trialsrfun

I had a Mikuni for my Bultaco from Motocarb Motocarb - Home not sure if genuine OKO are still available.

Villiers Services keep them in stock, sometimes ready built with rim.

You appear to have AJS or Matchless lower fork legs with more modern fork internals with a made up distance piece to fix them together. This is how they are normally made up irrespective of which forks are adapted. Your best option is dismantle the forks remove the oil seals and measure both seals and the space they fit in to get the best replacements.

Like Woody I had a troublesome Motoplat stator with symptoms similar to those you describe repaired by Bradford Ignitions and its continued to work well ever since. Steve Sell produces a full replacement ignition system for the OSSA should you need to go there. Electronic systems seem to be perfect just fit and forget until its troublesome then sometimes you think its anything but the ignition.

The Beta Rev 3 200 has a rear sprocket one tooth bigger than the 250 making it slightly lower geared. Check what you have fitted before buying one but from memory the 250 has a 40T the 200 a 41T. Changing the rear wheel sprocket does make a worthwhile difference along with a slow throttle and retaining the flywheel weight on the 250. The 200 I'm familiar with did not have the extra weight when new. With the carb nicely set up you should be okay. A reduction of one tooth on the gearbox sprocket equates to adding around four to the rear which would be much lower.

https://www.opieoils.co.uk/p-69390-silkolene-classic-2t-premix-sae-40-synthetic-ester-engine-oil.aspx?VariantID=91954&gclid=EAIaIQobChMI4qGQxbqk9QIVTOztCh3HlAANEAQYASABEgJ2l_D_BwE

Best practice is to always warm the hub around the bearing using a heat gun to expand it so that the bearing releases easily and the new one pushes fully in with similar ease. If you drive the bearing out without first heating the bearing housing it will likely remove some of the surface by dragging out material where the bearing sits then the new bearing will not be held firmly requiring bearing fit to hold it in place. Sometimes the hub can be ruined by driving the bearing out when cold. To refit the new bearings press in gently while the hub is still warm using a socket whose OD is similar but slightly smaller than the bearings outer diameter, NEVER press on the inner bearing race when replacing only the outer.

Best to carry out the Beta clutch fix detailed here on tc before anything else

Ttspud as I said previously you're most welcome to come along to the classic trials in this area in which I ride. Bring your bike and I'm sure you would have an enjoyable days sport and most likely make some new friends at the same time. At least then you would be getting some enjoyment from trials which clearly you are not at the moment. I would be interested to know just what bikes people were using back in the day as I asked in my question to you, please answer that.

I installed a grease nipple to the pivot tube on my Model 124 then its easy to keep it greased without having to dismantle it but obviously it would be best to remove it now to ensure everything is okay. This stuff is pretty good at freeing things off WD-40 Specialist Fast Release Penetrant 400ml (toolstation.com)

Yes I agree with b40rt that should be the best course of action. You could also disconnect the source wires from the HT coil so that there is no spark at the plug.

Use this https://www.trialsuk.co.uk/Pro-Clean-Tyre-Lube---250ml Brush all around rim and bead then inflate tyre with airline without a valve, tyre should bead easily. Never use washing up liquid or silicone sealant as both contain salts and will corrode the rim. If its already damaged by corrosion remove the valve stem from the rim band and fit a tube.

Treat the forks the same as any others and don't worry about the air valves. With the leg out of the yokes undo the top nut using a hexagon socket if possible so as not to mark or damage the alloy top nut keeping some downward pressure on the nut to counteract the spring tension, then you'll need something like a long flat bladed screwdriver down the chrome tube to engage with the slot on the damper at the bottom then you can undo the Allen bolt from under the slider. The slider will then come off the chrome tube you will then be able to see the circlip to remove the internal fittings. Just lay everything out in the order it came out and again take a photo. Dynasurf or Philpotts are the go to place's for a re-chrome.

You have a nice original bike there. I would work on one part at a time just a clean up and service, don't have to many things on the go at once. Photograph everything and try to replace only what is really needed. Do you have a photo of the damaged rear wheel. It's a while away but the show at Telford in February is the place to get everything you need if it can go ahead.

You need a carb connector that fits correctly at either end with no air leaks