Originally posted by InitialD
Usually, the preload measurement depends from engine to engine. Different tuning requires different measurement. Driving style and preferance also determines this preload.
So what I do is to start it tight (maybe up to 1 mm) and then loosen it step by step (quarter of a turn at a time) to find the best clutch engagement from standstill and out of the corners without the clutch slipping.
The method of measuring from the end of centax clutch-nut (6582) to the end of crankshaft as mentioned in the 705 manual will yield different results for different engines. It depends on hte shim behind the brass collet used and also the length of the crankshaft.
So a better method of measurement is between the end of the flywheel nut and the top of the tension collar. That way, the measurement stays relatively the same from engine to engine.
A larger measurement (tighter pre-tension setting) yields a harder clutch engagement. Engine may rev a little more for the clutch to engage. Most of the time, this setting goes hand in hand with the clutch gap spacing. The rule of thumb I use is smaller clutch gap, harder pre-tension nut setting. Larger clutch gap spacing, looser pre-tension nut setting.
That said, I actually like my current setup which is 0.7 mm clutch gap, 1.1 mm between the end of the flywheel nut and the top of the tension collar with the stock soft Centax spring with the 3 flyweights mounted in between the flywheel pivot post.
Yes, I realise measuring the clutch nut to crankshaft would not make any effect anyway. I guess above is the best practice to do it.