350 top end on 500 bottom

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
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Stuart Jenkins
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Posts: 50
Joined: Fri Mar 16, 2012 6:18 pm
Location: EAST SUSSEX UK

350 top end on 500 bottom

Post by Stuart Jenkins »

Hello,
I've posted this in the G3 section, but thought i'd post it here as well.
I'm using a set of 500 fly wheels in a 350 project, my question is will this have to be re-balanced? I know when doing it the other way (500 top end on 350 bottom) it has to be.
Any thoughts?
Many thanks
Stuart
g3l 1941
BMW r80G/S '82
Yamaha FZ750 '90(Project)
Dave T_LAPSED
Posts: 157
Joined: Tue Mar 29, 2016 7:19 pm
Location: CALVADOS FRANCE

Re: 350 top end on 500 bottom

Post by Dave T_LAPSED »

Hi Stuart, try downloading "Tuning For Speed" by Phil Irving and on page 60 he describes how to balance a crank. If you perform the weighings and calculations he describes you can easily see if your setup is within spec and decide from there what your best course of action is.
Balance is essential before you assemble the bike and find that the engine wants to jump out of the frame, no?

Dave.
burrage
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Posts: 88
Joined: Mon Jan 01, 1996 12:00 am
Location: WARWICKSHIRE UK

Re: 350 top end on 500 bottom

Post by burrage »

For all the facts on how to balance your crankshaft refer to Jampot March 2001 - Tom Walker's article on crankshaft balance.
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