inner rotor kit technical question

[roost]

hi, when installing inner rotor kit is it necessary to lighten oil slinger so engine is still in balance

[No-Fear]

as i said in email, it's better to lighten the crank, u never add a inner rotor & lighten the oil slinger.

[Mack]

If you fit a hc piston and shave the slinger you can get bad kickback. This has the known effect of cracking your cases. If you don't fit hc piston and you are careful how you kick it you can shave some off the slinger, but you will have to keep ya revs up when riding or you gonna be stalling it all the time.

[No-Fear]

thats going to severly set the crank off balance, either get an inner rotor + hc piston, or shave slinger + hc piston. Not many people do both because of the factor it could crack your case or even snap the crank due to it being out of wack.

[Mack]

Originally Posted by No-Fear

thats going to severly set the crank off balance, either get an inner rotor + hc piston, or shave slinger + hc piston. Not many people do both because of the factor it could crack your case or even snap the crank due to it being out of wack.

Thats a load of crap. Crank balance has nothing to do with one side of the engine to the other. It has to do with reciprocating weight. The reason it is not recommended has nothing to do with balance. It is because you have no heavy reciprocating mass to resist kickback. And when it does kickback (and it will) you can smash the kickstart gear and destroy its housing and your case. This is only the case with some motors because of kickstart design. The monster motor is one. There are also plenty of guys who do run inner rotor and lighten slinger. There are also plenty of guys who run one with the crank mounted clutch. Honda guys have been doing it for years.

EDIT -Just think about what your saying.. do you think the balance is correct with an inner rotor on one side and a full size slinger on the other? The balance from one side to the other was closer with the flywheel on. Shaving the slinger after rotor install actually brings the balance closer again. It has to do with the reciprocating weight on the bottom end to help keep the motor spinning at low revs and to resist kickback.

[roost]

yep Macks right , if you fit a inner rotor kit and dont shave oil slinger especially if it is a big bore 131 up you run the risk of spinning the end off your crank(i have seen a crank that this has happened to). The people i have spoke to(who have built 100's of race motors this is all they do) have strongly reccommened if installing inner rotor kit to shave oil slinger as for case breaking problems a couple said if you are carefull when starting this should not be a problem, the rest said there will not be a problem, that is coming from 50's Headquarters, Moto Scoot n Skate,Mini Bikes Australia and numerous USA companys. But as they say different horses for different corses ,thanks any way for your help Mack and No Fear