A M20 fly wheels.In the origanal spare parts list there are two
Part No.66-649 "Flywheel (D.S}"
Part No.66-651 " Flywheel{G.S]"

I find this site the best and wish all a happy and good safe christmas
Cheers Drew

email (option): bronte.nolan@bigpond.com

Re: flywheel

These are for the drive side and the timing side, but BSA also used different numbers in the parts lists for complete crankshaft assemblies just to confuse the issue.

email (option): davmax@ntlworld.com

Re: flywheel

Hi Drew..BSA flywheel numbering is a minefield...there are part numbers, forging numbers, casting numbers, individual flywheel and complete assembly numbers..and insufficient information to sort it all out in a logical sequence for all years.
Basically..Flywheels were made either from cast iron or steel for the M20 and M21. Materials were changed for different years and for different applications. Some users, such as the AA and the Government specified a particular material requirement. So at times both materials were used in the same period, for an M20 for example.
All OHV models used steel forgings for flywheels (M33/B33/B31/B30)
Generally steel wheels can be identified by numbers beginning with a 6..eg 66-635..and cast iron wheels with a number commencing with a 7..eg 66-705...
The set you have originate from the period when the M20 and M21 were redesigned with the inclusion of an extra main bearing on the timing side and as a result, a longer timing side mainshaft. This led to a part number change for the timing side flywheel...So they are a pair of steel M20 flywheels. The different numbers and more particularly the 'DS' and 'GS', indicate 'Drive side' and 'Gear side' (timing side) flywheels..I have put a piece in the 'technical section' of the website which goes some way to explaining it....Ian

email (option): ian@wright52.plus.com

Re: flywheel

Thanks Dave and Ian for your time.
Cheers Drew

email (option): bronte.nolan@bigpond.com

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