Mini Rok - Starting trouble

Hi there, got an odd problem with my sons Mini Rok engine.

The engine won’t fire up, everything seems to be turning over, but it just won’t fire up. Then all of a sudden it will go, and once running it is absolutely fine, great in fact as my son got a new PB time! But then the next time we go to start it, it won’t fire up again. I can’t figure out what would be wrong to stop it starting, and not impact the performance once running.

I did clean out the carb before the problems started, so guessing I messed something up, but can’t figure out what…

Any help greatly appreciated.

Most likely, a carburettor issue. Check float, float needle/seat, start jet. If something got in the float seat or blocked the starting jet, it may be flooding badly upon startup and prevent you from starting. Then once running, it would be a non-issue, maybe the excess fuel in the bowl corrected a lean condition and the engine was actually going faster because richer.

Thanks mate, I think you might be right, will take the carb apart again this week and see what I find…

Check the piston, if compression is low they take ages to start , look though the exhaust post for black marks lower than the ring . 100% is piston

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If your compression is gone it’ll be stone dead slow on the track.

Since it starts some times but not others, I’m going to speculate that it’s an ignition issue and specifically a loose or damaged ground. A plugged or leaking carburetor will act that way all the time, while a loose wire or bad connection will be great half the time and gone the other half. I’d go through the wiring before you destroy the ignition coil.

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Have you any experience with engine? I not saying no compression if its low it will not start but can still be quick.