Iv got a beta rev3 and my sons got a beta minicross, while we were out the other day his bike cut out, It would only run if I revved it, whilst revving it I heard a pop and then it won't start, iv he is only 5 and dosnt ride it fast, iv just removed the engine and can't see anything obvious, the piston and rings seem ok as does the bore, iv replaced piston and rings in 2 strokes before but that's as far as iv been, anybody have any ideas what the problem may be, cheers James

Iv got a beta rev3 and my sons got a beta minicross, while we were out the other day his bike cut out, It would only run if I revved it, whilst revving it I heard a pop and then it won't start, iv he is only 5 and dosnt ride it fast, iv just removed the engine and can't see anything obvious, the piston and rings seem ok as does the bore, iv replaced piston and rings in 2 strokes before but that's as far as iv been, anybody have any ideas what the problem may be, cheers James

First:

Check the plug for fouling

Then check for spark

Then check fuel delivery

Then check compression

Then change the plug anyway

Then test the plug cap resistance

Then pull the exhaust and look at the piston skirt

Unfortunately pulling the engine often leaves you in this situation where you can't check for spark of fuel delivery or compression so you did the last thing first

It's like if you get a flat you remove the tire without checking to see if the valve is leaking air

Tear down is not diagnosis, only tear down an engine AFTER you suspect a certain specific problem, you don't want to have the crankshaft on the bench when you find a piece of carbon on the spark plug or discover a stator problem

hi its john,its your stator thats gone,big problem on beta

After it popped I think it lost some compression, is the stator a fault on all betas, I know it's common on the rev3's

I'll put it back together and see what happens

the popping could of been the head gasket if its the rubbe o ring type