feetupfun

My understanding is that the function of the pickup is to generate a pulse as the magnet passes. Maybe your resistance measurements across the pickup coil are being corrupted by that pulse

Oops! I've just deleted some messages so it should work now

It does look like the header pipe has a tighter bend

I just had some custom made in Brisbane, Australia. Price was fine but but freight might be prohibitive from there to the USA. You can PM me if you want the contact details for the person who made them for me.

It would be helpful to be able to see the triple clamps

I reckon the reason that the location of the handlebar clamps relative to the steering stem axis is unimportant is because it is the position of the handlebar grips (not the bar clamps)relative to the steering stem axis that determines the spatial relationship between your hands and the steering axis. Adjusting the handgrip position by rotating the bars in the clamps allows you to get the ideal fore-aft positioning of the grips. The reason why your Bultaco feels different to your OSSA in turns is mainly the steering trail difference and yes it is great fun to experiment with different front forks and triple clamps, but the Bultaco is quite limited for increasing the trail dimension by how close the mudguard already is to the exhaust pipe. I had a ball a couple of years ago swapping front end bits between a TY250 and a KT250, much as Woody did with his bikes, and while it was great fun and I did manage to make the KT to steer just like a TY250, it looked quite weird and the front mudguard got quite scratched up from rubbing against the exhaust pipe. I also agree with Woody that setting up the ride height and the action of the suspension properly at both ends makes a huge difference to the way the steering works in turns. It shouldn't be surprising because the front and rear heights and the way the suspension reacts to bumps and body movement affects the steering geometry.

The stand on the TYZ in the photo looks exactly the same as mine. I thought that the air-cooled mono stands were different to that

No its different to the air cooled mono stand. It is all aluminium and made from two sections of tubing of different diameter and a pivot end piece machined from solid aluminium. There is an inverted aluminium cup on the bottom end. They are extremely flimsy. I remember having to straighten mine after every trial, and having to have cracks welded many times. Pretty sure I will have a decent photo at home but have not had a chance to look yet.

Yes those extra frame loops were a change made part way through the three years of Cota 348 production. Other changes made through the production were fork springs, fork caps, and to the frame gusseting at the steering head. The brake and gear change pedals also changed through that period. I suspect that the 27mm Mk 2 AMAL carby underwent development in those years too but am not sure of the details of that.

Ok a 6 heat range NGK plug is a good choice in an air cooled trials bike for trials type riding and gentle trail riding. Changing to a fancy plug will make no difference to any fouling that is occurring. Iridium plugs wear slower than a standard plug but it is vanishingly rare for a sparkplug to wear out on a trials bike unless it sees many thousands of km per year. You do have quite a lot of oil in the fuel mix but it more likely that your problem with plug fouling is in the fuel/air ratio. If you still have the standard 27mm Amal they are notorious for wearing the throttle slide, the throttle slide needle and the throttle slide needle jet and being generally crude in their air/fuel ratio control. It is very likely that those parts require replacement and if you do that it will solve your sparkplug fouling problem till they wear out again - and it will run nicer too. Yes a 0.015" gap is OK but I would recommend a sparkplug gap of 0.020" or 0.5mm in my language if you are running the standard points type ignition. Sparkplugs usually come standard set with a 0.040" gap but that does not mean it is correct for every bike. If you fit a fancy modern electronic ignition then I would suggest setting the gap wider than 0.020" to take advantage of the higher performance ignition. The gap makes no difference to the fouling rate, but a narrower gap will keep sparking longer with a fouled plug because it takes less voltage to jump a smaller gap, and fouling reduces the available voltage by leaking current through the conductive fouling.

There are some limitations for riding a trials bike fast. Yes on flattish ground generally OK but in spirited mountainous riding if you try and go downhill fast for too long, the (disc) brakes will overheat. In fast muddy terrain watch for blinding of the radiator air inlet

Yes I use an oxy torch for this too and one time I had to take the oxygen out for a short time. When it went back in the resulting boom was most satisfying

Crankshaft will be the same as TY175. Why did you think it was going to be different? Flywheel might be lightened but would have started out as a TY175 flywheel Who knows what piston is in it after all these years? You probably need to measure the bore before you start looking for a piston kit. You can buy a new or second-hand swingarm pivot bolt for your TY175 to replace the one you cut shorter for the Majesty. Suggest you post photos of the bike

yes the 198B is quite rare compared with the 199B

Its actually a very common problem Will. My technique is a bit different. I drill the steel stud away using a drill guide that fits neatly into the holes through the fins.

man who walks through security at airport with erection likely going to Bangkok

I too am finding the MOTOGP generally a bit boring compared to when it first went to 4 stroke, but I still watch the races in the hope that there will be some racing happen. I'm hoping Bautista gets some podiums on the Suzuki. He seems to be going batter than should reasonably be expected lately. Despite Ducati going so poorly, at least the soap opera aspect of it is entertaining. I find the 125GP races are easily the best to watch and hope the MOTO3 4 strokes replacing them are as much fun.

Maybe Scorpa tanks are made from a different plastic to other plastic motorbike tanks? My understanding is that most plastic motorcycle and car fuel tanks and portable fuel containers are made from high density polyethelene (HDPE) which is used for its mechanical properties and chemical resistance. Are we talking Rotax motor Scorpa fuel tank or Yamaha motor Scorpa fuel tank?

No 30 looked like Stefan Merriman to me

About the 348 clutch springs, the 348 clutch as standard is not far off slipping in the top two gears so the answer is no to less springs with standard plates. I found out a few years ago that there are other plates available that will fit that are the more modern type with friction material, which in theory should allow for less force from the springs for the same torque transmission. I bought some of those plates (Honda CB125 from memory)with the intention of trying them but have not gotten around to trying them yet. There are a couple of potential drawbacks with this approach though: The CB125 plates are quite a bit thicker than the steel 348 plates, so for the plate pack to end up the same overall thickness, there will be fewer plates, which may mean no overall benefit in torque capability relative to pressure plate force due to the reduced effective surface area. The CB125 plates have only half the number of drive tabs that the 348 plates have, and are made of aluminium, so the edges of the CB125 plates may get deformed against the thin steel basket fingers of the 348 clutch or might even shear off. back on the rough engagement, try heavier oil, it worked on mine. I started with a light gearbox oil (castrol VMX80) and it sometimes did protest noisily just as the clutch engaged. I then tried car diff oil (non-extreme pressure additive type) (80-140 I think) and it has been terrific since then. I agree with belldane that if everything is working well the clutch action is very smooth and I find it does not drag when disengaged. The only reason I am interested in trying the CB125 plates is to reduce the lever pressure which at my age I find a bit tiring in tight sections.

Possible sheared magneto flywheel key

Chris unless someone has modified your bike it should not have a condenser or points. It should have a Motoplat CDI. Something to check that is a weakness in the MAR design is that the LT ignition cables come out of the magneto housing underneath and can easily be damaged by the bashplate pinching them against the underside of the motor. Mine had been damaged in that way, but despite the wires being squashed and having conductors exposed, the motor still ran fine. If you search for OSSA on the Trials Central forums or the trials.com.au forums you should find a photo sequence of how I repaired and re-routed the ignition cables on mine out the front of the magneto housing, after a suggestion from Woody. Your ignition may be getting affected by this problem. Other things to check for are loose motor mounts,loose stator screws and a killswitch cable possibly shorting to earth.

They both look like M199 to me. One has earlier model sidecovers and the other has left side braking - both are common mods to M199 and M198. Neither is M199A because they are both missing the swingarm gusseting of the 199A and both have frame tubes under the motor.

I wonder if the seller of the Cota 348 has seen this forum string?

The runaway revving thing as the fuel level in the float bowl goes low can be due to the lean mixture causing detonation instead of the controlled burning that normally happens. It can also be due to the idle mixture being too rich, then becoming correct mixture as the fuel level goes low. No it can't be due to a vacuum leak, because it would do it all the time that the motor was at normal operating temperature, not just when it was running out of fuel.