XJ Experts, Am I rich or lean

I've been working on my XJ1100 and have run across some puzzling things. A little background on the bike,its a stock 82 XJ1100, stock exhaust and airbox with a K&N style filter. Stock jets 112.5 mains and 42.5 pilots. Valves are in spec and the compression is 130 across all 4 cylinders. Carbs are squeaky clean and vac synced. The engine runs good but I can't get it to run as smooth as my XS11. Right now I have the idle mixture screws out 3/4 turn and the bike starts and runs good and idles at 1100 rpm.
Here is what I observe that makes me think its running lean:
Since I changed to the K&N airfilter the pipes have started blueing
The bike "pops" through the exhaust when decelerating
Its a little hard to start when warm.
With all these indications of a lean engine my plugs are black and sootty. I know I must be missing something simple, but what is it?

 

Mine is the same way. It would be nice to find out what is up with the popping out the exhaust. I did move the idle up a tad and that seems to help with the popping. I set the idle at 1200.

MN

 

Sounds like an exhaust leak to me. Check the header flanges and crush gaskets.

 

Popping generally indicates a lean condition; as do header pipes turning blue.

Black sooty plugs can also be caused by leaky valve guide seals (if you're pushing a small anount of oil past them

3/4 turn seems awfully lean; I suspect you are in fact lean, and the sooty plugs are coming from another cause (like floats set too high or oil in the cylinders.)

The K&N may have thrown a new variable into the mix...

 

I did replace the valve guide seals last year when I had the head off to fix a bent valve(stupid mistake on my part buy turning the engine too far when adjusting valves). So I know the upper engine is in good shape. I did look for a exhaust leak with a piece of tissue paper, I found one small one on the left side muffler connection. I tried to tighten the clamp but it is still there. Its small enough you cant even hear it. Floats are a possibility, I'll check them tonight.
Fitz do you know where the level should be on the 1100. I'll check it with the bike on the center stand and put a clear tube from the bowl drain to see where the level is.

 

Mlew,

The float levels are the same as the Hatachi carbs. Should be at the washer under the float bowl screw should be where you want it to be.

My carbs are set and sync set (using the YICS block off tool). Mix screws out about 1.5 -2 turns average. I know the plugs are dark brown and black around the edge of the plug. The popping in the exhaust seems to be fuel being pulled in and making a weird lean condition when you back off of the throttle. It might be the waste spark set up doiing something here also. When I lower my idle speed the popping gets worse since the throttle plates are closed more. I'm not sure but these bikes have that boost sensor and I think it changes the timing and I'm wondering if for some reason when you back off if that moves the timing and causes the popping we hear out of the exhaust.
Just as a side note my pipes are blue and gold just to the downward bend on my Mac exhaust.

MN

 

YOUR pipes should be blue, the MAC is a single-walled pipe.

If stock headpipes turn blue then either in inner pipe is cracked or you're running WAY HOT (lean.) The only time I've seen blue double-walled pipes was on a destroyed (or about to be) motor.

 

You should quit guessing about how you are running and have a look.
All you need to do is Pull the Plugs and line them up 1, 2, 3, & 4.
Snap a picture of them babies business ends in a good close-up and let us have a look at them.

I suspect they are going to look pretty clean.
Running those Big Mik's at less than a turn out should be right down-town in "Lean City".
Throw the K&N in and you might be Critical.

That's why we NEED to check the Plugs.

You have a multitude of Carb Tuning options available to you.
The Mikuni's have a wide assortment of Jets, Shims and Needles along with Aftermarket Emulsion Tubes that will allow you to do your own "Designer Tuning"

http://www.mikuni.com/fs-tuning_guide.html

The first Tuning measure you need to do is: Enrich Mixtures.

 

Plugs are nice and black, I did pull the from the trash can to take the pic so I don't know the cylinder order. These plugs have about 500 miles on them. I have to change them oftem because they foul out and its hard to start.

Thats one of my big concerns Fitz, stock double walled pipes turning blue. But with black plugs like this, whats going on?

 

But we don't know how you ran the bike the last 10 minutes of those plugs' lives (was it idling in the garage while you were tuning other things?)

Suggestion - ride at highway speeds, cut motor, pull plugs, take a new picture.

The second plug appears darker than you want.

 

Plugs were pulled after a long ride, speeds ranged from 35 to 55 mph. The bike sat overnight and would not start the next day. Pulled the plugs and this is what you see. After 500 miles the plugs should not look like this. I easily get 2000+ miles on a set of plugs in my XS1100.

I did check float levels last night. Each carb level is right at the washer on the bowl.

 

mlew,

I would have to say my plugs look the same as yours. I'll see if I can post a pic later tonight. I had a problem with a hot bike restarting problem and that seemed to go away by itself. Not positive but it seemed like it was flooding when the engine was hot and you tryed to restart after 5-10 min. If it sat for maybe 30 min or so it would start fine.
I also went around with the propane to see if there were any vacuum leaks and I could not detect any.

MN

 

My bike starts belligerently warm. Run till hot, turn off and let sit 10 mins, belligerent start. Restart hot or cold, no problems.
Otherwise bike runs good, so I have little incentive to chase the issue.
I think cause is very slow leak past float seat.

mlew – your quote:
‘Plugs were pulled after a long ride, speeds ranged from 35 to 55 mph. The bike sat overnight and would not start the next day. Pulled the plugs and this is what you see.’

So the plugs were pulled after attempting to start engine. Some of what you see on the plugs could be what last happened, and that was attempting to start engine. If engine started and you rode till hot, at that point the plugs may look different (i.e. plug chop)

mlew - your quotes:
‘Since I changed to the K&N airfilter the pipes have started blueing’
‘idle mixture screws out 3/4 turn’

The K&N filter lets in more air and thus needs more fuel. W/o more fuel it will be lean.
Idle mixture at 3/4 turns out seems very lean.
Possibly lean at idle is blueing pipes.

Lets say your float seats are leaking overnight so the engine is already fuel rich. When you attempt to start next day you engage choke thus adding more fuel. The bike is now in a flooded condition and will not start. You pull plugs and they look rich.

 

Those are too black for it to be all from fuel, unless it's "dumping." You've got oil getting into at least two of those cylinders, or a float seepage issue. Running as lean as you are at speed, those plugs should not be black.

Something is amiss.

 

What is the condition of the petcock? What position do you have it set to?
If the float seats are leaking along with petcock, the carbs are getting a continuous supply of fuel while bike sits.

 

You can't tell anything from Plugs you pulled out of the trash.

You should get a set of New PLUGS and do the "PLUG CHOP" Routine.
Go find a safe place to run the Engine up to High rpm's and hit the KILL Switch.

From the looks of the Plugs you threw-out ... It does NOT look like you are running LEAN.
Those are too Rich and moderately Rich ... with the possibility of Oil or an additive making the Mixture rich.

Buy (2) 4-Packs of Champion Plugs.
Go have fun Plug Chopping.

 

Imagine this:
Both float seats and petcock leak over night.
The next day you engage choke and push starter but all that fuel has flooded engine. As starter spins engine, it spits the fuel out the exhaust but the plugs have now possibly fouled with fuel. So you pull plugs (thus opening cylinders venting more gas). You reinstall (possibly fresh) plugs. The engine is now less flooded and voooroom !

 

The carbs are plumbed just like the stock setup. There is a petcock on each side of the tank that feeds a manifold then to each pair of carbs. I know all the seals and diaphrams are good. I can pull the fuel lines off and no gas drips out, even after sitting like that for a day. I'm sure there is no fuel leaking into the engine when it is off.
I'm still puzzled why my plugs are showing running rich and other things say I'm lean. I know Yamaha tuned these bikes a little lean from the factory and with my jets still stock size why am I running rich?
I'll do some plug chops this weekend.

 

take some pics of new plugs with 20mi on them. take the pic so we can see down inside the bottom to the piont where the porcelin meets the outer body and the electrode strap is still in focus. Have you vacum synced the bike using the oily rag method of yics blocking???
Just a thought

-James

 

Open oil file hole and smell for gas.
Since it appears the bike is running rich at some point, there may be gas getting into the crankcase. The test may not be valid if you have changed the oil very recently.