feetupfun

Yes repair if you are worried. Only you know your own level of acceptable risk. If it was mine and depending on how much life is left in the rest of the bike I would either fit new peg mounts or let them wear down another few mm. Pre-formed peg mounts are readily available and you could fit them a bit higher than original.

Your idea of a swap sounds sensible. I've bought quite a few trials bike fuel tanks from overseas (UK, USA and France) and I'm not alone in doing that so I guess postage cost is not prohibitive to a motivated person. Your tank would be amongst the best (unrestored, original) of its type I've seen. If your tank was here it would sell quickly for $AU200-$300 (GBP 100-150).

Shane it would probably be good to put an ad for it on the Trials Australia website

I would love to be able to buy that tank from you or swap for one of my 115/116/137/138 tanks, but there is a law preventing sending second hand tanks from the UK to Australia.

The photo I posted is a 115 and the cylinder looks different to your 116 because it is a 250 and that is how 250 cylinders looked until around 1974. After they changed the 250 cylinder finning design to a more open spacing, the 250 then looked very similar to the 325/350 cylinder. The common name for motor in the photo I posted is round barrel because viewed from above, the fins form a circle. The round barrel 250 has poor heat rejection capabilities because the fins are too closely spaced. Bultaco realised it was a problem and when the 325 came out it was made with wider spaced fins that form a square when viewed from above. The 250 was later changed to a similar finning design to the 325. Other than the motor capacity and the colour of the stripe on the tank, the 115 and 116 are the same.

The 85/99 tank you have is more valuable than a 115/116 tank

This what your Alpina tank shape should be to fit your frame. This is a 115 which is the the 250 version. The 115 and 116 have the same shape tank. The 250 has a silver stripe and the 350 has a yellow stripe

That looks like a tank for Alpina models 85 and 99. That tank is made for the Alpina frames that don't have the frame element that runs upwards and forwards from the swingarm pivot

I'm in Australia, and every 1970s Spanish fibreglass tank I've lined looks the way you have described it beforehand or worse. It doesn't matter if it leaks or not before you do the job

They are all rough inside and petrol-soaked to start with. The prep work needed for relining includes very thorough degreasing. There's an Indian company making replica aluminium Alpina tanks but they don't make the 115/116 type (yet). They do make Alpina 85/99 and Alpina 212/213 tanks, neither of which look right or fit your frame. Second hand 115/116 tanks are available if yours is unable to be lined. I have a couple but am a long way from Scotland. New replica seats and clubfoot exhausts are available. Good second hand seats and clubfoot exhausts are very rarely seen for sale.

Yes have a look at Shedworks (UK) and In Motion (UK) websites and you'll see tanks they sell like this. Some people make their own. It's not hard because it doesn't have to be pretty. There are different brands and types of resin liner but the one I use is a low viscosity (brushing) epoxy resin from a marine supplier. Yes it is applied by moving the tank around with the liquid flowing to cover all inner surfaces and the excess runs back out. It doesn't swish though. It's much slower than that, more like how warm honey flows. The preparation of the inside of the tank is extremely important for a successful job. If you want to buy a kit, a popular brand seems to be Caswells

Being yours Shane it sure has provenance and there are people who have a thing about them so I have no doubt it will sell easily. I sold my well-used but fully functional 1993 TYZ locally in Gladstone for $2500.

That might work if you work the rear brake against the motor in top gear with the clutch lever pulled in, but it sounds like a fairly hazardous thing to do. Clutch RPM is not a factor in whether it will free up or not.

If you want to keep riding without pulling the clutch apart and servicing it, you will find that riding around in a high gear with the lever pulled in will free it up pretty fast. The higher the gear, the greater the torque that is transmitted by the clutch for the same torque at the rear wheel. Motor stopped, top gear, clutch lever in, your weight on the bike and push backwards with your legs is another gentle way to free it up.

Yes it is a normal thing to use a metal tank under the top part of the old fibreglass tank. Another option for old Spanish fibreglass fuel tanks is to line them with fuel resistant resin.

It is good to know that you are getting some voltage at the fan because it means that the stator coil is working. Yes the DC voltage at the fan is too low. I don't get what you're saying about the capacitor except that you think it s OK.

Yes Maybe What did you find when you measured the voltage at the fan?

https://www.ebay.com.au/itm/MICHELIN-TRIAL-X-LIGHT-FRONT-IRC-REAR-TUBED-TYRE-SET-NEW-BRAND-NEW-STOCK/233866345145?hash=item3673853ab9:g:-6sAAOSwDEtaAdDy&frcectupt=true

Check what is going on with a multi-meter. The most common reason for the fan not running on a trials bike is the thermostatic switch not making/closing.

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