[G.Walker]

I have a balance factor of 70% in my 500 OHV engine. The engine runs without strong vibrations. Also some miles with a speed of 60 mph and more I had no vibrations.
The next engine will get the same balance factor.
But 66% is a good factor for starting if you have still nothing experience.

On such a track the bike runs 250 laps with a speed of 60 mph. No quake in the fingers. The bike runs this year approx. 700 Miles on roads and tracks.

C.

[iansoady]

I suppose the only way to find out is to weigh an original flywheel / con-rod / piston as described in Tuning for Speed. Phil Irving suggests a default factor of 66%.

[phutton]

Balance factor is the proportion of the reciprocating weight that is balanced by counterweight in the flywheels. If the factor is 100% the vertical vibration is minimised, but the for-and-aft vibration is at a maximum. Depending on the application, frame design etc, the factor is normally between 60 and 70%. But what did Marstons use?

[shorrog]

Hi Paul, just to show my ignorance could you explain what a balance factor is?
Graham

[phutton]

Does anyone know what the balance factors should be for the various Sunbeam models? At this point I am particularly interested in the factor for the early (pre 1927) Model 7.

P.