feetupfun

because of the initials origin, we should say b.e.t.a

our OSET 16 was well and truly worn out after 3 years. What sort of condition are they in?

They are not commonly seen in competition, probably due to their low production numbers, and high desirability as a display item. I've only ever ridden one, about 20 years ago, and my recollection is that it was not remarkable in any way apart from having a very interesting appearance due to the long shockie mount horns and the elaborate expansion chamber exhaust. It did have a heavy and high feeling about it (compared to the twinshock TY250 I was riding at the time). The OSSA was for sale at the time, and the test ride put me off buying it.

It is unclear which are you calling the main engine casings. There are two inner casings and two outer casings. Inner casings are also called crankcase halves or cankcases The casing that covers the magneto is usually called the magneto cover while Yamaha call it the LH outer casing.

There is nothing unique about the properties required for a condenser on an SWM trials bike. The capacitance required is the same as for any other set of ignition points that have faces of a similar diameter and run a similar gap. Because of this you can safely walk into an auto electrical shop and look at the range of "points/coil" condensers and select one that has a nice mounting lug. Where you might have trouble is finding a shop that actually sells condensers for points/coil ignitions, because for many years, cars, motorbikes, chainsaws, lawnmowers, and outboard motors have not used points/coil ignitions. The last one I bought went on my 1968 Bultaco and it was a condenser made for a 1960s Mercedes car engine. It was BOSCH brand and has a nice big lug and a long piece of cable

It's good to know which bike we are talking about now (TY175). The reason you have had the result that you have by reducing the preload spacer length is because TY175 springs have a special design feature. The coils are wound with a section a few inches long with almost no gap between the coils. This creates a dual rate spring. When the legs are fully extended in use, the section with the small gaps still has gaps, but as the forks compress, the coils in that section of the spring touch each other, which causes that section of the spring to effectively become a spacer. Because there are then less active coils in the spring, it has a higher spring rate for the remainder of the fork travel. By shortening the spacer from its standard length, you have increased the proportion of the fork travel that has the lower spring rate. This benefits heavy riders too, because they can fit a longer spacer and cause the higher spring rate to cut in at less compression of the forks. You can test for correct sag with you aboard and with all your weight on the pegs, and none on the bars. The forks should ideally be at 40% to 50% of their total travel, if you have the spring preload right for your weight.

OK to answer your question. I'm 5' 10" and have a long arm reach for my height. I run the bars in different positions on my various twinshock bikes. On my standard-framed bikes, the furtherest forwards is with the rise section about 10 degrees forward of the line of the fork tubes and the furtherest back is with the rise section in line with the fork tubes. In the case of a standard TY250 twinshock I use about 5 degrees forward of the line of the fork tubes. Generally I find that the limit for moving them forwards is that I can't get my weight far enough back for all situations. I also find that moving them forwards and back makes a huge difference to the amount of kickback from the front tyre hitting little things off-centre - much more of an effect that fiddling with fork spring preload, spring rate or oil viscosity. Too far back and my hands are too close to the line of my body when the bike is acsending steeply under power. Also too far back and my knees get in the way of the bar ends in some situations. On one of my TY175s I moved the headstock forwards by 25mm mainly to give more room to move around without the bar ends being too far forwards of the steering axis.

Bar position, rise, sweep and width are all meant to be used to set the bike up to suit the rider. It's really up to you to set the bars up how you like them. Some people like a lot of room to move around. Are you talking TY175 or TY250? Fork oil viscosity can also affect the way the forks react on sudden compression

what's alkylat petrol?

bambam n chunx, I've read your posts and suspect that you may have added too much petrol down the spark plug hole for it to fire. If you have liquid petrol visible on the plug, you have too much petrol in there. I suggest you drain the carby, leave the fuel turned off, kick it over or push it along with the throttle fully open and the spark plug removed and the plug cap located where it can't start a fire when the excess fuel gets blown out of the engine. When you have dried out the motor sufficiently, refit the plug and have a go at starting it, first with the fuel still turned off You could also turn the bike upside down with the plug out and turn the motor over with the throttle open to get rid of excess fuel Carby cleaning in an ultrasonic parts cleaner bath is very effective and the solution you use in it should be chosen for what you are trying to remove. Fuel residue, dirt or corrosion? You mention a choke jet on the AMAL carby. I take it the carby is a MK2 AMAL, otherwise it would not have a "choke" (enrichment circuit) I've only ever known 247 Cotas to come with MK1 AMAL carbies which only have ticklers I can post your photos onto the forum via my phone but you might not want to send a text to Australia due to cost!! I'll send you a PM with my email and phone number No I can't - your message box is full

as far as problems that have appeared over the years on the TY250, for now all I can think of is corrosion of the outer engine casings (BCDE models) and the inner bush for the swingarm pivot siezing onto the bolt from corrosion. They are a bulletproof design generally. I have three of those motors in current use and none of them have required the cases split, and one has not even required rings or a rebore yet from new. Never had a frame crack either.

a friend of mine had to fix a bullet hole in the RH inner engine casing in his TY250D so anything is possible when it comes to damage in odd places kee, that bike is a great find and while it is dirty, appears to have had a relatively crash-free life for a trials bike

Some external rotor ignition flywheels on Bultacos are cast aluminium and some are cast in something that seems to have a much higher SG (zinc maybe). There are also different shapes. Yes there are markings but I don't know how to interpret them. I have quite a collection of Bultaco ignition flywheels and can do some photos of various flywheels and their ID numbers if it would help. It would help if you could say which era you are interested in

symptoms sounds like a blocked or part-blocked pilot jet. This time, remove it and have a look through it before you clean it. If there is any crap still getting to the float bowl the pilot jet will keep blocking

That number indicates TY250E sold from 1978 on. Same mechanically as TY250C and D. Lots in common with TY250B also

Plug BP5ES flat oiled foam filter MK2 AMAL has starting device lever on top MK2 AMAL has air screw Cota 348 comes standard with MK2 AMAL concentric MK2 is the AMAL with the square float bowl

it is the first four digits of the numbers that are relevant. It will probably be something like 493-2****** or 493-1********

If you are still having problems identifying the motor, post some photos showing the engine covers, cylinder and head

you could take the cylinder head off and measure the diameter of the bore. TY175 standard bore is 66mm diameter If you have a clever way of measuring, you could alternatively either take off the exhaust pipe or the reed cage and measure the bore The TY175 and TY125 have the same stroke Lots of TY125s have been made into 175s over the years

From memory, it's the pressed aluminium cover that has the OSSA film reel symbol and is held on with two screws. Located on the side of the clutch cover.

Those numbers give 50 pounds per inch

If you want it identified, post up a decent picture of it and have a look at the frame and engine numbers to see what they start with. Yes they sold twinshock TY250s until the late 1970s. The design did not advance since the 1976 model, but there a few changes of graphics after that and different-looking models were sold in different places around the world Before you start it, remove the powdered remains of the foam air filter and fit a new one before that stuff gets sucked into the motor. Clean out the carby especially the pilot airways and pilot jet Clean out the fuel tank and fuel tap Check for spark Motors sitting a long time without a good protective coating of oil on the crank and conrod bearings often suffer catastrophic bearing failure when put back into use. To avoid unnecessary damage to the cylinder piston and rings, consequent to a bearing failure, be ready to shut it down fast if it starts making odd noises.

Some 348 forks had soft springs that needed air assistance and some 348 forks had normal stiffness springs. Be aware that the springs in your forks may be either type so your forks may not need air assistance. I have both types of springs to choose from for my 348 and have found that normal stiffness springs and no air assistance provides a better action, most likely to having less friction at the seal lips.

Have you tidied up the bore of the tubes? I had a set of seized 348 forks caused by being full of water for a long time, and I had to linish/hone the surface of the bores to get the pistons to fit and work nicely