feetupfun

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.

http://twinshock.org/content.aspx?page_id=0&club_id=922050 There are alternatives to AHRMA

Yes the aluminium tank with fibreglass cover a good thing. I was after a tank for my M85 and was thinking about buying the Sherpa T tank from Inmotion but really wanted the Alpina shape and fuel capacity. Luckily I was soon able to buy another M85 that has a decent M85 fuel tank. I also have an M80 and two saddish M80 tanks and am trying to decide whether to fix up one of the old tanks or get a new one from Inmotion

How well the anti-bottoming will work will depend on how well you can match the original shape. The way you achieve the shape is not important

looks good shakennstirred. I've also seen a trials OSSA with a repainted steel KD80 or KDX80 tank that looked good

are you saying you saw a new replacement fibreglass over aluminium Alpina or Sherpa T tank?

Yes it's a common failing in those forks. The flare can be machined off which is what I did. I've also seen people make aluminium replacements

It's a fairly common procedure for people who rechrome fork tubes to straighten them before they rechrome them so if you want you can probably get yours straightened quite economically

If you line the bends up in both tubes so they are both point the same way (either forwards or backwards) you will have the best chance of the sliders moving freely

I can't remember if this bike was new to you or you've had it for a while before you broke the axle clamp. Welding up the axle clamp shouldn't do anything like you are seeing there unless the shoulder of the axle clamp now sticks out inwards compared to what it was before. If you are not familiar with the bike, it is possible that one or both of the fork tubes was already bent and you are reassembling the forks with the tube bend in a position that causes the problem you are seeing

If the motor has been sitting for years without the big end covered in oil then it would be a good idea to replace the conrod while it is apart. It's fairly common for a big end that has been sitting for a long time to show no movement or play but fail quite soon after going back into service, due to corrosion of the rollers or the surface of the pin. You can always have a look through the oil slot in the big end for any tell-tale marks (lines of discolouration running across the pin where the rollers run) on the big end pin. The bloke who rebuilds my cranks prefers to push them apart to have a better look but you might not have that luxury. The usual failure mode for two-stroke trials bike big ends is running the engine after a long static storage rather than due to hours of use. If you know it has been run regularly over the years then there probably isn't corrosion in the big end. I've got a few 1970s trials bikes that still have good big ends and have done lots of trials and trail riding work, because the oil in them has never had the chance to dry out.

Same as moleman except I machine the drum surface with a lathe. My "jig" is a piece of steel rod that is a neat fit in the backing plate hole and with a male thread cut on one end so I can pull the backing plate against the chuck jaws with a nut.

I have an early M49 (4900100) rider and from memory, the primary chain tensioner that it came with is different to later M49 and M80 engines. Maybe just the spring is different. I can't remember if the shape of the arm or the mounting arrangement was different, but it did have a brass rubbing block rather than a rubber wheel. After working out that the strange damage marks I found inside the primary casing were from a tensioner coming apart, I run it without a primary chain tensioner. Another thing to watch out for is that if it is an early M49 it might have a clutch that is different to the later single row chain clutches. One of my M49 engines has original fibre plates and the steel plates have no holes. I've not checked if later type (all-steel) plates are interchangeable with that clutch

I can't be sure of the question. Maybe "trials" and "trial" have been used instead of "trail"

http://amalcarb.co.uk/mk-ii-concentric-series/2600-series/needles.html sounds like the markings for an AMAL needle This link should take you to parts listings for MK2 AMAL concentrics so you can look to see what needle your carby would normally have

Sounds too loose, but they are usually able to rock a bit in AMALs. What markings are on the needle? If it's a foam filter, it should be oiled. If it's a dry paper element, it should be dry. They normally have a foam filter element The needle is normally held in a hole in the throttle slide. I figure that's what you mean by throttle seat.