feetupfun

Not true in Australia. We haven't had access to IRC tube type rears for about 5 years now.

There were quite a few design changes made during the model 49 production. Frame design, rear hub design, brake pedal design, seat/sidecover design and engine outer casing design all changed between the first and the last

When fitting a steel or cast iron liner to a previously chromed drum Bultaco hub, the new liner is sometimes made with an ID smaller than standard/nominal ID to minimise the amount of hub material that has to be removed ie machine the drum just enough to clean up the previously chrome plated surface. The shoe linings are machined down below standard/nominal OD to suit the new drum diameter.

I've bought from there. It did take a fairly long while to get the part but I would buy from them again because the price was reasonable and it was the only place that had the part at the time

Same concept as a dirt bike but takes more skill to do it smoothly compared to a dirt bike due to heavier flywheels and bigger gaps between the upper gears

Sounds like not quite enough pressure

This brochure photo shows how they looked when they came in Australia. Dealers would have fitted mirrors if the customer wanted the bike road registered. No battery, no indicators, no mirrors

I would think that most twinshock TY250s have had the lights and wiring for them removed. Yes it makes sense to remove the lighting stator coil too to reduce bike weight, but most people don't bother. My tips are: Keep it all in case you change your mind or want to sell the bike. Take care not to damage the ignition stator and its wiring while you are at it.

The 125 Bultaco Trials cylinders are centre exhaust port while the larger Trials Bultaco engines are side port which the twin front downtubes on your frame will not suit. Larger motor Trials Bultacos have single front downtube frames

Clutch slip on an all-metal clutch is not likely to be due to the type of oil. I suggest first checking for free play in release mechanism (most likely cause) If it's not that cause, consider that your motor has been rebuilt and the force needed to kick it over is greater than before the rebuild so if they used the same old plates and springs, it could just be that the springs are a bit tired/sagged/short and were adequate for the worn motor but not now.

If that was mine I wouldn't ride it with that rim due to the loss of strength of the metal where the spokes attach. It's fairly common to have to replace rims on off-road bikes due to internal corrosion

Your rear rim should be a tubeless type. Maybe post a photo showing it so we can tell if someone has fitted a tube type rim.

Yes that's the final version

Well the frame is not particularly early in the 187 production run. I don't know how many 138s were made but I'll see if I can find out.

Well I would have a good explanation if you had said your Alpina was a model 188 Alpina but not so good an explanation for a model 187 Alpina. The models 187/188 Alpinas are the models that followed on from the models 137/138 Alpinas. Bultaco are well known for bikes of one model coming with parts from another model, especially near the beginning and the end of the production run for the model. Their inventory control for components was not as sophisticated as some other manufacturers. So it's easy to imagine that there could have been some model 138 motors left over when they ran out of model 137/138 frames and the best place to put them would have been in the next model Alpina. What seems unusual though is that they put a 138 (350cc motor) into a 187 (250cc) bike. To help solve the mystery it would be valuable to know the (approximate) engine and frame numbers of your bike.

While the frames are not all the same steering head angle, all the Sherpa T triple clamps have the same geometry however the early ones are made for fork tubes that have a tapered connection at the top. Your tubes being non-tapered at the top limit your choice of triple clamps to Sherpa Ts after about 1974. If you are in a rush to get it finished, the Alpina triple clamps will work, but you end up with a lot more trail and less wheelbase and the front guard will be very close to the front downtube on full fork compression. Some people like the steering/handling with the Alpina triple clamps. It is very different to a normal Sherpa T.

Excellent. They are a good reminder of how much better modern tyres are

On mine the brake pedal up-stop is the engine cover. It's the perfect height with the standard footpeg location. I've just now looked at you photo and can see that your engine cover is missing the section that the pedal usually comes up against as a stop

I checked out an OSSA kickstart lever today and as Woody says, the spline diameter is way out compared to a Bultaco so the Sherpa T I have seen locally probably has a Bultaco bottom modified to suit the OSSA lever

Yes it's a normal thing to refurbish wheels. It's an economical way to get your bike looking good and nice to ride. Many riders do their own, motorcycle workshops can do it and there are even places that specialise in doing it. 1970s Spanish trials bikes are an amazing source of discussion points and the rear brake actuation on the MAR is one of the best conversation starters. The cush drive mechanism for the transmission is another.

I agree with the identifying features of a MK1 mentioned by fourex and add that the shouldered rear rim (and maybe the front rim?) are also a sign of a Mk1 MAR. The Mk1 came with a fibrous bashplate that has fortunately been replaced with the later aluminium item on yours

That's a pretty good price for an OEM spoke set. They are about $AU120 including taxes here and your currency is on par with ours. That sprocket looks expensive to me. A JT brand 13T 428 sprocket from my local shop is about $15. It's amazing what parts are still available from Yamaha

I see there are fork sliders for 4RT Tech forks for about 450 euros and 4RT Showa fork sliders for 308 euros from CMNSL

Be careful there are two different OSSA splines

Yes I had a cranked one on a Bultaco. It was fine. You could put a crank in yours if you didn't want to buy one