feetupfun

http://www.southwestmontesa.com/manuals.html Many photos of what they should look like on the internet too There are plenty of people on here who are intimately familiar with your bike so if there is something you aren't sure of just post up photos here of what you are wondering about

Use a M212/213 Alpina tank

I've got some early Bultaco front hubs and brake plates that might be what you are looking for, but I need photos to identify exactly what it is you want

Q1 yes you can buy 428 chain sprockets for Ty250 Q2 Chain size/type has nothing to do with gearing. It is the ratio of the sprocket sizes that determines gearing 14/53 ratio = 3.79 = too fast for trials 12/44 ratio = 3.67 = even faster! 12/53 ratio = 4.42 = good for trials - good choice for 428 chain 10/44 ratio = 4.4 = good for trials - good choice for 520 chain

This shows the thin flat sticker I bought in 1975 when I repainted this M99 Alpina

My memory is that the thin flat stickers were all you could buy at Frasers as replacements in the early and mid 1970s

Yes with a 14 it will be crap for trials competition. The BCDE models had 13 as standard. I would need to look up a book to see what A model had. No Idea about the number of links. I usually just buy a 120 link and shorten it to whatever is needed. Going from 12 to 14 on the front makes very little difference to the chain length. If the axle is near the rear end of the slots with a 12, it should allow a 14 with no extra links. You will need bigger than 14 to ride at highway speed.

The modern ones are much more crash resistant, but use a decent adhesive. Some modern ones come with a pressure-sensitive adhesive that does not work well when confronted with petrol, heat and vibration

Sad to hear, Guy

Thermal cycling is another possibility. This is how fuel tanks and magneto casings can collect water too. If the bike is stored somewhere there is day-to-night temperature variation, every enclosed (and vented) space will breathe in and out with each thermal cycle. In spaces like fuel tanks and crankcases and magneto casings and gearboxes, the air cools inside the space at night. Because it cools, the air contracts, which draws in some external (evening) air. If the metal gets cool enough overnight to go below the dewpoint temperature of the air inside, liquid water will form on the surfaces and collect at the bottom. The next day when the air warms up, the metal and the air inside will warm up and the space will expel some air. By then though the amount of water vapour in the air in the space will be less than it was when it entered (because the rest turned to liquid and ran to the bottom). Because of this, the air expelled will take out less water vapour than it brought in. Each thermal cycle that sees the temperature going below the dewpoint with the bike stored will add to the amount of water in the bottom of those vented spaces. While you can block the fuel tank vent and the gearbox vent and the magneto vent during storage, it is pretty hard to effectively seal up the exhaust and inlet of a two-stroke. It's a good thing to run each of your bikes at least every month to clear out the water from the motor and re-coat the insides with oil. I use semi-synthetic premix oil in my fuel because it gives added protection from corrosion damage between rides, compared with full synthetic premix oil. Another thing to consider is that if you run petrol (pump gas) that contains alcohol, there will be more water condense inside the crankcases each time after you run the motor and let it cool, compared with running petrol that does not contain alcohol. That's why racing engines that run on methanol are then run on petrol at the end of each competition.

Adjust the points so they start opening at the correct piston travel before top dead centre with the flywheel turning in the running direction. It is the opening of the points that causes the spark. The gap you end up with (when they are fully open) is not critical but once the points are set to provide the correct timing, is usually between 0.3 mm and 0.4 mm. The position of the piston/flywheel when the points reach fully open is irrelevant. TY backing plates are not adjustable.

The seal can be replaced by removing the clutch camshaft. The clutch camshaft is retained by its adjusting screw on the left side of the gearbox near the gearbox sprocket. To see this screw you will need to remove the magneto cover. The screw has a locknut which will need to be loosened to get the screw out. If the clutch camshaft won't come out with the adjusting screw removed, you will also need to remove the clutch pressure plate (inside the primary drive cover) to let the clutch pushrod move clear of the upper end of the clutch camshaft. There are service/repair manuals available for the B model which has the same arrangement for the clutch camshaft.

As for your fork seals, if you can, just buy seals of a width that takes up the space between the seat and the circlip. That spacer in the parts diagram is not a guide for the fork tube, it is just a spacer. Two narrow seals per side or one wide double-lipped seal per side will do the job of sealing the forks. The fork tubes are held centrally in the seals by the precision-machined bores of the sliders. If you are really determined to make plastic spacers for the fork seals, just make them the right width so that the circlip just touches the top of the seal. Bear in mind that a couple of my old Spanish trials bikes have no circlips on top of the fork seals and I have sealed up the vents in the fork caps and I run enough oil to firm up the last bit of fork travel using internal air pressure, and those fork seals have never moved out of position. From memory I think the seals are double-lipped and 10.5mm wide.

If you use the type of decompressor that resets itself, you set it to the open position using a knob on the end of it, move the piston to the right spot, kickstart the bike and it then closes itself. There is also a type of decompressor that has a handlebar lever so you can open it while easing over TDC, kicking it, and for braking effect while riding. Are you sure your head doesn't already have a hole for a decompressor? It was fairly common back then to have a decompressor hole. Cota 349s do take a lot of effort to kickstart. I have a 348 which is only 310cc and kickstarting it is usually the most tiring part of riding a trial and 349s are even harder to kick over. It would be good to just leave it running all day but it is fairly hot here and they overheat if you leave them idling for too long.

M99 was 325, marketed as 350. Here is my M99. Photo taken in 1976 in my parents' front yard

I could suggest places to try, but no I don't know for certain. The Cota 248 is such a rare bike it might be a good idea if you find out if it is the same part as used in other (more popular) Montesa engines so you can broaden your search. There is a reasonable chance that it may be the same as Cota 348 or 349. A new indexing plunger could be made by a machinist if you have something to copy

The swingarms are different weights because the A model has no stand mount on the swingarm. The B model does have a stand mount on the swingarm. The CDE model swingarm has a stand mount and heavier gusseting than A and B

and yes I have weighed a Ty250 motor but only recorded that it is 10 kg heavier than a Ty175 motor

A model magneto flywheel is lighter than BCDE models A model engine covers are heavier than BCDE models A and B models wheel rims are heavier than CDE models A swingarm is lighter than B model which is lighter than CDE models A model brake plate arms are steel. B are aluminium. D are steel A model has steel tank. BCDE are aluminium BCDE conrods are lighter than A BCDE clutch baskets are different design to A BCDE bashplate is aluminium. A is composite There are more differences that affect the overall weight than this

The best tuned and with the lightest wheel assembly

Further to JC2, Fuel tank cap for 115/116 is push-in while 137/138 is screw-in cap 137/138 frame has different headstock gusseting to 115/116. 137/138 has very thin gussets without folds Some 137/138 have same rear hub as 115/116 Some 137/138 have left side rear brake pedal

I'm thinking this either means south west US or south west UK

I have a theory that the people sensible enough to buy a Beta 200 are often also sensible enough to keep riding one bike until it is worn out. They are not usually a young person's choice for a bike because youngsters are only allowed to ride a 125 until they are 17 or whatever, by which time they are usually quite competent and full of beans and want something with a lot of stick. Riders starting trials or returning to trials when older than the "junior" age group fit well with the Beta 200. My wife started trials at about age 45 on a Beta 200 and loved it.

I'm not recommending this because it will cause the springs to sag prematurely, but I've seen people leave the clutch lever tied against the grip while the bike is parked. If you haven't already changed the gearbox oil you could try doing that. I'm not saying it will definitely work though because I don't know what is causing yours to stick and shiny clutch plates is the usual reason for them sticking rather than contaminated oil. I don't know if you have tried this but if you have somewhere with a bit of room you can start the motor, push off as you select first gear, shift up to 4th or 5th gear then pull in the clutch lever and work the motor against the rear brake. A sticky clutch will usually break free immediately. The higher the gear, the greater the torque on the clutch.

I see you have AMAL hand levers and that the lever at the engine end of the cable appears to have been slightly lengthened over standard. Those two things mean that the leverage ratio for the clutch on your bike is close to ideal for feel and providing enough pushrod travel for complete disengagement. Creaking is usually caused by a dry or rusty or dirty cable and/or dry cable ends. The clutch spring preload on OSSAs is adjustable so that is something else you can experiment with to get the ideal clutch set-up. You can adjust the nuts on the clutch springs so that the clutch has just enough drive to allow the motor to be kicked over with the kickstart lever without slipping, and that will usually allow just enough drive for you to use all gears without the clutch slipping under load.