carb issues

[ergojack]

1984 FJ1100. Present mileage is 36,636 miles
Original issues:
Bike ran good above ¼ throttle, but poorly at or below.  Running rich, burbling, hesitating, backfires at times.  Once you're are on the needles, it runs good.
Did a 10 miles test ride with mostly low speed riding (85% slow riding on neighborhood streets.)
Pulled the plugs (which are new): (See photo 1 & Carb test 2A photo)
#3 is very sooted – cylinder is running rich
#1 is slightly sooted
#2 & #4 look good – clean with tan colored insulator

Pulled the carbs:
Remove the #3 carb choke plunger and checked both it and the bore. Both look good. Blew air through the fuel and air passages for the choke circuit. All seem good.  Removed and looked closely at the idle mixture jet. It seems OK.
Removed the float bowls, rested the carbs on a 60°-70° angle and checked all the float levels.  I had set these a while back when I replaced all the float needles.  I read on the FJ Owners forum that lower fuel levels is better for these carbs, so I set the floats a few mm high.
This time I used a digital caliper and set them as close to 22.3 as I could. (Final on all 4 is now 22.7mm measured on both sides of the floats.  I confirmed these settings with a metric steel ruler. It shows 23mm – all floats, both sides

I then secured the carbs in a vice with them level in both directions and checked fuel levels.
All fuel levels are way off:
Carb 1 = 18mm below the carb body flange
Carb 2 = 20mm below the carb body flange
Carb 3 = 18mm below the carb body flange
Carb 4 = even with the carb body flange

I again removed the float bowls and re-checked the float levels.  They are all at 22.7mm.
I again re-checked the fuel levels. Same results as before. I don't know how to solve this issue.
Just to see what would happen, I re-installed the carbs and synced them with a Motion Pro carb sync stick tool.  Went for a 9 mile test ride:
Very poor low speed performance. Hesitating, skipping, etc.
Above ¼ throttle performance started off OK, but got poor also – with what felt like bad surging.  I pulled the spark plugs once again and found all but #1 carbon fouled badly. It is now obviously running very rich on cylinders #2, #3 & #4.
To review:
I have all new float needles; all new carb O-rings, I had checked all 4 floats in a bowl of gasoline earlier when I replace the float needles. They all float and all are consistent with each other.
All float levels are now set at 22.7mm – well within Yamaha specs. It is obvious that lowering the float level caused the running rich problem to get worse.  I will go back and set the floats at the high end of the spec range, but this won't solve carb #3 as it ran rich before even with a high float level.

[DieHappy]

What are your pilot screws set at and are they clean?  I set my floats 22mm+, never checked the fuel level.  When I set my pilots I used the thumbnail method.  Screw them in so you can get a thumb-nail to catch then back them out till it lets go.  This assures your starting point is consistent across all four.  I know mine wouldn't run/start for shit until I fully charged the battery..  Is it all stock?  Pipes, airbox, jets etc..  Also are you measuring the floats from the proper spot, from where the gasket sits to the lower round portion of the float?  Just throwing some ideas at ya...

[Tuneforkfreak]

Isnt lean or rich adjusted with the mixture screw? I would be looking at the O rings in the mixture screws and making sure the washer was not crooked or something to where the O ring could leak and cause problems.

[a.graham52]

Sounds to me like your pilot jets are plugged or their circuits are plugged.

[DieHappy]

If there's any doubt maybe a complete tear-down rebuild is in order.  There's a great go-by in the files section.  Nothing as aggravating as having to pull the carbs on and off chasing them fckn gremlins.. Been there, done that

[racerrad8]

1) What coils/spark plug boots are on your bike ? (At least the boots do not appear to be the correct Yamaha boots by looking at the plugs)
2) The carbs are not level on the bike when mounted to the engine, so you cannot use that as a reference.
3) I am not sure about the 60-70*, even though it says that in the GYSM. But if you look at the photo the carb is at 90*.
4) Have you confirmed you have the proper 2.3mm needle seats in all four carbs?
5) Have you synced the carbs with a proper sync tool?
6) When you removed the needles seats how were the carb bores where the o-rings seal (good or pitted)
7) Have you checked the pilot jets for the same ainxw in all four carbs?
8 ) What is the current jetting; Main, needle, pilot & air bleed?

Those are a few starting points.

BTW, I am not sure where you read the float level should be higher, we set all of our builds at 22mm. It does not matter if they are for a FJ or race car.

Randy - RPM

[balky1]

1) What coils/spark plug boots are on your bike ? (At least the boots do not appear to be the correct Yamaha boots by looking at the plugs)
2) The carbs are not level on the bike when mounted to the engine, so you cannot use that as a reference.
3) I am not sure about the 60-70*, even though it says that in the GYSM. But if you look at the photo the carb is at 90*.
4) Have you confirmed you have the proper 2.3mm needle seats in all four carbs?
5) Have you synced the carbs with a proper sync tool?
6) When you removed the needles seats how were the carb bores where the o-rings seal (good or pitted)
7) Have you checked the pilot jets for the same ainxw in all four carbs?
8 ) What is the current jetting; Main, needle, pilot & air bleed?

Those are a few starting points.

BTW, I am not sure where you read the float level should be higher, we set all of our builds at 22mm. It does not matter if they are for a FJ or race car.

Randy - RPM

Randy,

isn't it 2.3 mm needle seat for 1984?

Ivan

[racerrad8]

Randy,

isn't it 2.3 mm needle seat for 1984?

Ivan

Yes, 2.3mm for the non fuel pump bikes.

Thanks for catching my error. I corrected it in the original post.

Randy - RPM

[ergojack]

To Randy's questions:
It has Accel coils & wires and it ran with them for many years with no problems
I am pretty sure that I'm the only one who has ever been in the carbs and they are OEM. This was before the fuel pump models came out.
I will check with the previous owner about the needle seat size, but the bike did however, run great for many years on these carbs.
I rebuilt them several months ago, but I don't remember any pitting or anything else unusual in the seats. I will verify needle seat size and condition this weekend.
I installed all new O-rings then along with the new float needles
All pilot jets are new
Carb jetting is:
mains - 122.5
pilots - 40
air pilots - 160
needle clips - 2nd groove down from the top
idle mixture jets 2-3/4 turns out
Carbs sync with a Motion Pro carb stick tool

If I understand correctly, a higher float level would equal a lower fuel level would it not? The needle would seat sooner

Not sure what ainxw is in question #7. Is that a typo?

[Pat Conlon]

Jetting looks fine (to me) although #40 pilots with 160 airs are equivalent to 37.5 and 155's which is the stock USA jetting.
I like larger pilots, they don't clog as easy. Your #40 pilots will work better with smaller 155 air bleeds.


You are Correct, the larger the measurement number, the lower the floats and fuel level.
Are you measuring from the correct point? http://www.fjowners.com/index.php?topic=9560.0

Cylinders #1,2 and 4 will be dialed in with your carbs, I'm worried about #3
How long since your last valve adjustment? Any tight valves found on #3?
How are your hot compression numbers?

[FJ_Hooligan]

Have you had the needle jets (emulsion tubes) out?  Perhaps the main air bleed is clogged?  What brand of air filter are you running?

Not enough mileage for the needle jets to be elongated and at 1/4 throttle it sounds like an idle circuit problem.  The PO made the common mistake thinking a larger number means a richer jet.  The 160 air pilot jet basically negated the 40 idle fuel jet.  122 mains seems big to me but that's not your current problem.

When you try to measure the fuel level, you need to let a bit of fuel run out of the float bowl before making the measurement.  I lower the clear tube to let it overfill then raise it back up so fuel needs to run back into the bowl then make the measurement.  Sometimes I even blow fuel back into the bowl and let it refill.

Randy,
Not picking on you, but if the fuel level is measured at the center of the float bowl then it doesn't matter what angle the carbs are sitting at.  The level pivots at the center of the bowl and is the same at all angles.

[ergojack]

Some history on the bike.
P.O. had the engine reworked at 18,000 miles- Bored to 1,188cc with 10.25:1 ratio Wiseco Pistons, Ported heads and oversize stainless steel valves. Cam sprockets were slotted for precise cam timing. He installed an oversize oil cooler at the time of the engine re-work. It has Accel Super Coils, and a 4 into 1 Supertrapp exhaust with K&N pod air filters.
The bike sat up in a garage, partially disassembled for 8 years.  Some gas was inadvertently left in the removed carbs, but the gas tank was drained dry. I thoroughly cleaned the carbs and installed all new O-rings and float needles a few months ago when I bought it.  It has had this low speed running issue since I got the bike running.  It also was very cold natured, so I went back and installed #40 pilots which helped the cold starting issue.
I have removed and closely examined the emulsion tubes. All 4 look good. I actually removed and re-checked #3 again last weekend.
You are correct that the main jets are too large still. I had to start somewhere, so I went down one size.  Even so, it still runs damn good at high throttle openings, but the exhaust is still black. 
My current problems are before the needles even start to affect things in any significant way.
I am checking the floats from position "B" if you look at Randy's post about setting float levels.

Recent compression test results are: #1 = 120 PSI, #2 = 120 PSI, #3 = 110 PSI, #4= 110 PSI (Repeated 4 times on a warm engine with the throttle wide open)   

Recent valve adjustment done – all are in spec and at the loose end of the range

This bike was running great when the P.O. stored it.  He had gotten a newer bike and had just quit riding this one. His goal was to do some restoring on it, but he lost interest.

[ergojack]

Took the carbs back off today.  Removed all needle & seats.  All look fine.  They are 2.3mm, but this is the correct size for my gravity fed bike.
Put all 4 floats in a bucket of gasoline again. All are floating and all are consistent with each other. Removed and checked all 4 pilot jets.
All are clear and all have the same #40 on them. (Of course if they were plugged, it would run lean or not at all once the choke was closed)

[Pat Conlon]

Does the choke linkage articulate correctly? #3 choke hanging open, even a little?

I wonder if you have a leak in the choke circuit causing the extra fuel?

[ergojack]

The choke circuit and linkage system is the 1st thing I checked. Everything is working correctly. The choke plunger for #3 looks fine.
I'm still thinking it's something in the float system because when I had the float levels set high, only #3 was running badly rich.
#1 was just a little rich. #2 & #4 looked great (refer back to the 1st plug photo)  I feel sure that if I set the float levels high again,
it would do fine on 2 & 4 and just a little rich on #1.  Setting them too high doesn't solve the problem, only masks it.

This is so frustrating to me.  I don't want to toot my own horn, but I am an ASE Master Certified Auto technician from way back when
all cars had carbs.  I have rebuild 100s of them!  I have been a motorcyclist for over 40 years and have always done my own work. 
To have these simple carbs kick my ass is very humbling. I have taken these things off this bike about 7 or 8 times now.
OK, I'm done pissing & moaning now.  I really need a solution.