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This short blog is just to cover a simple check which needs to be made every time you fit a variator, whether you are just changing your mopeds rollers or fitting a new aftermarket performance variator !
The splines on a moped crankshaft and on the outer variator pulley/ kickstart gear aren't strong enough on their own to withstand the high rotational forces applied to them during normal use.
The crankshaft pulley nut doesn't just hold everything together but applies the compressive force required to prevent the splines from becoming damaged and spinning on the crankshaft. In fact so long as the variator is spaced correctly and the crank nut done up correctly it does not even really matter if the splines are there or not, the compressive force of the crank nut holding everything together is all that is required.
It's therefore vital that the variator is spaced out correctly, if the crank nut tightens onto the crankshaft shoulder *before* it reaches the front of the variator assembly (see photo below) then it is certain that the splines on front pulley assembly will strip very quickly. As soon as this happens the front pulley is free to spin independently which affects performance and if not fixed very quicky will lead to the front pulley hole wearing considerably followed by it subsequently wearing a groove into the crankshaft which can result in an expensive and uneccessary premature engine stripdown to replace the crankshaft.
For this reason the crank shoulder must be recessed by approx 1mm as shown in the right hand picture
Worn crankshaft splines or worn a front pulley are almost certain to have been caused by an incorrectly spaced variator unless the variator crank nut has become lose (which would be obvious on inspection). If the variator isn't spaced correctly according to the photos above then something is definitely wrong and most likely you have missed out a washer somewhere !!!
Stop and recheck carefully !
It's worth noting that loctite must always be used on the crankshaft nut, one moped manufacturer even has a policy of automatically voiding variator related claims where loctite has not been used.
