feetupfun

I'm 15 stone and reckon 360mm with 40 pound springs is perfect for Mk2 MAR

The grooves are to improve the sealing of the head-cylinder joint. No O rings or gasket or sealant are needed. You could fit a copper or aluminium gasket if you want to reduce the compression ratio, but it is not needed for sealing. Having the grooves reduces the force required to create a seal.

http://www.mid-atlantictrials.com/OKO.html

Yes lots of piston slap when cold and warm. The modes of piston rattle are different at different RPMs and temperatures which is why the noise changes Are the rings freely moving, or gummed up? The cylinder fins sounded like they were ringing. Are the fin dampers OK? It might just be the way the phone records the sound Possible noise from crankshaft main bearings Could not hear any conrod or primary chain noise

thankyou the_oil_baron

What did you do to the brake pedal arrangement to suit the new peg location?

They are similar enough in design that it depends on how well each bike is set up, as to which one is better to ride

The KT has very cool sounding primary drive gears though

Possible reasons: Maybe not enough people want them. The standard seat is much more comfortable than what you are seeking. It would be quite easy to make a seat like the one in your photo so if someone wanted one they could easily make their own. The TY175 is a far more popular choice for competition, so the market for them would be bigger

Get a new air filter. The old one will be very fragile, and may get sucked into the motor, or be restrictive 25:1 is a lot of oil in the premix If you have put oil down the spark plug hole a few times, it will be very smoky when it starts The crank seals may need to be replaced due to old age May need to disassemble the clutch to free the plates if they don't release when you have a test ride Go for a test ride long enough to fully warm up the motor before you drain the oils

Montesa Cota 247, 348 and 349 also drive the primary gear with a taper

If its sustained riding - like along a road - that you are talking about then the cause might be poor tank tank venting creating a slight vacuum in the fuel tank

John what is that light coloured thing visible through the bearing hole?

TY175 does have a weakness in the design of the return stop peg on the shaft. It can slip around on the shaft. Common problem. If it has slipped, work out where it should sit, move it back and weld or bronze weld it in position. The original design is a press fit that can slip if the kickstart is allowed to slam against the return stop. If that has gone wrong, you are lucky not to have holed the clutch casing Before you start pulling it apart though, a TY175 kickstart that is working correctly engages when the lever is horizontal (about level with the footpeg) They also develop looseness in the knuckle joint which causes the end of the lever to be lower

electronic ignition supplier should tell you what gap to use, but there will be no harm done using 0.4mm. I use 1.0mm plug gap on my bikes that have modern aftermarket electronic ignitions.

A local engine rebuilder here makes replacement crankshaft halves as an alternative to the build-up/grind back technique. Both will work

Probably depends on who does the welding, but the ones I've seen done with welded nuts still work fine.

You can get aluminium nuts welded to the WES and fit the standard heat shield. I think this looks great

There are different width 520 size chains depending on brand and if they are non-sealed, o ring or x ring What size front sprocket is it? A photo showing where it rubs might help solve your mystery

The reason that there is still a throttle cable but no cable for the clutch or brakes is simple; The brakes and clutch provide extremely important feedback through the controls. For the brakes the feedback is pressure variation under the foot or against the lever. The important feedback from the clutch is the accuracy with which the rider can feel the point of engagement which is marked by a rapid reduction in lever pressure as felt by the riders fingers. With both these systems, feedback is better with hydraulics. In the case of the throttle cable, the only feedback is from compressing the slide return spring. The force from the spring is only there to overcome friction so the throttle self-closes. In the quest for better emissions, reliability and performance, the future of two stroke trials bikes includes electronic fuel injection and this will consign the humble throttle cable to oblivion. Maybe not next year or the year after, but eventually it will

the standard number for getting to world class level in any sport or endeavour that requires brain and body coordination is 3000hours of practice, so it pays to start at a young age and do lots of it every day

The OKO carby also goes well on the 325 Bultaco Sherpa T

I will have a go at translating Dabsterese into Aussie English "Guys, admit that you are wrong. The reason people reline Bultaco hubs is because the chrome lining fails. If we didn't have to reline Bultaco hubs the discussion would not have begun"

Note that Moto GP use carbon fibre composite discs in fine conditions (carbon fibre only works while it is hot) and ferrous discs when it is a wet race. What racing vehicles use is not of much relevance to trials bike brakes I would say