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Carburation Questions!

Started by pict, August 01, 2021, 08:20:15 PM

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pict

Have the carbs pulled on a 1986 FJ1200, and found 3 issues on the way in.

(1) The air filter (standard paper in original airbox) had a perished foam seal, so repaired that with foam insulating strip.
(2) The choke cable termination bracket on No.4 was between the carb body and the carb top cover, so the cover wasn't snug to the carb body. I'm guessing this bracket is supposed to sit on top of the cover?
(3) Float heights appear to have been set from the gasket surface to the very top (with carbs upside down - actually the bottom) of the float, and not to the top of the curve which I believe is the correct datum.

I presume all of these issues might have a detrimental effect?

Here's what was in there...
Main Jets : 112.5
Pilot Jets : 40
Pilot Air Jets : 155
Needle Jet (Emulsion Tube) : Y-2
Needles : Have 5 slots with clip in middle one.

Comparing this to a Haynes manual this all looks to be standard apart from the needles which should not be adjustable? All the jets *look* good apart from the screw slots on the pilot jets which are all a bit chewed. No sign of egginess at the tops of the needle jets.

Now I also have a Factory Pro rebuild kit from 2004 with new parts. The kit says it is for a 1986-1992 FJ1200. This contains:
Main Jets : 4 x 112.5 and 4 x 115
Pilot Jets : 4 x 42.5
Needle Jets (Emulsion Tube) : 4 x Nickel plated marked FACTORY 112K. The original tubes have a hole in the side just below the main jet. These don't.
Needles : *3* x Titanium needles with 5 circlip slots P/N 1175i-90q-70r-45t-TI (missing one)

Not sure if I should replace anything when I put it back together. I'd like to replace the chewed pilot jets but that is a change to 42.5 from 40 and I have no idea if that is sensible without changing the rest. I can't use the new titanium needles as I only have 3. These needles are around 1mm longer than the originals so not sure if I can use the new needle jets as they don't have the hole like the originals, and the matched needles are longer. I might as well throw the new main jets in there.

Can anybody knowledgeable on carburation please suggest the most predictable parts to reassemble with please?

Many thanks,
John
1986 FJ1200 1TX

balky1

Regarding number 1, buy new filter. They are cheap and you won't risk something getting in the engine.


FJ 1100, 1985, sold
FJR 1300, 2009

Pat Conlon

Use genuine Mikuni jets, emulsion tubes, and needles.
1) Free Owners Manual download: https://tinyurl.com/fmsz7hk9
2) Don't store your FJ with E10 fuel https://tinyurl.com/3cjrfct5
3) Replace your old stock rubber brake lines.
4) Important items for the '84-87 FJ's:
Safety wire: https://tinyurl.com/99zp8ufh
Fuel line: https://tinyurl.com/bdff9bf3

Troyskie

1984 FJ1100 Ms Effie brand new :)
1984 FJ1100 Pearlie, stock as.
1985 FJ1100 Mr Effie 647,000K and still running hard.
1985 FJ1200 'Yummy' takes a licking & keeps on ticking
After all is said and done, more is said than done :)
2013 Trumpy Tiger 800, let's do a lap of Oz

pict

Quote from: Pat Conlon on August 03, 2021, 09:46:16 AM
Use genuine Mikuni jets, emulsion tubes, and needles.

I have reinstalled the original needle jets, 112.5 mains and 42.5 pilots. All genuine. Thanks.
1986 FJ1200 1TX

wainot-Phil

,Hi from Aussie,,,
That all sounds about correct to me with what your existing Carby's have  in them  ,,,
BUT , If I was doing it ,
I would use the  existing Tubes and Needles ,
I would install and set the Carby's  up as follows:
PILOTS ====  Fit the  42.5
MAINS === 112
Move Needle Clip to 2nd groove from the Bottom on the 5 slotted Needle
Set the Float Height 22.3 from surface that the Gasket sits on to the top of ROUNDED Part of Float ,
I have set all my past and present FJ Bikes to the above settings and all has been good,
Just Make sure everything is Clean and that the Passage's in the side's of all of the float bowl's are not blocked  and that  Fuel runs through them all ,
Re-Fit Carby's
Set Mixtures ( which will be around 2 .5 Turns out
Then Balance the Carby's
then you should be good to GOOOOOOO
All the best
""Past Bikes""
Suzuki Stinger 125        
Honda 350/4
Kawasaki Z1000
Suzuki GS1000
Kawasaki GPZ900R
Yamaha FJ1100 84
Yamaha FJ1100 85
1991 FJ1200
1990 FJ1200  Pinky
2006 FJR1300
1980 GS850
Z500 /4
XJR1300
"""Present Bikes""": 
  1985 FJ1100
FJ1200  94
GSX1400

pict

Quote from: wainot-Phil on August 04, 2021, 12:21:01 AM
,Hi from Aussie,,,

Thank you sir, and Hi from Manitoba. Yesterday I reassembled the carbs with the original needle jets, the 112.5 mains and the 42.5 pilots. The floats were adjusted to 22.3mm gasket surface to rounded float bottom as best I could, so completely consistent with your recommendations. After reassembly I filled the float bowls and checked the fuel levels with tubing on the drains. They are all pretty close but there could be a 2mm variation or so. I found small changes in the attitude of the carb bank really effected where the fuel level appeared to be adjacent to the carb/float bowl join. I'll double check them today with a level on the carb tops. The needle jets don't look to be worn, but they may have opened a little bit at the top, so I'll leave the clip in the middle for now and can always richen it a notch once they are back on the bike as I can do that without pulling the carbs again. Really appreciate you detailing the settings that work for you.

When it comes to balancing, do you know if I should leave the vacuum tube to the igniter box connected or does it make no difference at low revs? I'm thinking I can connect the gauge via a t-piece if required.

Cheers,
John
1986 FJ1200 1TX

Pat Conlon

You need to disconnect the vacuum lines to hook in your manometer gauges so it's ok to leave the vacuum line open at the ignition box.
Remember, you are just balancing airflow between the carbs, so ignition timing does not come into play.
1) Free Owners Manual download: https://tinyurl.com/fmsz7hk9
2) Don't store your FJ with E10 fuel https://tinyurl.com/3cjrfct5
3) Replace your old stock rubber brake lines.
4) Important items for the '84-87 FJ's:
Safety wire: https://tinyurl.com/99zp8ufh
Fuel line: https://tinyurl.com/bdff9bf3

pict

Thank you Pat. That makes sense but didn't know for sure.
1986 FJ1200 1TX

wainot-Phil

Just disconnect the Vacuum Hose that goes to the igniter , Hook up a temporary  Fuel Line directly to the Carbs ,,,, You then put your 4 Balancing Hoses onto the 4 Brass nipples  coming out of the Manifold Boots , Start the Bike up , You then Adjust/Balance  the 2 Right Carbs using the right hand screw only  ,YOU then Adjust /Balance the 2 Left Carbs using the Left Hand Screw only ,  You then  bring the 2 Right side Carbs and the 2 Left Carbs together via the Center Screw ,You might  also have to slightly re-adjust /Balance 1&2 or 3&4 to get them all the exact same , hope that helps ,    I use a Morgan Carby Pro  Balancer  it is a great bit of gear ,Very easy to use and impossible to damage while using it , ,
""Past Bikes""
Suzuki Stinger 125        
Honda 350/4
Kawasaki Z1000
Suzuki GS1000
Kawasaki GPZ900R
Yamaha FJ1100 84
Yamaha FJ1100 85
1991 FJ1200
1990 FJ1200  Pinky
2006 FJR1300
1980 GS850
Z500 /4
XJR1300
"""Present Bikes""": 
  1985 FJ1100
FJ1200  94
GSX1400

Old Rider

I'm sure Wainot Phil meant that you should start on the left side first adjusting the carb 1 and 2 first then 3 and 4 then the middle screw to sync 1-2 and 3-4 together since the nr2 carb is the main carb where the throttle cable and the idle screw connects directly and the sync adjustment screw between carb 1 and 2 has no effect on the butterfly  opening or closing on carb 2.(Carb 2 is non adjustable)
Carb nr 2 also controls idle speed so set the idle first with warm engine

pict

Thanks for the pointers. Have an auxiliary tank for fuel supply I can rig up. I thought you were supposed to start with balancing 1&2 though? Going to use a DIY manometer with clear PVC tubing and ATF. Cheap, works well, and no calibration checks required.
1986 FJ1200 1TX

pict

Quote from: Old Rider on August 05, 2021, 02:06:43 AM
I'm sure Wainot Phil meant that you should start on the left side first adjusting the carb 1 and 2 first then 3 and 4 then the middle screw to sync 1-2 and 3-4 together since the nr2 carb is the main carb where the throttle cable and the idle screw connects directly and the sync adjustment screw between carb 1 and 2 has no effect on the butterfly  opening or closing on carb 2.(Carb 2 is non adjustable)
Carb nr 2 also controls idle speed so set the idle first with warm engine

This was the balancing order as I understand it. Thanks for confirming.
1986 FJ1200 1TX

ribbert

Quote from: pict on August 05, 2021, 08:51:40 AM
Quote from: Old Rider on August 05, 2021, 02:06:43 AM
I'm sure Wainot Phil meant that you should start on the left side first adjusting the carb 1 and 2 first then 3 and 4 then the middle screw to sync 1-2 and 3-4 together since the nr2 carb is the main carb where the throttle cable and the idle screw connects directly and the sync adjustment screw between carb 1 and 2 has no effect on the butterfly  opening or closing on carb 2.(Carb 2 is non adjustable)
Carb nr 2 also controls idle speed so set the idle first with warm engine

This was the balancing order as I understand it. Thanks for confirming.

What happens if you do the LH pair first, as you suggest, then the RH pair, if you then go back and tweak the LH pair again, haven't you just reversed the order?   :biggrin:

Noel
"Tell a wise man something he doesn't know and he'll thank you, tell a fool something he doesn't know and he'll abuse you"

Old Rider

carb nr 1-3-4 has to be adjusted to carb nr 2 since nr 2 is the non adjustable main carb.(nr 2 can only be adjusted with the idle screw or throttle cable)
When turning the LH screw all that is happening is that carb 1 is being adjusted to carb nr 2 nothing happens to the carb nr 2 butterfly, so when nr 1 is synced to
nr2  they are done and should not need any tweaking.  Then when turning the RH adjustment screw both carb 3 and 4 are adjusted to match (Butterfly is moving
on both 3 and 4 )
Then when centerscrew is turned only carb 3 that has been synced with 4 is adjusted to carb 2 the main carb that was synced with nr 1 when started the work
I'm not sure about what happens if starting with the  nr 3-4 carbs but if one of them is way off and they are synced first it can be difficult to adjust the 1-2 to them
That's how i understand it   :scratch_one-s_head: