feetupfun

pitted big end pin = conrod kit pitted big end rollers = conrod kit

When geared for trials riding, they are fine for trials riding. Steering and geometry are excellent. They can be made lighter and handle even better than standard with lighter exhaust, fuel tank and lighter wheel rims. WES exhausts are quite quiet. It would be the first thing I would do to prepare a Reflex or a TLR200 for competition (because of the weight). You may be a bit light for 50 pound shock springs. At 5"9" you may feel a bit uncomfortable with the standard bar mount/bar rise/footpeg location setup. Yes lowering the pegs is better for balance than raising the bars to achieve a comfortable riding position. No you don't need to alter the brakes. Pirelli MT43 are good for the road and trail riding but terrible in trials sections (due to extreme carcass stiffness). MITAS make a road legal rear trials tyre that is better than the MT43 for trials but not as good as a proper competition trials tyre (due to the lower carcass flexibility). Note these are both tubeless tyres so you may have issues getting them to fit properly on a standard Reflex rim (which are made for tubed tyres). You didn't mention tyre pressures but your comments about gearing make me think you will want to go faster than tyres with 3-4 psi will cope with (overheating tyres and weird handling on the road). It's very rare to touch the bashplate on anything nowadays using proper technique but if you ride amongst rocks and are not confident, it's probably a good idea financially to have a bashplate that is effective because engine cover repairs or replacements are expensive. Back in the 1970s it was a fairly normal thing to ride on the road with road gearing and change to a smaller front sprocket when you got to the riding area. It's not clear why you need to go fast on the road anyway. Can't you do the 2-3 miles on the road at a sensible speed?

Based on previous postings on this subject, if you buy the shaft for the motor that the clutch cover you have is from, it will protrude the right amount. There is a search facility for these forums where you can find previous postings on this subject.

That U shaped bracket came with the footpegs

It's very nice to see an original Yam framed Majesty looking so beautiful. Something looked unusual and I've just worked out that it's that the fork legs and front wheel are fitted the opposite way to normal

This is an old photo of one of my TY250s. The lower cross tube on some models of the TY250 has a threaded hole, as this one has, which I think has a TY250B frame. People who have a TY250 without the threaded hole fit a threaded steel plug into the tube. Some are welded, some with an interference fit. The stand is not an issue on this bike. It is mounted to the right hand side of the swingarm and does not interfere with the footpeg. It sounds like your TY250 might be an A model with the stand mounted to the main frame under the left side footpeg. This is an old photo. It now has countersunk internal hex titanium screws instead of those external hex head screws.

Maybe the header pipe is bent. There is meant to be a metal crush sealing ring in there to seal against the flange. The flange needs to be quite close to being parallel with the mating surface for this sealing ring to work. When these header pipes are being fitted new, the first thing to do is fit the header pipe up fully to the cylinder then make whatever changes are needed to get things to fit. I remember fitting a header pipe that looks a lot like yours and had to reshape the header pipe (heating it with an oxy torch) to get the rear end of the header pipe in the right spot to fit to the front end of a WES mid box.

Depending on the shape of the pipe and if it has a fixed flange or not, it may need to have bolts used where the pipe flange bolts to the cylinder, instead of studs and nuts, to allow the pipe to be fitted. Some TY250 twinshock cylinders have exhaust flange mounting holes that are M6x1.0 threads and some have M8x1.25 threads. The standard arrangement from new is studs and nuts. The standard exhaust pipe flange can rotate on the standard pipe. Some aftermarket pipes have a fixed flange.

Maybe it's a trailbike of the era with a TY250 motor. Is that number you posted the motor ID number or the frame ID number?

With that number, it started out as an A model TY250. Hard to say more without photos

If you had an OEM sprocket to measure, why did you not just compare it with the one causing the issue on the bike?

The standard offset is 4.8mm

Yes original is aluminium. I'll measure the offset on an original sprocket

No of course it shouldn't rub on the swingarm. Here are a few possible reasons for why yours is rubbing. The axle may not be square to the centreline of the bike. The swingarm arms may be bent to the side. The sprocket may have too much dish. You may have the wrong length spacer on the brake drum side although it looks right to me in the photo. The sprocket looks like an aftermarket one I ordered in at a local shop 25 years ago and did not accept because it had too much dish.

I've ridden a 2022 300 TRS One RR recently while getting it running well for a friend. Yes they are very well-made. It had lots of mumbo on tap. The handling, brakes, suspension and steering are excellent. Initially the footpegs felt further forwards than what I am accustomed to but the feeling went away after a few minutes riding.

One thing I have noticed is that the standard Sherpa N has a very long horizontal rear frame loop (for a dual seat). The prototype Matador, Mk1 Matador and Mk2 Matador all look like a Sherpa S frame to me because of the steep short rear frame loop. On the Miller Sherpa T prototype, the rear frame loop and shock mount area doesn't look like any of them. It's rear loop is short and steep but the tubing looks smaller diameter and the gusseting at the shock mounts is very different. The photos I'm looking at are in Bultaco Todo un mito and Don Morley Spanish trials bikes. I've also looked at two frames. A 5 speed Campera frame from 1966 which I think is an M21 and a 1963 M3 Sherpa S frame.

It's fairly common practice on multiple brands of twinshock trials bikes to have the top mounts closer to the mid-line of the bike than the bottom mounts are. It was done to make the bike slimmer where it counts

Yes that is great value. They are a fabulous motorbike. The ignition system is not connected to the lighting system. Each has its own stator coil in the magneto. Blowing 6V bulbs was standard back in the day for TY250A. Fitting 12V bulbs was one way to avoid it, but the lights then became dimmer. They came with no voltage regulation on the lighting circuit so as the RPM rises, the voltage rises. Nowadays there are a myriad of options for the lighting circuit on motorbikes.

My memory of riding the big-wheel Beta 80 is that it was OK for me at 5'10" but I would think it might be a bit cramped for someone tall. The motor was easy to use in sections. Modern 125 two-strokes are excellent. The modern mecatechno (electric) trials bike is extremely light.

I've just done a top end decoke on a friend's (low hours) 2022 TRS 300 and was astounded at how tenacious, dry and thick the carbon deposits were that completely covered both the piston crown and the inside of the head. It ranged from 0.25 to 0.5mm thick. The tenacity and hardness of the carbon in this TRS reminded me of the carbon that formed in my 1970s air-cooled two stroke enduro bikes running on 20:1 castor oil premix. Sure enough, when I then asked the owner what premix oil they use, they told me it is castor oil based. I'm accustomed to seeing soft, wet smudges of carbon that cover about 40 % of the piston crown on my 2 stroke trials bike pistons. Is using castor oil premix in modern trials bikes common practice?

Piston position can be used to make timing marks and it's easy to measure through the sparkplug hole

You could take the exhaust header off and measure the bore diameter through the exhaust port. The Beta 125s I've seen have a different exhaust header shape to the 200/250/270

Yamaha was selling genuine spoke sets for TY250 last time I bought some. They are zinc plated. Stainless steel spoke kits for them are available from In Motion in the UK. I know you can get spokes custom made by a bloke in Brisbane. You will probably have to send him samples to copy. There are probably people all over Australia who can make spokes for you from samples. Another option that people do is to re-plate the original spokes.

If its is a standard 348 engine then it is approx 310cc displacement..

When that casing is on a 348 motor there is a screwed plug there.