feetupfun

The fluid only dissipates a miniscule amount of heat compared to the discs and calipers. There may be higher boiling point fluids available, but even if you raise the boiling point, the discs will just get hotter and melt the pad surface (losing their frictional properties) and maybe also catch fire. Bigger disc brakes as fitted to enduro bikes would work well for the sort of riding you do.

or fit a tubeless rim

I bought a TY175 that had DT front forks (in-line axle model) on it and they had used a brake plate which fitted both the DT fork leg and the front wheel, which is from an IT125, but has the same drum and axle dimensions as a TY175/250 front hub. If yours are in-line axle DT forks, you should be able to use the brake plate from an IT125 (or possibly DT125 E) for your DT forks and TY wheel. I fitted TY forks and TY brake plate to that bike so I'm happy to sell the brake plate that the bike came with.

oversize pistons usually have numbers stamped on the crown indicating the size that piston is bigger than standard size. The numbers could be imperial or metric values. If it says 010 it would usually mean 0.010 inches over standard size. If it says 25 that would probably be 0.25mm over standard size Pistons made for Yamahas would usually have the piston oversize in mm units Standard size pistons do not usually have size numbers stamped on them Sure-fire way to work out if it has been rebored is by measuring the bore diameter No idea what the > might mean

Welcome to the forums Steve. Please post photos of your Montesa when you get it. If it is from 1970 it will be a 247. If it is a 242 it will be 1984-86.

possibility 1 - when you put the carby back on you might have aligned it slightly differently with respect to vertical compared to before you took it off possibility 2 - maybe there was something holding the float valve open and you cleaned it out when you took the carby off

I have a lovely 1968 M49 so am always interested in other peoples M49s. I was pretty shocked and speechless initially with you making a tailpipe using plumbing parts, but accept that everyone has their reasons for why they do things. You did ask for feedback though so here is my 5c worth: The main section of the exhaust is probably not made of copper. Maybe it has been repaired using bronze welding which made it look like copper. Those mufflers are usually made of pressed steel. I can even see the weld along the seam on yours so it's probably just a normal Bultaco item made of steel. By using such a long tailpipe of such small internal diameter, combined with the 45 degree elbow and the steps in internal diameter that accompany the use of BSP plumbing fittings, you have probably created a design with more resistance to flow than the original triangle muffler. The piece of 1/2 steel pipe and the gal elbow with the super trapp on the end will put a lot of load on the end of the Bultaco muffler when you ride the bike on rough ground so probably need to be supported from the frame somehow. That is a pretty cool idea to use that super trapp muffler and I'm wondering what it came off. I haven't seen one with a 1/2 BSP thread on it before and was thinking maybe it came off a Briggs and Stratton stationary engine because they have a threaded exhaust port. One thing about the Super Trapp is that because the gas comes out all the way around it is hard to avoid the exhaust gas overheating things in line with the louvres. I managed to melt the edges of a few rear plastic guards when I had a super trapp on my 4 stroke enduro bike in the 1980s. I figure that might have been why you relocated it from where the previous owner had it mounted. Another way around the heat problem is to fit a heat shield part way around the outlet of the louvres. That did work for the heat problem, but after the super trapp fell apart for the fifth time despite reinforcing all the bits that failed previously, I put a normal muffler on. A super trapp on a M49 will have a much easier life than on a 400cc hotrodded 4 stroke enduro bike so it probably won't self-destruct for years. An alternative way to fit a low resistance tailpipe and muffler is to use smooth bore steel tubing of approx 22mm ID leading to an absorption muffler supported from the rear frame loop. If you need it to also be a spark arrestor, then something like a TY175 or TY250 muffler would do the trick. That size tubing should fit inside the shockie, and additional clearance for the tyre if necessary could be gained by making the tubing flat-sided where required. Regards David

Where I live most motorbike shops have that needle and seat set on the shelf

el cheapo chinese 240V approx 15 litres tank

You take the bits off that stop you seeing the frame and wheels, like the tank, seat, exhaust, mudguards, airbox and leave the wheels in place, then sight from the front and rear from all heights. Common frame bends with Sherpa ts are: Front end of frame pushed to one side or twisted at an angle to vertical or both Swingarm twisted (one side higher than the other) Swingarm arms pushed to one side (symptom will be rear wheel not in middle of bike) Front and/or top frame tubes curved (from frontal impact) Tubes under motor curved from banging on things

I'll bet the builder assembled the case halves with the crank seal retainers in place

Michelin rears $180-$200 IRC rears $150-$180 depending on Tube or Tubeless type

Can get IRC front and rear pretty easy up here in Gladstone through any of the three motorbike shops and sometimes they even keep them in stock. Can get Michelin too but Michelin sometimes takes months to arrive. No idea where to go in Brisbane for trials tyres. Sometimes at big trials in SE Qld, trials bike dealers set up shop and have tyres for sale. I use Michelin fronts and IRC rears Regards David

there are probably lots of free how-to videos on youtube, and there are also training DVDs available for sale. I bought a DVD to learn how to bend and do welded joints in metal tubing (on motorbike frames) and it was quite good

Depends on which type of tubed rim. Some are ok some not. I may be wrong, but from what I've heard, standard TY250R rim is OK with X11 Michelin. Do you know different to this? By the way bird, which Michelin is on the rear now?

Dunlop bead wont stay on the rim below 10psi if you have standard rear rim Pirelli rear has very stiff carcass, stiff compound and smaller gaps between the knobs IRC tube or tubeless is fine Michelin tubeless is fine

there is a Scorpa forum on here - there is more probably chance of getting your answer if you post there

That SWM looks quite non-standard to me. The tank, seat, sidecovers and forks all look odd and at first viewing I thought he was on a mid-1980s Montesa. Is that what the last of the SWMs really looked like? Gilles does still ride very well

good video Zippy and it's good to know that Biff's footwear has a sensible name there - they are "Thongs" here in OZ and I think in New Zealand they are "Jandals" Kinda like how sticky tape here is called Durex and the most popular beer in my state is called XXXX

The rate of mechanical failures does seem to be high in Spies' bike compared with Lorenzos' bike, but those failures have also affected Yamaha's points in the manufacturer's championship as well as Spies' rider championship points, so it is unlikely that the failures are anything deilberate on the part of Yamaha, if that is what you are suspicious of. My guess is that there is something different happening within the group of people who work on Spies' bike that is resulting in the work standard being lower than it needs to be.

the photos are "SSDT photos courtesy of Peter Paice (Mick Andrews' Aussie riding companion in the 1975 SSDT)" ie they were taken by one of the riders (Peter Paice) and have not been published in a magazine or a book

Yes it will weaken the clutch springs. If you roughen the surfaces of the steel plates it will stop it sticking

That bike has similarities to the bike ridden by Mick Andrews' Japanese (Yamaha employee) riding companion in the 1975 SSDT (kickstart shape, tank graphics and top shock mount location) There are also differences - the bike in the SSDT photos has strange extended fork tops and a standard TY250 exhaust heat shield SSDT photos courtesy of Peter Paice (Mick Andrews' Aussie riding companion in the 1975 SSDT)

Guy from memory the modern off-the-shelf VM26 is a physically bigger carby than the standard carby so it may not fit in the space available

did the abrasive blasting remove the chrome plating or just make it rough enough for the powder coating to stick?