lemur

I inspect all the small brass parts with a stereo microscope but not everybody has one of those.

After the float bowl is the main jet and emulsion tube which is the most common source of problems, that assembly can get pugged very easy. The carburetor operates on intake vacuum pressure to draw fuel up through the emulsion tube and jets.

That's how I test the float needle and seat operation and float height and it 100% works, if the float needle and seat is leaking or sticking or plugged you are going to see it.

So if you remove the float bowl completely and turn on the fuel tap, nothing comes out? That would narrow the source of your problems significantly. ... is that one of the carbs where you can accidentally install the floats in backwards or upside down?

Carburetor performance is dependent on the engines ability to move air. Highly recommend you inspect the reed valves, test the engine compression and the integrity of the bottom end seals first. The engine needs to move air efficiently for the carburetor to operate to its best efficiency and no amount of carburetor adjusting can overcome that.

How much would you pay to rent a trials bike at the venue with a hired guide, would be more interesting and as the renter how could you secure your investment in the likely event there will be damage to the rental unit and possibly the riders. Risky motorsport business is complicated as soon as you involve money. I allow a non groomed snowmobile trail through my property, also a freebie, also not a liability to me and there are hundreds in the same situation. I rarely use it myself, snowmobile trails are boring but as the land owner the trail has never been a problem.

You've set out great events and your contributions are greatly appreciated 😎

The reason I have guests here is so I have people to ride with, it's as much for my benefit as theirs, weather is improving here for winter riding and it looks like lots of stud season left 👍 That's my retirement plan in action, if your plan is to host for profit I think you are doing it for the wrong reason, it needs to be driven by your personal passion for the sport.

Stock original is just like the parts manual shows, every Montesa I ever bought new came with an excellent printed service manual and the bike will be just like the parts list shows. Best one I ever home built was from 1/4" Thordon elastomeric bearing plastic attached to the plate with large flat head socket cap screws.

From what I recall of a friends Fantic with the Dellorto carb his low speed adjuster was a fuel circuit and not an air circuit so logic when adjusting it might be counter-intuitive to typical. In the absence of a service manual 1 and 1/4 turns out is a good start point no matter what kind of small engine it is and I would expect to need to turn it in slightly on one of them. Sounds like you have the slide idle adjusting screw figured out 👍 the idle adjuster screw bumps up against a ramp machined into the slide, opposite side has a slot cut in the entire length of the round slide to follow a guide pin, intent being to stop the round slide from rotating. Been 6 hours so guessing you already have it running by now.

Respect is all I ever charge.

If they do it that way the vacuum sensor must be incorporated into the 4RT throttle body. Wasted spark is not a problem wasted fuel would be a problem, only makes sense they would need to inject only when an engine vacuum is present 👍

I would want to think the part called the 'ignition pulse generator' has something to do with ignition pulse generation.

Rule of thumb to determine if a spark is wasted or not is to look at where the timing in taken from. Crankshafts rotate at twice the speed of the valve camshaft so if it is ignition timed off the crank logic would dictate a wasted spark and if it is timed off the camshaft rotation that will happen half as often.

Ride the pegs more and the bars less. You know you are making progress when you can go over the bars and not let go of them until you are laying on the ground 😆

Only advantage I can think of is Full knobby works better for deep snow, because you can fit them with larger tire studs and that would be great for about 1 or 2 months of the year.

Then he might better reassemble it with as few replacement parts as possible and dealer trade it for something more reliable 🤔

I would be replacing any part that has visible signs of brinelling and once I had a new part in hand I would stroke a file against that failed bearing surface to see if it was ever hardened. If a file bites into the steel bearing surface easy then the bearing surface was never adequately hardened and that would indicate a defect in the parts manufacture.

Flatlands dilemma 😎 if the ground is soft I just bury the rear wheel a little and stationary balance the bike to park it. Your dog bone link looks like it has taken impacts, this happens because the OEM bash plate is poorly designed and fails to protect that part adequately. If impact damage compromises the bearing seals, water infiltration will fail the bearings very quickly. The dog bone part is symmetrical so you can swap it end for end and smash the other end for a while. Best way I found to prevent the impact damage was to modify the bash plate so it extends back more and protects the linkage, similar to how the Mitani does on one of their aftermarket skid plates. 🤓

Sure sounds like the same problem with a resolution found.

Sure does look like Cota. My riding buddy just picked up his new Beta Factory and the kickstand self retracts the same way, you can fix that quick with a hand file. I had a collection of Montesa side stands from 2001 to 2017 and yes there were variations on the theme, they all were removed after the first time it cost me a 5, the stand with a foot pad welded on the end caught logs and would stop you dead. lol I stored them with my MV Agusta F3 passenger pegs in the useless parts drawer.

In 1974, that's easy, you oiled the chain with the used oil that you drained out of the engine.

Just noticed a small something, your side stand is welded onto the swingarm, that's not stock because I always removed it with the 2 bolts in the swingarm, don't need side stands around here because we have trees and rocks everywhere. 😎

You got it right; the lobe with the larger contact surface goes to the swingarm, smaller one bolts to the dog bone linkage, longest arm bolts to the shock.

Is that anything like an MV Agusta 👍 great ride if you want to go really really fast.