thovda said:Thanks Teazer, that's one thing I haven't checked out in the manual yet, haven't been serious about ordering a new one. Once I can get the idle mixture right, I think the jet needle setting will be the next thing I adjust, I'm at the top clip now with the 6F4, so if it's too rich still I'll have to look at a 6F5 and/or a leaner needle jet. The pilots should be here before the end of the week so I'll be able to see how it is soon.
Firebane, what symptoms at what throttle position caused you to order a leaner needle and jet?
teazer said:That's not right. On a VM the screw/passage allows air into the upper part of the slow jet where it mixes with the fuel from the bowl. Open the screw and more air is allowed in. Fuel is pulled in by the difference in pressure between the venturi and float bowl (atmospheric). Air traveling through the air screw/passage does not create that pressure differential and effectively replaces fuel with air as it's opened up.
It's true that air in that system is slightly below atmospheric pressure but it has little effect on pulling up more fuel. The Mikuni manual shows it pretty clearly - Page 10 on my copy Fig 16.
In this particular bike there is something odd happening and it almost suggests that the wrong type of slow jets may have been fitted or there's a blockage in the air side of that circuit. Are you 110% sure that you have VM22/210 slow jets and not BS30/96 or jets without bleed holes?
If you remove the slow jets and air screws and spray carb cleaner down the appropriate air drilling in the bellmouth, does it spray out of the pilot jet position?
fresh_c said:First let your engine warm up. Then try setting your idle screws and air screws to 1.5 turns out and restart the engine.
Begin by adjusting the idle to about 1500rpms by turning the idle screws only.
Then turn your air screws 1/2 turn in either direction (and no more) to determine which setting increases engine speed. Leave the air screws set at the position corresponding to the highest engine speed (within 1/2 turn from the starting point).
Adjust the idle to 1200rpms by turning the idle screws only.
Again adjust the air screw 1/2 turn in either direction to see if that yields an increase in engine speed. Readjust idle screws to get you back to 1200rpms.
This is your starting point to determine if the pilot jets are the correct size.
teazer said:Did you replace the choke (enricher) plungers? If they get hard or don't seat properly it will basically have the choke on part way all the time.
The main air jet on most 4 strokes should be much smaller 0.5-1.0mm but it only changes fueling through the main jet as revs rise and we are not really worried about the main jet just yet