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
Regarding number 1, buy new filter. They are cheap and you won't risk something getting in the engine.
Use genuine Mikuni jets, emulsion tubes, and needles.
Quote from: Pat Conlon on August 03, 2021, 09:46:16 AM
Use genuine Mikuni jets, emulsion tubes, and needles.
+ 1 :good2:
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.
,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
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
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.
Thank you Pat. That makes sense but didn't know for sure.
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 , ,
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
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.
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.
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
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:
Rolf, that is incorrect.
3 Is the throttle cable carb. Also, it is possible to have the adjustment so far off on 1/2 & 4 that you can not adjust 3 closed or open in some case. Then the bike will either be idling too high or way too low to get it to run. You can take the idle adjustment screw completely out and the 3 carb will be hung open.
It really doesn't matter which side you start on. If I am doing a valve adjustment I sync them 1/2 then 3/4 & then 2/3. Simply because I am usually standing on the left side of the bike with the Aux. fuel tank.
When I tear the carbs down and break them into individual bodies, the carbs can be wildly off after reinstalling the springs. In this case I actually start on number 3 as I am shooting for a certain number with the vacuum of the bench sync, to let the bike idle. If I can't get it close, I know one of the other 3 carb bodies, or a combination of them, is holding the 3 carb either open or closed.
So long story short. It 100%, does not matter if you start left or right. You are adjusting 1 to 2 and 3 to 4 and then you finish by adjusting the left 1/2 combo to the 3/4 combo or vice versa
Quote from: RPM - Robert on August 06, 2021, 10:53:47 AM
Rolf, that is incorrect.
3 Is the throttle cable carb. Also, it is possible to have the adjustment so far off on 1/2 & 4 that you can not adjust 3 closed or open in some case. Then the bike will either be idling too high or way too low to get it to run. You can take the idle adjustment screw completely out and the 3 carb will be hung open.
It really doesn't matter which side you start on. If I am doing a valve adjustment I sync them 1/2 then 3/4 & then 2/3. Simply because I am usually standing on the left side of the bike with the Aux. fuel tank.
When I tear the carbs down and break them into individual bodies, the carbs can be wildly off after reinstalling the springs. In this case I actually start on number 3 as I am shooting for a certain number with the vacuum of the bench sync, to let the bike idle. If I can't get it close, I know one of the other 3 carb bodies, or a combination of them, is holding the 3 carb either open or closed.
So long story short. It 100%, does not matter if you start left or right. You are adjusting 1 to 2 and 3 to 4 and then you finish by adjusting the left 1/2 combo to the 3/4 combo or vice versa
Ok that's strange i always thought that the bracket that the idle adjustment screw pushes on and throttle cables are connected to sits on carb 2
and only moves the nr 2 carb butterfly. But seems I'm wrong and don't want too argue with professionals. :flag_of_truce:
It is, on the number 2 carb, if you are counting cylinders from right to left. :empathy2:
Regardless. It doesn't matter on these carbs, which side you start to adjust on. :yes:
OK making progress. Coil mod done. Carbs cleaned and set up with 42.5 pilots, 112.5 mains with needle in middle of 5 notches. Mixture screw out 2.5 turns on all carbs. Rigged up auxiliary tank, blanked the no.1 manifold port normally connected to the petcock and pushed start. Fired up pretty quick with a touch of choke. Idle seems pretty good and even, so presuming balance is decent, but plan to put the carbs on a manometer tomorrow. It revs freely with a slow roll on of the throttle, but if I blip it open quick it threatens to die. Am I correct in thinking that I am probably too lean on the idle mixture screws? Wondering do I try and fix this first and then balance or is it just an iterative process and could go ahead and set balance first and then visit the mixture screws - then back to check balance?
Get the balance done first....then fine tune your idle mixture.
You want your air flow even across the board before final tuning.
Warmed it up, and put it on my DIY manometer and balanced as best I could. The small divisions are 0.02 psi and the large ones are 0.1 psi. The balance drifts around a little but generally stays within 0.15 psi max difference between the highest and lowest cylinders. My Haynes manual states the max difference should be 0.19 psi so I assume I am good. Once balanced, there was no hesitancy in the throttle response so I didn't adjust the idle mixture from 2.5 turns out on all carbs. Thanks for all the input everyone.
Yes, it's amazing how carb balancing cures different symptoms.
I expect you will also notice a smoother running engine.
I'm very pleased. Responds much better than before and sounds happier.
Too late for this thread, but when syncing carbs don't forget to turn your front wheel so you don't cook the fender and be sure to use a big ol' fan to move some air through the engine. The fan should be obvious but you never know...