teamferret

The normal practice is to weld a piece of flat pate across the bearing. They will normally fall out or can be easily tapped out

I couldn't find any tubless ones a couple of weeks ago, thought I had bought one off ebay but they refunded my money the next day. Ended up with and X-Lite

Carb is blocked somewhere, suspect bike has stood for some time. take apart and make sure you can blow through every gallery

Try dropping the needle a notch or two first

Most people fit the REH ones, they are expensive though. We used to chuck all the internals of the heavyweight forks away then turn down a set of modern forks and loctitie them into the shell, still heavy though

doesn't sound too bad, these engines are particularly noisey. If it goes OK I would keep riding and see how it goes

Brother does have a spare Tc120 frame, no swinging arm - tubular

As you have found out, the removal tools are hard - either carbon or high speed steel. The engineering solution is to 'burn' it out on an EDM machine but not cheap - probably more than a second hand yolk. Can you weld anything on the tool? or get to the back of the broken screw even drilling another hole to it?

I think my brother has a TC120 frame and a few other bits and bobs

There was a B120 engine on facebook recently, don't know if it's still there. I have seen Students on Ebay too and these are virtually identical, the tank is smaller being the only major difference. The Gaunt version used as much as the B120 as possible so a Student is a good starting point

My brother sometimes rides a Blooper special some of which we had as schoolboy competitors. The engine is the one he won the 1969 schoolboy scrambles championship at that time it was housed in a pressed steel K80 frame but soon after my dad bought a tubular frame which was made by a Mr Davis for his lad but he went on to make him a better one. It was using this that I won the YMSA trials championship. At the time it had a 17 inch rear and 19 front. It now has Fantic 125 wheels forks and swing arm. My dad had it bored to 128cc using a piston from the super six twin and now it is 132cc which is helpful on hills as it does lack omph. We have never had the high and low speed box as it's never been used on the road (did do a road trial once, but trailered it between sections). It's a fine little bike, bit wide and short and suits a learner rider and ours has seen many of these. The later Student is almost identical and often a good source of spares

allowing 4-speed Bantams into pre-65 trials

Our nearest course had a similar stipulation, it doesn't have to be another rider - just someone who could raise the 'alarm' if necessary

Something fishy here I think. I can't see it ever getting to that much clearence, it should be more like 0.10. If it has worn it's way through the very thin coating on the aluminium bore then yes, rapid wear will occur but normally they seize up. The pistons come in a range of sizes but only fractionally apart as manufacturers find it easier to match a piston to a bore already produced.

I think (90% sure) the RL250 flywheel will go straight on, but might be too heavy so try the TS250 which again has the same ignition system