feetupfun

Are you asking about the skirt protruding beyond the sleeve in the bottom photo? Or are you asking about the transfer port sleeve hole being partly obscured by the piston?

Logically how could those pegs ever fit to the standard Bultaco footpeg mounts? And they look amazingly similar to these which are listed as needing brackets welded on https://www.inmotiontrials.com/product/footrest-kit-alloy-universal-with-weld-on-brackets-wide/

To test the fan switch, an easy way to do it is to unplug the fan switch and fit an electrical bridge across the connector. To test the fan and the bike's power supply, unplug the fan and connect 12V DC from an external source to the fan motor.

If the clutch pushrod has any load on it at all, the clutch will slip. The adjusting screw in the clutch pressure plate has to be backed away from contacting the pushrod to avoid clutch slip. Do this adjustment of the screw with the cable disconnected then fit the cable and make sure the cable has some slack too. As for the kickstart lever not returning by itself, does it have a return spring fitted? Have you fitted both dowels in the gasket face of the magneto cover? Is the kickstart shaft straight? Are you trying to use the kickstart without the magneto cover fitted?

If you can accelerate the the bike hard in top gear without the clutch slipping then the problem is with the kickstart mechanism. If you find the clutch slips when you try and accelerate hard in top gear, then it is the clutch slipping that is causing the kickstart to "not engage". If you can't start the motor because you can't get the motor to turn over with the kick start or by push-starting in 4th or 5th gear, then the clutch is slipping or the primary chain is broken. If you provide more information about the recent history and condition of the bike, you will get more relevant help.

What bike?

Yes that's the standard setup on the MAR. It is an odd and quirky design. I did think about doing something for a while and was considering using a rear wheel hub with the brake plate on the same side as the sprocket so a simple brake rod could be used. If I was going to do that I would choose a wheel hub that also had a bigger diameter axle than the problematic 12mm standard axle. If you do change it to a more conventional design please post up photos.

There's lots you can do to avoid the clutch-sticking-when-cold thing happening but lots of people don't bother doing them and just get good at freeing it up. Are you willing to do a bit of work on the Sherco to stop it happening?

The properties of different oils do make a difference to the issue of the plates not wanting to separate but the underlying cause is that the friction plate pads can act like suction cups against the steel plates. The proper fix is to roughen the finish of the steel plates to help break the vacuum and to remove any grooves in the basket fingers. Grooves there can hold the plates together when the clutch has load on it. For a temporary improvement, use the lowest viscosity oil that will also provide enough lubrication for the chain. If it was a racing motor, the primary chain would not enjoy it if you use ATF but for trials use, ATF is usually OK for lubrication and is very good at breaking the vacuum seal. There are also name brand low viscosity gearbox oils that will work well for this issue and questions like yours usually get lots of suggestions for which oil is the best. OSSA primary drive casings retain some of the old oil during an oil change so if you want to get rid of all the old oil, an easy way is to loosen off or remove the clutch cover to drain the remainder out.

Two thicknesses of that plastic coating and that washer being new would not be helping the situation

Fan running backwards. Air trapped somewhere in motor coolant space. Radiator coolant passages blocked. Radiator finning blocked. Blockage/restriction inside coolant hose. Coolant lost into gearbox through water pump shaft seal. Coolant blown out through overpressure valve by head gasket leak.

I'm not going to yell at you about learning to ride with rubbish brakes. I hate rubbish brakes. Great brakes make riding trials or avoiding your older ladies on the road so much easier. I am going to yell at you because you can make your brakes amazing without fitting bigger (heavier) hubs. Get the brake drum surface re-machined. Get modern high friction linings fitted to your brake shoes. Get those high friction linings ground or machined to match the drum ID. Enjoy your amazing drum brakes.

Corrosion inside the rims. Not usually visible from the outside but very common on this bike and if the spokes also need to be replaced, they are a very unusual Z design which can be a problem to find replacements for.

Post up a photo of what you have there

With the Alpina yokes, how do you go for mudguard and mudguard stay clearance to the exhaust and front downtube when the forks are fully compressed

Sounds normal to me

The offset is very different on those Alpina/Pursang yokes so you would need to change both top and bottom yokes. Using those Alpina/Pursang yokes increases the trail a lot so the steering feels very different. Some people like it that way some don't.

You will "progress" faster on the Beta but it sounds like you don't want to "progress" anyway. Alexyz is right in that a TY175 or Fantic twinshock is a totally capable bike for novice/clubperson level competition and if you get a standard motor TY175, it is even easier to ride for a novice than a Beta 200 due to the gentleness of the standard TY175 motor response.

I read it as the $800 includes the spokes, rim refurb labour and wheel build labour. That sounds like normal commercial rates to me and a good reason to do it yourself

Yes but they may be on the opposite of the world

It's your bike. Do with it what you will.

total

If it's a contest for reliability without performing maintenance, I would vote for the 4RT. If it's a contest for the bike that will let you ride in the most competitions, then I'd vote for whichever one has the best after-sales support where you live because riding in trials you are going to break things.

About 0.5mm side clearance cold for conrod to piston if the conrod is being held in position at its top end. If the conrod is being located from the bottom end, the side clearance at the conrod to piston connection can be greater

Most people fit preload spacers between the top end of the fork spring and the fork cap. They work by pre-loading the spring so that the neutral position of the forks in their travel is right while you are riding. The more of those preload spacers you put in the forks, the higher the bike rides at the front.