feetupfun

If your clutch spring posts are adjustable, set the spring preload so that the kickstart will just transmit enough torque to kick the motor over cold. Also set the individual spring preloads so that the pressure plate remains parallel with the plates as it moves in and out. There are so many variables with clutch hub design and plate thickness and number of plates and spring length and spring stiffness and nut thickness and post length on Bultacos that there is no logic in recommending anything for someone else's bike regarding where the nuts should sit relative to the posts.

Unlikely to be crank seals. Sounds like gunk in the pilot jet. If it is air ingress, check the cylinder base gasket before you go pulling anything apart. These bikes have a weakness in the seam of the main chamber of the exhaust which sometimes splits when there is a decent "backfire". If you had said that the exhaust sounded louder I would have suggested checking this out. If it revved high for a long time before you got it stopped it may have done some damage to the cylinder, piston or rings. You can check for damage by looking up the exhaust port with the pipe off. Sounds a bit odd that you say it stopped with a backfire when the fuel supply was shut off. It usually takes quite a while to stop an engine just by turning the fuel off. Next time I suggest you block the exhaust outlet or turn the bike completely upside down to stop a runaway motor.

Good to see it going. Very cool-looking header pipe. Did you make it? Also where is the beautiful fuel tank from?

Have Racetech gold valves in 34mm Yamaha-Kayaba TY250 forks on 250 Godden Majesty. Better than standard forks but I wouldn't claim them to work better than well set up 35mm trials Marzocchis. Racetech don't list TY250 forks either but Yamaha MX bikes with 34mm forks of the same era have the same design damping internals as the TY250.

TY250 twinshock for trials with 428 chain 12/53 for trials with 520 chain 10/44

75W80 is what would be used in a manual transmission in a car and yes it has a higher viscosity than ideal for a Beta clutch and yes the viscosity is the problem. There are easily available oils for trials bike gearboxes that give the best clutch action possible. Which one is the best is often the subject of discussion on these forums.

Bike in photo looks like M85 Alpina (round barrel) 250cc. This model was introduced in 1972. M99 is (square barrel) 325cc

The 75W80 will probably lubricate the gears and bearings OK but may cause clutch drag problems

yes kill switch goes between coil wire and earth. Kill switch should be the "normally open" type ie it should be open circuit in the "run" position and closed circuit when activated.

It should be fairly easy to source a FEMSA magneto flywheel. I thought that some of the kits came with a flywheel

There is a moulded plastic piece that the airbox is normally riveted to that forms the lower rear mudguard. Replicas of these are available. Lots of choices for the mudguard that fits behind the seat. High quality replica plastic available ex UK in white or yellow. Low quality replica plastic available ex USA in white. Fibreglass replicas are available from time to time. Universal (Gonelli) plastic rears from many sources and lots of colours - but needs additional brackets. Note that the 1974 (A) and 1975 (B) TY250 rear guard is a shortened version of the 1976 and later (CDE) mudguard if you use the original fibreglass seat surround

Yes sorry I was thinking clutch cover. I've got a TY250A magneto cover in great condition I'm thinking about selling. There are some rules about selling things on this website. I'd better read them before I say any more.

If you are talking about shocks at the cheaper end of the spectrum, it can cost the same or even more to rebuild a set of shocks than it costs to buy a new set

There are about 10 of them advertised on eBay at the moment

Yes the pushrods and ball can only fall out via the right hand end of the clutch shaft. From your description it sounds like you are expecting to be able to rotate the sprocket by hand with the clutch pulled in. Even a perfectly good clutch will have too much drag to allow this to happen.

except TY and RD forks are 34 mm not 35 mm

Do you want to sell them?

They look like Falcon Classic steel bodied Trials shocks and they may have no damping because they are fitted upside down. Try them the other way up before doing anything rash. You can get Falcons made so that they will work up that way, but standard Falcons only work properly the other way up to yours in the photo. The spring rate is usually engraved on the end of each spring in pounds/inch. If they are trials springs they should have 40 or 50 engraved. You will need to remove a spring to be able to read the engraving

New tubes for TY250 twinshock are available, or are you after 2nd hand?

What is visible looks original. Can't tell if it is straight from that photo and can't see LH footpeg area

434 (A model) and early 493 (B model) seat bolts to the inside ends of the shockie mounts. 493 (CDE models) seat bolts to small additional brackets on frame. CDE seat is different to AB CDE rear guard goes with CDE seat. AB seat goes with AB rear guard. 434 has stand mount near left footpeg. 493 has stand mount on RH side of swingarm. 493 has threaded holes in the ends of the cross member under the motor (for the accessory trail riding footpeg kit) Frames otherwise the same. 434 and 493 swingarms are different structurally but have the same overall dimensions and are interchangable. Early 493 (B model) has 434 swingarm structure with stand on RH arm. Motors are different inside but interchangable. If you have concerns about specific bits fitting just ask

You have a custom bike which means that aftermarket parts are not designed to fit it. If you do decent photos of the RH side with the heat shield removed, people might be able to help determine if a WES main chamber will fit. You haven't shown the header pipe so can't tell what has been done there. Side panels - no. Can't tell about the seat either without good photos of what it looks like underneath. It may be the correct seat on it already. TY frames are often modified but the way yours has been done is not common.

Before you pull anything apart, check for weird stuff like little rocks rattling against the bashplate or loose engine or bashplate bolts

Yes the rear frame upright has been moved forwards at the top end. Was probably done when the top shock mount was relocated further forwards. Hard to tell from your photos, but the seat rails may have been lowered too. Moving the top shock mount forwards and/or down increases rear wheel suspension travel. Lowering the seat rails improves mass centralisation and gives the rider more room to move. Looks like they have shortened the main exhaust chamber to fit the reduced space from moving the upright forwards. Yes there will be standard frames about.

There are magical shocks and magical fork springs. I haven't heard of magical cartridge emulators