Any help is greatly appreciated.

I have a new hellfire rtr it has a stock engine but I put on a rotostart and aluminium clutch (with weights) before starting break in of the engine. I am finding that I can't keep the engine running properly to do a break in correctly. At first I couldn't get it to start after several attempts.

After this it started firing up but would go nuts and start revving like mad with the throttle right down. I had to pinch the fuel line to cut it off as it was revving like crazy unless I had the breaks on and wheels turning on the idle.

It seems to be running a bit lean when it idles and not giving out much smoke but when it gets going and revs for a bit it puts out smoke if the revs are increased.

I haven't been able to get the engine running for more than 40 seconds to start breaking it in.