kingscorpion

You'll need SAE 10W30 for the clutch and SAE 90 for the gearbox (API 4 if possible). 300 cc in both cases. I think that is 10,5 GB fl oz. Mix can be 1,5% with modern synthetic oils.

The 248 is a decaffeinated 349 that was produced to avoid higher taxes in some countries. It is not an interesting bike unless you are a collector.

The frames with tubular loops welded under the front of the engine correspond to the "second series" 348. Those bikes also had another improvements like an optimised shifter for the gearbox, the air assisted fork, and many other details.

Both numbers should begin with 51M. That was the factory code for 348's to 349's and 350.

No Bings on Montesa trials. You need an Amal 2627/411 with 150 main jet, 20 idle jet, 106 needle jet, 2B1 needle, and 3 cutaway throttle slide. But the symptoms you describe are more likely to be electrical. I'd check the ignition point.

Change that crank seal and the blue smoke will disappear. It's a very common issue with these bikes.

Do you happen to have some pics? It would be easier to see what kind of mod you've found.

The only reason for that rubber could be to avoid moisture if the castings are damaged.

As far as I know, every Montesa hub is ribbed unless it has been modified by its owner.

RAL 3020 is very similar to the Montesa red.

I don't know if the 247 will be suitable for your swingarm. It's not only a matter of chain side, but also of physical measures. The 123 swingarm can be narrow for the tyre, be careful.

Not sure if you're gonna need a 172 swingarm ... But the rear 18 is the best option, of course. You'll find all kind (and prices) of tyres for that rim.

The easiest way to get that case out (after having released all the screws) is to press the clutch lever.

Just let me know if you need some help. But I'll be offline until next tuesday. :-)

That's the easiest way to do it, allyboy. I'm not sure if you also could buy a complete 21 wheel from another trials Montesa. The hub must be the same, but maybe you'll need some spacer.

Everyone of us was a novice sometime, samwisemcg. And everyone of us found good people that helped him to learn. That's how life goes. :-) And thanks for your post!

I'm glad that you succeeded with my advise. It's a typical problem with Montesas. By the way: the puller you've used is very similar to the official tool for that bike. It's tougher than the legged pullers.

The rear tyre is not hard to find here in Spain, but the front one is almost impossible. If you want to ride the bike, you'd better change it for a 21.

My MkI goes with the standard rear sprocket and a 9 teeth front one. 10 is unusable for serious trials. I know many pilots of those years and the first improvement they did was to change the 10 teeth for the 9 one.

I'm glad you like it. It's a nice machine. And a very special part of my life, now that John has passed away.

Next time, just use a cotton cloth between the clutch and the primary drive gear. Like this: You'll block the mechanism without damaging anything.

There were seven different swingarms for the 247 along the years, but only two chainguards: the fiberglass one from 21M0001 to 21M4381, and the plastic one from 21M4382 till the end of its production.

I'd take a look at the clutch oil. Almost sure that is getting to the crank through the oil seal.

Thanks, Johnmartin247. I really love both.

My 247 MkI ex-John Haberbosch. And my 349/4 at Robregordo 2008. The guy in red is Manuel Soler, who developed this bike after leaving Bultaco.