3 plugs nice light brown, one lean?

[xj11john]

seems no matter how much I mess with #3 it is either rich or lean, so my question--on an xj is in or out lean it up?
thanks in advance, I going to ride it more and check it later.

[xj11john]

Is it fuel metering or air metering

seems like that if I turn the screw out it gets richer, but if it is air metering wouldnt turning the screw out give you more air.....
ergo-- more lean mixture?

[John]

The pilot screws meter fuel. Some one here posted a good rule of thumb...if the screw is before the throttle plates (butterflies) it controls air, if it is after the plates, then it controls fuel.

[xj11john]

Thanks !

I appreciate the responce, that rule makes sence.

Lately that screw has been moved so much, I couldnt remember which way to go, and I couldnt seem to find the answer in a search, thanks again.

[xj11john]

Any suggestions?

As to why three plugs look good color and one either dark or light, no in between.

Some things I've checked are-intake boots-sprayed brake cleaner to see if engine speed changed, it did somewhat- but i couldnt find any cracks but put some sealer on the part that was poss. leaking, I also pulled carbs and tightened that boot up.

switched oval filters with another carb to see if one may have been more or less restrictive to induce air flow.

Played with the mixture screw alot, and the sweet spot just doesnt have the pretty plug color that the others do.

I know I am not tring to win a "prettiest plug contest", just dont want any holes in piston or bad gas mileage.

[TopCatGr58]

Hey XJ11John,

As far as burning holes in your pistons, it won't happen just from adjusting the pilot screws. Now if you were to run very lean main jets then possible. You're talking about plug color , but are you checking them with the throttle chop technique, or just when you get back home from a run?

It's been commented before that it's a bit more difficult to gauge performance from plug color due to cleaner burning unleaded fuels. So...I say set your pilots to the sweet spot, and if it's a little lighter color than the others, then that's okay. Just verify that you don't have an intake vacuum leak, and that you've got your floats set even and properly.
T.C.

[xj11john]

T.C.,

I check it when I come back from a run, In which I try to keep rpm up between 3000-4000, they are alittle leaner at these revs, but still look pretty good. At idle I get the nice tan color on the three and grey on the #3,

Was thinking about pulling carbs and lowing float #3 for alittle richer condition, but for now bike is running good with an idle around 1000, at times sounds alittle like it could stall once in awhile though.

I also read a post on raising the slide needles using a lock washer that would fit between the needle and the plate that is held in by two screws (since the Maxim doesnt have adjustable needles) Ive heard this helps richen up the mixture and gives better top end performance.

any other comments welcome.

[Ken Talbot]

I would hold off on resetting just one float, John. Instead, maybe have a close look to see that each lobe of each float is set the same. It is pretty easy to tweak the float assemblies and end up with one side sitting high or low. Once all the float levels are the same, and theoretically the fuel level in each bowl is the same, it should be possible to get the same amount of fuel into the fuel/air mix in each carb. By this time, is it safe to assume that all of the jets and orifices are spotlessly clean?

[xj11john]

Ken,

On the cleaning, I have srayed carb cleaning through the orfices, and I had been running some red-line fuel system cleaner through for several tanks, but I could have missed some crud.

I am taking a trip down to my sisters this Sunday (about 70-80mi)
to check out my Brother-in-law's new bike (Kaw. kz750m1)
so we'll see how it does without changing anything for now.

Last time I had the plug out it looked better, kinda dark-not tan but I think not too overly lean.

T.C,

As far as the throttle chop test, I havent done that yet, I just tested at the rpm's I run at- 3000-4000.

I will prob. do this test when I get another set of plugs (the set that is in is new-but now colored) so I'll get another set to do it later.

Thanks for the replys, I'll let you know what happens.

[xj11john]

Oh, I had checked the hieght on both lobs of each float, but you never know-those gremlins-you know could have got me.

Also what do you ya'll think about the washer trick?

[Ken Talbot]

The washer trick will lift the metering needles and yes, that will richen up the mixture a bit on the upper end. That doesn't necessarily mean you'll get any better top end performance, though.

If you're already at the optimum needle position, you will lose performance by going either richer or leaner. You can also affect the mixture by changing the float setting by one or two millimeters either way, and of course by changing jets.

Because there are so many ways to affect performance, it is critical for everything to be absolutely clean first so you have a baseline to work from. Without actually removing every jet as part of the cleaning process, you could still have deposits in the various passages. Fuel system cleaner will work away at that stuff over time, but while that's happening, your baseline keeps changing too. Change the mechanical stuff before that's done, and you could end up having to backtrack.

Sorry to keep harping on about this, but I've seen too many people get frustrated when they start with changing jets and needle settings and nothing seems to work.

[xj11john]

Thanks ken,

I appreciate your reply, I'm pretty sure everything is clean and I did remove all the jets and clean. I didnt use compressed air, just spray carb cleaner-and had been running red line cleaner through on several tanks before I went into the carbs.

I'll wait on messing with the needles, and maybe after I do the chop test move up on the jets first. Thanks again.