Lean condition - what could be causing it?

I am all kinds of fed up with this bike :? . Colortune arrived yesterday and every cylinder is quite lean. Turning the screws out up to 5 turns did not produce any change in the flame color (light-blue). Since every pot is lean, I figured I must've reversed the screws somewhere. After some searching and looking through the various write-ups, I found some contradictions about which jets go where. I took some pictures so I could be 100% sure. Can someone confirm that the below positioning is correct?

 

I have Hitachi's and can only speak for them. That's how the fuel and air jets should be installed on mine. The pilot fuel jet has a smaller orifice than the main fuel jet. The air jets are different. The Pilot air jet has a larger opening than the main air jet. Your's look to be correct.

 

If the mixture screw does not make a difference, then the pilot circuit in the carb is still dirty and clogged.

If you run the screw all the way in, but without crushing it, the bike will start to stumble, the RPMs will fall, and she will probably stall out. If that happens, then the pilot circuit is clean.

Spin it all the way in, then turn it out at least 3 turns and start the colortune.

I can change from pretty purple to bright yellow in just a 1/2 turn. My mixture screws are 3.5 turns out.

After you clean all the circuits with carb cleaner, force some compressed air through each circuit, to make sure you have air flowing. It doesn't take much debris, lodged in a circuit, to disable the carb.

Recheck your coils and make sure the readings are in spec. A weak spark may cause a lean burn.

If there are any mods to the bike, like after market exhaust, K&N air filter, etc, you will have to jet up.

I have a MAC 4 into 2 and DynaTek coils and I increased my main jet size to #112, and kept the pilot at #40.

Rosie runs better than new! And she gets about 48 MPG! Even with my fat a$$ on her!

Don't give up, these XJs are simple, easy bikes to get right, and once you do, you will have a blast riding them!

Report back what you find.

 

After nearly 30 years; the Carbs need an Overhaul and you have to do a thorough examination to find and eliminate Air Leaks.

Moving-up the Bug List for why the Bike isn't running right is (are) Manifold O-rings Seals.
If you have Flattened and Hardened Manifolds Seals ... you got a very mean Air Leak to contend with.
The Manifold Securing Cap Screws are seized on many Bikes.
Trying to dislodge them will shear them off and leave you with a dilemma on you hands.

Seal the Manifolds to the Head.
Use RTV or a HighTemp Silicone and "Run a bead" around the Manifold where it meets the Head.
Force the material into the seam.
Seal that Manifold Seam air tight.

Retest with the Colortune after the Sealant cures.

BEWARE: Manifold Cap Screws will seem to be moving out upon the application torque to undo them.
You might be just twisting a soft-as-butter fastener the will suddenly snap.

 

Yikes, that could be a mess!

When I got Rosie, I saw on Rosie's head that two of the bolts holding the manifolds were different. That explains it! Also, they were replaced with SAE hex head bolts. Looked like crap.

I got them all pulled and cleaned the head surface, bought new ones from Chacal, and the correct got metric cap screws, but had to rethread those two buggered up holes. I then had to buy two longer, 30mm cap screws to draw them in.

I used anti-seize on the new cap screws and torqued them to 7.2lbs.

Nice and tight now.

 

Thanks for the tips. I'll give the manifolds (carb holders right?) a going over with RTV sealant and flush out the pilot circuit this upcoming weekend. Luckily, all my manifold fasteners turn freely.

One thing I have not had to worry about on this bike compared to other (even much newer) bikes is stripped/broken screws/bolts.

 

Well, sealing the carb holders and flushing the pilot circuit (again) has done nothing. Bike still runs super lean all-around with frequent misfires. I suppose now I have to troubleshoot a weak spark because I can't think of anything else it could be.

Problem is I took this bike off the road due to gas in the transmission. It was running just fine before that so wiring/plugs/battery etc should be fine. The only mistake I made was not recording the original pilot settings, and I tried fixing that with colortune but even 5 turns out produces a lean combustion.

 

5 turns out is wide-open, brother ... so, you got to find-out...
IF:
Its too much AIR ...
-or-
Not enough Fuel ...
-or-
Both.

Since you have a 5-turn-out Lean problem
We MUST Verify
Correct Value of Pilot FUEL Jet
Correct placement of Pilot AIR Jet
Fuel Passage open
Air Passage open
No Air Leaks
Synthetic Grease Throttle Pivots
Verify Fuel Flow into Carbs is unobstructed
Verify Fuel Distribution Gallery is clean.
Float heights
Remove Inline Fuel Filter and Run ON Prime

 

Pretty good thread so far...
I have #3 cylinder showing lean no matter what I do with pilot mixture and a bunch of other checks are not providing fuel to #3.

When you get an answer to your lean condition, please post.
Greg

 

Just one more thing to add. I found the gasket (foam) on the air cleaner where it presses against the air box missing in places. That was letting all kinds of air in to the system with out restriction. The 650 dose not like that as the inlet side is the choke point for airflow thru this engine. Replaced the foam gasket with window weather stripping and all the lean went away.

 

Petcock vacuum line (usually from #3, to petcock) VACUUM LEAK?

Split/cracked/loose?

"Fuel in the transmission" means petcock AND float valve issue, together.
What have you overlooked?
How did you set your float levels?

 

^^I just got a new air filter. Thats an excellent suggestion - I'm going to check to make sure the seal is proper.

I've recently replaced all my vacuum lines and all clamps are set. Fuel in the transmission was caused by float height + me leaving petcock on PRI. I've since readjusted the floats to proper height (checked by running clear tubing from the drain hole) and I no longer get gas in the transmission. THAT problem was solved, thank goodness.

 

Verifying Fuel Gallery Cleanliness.

Remove Float Bodies
Inspect Float Body "Beenie Screen" Filters
Examine the Fuel Supply Gallery for debris.

If the Gallery is severely discolored or there is an excess of foreign mater on the Beenie Screens, ...
Remove the No. 1 Carb from the Rack and remove the Fuel Supply "T" Fitting.
Use Pipe Cleaners or a Small Bore Rifle Barrel Cleaning Brush to clean any deposits within the gallery chamber.

 

Have you set the float levels yet?

 

I examined the airbox after work today and while the filter appears to be held air-tight against the opening, I did notice a portion of the airbox lid was cut away.



Gonna seal that hole up somehow, needs to be air-tight. Could be the cause of the leanness, but this is just a small pre-filter hole. Shouldn't be affecting the airflow too much.

The float bodies are great. I cleaned them thoroughly when I cleaned the carbs. Polished them too, along with the needles. Clunk test, float-needle action and float-height are all OK, for the record.

 

That's a sign that somebody lost his patience trying to put the Airbox Cover back in place after having it off for maintenance.

I've seen the Outside Diameter of the Oil Filter Dome Cover grinded-down a little bit to make it easier to pull the Cover for an Oil Change.