feetupfun

Cable and mechanism both need free play

Yes you should check the adjustment. If that is OK it probably needs new springs and/or plates. New oil does not usually make any difference to a clutch that has sagged springs or worn plates.

There are clear period photos of Bultaco Wasps in "20 years of twinshock trials" volumes 2 and 3

if you have a leaking crank seal on the drive end of the crankshaft, you can test for it by measuring the quantity of oil that comes out when you change the oil. The discolouring of the oil with use you describe sounds pretty normal to me. If the oil is doing its job, it holds the fine wear particles from the clutch plates, bearings and gears in suspension and these fine particles change the appearance of the oil. Also if you are looking at the oil soon after riding the bike, the oil will be full of microscopic air bubbles, which also change the appearance of the oil. As far as change frequency goes, base it on the number of times you have to refuel the bike, or number of riding sessions, rather than in elapsed time. However if you don't ride much, the 6 months oil change is a good idea because oil absorbs water from the atmosphere whether you ride the bike or not. If you ride in water, check for contamination of the oil after each ride and change it if there is any water contamination. Trying to answer your question about a possible link between the condition of the gearbox oil and a smoking exhaust - no, old oil will not leak more easily through the crank seal than new oil. Maybe you are worried that crankcase fumes are leaking past the crank seal and discolouring the gearbox oil? If this is a problem you could test for it by extending the gearbox breather tube and putting the end of it in some water with the motor running and see if bubbles come out. Another thing you can do to put your mind at rest is to take note of when the pipe smokes. As has been mentioned earlier, oil condenses inside the exhaust when you ride as if you are competing in a trial, and it revolatises when the exhaust gets hot (when you ride up a long hill, or ride along a road at speed). You should see more smoke when the pipe is hot, compared with when you are puttering around gently. It is good to give the bike a hard run and heat things up, because apart from cleaning out the exhaust, the piston rings may otherwise become gummed into their grooves.

maybe because the TY fork tubes were bent in a frontal impact????

Standard TY250 twinshock frames have straight front downtubes. That one has either had an accident, or someone has deliberately bent those tubes to change the steering head angle. Have a look with the tank off and see if the top tube is bent too. I've seen a few with the top tube bent from a frontal impact

125mm from the top with forks fully compressed and springs removed works very well. If you don't care how well the level is set up, the A model has a different volume to the BCDE models and my specs sheet for the C model says 162 ml/leg of 10, 20 or 30 wt oil. Unless you are pretty heavy, 10 WT works well. If you are heavy then go for the 15 WT. Gearbox is 1000ml and any lightweight gearbox oil is OK. I use Castrol VMX 80 or Castrol MTX and they both work fine. Book says 10W-30 motor oil but remember the book was written in 1976 and things have moved on a bit with oils.

I agree with Jon about the financial benefits of the old bikes not depreciating. Trouble is I tend to spend any savings on restoring multiple old bikes

It looks like it was set up for a small rider with the fork tubes slid through the clamps like that. Unless they have limited the fork travel, the mudguard will smack into the lower triple clamp. That might be why they don't move far Standard wheels on Cota 200 are 21 inch and 18 inch. That front hub is a Honda design that was introduced to Montesa trials bikes in the early 1980s, and may be from a later model Montesa 242 or 349. Those front hubs are notorious for the spoke flanges breaking

I generally practice ride after it cools off a bit in the evenings just before dark I wear a thin T shirt and long cotton work pants in summer. If you think you might crash though you should wear your elbow and knee guards. I don't do huge obstacles or take chances in my summer trials clothing, its really just for fitness and to maintain riding skills. Chilled water in the camelback helps if you are riding for an extended period The creek cool-off technique works well too Another thing to do is to go out straight after a storm while it is still coolish Mix up the trials practice with a bit of trail riding to get your body temp back down

The tap filter is inside the fuel tank and is attached to the fuel tap. Filtering the fuel as it goes in is a noble act, but this filter may still be causing a restriction to flow. You did say you changed the tank cap hose, but didn't say that you tested the fuel flow rate to the carby. That would prove if there were any problems with fuel supply caused by tank vacuum or flow restriction. It is also possible to get a vapour lock in the fuel line that stops the fuel flow. I can't see the fuel plumbing on your bike to know if that is a likely problem or not

you didn't mention checking the filter in the fuel tap and you've got some pretty bizarre things going on there (a steering wheel and a kill switch on the radiator hose)

suggest you fit a new air filter before it gets sucked into the carby and reeds. The filter will be quite crumbly by now Not going to get into the premix debate also suggest you post in either "Yamaha" or "air cooled monos" forums

might sound a bit obvious, but some shocks only have damping when they are the one way up, while other shocks work either way up. For example, standard spec Falcons only have damping when the shaft is at the bottom. I've not had Rockshocks to know if they have to be a certain way up to work. I have had a terrific run with four pairs of Falcons since about 2003, and find the action to be extremely good in competition trials sections. All four pairs still work as well as when they were new, and they have only needed oil, seal and bump stop rubber changes to keep them going. For general (trail and play) riding however, I find that Falcons have too little compression damping and would recommend Betors for that, because Betors have more high-speed compression damping.

it helps to let the clutch partially engage a few times while you are holding the shift lever down (with the motor running). If it didn't go into gear fully before you do this, you should be able to feel and hear it going in fully by doing this. If it did go in fully the first time, there will be no extra clunk when you do this.

the best way to do non-invasive condition monitoring on the effectiveness of the rings in a two stroke is to look at the surface of the cylinder, looking for carbon deposits (brown smudge) in the area wiped by the rings. If the rings are leaking there will be a thin film of carbon there. You can use an endoscope through the plug hole, a torch or endoscope through the exhaust port, or take the head off to check this. If you have owned the bike from a time when you are sure it had effective ring sealing, you should be able to tell that the rings are worn by how hard it is to push over compression, and if the low-RPM end power has reduced. Some 2 stroke trials motors develop a 4 stroking/misfiring mode above mid RPM when the rings are worn out, but this is not a universal symptom. Sometimes it is necessary to rebuild the top end based on piston wear, even if the rings are still sealing OK. For this you will also need to have known how quiet the piston was originally, or to pull the cylinder off and do some measuring.

what little step? all I can see in your fuzzy photo of the steering head tube is the top bearing seat maybe its just a terminology thing? the seats in the headstock tube are what the bearing outers rest against. The bearing inners go on the stem/axle Bearing parts for those sort of tapered roller bearings are called outer race, inner race and rolling elements/cage

Top head stock looks normal and ready to accept upper bearing outer race Yes you need to remove the old lower race before fitting the new lower race Sammy Miller Products sells footpeg kits for TY175. The RH footpeg from the kit sticks out too far for the kickstart to clear it. Some people run without a footpeg spring on that side to allow for kicking. If you have to have a spring (to pass tech inspection at a trial) you can make a catch to hold the peg up when you start the motor. The SM footpeg kit pegs tends to sag with use. Also if yours is a TY175JC or TY175JE (with the stand mount as part of the LH footpeg mount), then you will lose your stand mount if you fit them. There are lots of better aftermarket footpegs but you would need to make your own mounting plates to use them.

If the conductor in the HT lead where you cut it was nice bright copper it should be OK. Plug caps can cause problems too and fitting a new one is pretty cheap. Some just keep turning even after they are fully screwed on because all you are doing is screwing the thread into the hole up the middle of the lead. Generally the cap is mainly held in place by friction between the OD of the lead and the socket in the cap. No you can't fit a new HT lead directly to the HT coil winding. Have you checked the LT wiring and the LT connectors for damage? If you still have the keyswitch fitted, you should do a test run with it unplugged at the coil end. You may have a problem with it's wiring or internally.

What about the HT lead and plug cap? Does it still have the original ignition keyswitch fitted (under the left side of the fuel tank)? A much better test of the rings sealing would be to look inside the bore for evidence of blowby (through exhaust port or plug hole or to take the head off). Compression tests give widely varying results on the same motor depending on how oily the rings are and how fast it is cranked over and for how many revolutions it is cranked over for.

whatever you want. Fixed points timing is set as a compromise for low and high rev operation. If you want to set you electronic ignition for the smoothest and most reliable response at low revs, set the timing to be a bit later than standard fixed setting at low RPM. If you want to maximise top end power, set the timing with the low RPM setting at the standard fixed setting. It really is something you should play around with until you are happy with how your motor runs for the way you like it.

Check the conductor inside the HT lead where it connects to the plug cap Check the HT lead for touching the exhaust - I've seen a few KTs with melted HT leads Check killswitch and killswitch wiring (disconnect it at the HT coil end) Do you know if there was any motor work done before you got it? (it might not have the right length rear piston skirt) Are the rings worn out, or not sealing for some other reason? (two strokes can still start OK but then run in a way that makes them sound very rich if the rings are not sealing well) Did you run it before you got the carby overhauled? (ie did you get the carby overhauled because of the problem) Are you sure the start enrichening device is closing fully?

I'm interested to see how you get a significant increase the steering lock. On most of the TY250Zs I've seen the owners have increased the steering lock by grinding the frame away where the fork tubes touch. This provides a modest improvement, but is still way less lock than what is on the air-cooled mono Yamahas. I'm sure you will enjoy riding the bike, the suspension action is well ahead of what the other bikes of the early 1990s had, the main frame cradle is amazingly rigid and robust, the big diameter forks tubes resist flex very well and the motor and gearbox are pure bliss to use. They are great to ride in everything except extremely tight stuff

Footpeg lowering kit? That would be pretty interesting on one of those bikes. The footpegs are already as low as the bashplate. I rode one of these (first model TY250Z) for a few years in the late 1990s and could not come to a happy agreement with some aspects of the design. What caused me grief was the very limited steering lock, and the long wheelbase. It made for a very big turning circle which might be fine if you like hopping the bike in turns, but I don't.

I think it was MT125 front end on that one. He has a couple that are very similar. The tank was custom made by the rider to clear the fork tubes and look something like a TL125 tank