I have a problem with keeping my sons beta rev 80 running consistently , We can go to a trial one week its fine and go to another and it fails to pick up cleanly, carb air filter are spotless , i have drained and refilled the petrol tank the ignition is dry and all connections are sound , When it runs ok the bike runs perfectly pulling cleanly right from the bottom end but when its acting up it wont pull cleanly from the bottom end and it struggles to rev out. any ideas?

check killswitch isnt shorting out or better still put a good quality one on it like the yamaha type

We had a Rev80 and it would burn out a plug every other trials, so when it plays up try a new plug.

This my help.