I'm helping a friend of mine to rebuild his Ossa mar we have got to the point of starting it but even though it fires up ok it refuses to rev up, we have the correct needle and jet in the Amal carb but as the throttle is opened it just seems to spit out fuel from the carb and doesn't rev up. The timing is set at approx. 3.5mm btdc and the bottom end has been rebuild by an old school motor bike engineer are we missing something obvious ? Any help would be appreciated.

 

 

3.5 mm seems too much advance!! I would set at 2mm. would be better if you could strobe it to check whats happening???  mark flywheel with paint at TDC, THEN ROTATE FLYWHEEL CLOCKWISE UNTIL PISTON HAS DROPPED 2MM DOWN THE BORE AND MARK AGAIN, you need a car type strobe that has a 12volt battery hooked up, and at tickover your second set of marks should line up. for the TDC gauge you could use a piece off wooden dowel, mark it off level with a fin at TDC then mark 2mm above and do as above, if you're man is old school like me he would of done this many times..  ;-]

 

just found this link..that says 2.7 to 3.2 for timing, it is electronic is it??  as there were some models with points??

 

ossaServiceBulletins2(1).pdf

Thanks for the info much appreciated.

Update on my last post, we have solved the problem about it not revving up turned out to be the ignition coil, it was not producing a good spark fitted a replacement coil all ok now sounds sweet as a nut.