feetupfun

For flat turns, lean it over. Counterbalance the bike weight with your body so you can ride very slowly. Try it stationary to start with. This trains your brain. Control speed in the turn using the rear brake working against steady throttle. If you want to learn to do turns with the front tyre off the ground, one way is to practice turning slowly on steeper and steeper slopes (going up to going down turns). This gets you accustomed to riding turns with little/no weight on the front tyre.

Looks like they have a heel

The lack of kickstart train parts for this bike and the other Montesa models based on the Cota 123 (Cota 172/200/242) is well known. There have been batches of suitable parts made in different parts of the world over the years, usually by individuals who needed parts and had a batch made (France, Australia....) and sold off the rest. I haven't heard of anyone doing this recently. I wouldn't expect that the usual commercial suppliers would carry these parts for such a small market.

My laptop opens the site but my AVG virus protection produces a warning each time I open Trials Central. The warning message is "Dangerous webpage. Threat category: URL blacklist" The Trials Central page continues to work normally apart from this AVG warning message

Here are photos of a TY250 head to show the cast-in boss that mcman56 is referring to.

Standard TY250 twinshock head has a single central plug hole. None of the TY250 twinshock heads came standard with a decompressor or a hole for one. The first series of 434 TY250 cylinder has a boss on the front of the cylinder that would allow the use of the type of decompressor that Yamaha fitted to some bikes, that opens a small hole between the cylinder wall above the exhaust post into the exhaust duct. There are plenty of other 250 Yamahas that have a head that will fit on the TY250 cylinder and have two plug holes. The bike your head came from could probably be identified using photos of the head. Aftermarket Yamaha heads in the 1970s were made to look spectacularly different to OEM Yamaha heads in a bid to make it obvious visually that they are aftermarket.

The frame stamping is for model 199 not model 199A. The bike in the photo does resemble a 199A but may be a modified 199.

As well as the gasket thickness, the new float may be slightly different shaped, causing the tickler to miss it. I had the same issue with the tickler not pushing the float down on the same carby. I didn't pursue a solution because I didn't like the carby anyway and fitted an OKO

Ray certainly is very good at explaining why to get which 2T but it left me wondering why he rides the 4T Beta in preference to a 2T

Yes the trials bike manufacturers don't seem to lubricate anything properly when they put the bikes together. People either pull their new bike apart and lube things properly, or replace the rusty and seized parts when they fail. In my experience the steering head bearings, swing-arm and shock link bearings last about one season unless lubricated post-purchase. Many people also lube the spoke threads as part of their new bike ride preparation.

If you haven't pulled a Montesa cylinder off before, you may not know that you will need an (uncommon size) 7mm hex drive tool for the (recessed) cylinder nuts. If the rings are stuck, they may still be fine after cleaning out the ring grooves and the rings.

No it should not sound like that. To me it sounds like a top end noise. Probably stuck rings (because you said it had been sitting for ages) or a failed little end bearing Pretty easy to pull the cylinder off and check it out

The D slide OKO provides faster response in both directions than any round slide carby. Venhill and others make suitable throttle cable kits. Yes different carbies require different length inner cables, unless you are very lucky. The important Teikei carby parts for the carby that came on the TY250A have been unobtainable for many years. The Domino twistgrip is a good thing. I have broken many AMAL T200 twistgrip cable attachments in crashes. The Domino is more crash-resistant and is lighter and you have a choice of pulley sizes. The Yamaha TY250A and the later TY250 twistgrips are also easily broken and the cable loop catches on things.

I bought a set from Anglia Vinyl Art

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?