feetupfun

probably depends which majesty tank you are talking about and which TY frame. There are quite a few different majesty tanks

Riding with peeling chrome will not make the hub irrepairable, it will just have poor braking and will chew up the shoes faster than a good drum would. Just inspect the shoes for thickness after each trial to avoid going metal to metal

The ball is the same diameter as the rod whatever that is (5mm maybe). You can file or grind the face of the cam flat again, just make sure it ends up smooth where the rod end contacts. I've successfully built worn ones up with mild steel weld and machined the OD back to size when the pit in the cam was too deep. I don't think the cam face needs to be especially hard, but smooth is important

modern trials bikes overheat if you flog them along a road. the cooling system is only made to cope with intermittent high load operation.

You can generally run a lower preload on the clutch springs with the plates that have friction material, so you can achieve a lower lever pressure without any slippage. In my experience they are only a real benefit in a 325cc motor, because the 238 and 250 motors can be set up with a nice light lever pressure even with all steel plates and not slip.

I think naichuff is saying that a Bultaco will run backwards even with the timing set quite a way before TDC. I agree with this and add that advancing the timing can increase the tendency for the motor to run backwards, because at very low RPM (when kicking over, or when motor on verge of stalling), the motor is more easily be stopped and reversed because it fires with the piston further before the top of the stroke. A different factor that can muddy the waters in discussions is that the motor will run better in reverse the more retarded the timing is. Some bikes have a diode in the primary circuit to prevent ignition when the motor is rotating backwards

In case you are wondering why it is OK to have no retaining circlips, it is just that the internal pressure when the forks are compressed is not enough to cause them to slide upwards. Some Bultaco forks have vented caps, which limits this pressure, but the odd thing is that there are many Bultaco forks without vented caps and also without circlips. A bit of a mystery so far to me. Anyway, I run (non-standard) unvented caps on my 1968 M49 (the bike in my avatar) and do not use circlips and despite quite a hammering, the seals have stayed put.

I did mine similar to Guy's

The SM kits I have seen do not require removal of the original mounts

It was to avoid scraping one's boot edge on things, which (once upon a time) used to earn the rider a point. I'm used to the standard peg position on all my 1970s bikes and after trying out lower pegs on one of my TY250s, do not want to lower the pegs on any of them.

Depending on how long your legs are, lower pegs mean you may get hit in the bum more often by the rear frame loop when unweighting on obstacles. I lowered the pegs on one of my TY250s a little bit more than the SM kit pegs and while the bike was easier to balance, it made it a bit more restrictive to move about on the bike (I am 174cm - 5' 10")

If you have the front hub as used on most 247s and all 348s, then yes the front spokes made for TY175/250 front wheel will fit. Would you like a photo showing my 348 front wheel recently respoked with genuine TY spokes?

also do you mean the end that goes through the cover? or the end that turns in the gearbox casing? I found that I needed to rebush both on one engine,

The tank looks long because the top shock mount and associated frame joint is further forward then standard

No they are a very good clutch if working properly Things to check: edges of basket fingers need to be completely smooth not ridged steel plates need to have a rough finish (not polished smooth) cam surface smooth end of pushrod smooth newish friction plates (originals would have lost their frictional properties by now) suitable oil in good condition

The shape and location of the AB and DE airboxes is the same, but the lids are slightly different because the CD models breathe through a slot in the lid. Nothing that will cause a problem with the seat screws.

It's not raining so I can get to my shed and take photos These are photos of later model TY250 frames showing the seat mounting lugs. The photo showing the RH side of a frame is of a D model and the one showing the LH side seat mount is of a C model. The inner surfaces of the lugs are flush with the inner edges of the frame tubing

yes but you will need to add seat mounting lugs to the A model frame. I can do a photo if you want

I'd like to use Greg's top picture to show people what normal 1970s handlebars look like when they tell me that mine look like ape hangers

It looks like a YZ or IT Yamaha to me. See if you can get a photo that shows more of shape of the hub (between the spoke flanges) and another that shows the backing plate.

Bondy if you post photos of the rear wheel someone might be able to tell you wnat bike it is from so you can easily source a sprocket

Very nice job. I especially like the rubber slipper for the lower chain run

Yes

Unless the nut rubs on the cover you don't need to do anything as there is no problem

Old geezers can have problems getting their boot high enough to kick start some twinshocks. I can get my boot high enough even for my Cota 348, but then it takes such a big hummmph to kick it, it seems to be the hardest part of riding a trial on it. I think JonV8's electric start twinshock has a lot of merit for that reason. As far as standard bikes go, my least tiring bike to kick start and compete on is my M49 (250cc) Bultaco. It is very relaxing to ride and I guess because it is so old, it has somehow learned how to ride.