feetupfun

do you mean setting them up properly, or replacing them with different forks?

They were innovators in many ways. When the 348 came out in 1976, it had so many innovations that it seemed like it was something from another planet. I still remember how I felt seeing a 348 for the first time

I've pulled apart two more Bultaco engines since then and in both cases that seal sleeve came off without effort. The knowledge that a new seal sleeve jams on the shaft means that the problem is probably the shaft. Being a very close fit, it would not take much of an imperfection to make the sleeve jam, so I would probably study closely to see exactly where the new sleeve starts to jam and try and find what the imperfection was and then deal with it. It may just have something there that can be removed with a hand-held oil stone. If you heated the shaft when you were trying to get the old one off, there will be combustion deposits and maybe some oxide that should be removed (there are deposits visible in the photo). You should also clean the inside of the new sleeve of any rust spots. A scotchbrite scouring pad is good for removing deposits like rust, combustion product and oxide film. I can see a lip about 12mm in from the flywheel shoulder that indicates that the shaft has been deformed a bit. It may not be that bit of deformation that is your problem area, but deformation of the shaft somewhere is likely to be the cause of the jamming sleeve. The high areas can be reduced or removed using an oil stone. If you have doubts about knowing which areas are high you can colour the shaft with a whiteboard marker or with chalk and do a test fit. The high bits where it jams will be wiped clean.

I haven't tried using my left leg with the 348 and don't remember seeing anyone else do it either. I suspect it might be awkward having to hold the bars and lift your foot so high. It works OK doing it off the bike on a Bultaco though (but on the other side). You've got me wanting to give it a try now

I've got a MK2 MAR and I think the exhaust is the same as yours and yes the rear guard needs a piece cut out to clear the exhaust pipe and yes the muffler is close to the tyre. The mudguard I used is a Gonelli plastic universal rear.

Not certain what you said there but am thinking you were hit by the kickstart because the timing is out and you want to know where to set the storage position of the kickstart lever. Next bit about first and second kickstart setup I'm totally lost. The return stop should hold the lever at between 1 and 2 o'clock. You should start the starting stroke with the lever at about 10 o'clock and with the piston just past top dead centre. Use the clutch to get the lever in the right spot after you position the piston. Don't worry I'm still recovering from a fairly severe calf impact from trying to kickstart a Bultaco with a faulty capacitor. The wound has healed but I've still got a beaut haematoma and it happened a month ago.

Yes some model DT175s had the same diameter (but longer) fork tubes. TY175 is 30mm so you are looking for for DT175 ABCDE. F and later are bigger diameter. Unfortunately they are as old as TY175 fork tubes so good luck finding any that are in better condition. You may do OK with some models of CR80 and other 80cc MX bikes which also had 30mm fork tubes and are newer than TY175 era

Both. They take up no floor space that way. The black frame is Bultaco Campera (project). The red 348 frame came with an almost-complete 348 which I was doing up to ride, then got my "good" 348, now that other one is spares. That red 348 frame is fairly rusty but might be useful for something one day. That other frame is a Yamaha frame that is very sad but I couldn't bear to throw away (spare/project). I can only lift them up to hang them if there is no motor or wheels fitted.

I've seen it done successfully on a TY250 twinshock using a 3/8" UNC bolt at each end

Better late than never. Here are a couple of photos of 348s. One has the loops and I think it is the final model 348 frame. The other one is my 348 ride bike and the side pieces are made of curved 3mm steel plate welded to the frame rails. It was like this when I got the bike 15 years ago and it works pretty well so I have left it as-is

Fork spring preload spacers are used to tune the preload to give you the right "sag". You adjust the sag with the bike assembled by taking the caps off. If someone rode it successfully before you got it there is a good chance that the sag will be in the ballpark already. With fork seals in your 349, you can use two skinny ones or one wide one. You are only limited by the depth of the hole below the retaining clip. Yes, In Motion sell the skinny ones and using two skinny ones was common practice when the bikes were new, and is still commonly done and it usually works well. Some people seeking to reduce the friction fit only one (wider, double-lipped) seal and some people reduce the tension on the tiny springs that hold the lips against the tubes. It's a free world. What you are doing has a good probability of success. SKF have started making fork seals from some modern fancy low friction material and they are available in your size and are expensive. I've yet to try the SKF seals and the Spanish forks I put together last week (Bultaco M85) have the In Motion seals in them. The Spanish forks I did before that I fitted a single 10.5mm wide seal (Bultaco M49) and they worked fine too. One problem cropping up with our old bikes is that the sliders can develop enough wear to cause the tube to move about too much (radially) in the slider for the seal to work properly. Modern forks have replaceable bushings in the sliders but the old bikes don't have this. If the play is causing problems, they can be machined out to take a sleeve or maybe replaced with less-worn second hand sliders.

The big lips point downwards. Small lips (if any) point upwards. The side with the writing faces up. If you have two seals per leg, yes both seals go the same way up. What spring spacers are you asking about? Those forks sometimes suffer from a plastic part at the bottom of the damper rod becoming a tight fit in the hole they go into as the forks bottom. You can test for this by working the sliders. If they stick at the end of the travel, it is a good idea to machine the part back to size or make aluminium replacements while the forks are apart. They are white/translucent plastic tapered cylinder shape and fit between the bottom end of the damper rod and the slider. They are called anti-bottoming cones

Yes it is good to make a drain hole. Whatever way the water gets in, by condensation or by getting sucked in with the cooling effect of the warm casing going under water, a drain hole will allow the liquid water to drain out. I use both a vent and a drain on my magneto casings. I usually make a plain hole about 5mm diameter in a place that is unlikely to be blocked by debris. Depending on how free-flowing the vent system is and how cold the water is in the creek, some water may be drawn in through the drain, but of course any water drains straight back out again. The only weakness with the drain concept is that if the bike engine is submerged for a long time, the casing will fill up, whereas if there is only a vent it will suck a bit in, then stop filling. It is good practice to remove or loosen the magneto cover after a wet ride or after washing the bike so that it drys out fully inside, even if there is a drain and a vent, to minimise corrosion.

Alternatively, you can buy the bolt as a Yamaha part. I've seen them advertised on eBay Can't see any at the moment though

Pretty sure I machined the nut, leaving just enough hex there to tighten it with

There are two reasons why people remove the bottom rails and fit a structural bashplate on Montesas (and Bultacos). One is that the original tubes become so badly damaged from impacts that fitting a structural bashplate is cheaper and easier than replicating the original design. The other is the improvement in ground clearance without raising the C of G. Montesa and Bultaco eventually moved to using the structural bashplate design in the late 1970s (Cota 349 and Sherpa T 198/199A). From what I've seen in old photos, it is a concept that appeared in about 1968 or 1969, initially on the Sammy Miller Highboy Bultaco frame. I reckon if you did it to a Cota 247 or an early Bultaco, you would have to be very careful with the design to avoid reducing frame integrity, which is marginal already on those bikes.

The third model 348 (1978?) also has those tubular loops for case protection

are you saying you can make this gear from a drawing at a lower cost than buying the part from Beta?

From what I remember, the narrow spacing was considered a success for making the front end narrower and a failure because it jammed up with debris too easily and they went back to wider spaced fork tubes again. I'm thinking the narrow spacing triple clamps came out in about 1981 and by 1983 they were back to wider spacing.

I'm lost now. I thought this was about front tyre side clearance on an MH200

That's true that the exhaust header is probably the same shape, but the Alpina frame on some of the models with the Pursang triple clamps is different to the M199 and M199A Sherpa T frames and those same Alpina models have longer fork tubes than the Sherpa T, which increases the clearance to the exhaust. I have a M138 which is one of the Alpina models with the Pursang/Frontera triple clamps and preventing the front mudguard from touching the exhaust (and also making sure the front tyre knobs miss the mudguard on full compression of the forks requires a great deal of care when setting it up. Yes the bigger Alpina/Frontera front hub/brakes are amazing, but are a fair bit heavier than the Sherpa T front hub/brakes

Some people do use Pursang/late Alpina/Frontera triple clamps on their Sherpa Ts to increase trail, but beware that the front guard may then hit the exhaust pipe if it is a standard exhaust header. I didn't notice what was done with the steering stops and haven't tried it myself. I like the way standard late model Sherpa Ts steer when the suspension is set correctly so am not tempted to make changes.

What you have described is an indication that the trail dimension is currently less than ideal. You can increase the trail by lowering the rear of the bike or raising the front, or both. It can also be increased by reducing the offset as you have said. Riding technique also has a big effect on what you are experiencing. For the front end to work properly in tight turns on many twinshocks, the bike needs to be leaned towards the inside of the turn (probably a lot more than you think is normal) and the rider's weight should be on the outside footpeg.

I've bought some of these to get the pads https://www.ebay.com.au/itm/New-Chain-Tensioner-Tentioner-Universal-Fitting-kit-and-pad-motorcycle-classic/222778684239?hash=item33dea4f34f:g:hnQAAOSwqu9VJP1M When I look at eBay it says 12 UK pounds

What does your tensioner look like? There are few different types and some are easily available at low cost