Stable idle?

[Neil E.]

Is it the holy grail of 2T jetting? I just tried a #8 slide thinking it would help clean up the off idle jetting compared to the stock 6.5 slide. I couldn't notice any real difference except that it was much harder to get the bike to idle. I think this was a reslut of the new #8 not having a notch.

The 6.5 has a notch that measures .095 wide x .040 deep. This would allow the slide to be closed further (less pullover). Current jetting is 40P, AS 1.5, JD Red #4, 175 main. I rarely ever exceed 1/3 - 1/2 throttle when riding.

The AS is not particularily effective. The bike will idle OK for about 20 seconds, then the RPM drops and it flames out. As long as I blip the throttle once in a while it's OK. I don't usually idle for more than 15 seconds when riding.

Does this behaviour suggest a low float level?

[Neil E.]

stainlesscycle put in a stronger spring
http://www.gasgasrider.org/forum/showthread.php?t=10909

desertgasser300 found a loose adjuster nut
http://www.gasgasrider.org/forum/showthread.php?t=10912

I added a knurled brass cup to my slide adjuster screw so I could easily give the screw a bit of a turn out on the trail. It works very well and saves getting out a screwdriver.



However since doing the mod, I notice it's harder to get a steady idle. The stock plastic screw had a white thread sealer/locking compound on it. Since I removed and replaced the screw, most of this compound came off. I think the screw is not held as snug in the hole now. It is the stock screw with a brass piece added.

Any idea what this stuff is? I might try some watered down blue loctite as a replacement. I suspect the reduction of original sealant is having an effect on the slide screw position.

[Jakobi]

I have a number 7 non notched and have the same kind of scenario. Its taken alot of work getting the right needle diameter and pilot to work well. The idle screw itself is a very fine line between idling too high and flaming out quickly.

[GMP]

Your pulling over to the needle jacking the slide up with the idle screw. Maybe try a #7 slide. This new carb seems like a PIA, even on a 250, which have been traditionally easy to jet. Guess I'll find out for myself.

BTW you don't need the plastic "T"s on the vent hoses. They are "T"ed inside the carb body casting, run the horizontal lines down, vertical lines up.

[gasgasman]

Originally Posted by GMP

BTW you don't need the plastic "T"s on the vent hoses. They are "T"ed inside the carb body casting, run the horizontal lines down, vertical lines up.

Those vent tubes may be some of your issues. The float bowl has to have atsmospheric pressure to work. Those "Ts" may have too much restriction in them.

[Neil E.]

The tees have a large bore and shouldn't be an issue for my riding. I connect all the vents and run a single line up to the airbox. I haven't had any issues after falling over on a hill (with the bike on it's side, wheels uphill).

When you look at how very fine the slide stop screw thread is, the slide is being moved extremely small amounts to make idle adjustments. The JD red needle should minimize pullover (assuming the needle jet bore is correct).

I am thinking that the slide screw spring pulls the screw back centering it on the thread pitch. The slide closes pushing on the screw and after a bit, the screw moves to the side of the threaded hole. This allows the slide to drop that extra thou or two, enough to change the idle speed.

A heavier slide spring might push the slide to a more reliable "home" position. I suspect the lack of sealing compound is letting the screw move.

[Neil E.]

Originally Posted by GMP

Your pulling over to the needle jacking the slide up with the idle screw.

Let's review this. Lifting the slide means more air to the motor (needle is still on the straight section). If we need more air, is that the result of too large a pilot jet?

[webmaster]

To minimize pullover - you also need to go with richer pilot along with GMP suggestion to back out your idle screw.

jeff

[Neil E.]

Originally Posted by webmaster

To minimize pullover - you also need to go with richer pilot along with GMP suggestion to back out your idle screw.

To verify: idle screw = slide stop screw (not air screw)

I would expect that if we are trying to obtain an idle with the slide as closed as possible, the pilot jet would have to be larger and the air screw turned out more so the idle air is supplied via the air screw instead of the slide.

[GMP]

Yes, exactly. Raising the slide too much to achieve an idle is a crutch for a poorly tuned idle circuit.