Pull a bristle from a wire brush and have a probe to ensure the holes in the mc are clear. You obviously need to be able to relief back into the mc or the brakes would stick on.
Where did you see the stream of micro bubbles coming from?

It's obviously working as it should or you wouldn't have had the small stream of bubbles appearing in the mc. There is obviously still air in the system. Make sure everything is tight so there's no chance of air binging sucked in on lever return the reverse bleed them using a serynge slowly to allow...

Possibly sticky fly weights on the advancer? Maybe?

Same set up on my J2. There's also a plate that controls the side stand override switch. With the bike on the side stand you can start the engine, if you lift the bike upright the side stand springs back a bout 15 deg and the side stand switch kills the engine unless your pressing the override switc...

Getting there. Think your next start attempt will prove more successful. Correct jets, needles, float heights, fuel level, plunger seals, airscrews 1.5 out and things should be different from last time! Just ensure no carb to head rubber leaks.

Fully open 2 will have rich mixture and 2 will have very rich mixture. Partially open 2 will have rich mixture and two will have lean mixture. Solder and re drill em as small as you can at least they'll be similar if not identicle. Any vm carbs would do for those parts. There's parts or full sets on...

Parts set = parts bank of carbs. 90% of the bits are common between all the vm carb sizes. It's always handy to have a cheap junk bank of carbs to "borrow" the odd bit from. Those choke pick up tubes are common to all sizes but are not included as a replacement part in any kit. Heat the ca...

You can solder it and re drill. If the choke plungers seals are good then they are only operational when the choke is on. Alternatively if you have a parts set, with a bit of heat they just pull out and replacements push in.

Good spot. Another issue. All four should be as top one. They are the choke fuel pick ups.

As Nigel said poor running is gererally down to several issues accumulated over the years. Those jets are suspect and I would replace them. As they not genuine I would suspect both the needles, needle valves and airscrews are not either. Your right itheres no guarantee a replacement set would be a y...

Mikuni jet logo. Appears on both genuine main and pilot jets.

115 in the center two and 117.5 (118 no such thing) in the outside is wrong. The middle two are the ones that run hotter so if anything you want bigger jets in them to be run richer. Do the main and pilot jets have the Mikuni logo on them? For sure someone's been in there and messed with them. 2022_...

When checking the jet sizes look to see how the size is stamped, if they look like second rate stamping, at an angle or generally just naff chances are they are after market dross. Genuine mikuni jets have size and their logo stamped appropriately neatly. If they are after market bin em for sure. If...

The ones on the carb sides are airscrews,. So screwing them in richen the mixture and turning them out weakens the mixture.
If you still show rich at 3 turns out your pilot jets are too big. The jet size should be stamped on them. Both pilot and main.
Check sizes and report back.

Fingers crossed for you Graham, sure someone will step up, but if they don't the offer is open