I did this conversion on the BB combat motors for a friend and they ran OK but faster as th crank timing is different. Combat head needs a baffle cut in it |
Just checked my unprejudiced ! measured figures for the 21 / 35 B B Crank timing , 35 , 45 . SAME as stated in test for c 35 Stunt .
also 21/46 passage 9 mm Dia. , presuming 21/35 the same , matches C35 Stunt shaft passage Dia .
My 21/35s are the series with the small square flats on the casting on the exhaust stack , would assume all run same timing , unless the Combat Blokes have been at them .
So would assume similar power characteristics , and differance being the ball race supported shaft , being less frictional . C 35 Combat I had was V Tight- draggy in the shaft .
Suggests the 21/35 B B is a prime candidate for the A B C Conversion , with baffle slot cut in head . Assuming you dont want to use a 21/46 which weight would be comparable .