Balance factors

Andy,

hopefully someone more knowledgeable chimes in, but i have been told that all Norton Singles left the factory balanced to 50% (i don't know whether that should have been qualified as all roadgoing Norton singles?). It seems that BSA used 58% for their singles and i have seen comments on another forum about 60% or higher working better for Nortons at modern road speeds, so it sounds like you are on the right track.

best of luck

Iain.

Previously wrote:

I am going to re-assemble my crankshaft this weekend and was wondering if people have experimented with balance factors in the past and if so what sorta numbers do you reckon? I think between 60-65 is about normal for singles but was wondering what people reckon? Its a 1936 inter im doing but it has a manx crank and big end in it. I wont be racing it so am looking for smoother (yeah right!!) low speed running.

Andy- I balanced my 1950 ES 2 crank at 66 % as recommended by Mike Pemberton and also Phil Irving in his tuning book- It runs beautifully at 50- 55 mph. I do not know what rpm this is as I have no tach but I am very happy with it-Hope this helps-Richard

I'm confused - what makes you think Norton got it wrong when they built your engine?

Hi Andy,

A while back I fitted a Big 4 piston to my 19S. This isabout 60gheavier than the original piston and gave a balance factor of 47% (original was 51%). Vibration was intolerable. Since thenthe piston was swappedfor a Matchless item and the crank rebalanced to 64% (my target was 65%). I am not convinced that it is noticeably smoother than Norton's original balance - but it could be that I am riding too slow! My '37 CS1 engine is in pieces at the moment so if I get time I will check the balance factor for that - vibration on that bike is very acceptable.

Cheers, Ian McD