Cheers for the suggestions, but I have tightened the spur gear onto the motor, and adjusted the motor end bell timng! now it flies!

And by the way it's a Reedy Kr 10 x 1, not Mr. Bit worried that there's talk that these battery cells may destroy the motor! :(

The KR is perfectly fine, i have several, you said MR which are the old school ones ;)

Nice one thats a relief, I figured the motor looked in good condition to be a really old one!