Carb help

[cruiser]

I have encountered a miss at idle on #1 so will be doing a carb cleaning on my 82 XJ1100. Slowing down from road speed I hear popping noise from exhaust and assume it's due to miss.
I suspect the idle circuit is plugged on that cylinder as it has no ouput at idle removing and grounding the spark plug wire but does at higher rpm.

Factory manual says not to adjust idle mixture screws so when I want to remove them to clean port where do I start to reset them? How do I know they are set right?

Also, I find no float setting as I will be replacing needle and seat assm. on all. I see the part about using clear tube off drain screw but no info on where to get a fitting with proper thread and barb to connect hose. I would like to pre-set the floats closer to avoid having to remove many times to adjust floats.

Does my diagnosis sound correct? Any tips to help me out??

[TopCatGr58]

Hey Cruiser,

Well, the XJ's a bit different than the XS's, but the pilot screws are usually set to 1&1/2 turns out from gentle seat. Again, you can turn them IN first and see how many turns it takes to "GENTLY SEAT" them, and again you can use that as your starting point. There has been a couple of great posts by Ken Talbot on how to perform an Auditory "colortune" instead of having to buy the actual tool!

NOTE: Ken, we need to copy that and make it a TECH TIP!!

As for the floats, the clear tubing technique is a real PITA!!! Once you get the bowls off, measure them, and then just reset them as needed close to that setting. The 80 carbs state to set them to about 23mm, vs. the 25.7 for the 78-79 series. The 81 states to use that tubing system also, but I just used the 80 settings, and works well!

An easier technique that "MIGHT" help to clear the pilot circuit would be to put some(LOTS of) SEA FOAM or Techroline in the gas tank. IT can quite often dissolve gum and varnish and may return the pilot circuit?

The XJ has the YICS and so you need a special tool to temporarily close off that to vacuum synch the carbs!

Your diagnosis sounds about right, since at higher rpms, you're getting into the mains, and so the carb IS getting fuel then, so pulling the plug then does affect it, but at the lower rpms, it's running only on the pilot circuit, but if it's clogged, then that cylinder isn't getting any fuel, and pulling the plug then doesnt' have any affect!! Also, popping on decel could again indicate a leaning out affect, again the transition from Mains to pilot, and being clogged goes too lean!

[cruiser]

Thanks for the reply. I have already manufactured the YICS tool per directions on this site. Thanks a heap.

I turned one of the pilot screws in to take a reading and after 7 turns I hit gentle seat. Seemed it should not be that far out for proper operation. Seems the next two were the same. Guess I will go with that setting and see what happens. Visual on all spark plugs seems to have normal coloration and it was running great until this.

Had thought about seafoam but wanted new needle and seats so might as well do the cleaning while I've gone through the trouble of getting the carb set out...whew, that's no fun task.

What are others using for a fitting to thread into the drain screw for using the tubing. I checked local hardware store and nothing that small. I assume it's metric thread.
Where do I look for that?

I'll do a search for Ken's auditory colortune tips.

[TopCatGr58]

I found Ken's tip!

Cruiser, you're right in that 7 turns sounds like a lot. Are you sure you counted FULL turns, not just when the screwdriver blade rotated 180 degrees?? That would then be about 3.5 turns,much closer to what folks have used, at least on the XS11s, I can't speak authoritatively about the XJ's carbs. Jerry and a few other's that own an XJ could probably tell more about whether what you found is common!

I don't know what the "FEW" others who have actually done the tubing float setting technique have used, most folks just set them manually with the bowls off, and leave it at that!
T.C.

Those pilot screws sound to me like they may be a bit on the rich side. Try fine tuning them as follows:

- warm up the engine and sync the carbs with a mercury tool or vacuum gauges
- adjust the idle down to approx 700 or 800 rpm
- adjust one pilot screw out slowly while listening very carefully to the engine sound and watching the tach needle
- listen for the engine speed to pick up a bit then fall off
- if it doesn't pick up, adjust the screw slowly in, again listening for any increase in idle speed
- when you her the increase, adjust past it a half turn or so, then come back to it again until you've got the sweet spot
- adjust the idle speed back down to your low starting point
- then work another screw, again looking for its sweet spot
- each time you get a screw adjusted, drop the idle back down
- once you've got all four screws set, resync the carbs
- take one more pass through the pilot screw adjustment for each carb, still working at 700 to 800 rpm
verify that the sync still looks good
- adjust the idle back to 1100 or so depending on your personal preference
- go for a ride!

This procedure is basically what you're doing when you use a colortune sparkplug, only it is a lot faster. You are adjusting the pilot screws to achieve the optimum fuel/air ratio at the bottom end, which is why you will hear the engine speed up a bit and sound smoother at that low rpm.


__________________
Ken Talbot

[cruiser]

Oh ya, 360 degrees per 1 turn rotation, at that point I could see the tip showing through the carb bore. Scares me to turn in that far yet it always ran so well????
Seemed to me that far out would be running as fully rich as possible. I wondered if it had something to do with being the YICS style.

I found Kens tip, that should work fine. Have tuned many automotive carbs so understand what he's saying.
I guess it will be necessary to have YICS tool installed while making this adjustment though, right??

Thanks TopCat.
Any XJ owners have comments??