Idle jet not working!

[lsippell]

I just recieved my Motion Pro sync tool and a Color Tune. They work great, but.
I've got a problem. Using the Color Tune in #4, it showed rich at an idle. Ok, so I start turning the idle jet in (leaner), and it has no effect. Bottom it out and I see no change in the color of the flame, still bright yellow. It doesn't turn blue untill I open the throtle to over 2200 rpm's.

One of you carb experts please tell me what other circuit in the carb to look at. Or do I need to pull the idle jet out and look at it for damage? It was in fine condition when I put it in about 4 mo. ago.

Louis

[skids]

Re: Idle jet not working!

The synch should be done at or near idle rpms. This should be done prior to attempting to adjust mixture screws. OK, with that out of the way and I assume that you did it like that...

If you screwed the pilot screw all the way in and it still shows rich:
* maybe the float is adjusted too high or has a hole allowing too high a level, or,
* the pilot jet is not genuine OEM Micuni #42.5, or,
* the pilot air jet and/or its passages are clogged, or,
* the pilot screw is buggered (I have seen them badly bent or just incorrect as a screw from a rebuild kit),
* the detent screw for the "choke" enrichener is loose allowing that carb to be too rich.

I am of course guessing at possibilities, but maybe it will give you a place to start.

Originally posted by lsippell
I just recieved my Motion Pro sync tool and a Color Tune. They work great, but.
I've got a problem. Using the Color Tune in #4, it showed rich at an idle. Ok, so I start turning the idle jet in (leaner), and it has no effect. Bottom it out and I see no change in the color of the flame, still bright yellow. It doesn't turn blue untill I open the throtle to over 2200 rpm's.

One of you carb experts please tell me what other circuit in the carb to look at. Or do I need to pull the idle jet out and look at it for damage? It was in fine condition when I put it in about 4 mo. ago.

Louis

[lsippell]

I'll have to check the float level in the morning, but it was dead on about 3 weeks ago (had the carbs off to replace the float bowl of #1).

The pilot jet is identical to the other three, a 47.5. This is a XJ.

* the detent screw for the "choke" enrichener is loose allowing that carb to be too rich.

Verrrry possible! A month or so back, I had the setscrew back out and lost it. I replaced it with a ss allen head screw of the correct size and have not looked at it since.


Louis

[skids]

Oh NOW ya tell me! ;-)

Originally posted by lsippell

The pilot jet is identical to the other three, a 47.5. This is a XJ.

Louis

[lsippell]

Well, I checked the float level and its spot on and the enrichment circuit is working properly.
I put the Color Tune back in and while watching it, backed the pilot screw out all the way (loose) and got a blue flame. Screwed it back in a couple of turns and the combustion stayed blue (with a flash now and then of yellow). But now I have a midrange that is on the rich side, no true blue until 4000 rpm.

The bike runs ok with this, but I want it right. I'm going to wait until the weather cools off and I’ve got more bearable tempetures in my shop and I'll pull the carb bank off and go at it again!

Louis