Slow to return to idle

[Troyskie]

Bike has a 'big bore kit' not sure what size. It could be anything for an 84, I suspect a 1219.

Original cans, but with Motad header and balance tube, pretty loud for stock cans, bit of a leak from RH can/collector connection, but no too bad.

Mains 120.
Pilot 42.5.
Needle 3rd clip down.
Mixture screws 2.5 turns out.
Barbies balanced.

CDI swapped, & suck check on pipe & unit ok (no I didn't lick it  )

Had pods with same settings, put an airbox on, same issue (air box still on).

Lines checked for leaks, seems good. Same for boots.

Mixture screws turned at 1/4 increment turns and slow return to idle remained regardless of all the way in or out. Now set at 2.5 turns for want of a better idea.

Ignition advance done to see if it is timing, no change.

Any ideas?

[Troyskie]

not sure if its related, but there was a bad flat spot till near 3k before the airbox was put in. Now gone.

Carbies have also been swapped, with a mix of original jetting, then change to current setup.

[roverfj1200]

Could be a stupid reply but have you refitted the balance tube caps...

Sure sounds like a air leak or such.

[Bones]

Bike has a 'big bore kit' not sure what size. It could be anything for an 84, I suspect a 1219.

Original cans, but with Motad header and balance tube, pretty loud for stock cans, bit of a leak from RH can/collector connection, but no too bad.

Mains 120.
Pilot 42.5.
Needle 3rd clip down.
Mixture screws 2.5 turns out.
Barbies balanced

Your Barbies might be balanced Troy but their either sucking air somewhere or just highly strung, ie" throttle cables sticking :

[Pat Conlon]

Big pistons pull big vacuum.

Bump up your air bleed jet from 155 to 160. This helped on my big lump.

[FJ Flyer]

Carbs sync'd?

[racerrad8]

Does the throttle plates snap back when released?

You should hear them regardless or air box or pods.

Secondly,  flat or curved bottom slides¿

Randy - RPM

[FJ_Hooligan]

Check o-rings on the intakes between the intake and the head.

Pat, going from a 155 to a 160 would make it leaner.

[Pat Conlon]

Yea, I hear ya David, a hanging idle (assuming no vacuum leaks) typically means a lean idle mixture, I agree.
However, something goofy happens with bigger displacement pistons, higher vacuum and the stock 155's.

Good news is that the air jets are the easiest of all to access and change.

[edit] Never mind, I mis read the first post where Troy mentioned the engine size, 1219cc is not that big.

[wainot-Phil]

Hi Troy ,   If the Carb's are  doing the same thing as before  when you and I  had a play with them  ,IMO  I would say that the idle is not really hanging as such ,like being to Rich or Lean,, ,It looked to me  that the Butter fly's are not snapping back closed onto the stopper as they should ,,,What I would do is undo/Remove  the Pull and Push cable  Nuts and remove  the cables out of the holders on top of the Carbs ,I would then start the Bike up and Rev it up a few times via pulling the Butter Fly shaft  BYE HAND and then letting  it go real quick and just see if the Butter fly's are Snapping  shut 100% back onto the idle adjustment stopper , If its still hangs up after this test ,,,You will 100% know it is a Carb adjustment or Air Leak ,, If needed,,,,,,,, I have another Bank of Carbs we can slip on to your Bike for a test ,,,,  just to  see if that makes any difference 

[Troyskie]

roverfj1200
Sure sounds like a air leak or such.
Yes mate, it is my second suspect.
Bones
Your Barbies might be balanced Troy but their either sucking air somewhere or just highly strung, ie" throttle cables sticking.
This is my first culprit. It looks and feels ok, but I'll check it out.
Pat Conlon
Bump up your air bleed jet from 155 to 160.
Nice! I'll keep that one up for an option if it is not cables or vacuum. I say 1219, but the PO was certain it was at least 1250.
FJ Flyer
Carbs sync'd?
Yep, well, as best as I can do .
racerrad8
Does the throttle plates snap back when released?
Yes, but I am going to check,
Secondly,  flat or curved bottom slides?
Curved.
FJ_Hooligan
Check o-rings on the intakes between the intake and the head.
I believe these had that done, but I'll check.
wainot-Phil
What I would do is undo/Remove  the Pull and Push cable  Nuts and remove  the cables out of the holders on top of the Carbs ,I would then start the Bike up and Rev it up a few times via pulling the Butter Fly shaft  BYE HAND and then letting  it go real quick and just see if the Butter fly's are Snapping  shut 100% back onto the idle adjustment stopper , If its still hangs up after this test ,,,You will 100% know it is a Carb adjustment or Air Leak
Thanks mate! I'll be doing that. I'm away for the next couple of weeks (zzzzz sounds familar) but should be able to do this check before I go.

Troyskie

[Troyskie]

I've finally been able to get back to the shed to continue with this fix.

Looks like it is fixed, but not fully.

I've a wealth of practice removing and re-installing the airbox now. A simple change in sequence from the Yamaha & Haynes method of install carbies to intake boots then 'push' the airbox over the back is now put the airbox on the carbies, then push the lot into the intake boots. Waaaaaay easier. This was with the subframe top mounts removed and the bottoms loosened.

I did try OldRiders' method of cutting some holes in the back of the airbox to help align the base of the airbox boots, but this is quicker and easier.

All told, not as easy as PODs, but, just personally, I don't like the induction noise and feel I get smoother power with the airbox on.

I feel the aftermarket pilot jets are just not quite right, so I've bought some OEM jets of the same size and will fit them later. I did check all points for vacuum leak and found none. Intake boots are good, hoses, caps, CDI hose, etc, etc, all ok.

I went back to super basics as Phil suggested and checked the throttle cables, all good, snapped back ok.

It finally came down to the cable free play adjustment at the carbies was a mickey whisker out. A 10 minute test ride and all is ok.

I'll be pulling the carbies one last time, swap the pilots, re-balance/sync & then re do the mixtures.

I'm really not a fan of the Motad exhaust system note. They are beautifully made, super quality welding and are well worth the coin they cost. Unfortunately I like the FJ as it sounds in OEM config, so I'll have to think about changing the headers out for original, but not yet.

On the end part of the test ride, although running a bit rough, Bendy HAMMERED!!!!! She certainly does have some Kookaloo!!!!!

Troyskie

[Sparky84]

On the end part of the test ride, although running a bit rough, Bendy HAMMERED!!!!! She certainly does have some Kookaloo!!!!!

Troyskie

Man I hate taking the carbs off but next time I'll try it your way.

So, have you taken it for a test run to the Pie Shop yet?

Looks like some nice weather this week!
I might have to take some time off from trenching in the cemetery.

Cheers
Alan

[Motofun]

You don't know carb pain until you do it for a CBX.  6 carbs in a "V" pattern...nothing is straight.  It takes a 4 ft long 2X4 to lever that bank of PIA into the boots!  Count your blessings.   

[Troyskie]

Al, I'm taking three of the girls to the Berry bike show this Sunday to remind people that the FJ exists. The only time I've seen an FJ at that show is my bike in the car park  .

Motofun, I think I'd lose the will to live with 6 carbies.