feetupfun

The reason that an ideal points gap, or an ideal range for the gap to fall within is specified by the manufacturer, is because the sizing of the capacitor is chosen to match that gap (and the area of the contact surfaces of the points). The actual gap is not particularly important in the scheme of things, but the position of the piston/crankshaft when the points start to open is very important. On some bikes you can rotate the backing plate or change the points gap to adjust the timing and on other bikes you can only change the points gap to adjust the timing. As you move the backing plate away from the mid position in either direction, the voltage being generated in the stator coil (the primary circuit) at the time the points open will be (slightly) lessened, compared to if the backing plate is in the mid position. This means that if you want the strongest spark, keep the stator near the mid position and get the timing right by adjusting the points.

If you want an easy way to ride your Cota at night and don't need to get road registration, you can use a cheap LED light bar that will fit across the front of the fork tops, do a great job of lighting the way and not be sensitive to voltage. Bikes like yours can be started with the de-compressor engaged, if you use the type that are fitted to some chain saws. This type are "cocked" by hand prior to starting the motor, and as soon as the motor fires, they snap shut automatically. A friend has fitted one on his 325cc Italjet in an effort to prolong the life of the notoriously weak kickstart shaft, and it works beautifully. No good as a kill switch though!

Yuk

OK If you are familiar with the Bultaco then I would describe the 348 as compared to the Bultaco 325: Motor has faster pickup Motor feels a bit more powerful Motor not as smooth as late model 325. Similar to first model 325. Higher footpegs (riding position) Feels like you are closer to the font wheel Front wheel placement slightly less important Feels light until you get a bit out of shape Gear selection is sketchy Clutch has unpredictable and delayed engagement More susceptible to overheating (in my climate) Less ergonomic and heavier kickstart action

I find that the Cota 348 and 1977 Sherpa T are a joy to ride but both are hard work in tight sections. They are both suited to sections that are more open and have stable, relaxing handling. They feel different to each other in the handling and steering and which one feels better to someone depends on personal preference. If you are talking about the 325 Bultaco, both the Cota 348 and 325 Bultaco are difficult to ride with precision unless the motor is running perfectly, because the behaviour of the motor dominates the behaviour of the whole bike. If you were wanting the best chance of a low score in modern twinshock trials with tight turns and stop-allowed riding techniques, you would probably not ride a standard version of either of them. If you want a twinshock that feels amazing to freeride and has awesome power, then they are a great choice.

The wearing points that make it run rich are the slide needle and needle jet. A worn slide can also cause a few problems. In your case the plating is coming off the slide, which can sometimes cause the slide to jam (open), which is very dangerous. As far as the sloppiness of the fit of the slide in its hole is concerned, in the case of your TK carby, I suspect that the hole that the slide fits into would be where most of the wear would have occurred, and this wear would have been hastened by the way the plating has been coming off the slide. The plating is chrome which is very hard and the pieces that come off the slide will damage the piston, rings, cylinder bore and engine bearings as they are digested by the engine. If that bike was mine, I would fit a new carby to avoid further damage to the engine. If you fit a new slide, it will probably not change the sloppiness of the fit because the carby body will be worn. Carbies can be resleeved but it is not cheap. If you wanted it to look totally original then it might be worth the cost of resleeving and fitting a new slide. Yes a 3.0 slide will give different jetting compared with a 2.5 While I said that the original TK carby on the A model TY250 worked very well when in good condition, my own TK carby eventually developed wear on the slide needle and needle jet and a few weeks ago, I fitted a new OKO carby and it was back to running sweet as a nut.

My Bultacos and OSSAs have Betor forks. The brand is stamped into them. I can't remember what is marked on Montesa forks apart from the big M. They are similar to but different to Betors on the inside. Montesas had Telesco shocks while OSSA and Bultaco had Betor shocks. What prompted you to wonder about this? The Spanish bike brands had lots of parts made by external contractors. I learned today that a Bulto company made the Mahle branded pistons used in Bultacos under licence in Spain (and a very nice job they made of them too). The handlebars for Bultacos were made by another company, as were the frames and probably lots of other parts (a lot like nowadays where the parts for a new trials bike are made by a myriad of suppliers). In the case of the Spanish brands in the 60s, 70s and 80s, there were import limitations imposed by the government so most (all?) of the components had to be made in Spain. Today's bikes come together from all over the world.

Definitely bent shaft. Will need to split the cases to change it if you can't straighten it enough in-situ. Normal practice when using a strobe on a Bultaco is to start the engine with the cover on then take the cover off. Same for Montesas. Fully equipped workshop would start the motor on starter rollers driving the rear wheel. I have no idea how you got away with starting it that way before, even with low compression.

Fantastic. Thanks for allowing us to enjoy those films. While watching, I kept thinking about how much improvement there has been in tyre and rear shock technology since then.

Nice introduction Dean. Thank you and welcome. I loved hearing that you built a bike with an XL350 motor in an RM frame. I've got a 1978 RM with an SP370 motor in it. I built it when I was a fourth year Fitter and Turning apprentice in 1980.

Nowadays I use a home-made lever tool and wish I'd thought of making such a thing when I was a kid working on my M99 clutch spring retainers using pliers

I've done an early series M49 which has the same design frame and rear hub as your M27 and did it by making sure the sprockets are aligned with each other and the wheel parallel to the frame centre-line then adjusting the spokes to get the rim onto the centre-line of the frame.

Be aware that your model 349 is already an inch longer than the preceeding model (348) and later model 349s. Your model 349 is usually considered a bit too long for trials, compared with other models of Montesa 348 and 349

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