feetupfun

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