feetupfun

Generally a trials swingarm should be as long as possible yet still achieve the wheelbase that you want. For a bike with something like your B250 engine (an engine that is long from front to back) you will probably end up with as short a swingarm as will fit an 18" trials tyre and the wheelbase will still be on the long side of ideal.

For comparison, this is a standard Kawasaki KT250 front end. I chose this photo because this bike has the most steering angle of any of my bikes.

Excellent. Thank you. That is fairly serious steer angle

90 degrees is an awesome design target. If you've got it, flaunt it. I'd love to see a photo.

Maybe try googling Leonelli instead of Lionelli. Have you looked in the owners manual for your bike?

The SWM Jumbo came with 38mm forks

I'm still working and may not even get any time off due to working at a power station. Plenty of things I'm ready to do in the workshop, mostly involving 1970s trials bikes

and if I could source IRC I would use IRC also. They are both very good.

People (including me) fit Tubeless X11 Michelins on Tube Type rims.

Who cares what people do on ebay? Isn't there a for sale section here on Trials Central? That would be a pretty good spot. There's also the various facebook Montesa pages which are 100% Montesa enthusiasts

depends where you compete

The threaded holes in the hub normally go all the way through so maybe there is just some crud in the holes stopping the bolts going all the way in. If that is the problem and you don't want to clean out the holes, you could fit some 8mm washers under the bolt heads or buy some shorter bolts..

The TY250Z motor is based on an early 1990s YZ250 motor. The TY250 air cooled mono motor is based on an early 1980s YZ250 motor. They started with a clean sheet of paper for the TY250Z but did use the pinky front wheel.

There is a plastic toolbox that sits in the space but none of mine still have it

I had an aluminium tank that had developed a line of corrosion holes in the bottom of one side which were in conjunction with the gum that forms when modern fuel is allowed to evaporate in-situ. The corrosion holes were under the gum. I suspect that there may have been some water also present during the hole-forming process but by the time I got the tank it was dry and just had the gum and the holes. If you don't allow things like that to happen to the tank, aluminium is one of the best (longest-lasting and lightweight) materials for a fuel tank. I've seen zero corrosion damage on any other aluminium trials bike fuel tank.

nothing there on either of mine

its a right hand thread

There is nothing stopping you fitting the new outside bush further in from the end

What is the problem with the bush going right to the end? One thing I do know is that I couldn't source the right size bushes for a M85 sleeve gear last year so I bought bushing material with a smaller ID and bored it to size once it was in place in the sleeve gear. Haven't tried the motor yet. I've always wondered why some 5 speed motors have needle roller bearings there and some have sleeves.

Yes

Yes the top bend is made from a pre-formed exhaust pipe bend. They come in various diameters and one size is smaller than TY250 and the next size up is slightly bigger than TY250

The diameter is as close to standard as you can get when using pre-formed exhaust pipe bends. The vertical run has been shortened from standard to get the pipe closer to the head to provide clearance for the underside of the fuel tank.

Suggestions if you want help identifying the bike: Don't use the current fuel tank to try to identify the bike. Post up photos on the bike on here. Read and post up the frame number. Read and post up the engine number.

Sounds like you might have a few more special design features to discover yet

Looks like the fuel tank was borrowed from a works bike too