Balance factor

The Balance Factor is very important ........ especially if the pistons have been replaced.
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Hi. I bought a pair of Thunder Engineering rods when I restored my 1958 99 fives years ago. When I worked out the balance factor for the new rods it came out at 82% with no alterations - within the range of what I wanted. Being somewhat surprised at this, considering the increase in rod weight, I worked out the balance factor for the old set up. The bike was my Dad's and he had it from 1963/4. It was unused for much of this time until 1976 when we rebuilt it together so I know much of the history of the motor. The pistons were +40 (8.2:1 CR as supplied as the factory 1958 'Sports Equipment') and I still have those and others (7.4:1 CR) of various bore sizes we've used over the years. When I worked out the factors with combinations of these various set-ups I got figures ranging from 97 - 101%!?!? Thinking I was going nuts, I went back and checked my calculations again and again but came up with the same figures. So, I took the chance and built the motor up. It's remarkably smooth and will happily whizz up to 8000 revs if allowed to do so (it's been 'worked on' a bit by me).I couldn't find a definitive figure for the balance factor in any literature that I have but 82% works fine for my Dommi.

A great photo, reminds me of the red one I had in the sixties. But why does'nt  58 TMN show on the DVLA tax site ?

In between the rain showers at Jurby last year my wife asked me if the Manx fire department had entered for the meet at any time during the day! Now I know why.

I think the VMCC. Is not doing it again?shame if so.  I have done about 50 laps at Jurby on my Ducati 250 and was nearly blown off the track by bad weather last time , great fun though .