Kiehin race carb throttle return springs

[CanDman]

Hey guys....snowy is getting the complete maintenance package.  When I bought her she went straight to the mod clinic.  Anyway her throttle appears to have been set up for the drag strip....it never had any snap back to her the way CanD does....anyway...the throttle is very sticky in fact it gets stuck, so throttling back is done manually.  Does anyone have a Kiehin 39 carb and if so...do you have any photos of the  throttle return springs for those carbs. Any tips would be appreciated.  Kev

[Pat Conlon]

Paging Frank, please come to the white courtesy phone.....

[CanDman]

Paging Frank, please come to the white courtesy phone.....

 It's a ....nice day for a...white wizard  !!! Pick it up.... take me back home ya....   

[Flynt]

Paging Frank, please come to the white courtesy phone.....

Assuming you mean Flatside Frank from the west coast, here's a recent pic from the top.  I use the pull side cable only and the standard spring from the Keihen kit...  no return cable, so the kill switch is my fix if throttle sticks open.  It hasn't done that so far...



Frank

PS - Pretty lump isn't it...

[yaman]

Paging Frank, please come to the white courtesy phone.....

Assuming you mean Flatside Frank from the west coast, here's a recent pic from the top.  I use the pull side cable only and the standard spring from the Keihen kit...  no return cable, so the kill switch is my fix if throttle sticks open.  It hasn't done that so far...



Frank

PS - Pretty lump isn't it...

Yes, that is quite the beautiful sight!

[yaman]

well, it will be a couple days , but i have to remove the flat sides from the fzr to try to sync them(quite the task as i cannot adjust them while installed)
they are smaller but the same item
i do run the return cable as i used to run Mikuni RS flats on the old gixxer1100, the miks were known for hanging up without a return cable because the did not have the nice bearing rollers on the slides and just slid in a channel in the body of the carb, i guess they could get held in place buy the suction created by the motor
which brings me to this, i have been chasing a hanging throttle with mine just at a closing throttle, exactly like it was lean on the pilot- its not
one of the things i tried while  troubleshooting  was removing the slides to check for a bound roller or crud (this is where i lost sync as i was not able to locate the info on how to keep it after removal and reinstall of the slides)
FWIW i did find that servicing the slide plates and rollers made a noticeable difference , for the positive, in how the freely the slides moved
either way, let me know and i can get you some detailed pics when i get them out
unfortunately, my bench sync was so far off, its pointless for me to continue chasing my gremlin until i figure out how to get them properly synchronized, maybe i will get lucky and find that the the original issue was caused by poor sync in the first place 

[Flynt]

I found I could synch these live on the bike with vacuum gauges in the intake boot nipples, just like the CV carbs.  Difference is you have to measure, remove the "CR" cap and loosen the lock nut on the adjuster, then hold the cap down tight and measure again...  then adjust to get where you want.  Tighten the lock nut, replace and tighten the cap, then check balance again.  Sounds like a complete pain in the ass, but the adjustments are pretty easy and I believe they have very stable balance.  I checked balance after the valve adjustment done right after that picture and it was still great...  think I set it last a couple of years ago.

Frank

[Pat Conlon]

Frank, remind me, you have the FCR 39's correct?

Was it hard to get them into the 36mm oem manifold boots?

Yes, I like your XJR valve cover. I'm glad Robert talked me into doing the same on mine.

How's your oil consumption on those Pro lite's?

[fj1289]

Kev - sounds like an issue with the carbs.   Mine never "snapped back" as hard as the stockers or Mikuni flat slides (when the engine wasn't running), but they would close on their own. 

But, the roller slides made for very nice fine throttle control compared to the stick-and-yank action of Mikuni non-roller flat slides. 

[Flynt]

yes 39s.  They came with a thread in throat that fit the boots perfectly (sold as an FJ kit).  Oil consumption isn't an issue I notice.  I top it up between changes a little here and there.  It's much more adept at burning fuel...

Frank

[yaman]

i apologise for the hijack but, i would like to pick some of the brains here for my benefit
could y"all take a look at these pics and throw any opinion on trying to sync them?
i'm sure i can get the sticks onto the nipples on the manifolds, but its adjusting the slides
as you can see the caps are not accessible when installed and running
-i do think i could free the coils from the mounts if that looks like it would help
 

[yaman]

another

[fj1289]

May have to bench synch them.   Use a small drill bit shank as a spacer
We to set the slide height on each one equally.  May have to crank in the idle speed stop to raise the slides enough to make a good measurement.  A good bench synch should be fine for them. 

[JMR]

I found I could synch these live on the bike with vacuum gauges in the intake boot nipples, just like the CV carbs.  Difference is you have to measure, remove the "CR" cap and loosen the lock nut on the adjuster, then hold the cap down tight and measure again...  then adjust to get where you want.  Tighten the lock nut, replace and tighten the cap, then check balance again.  Sounds like a complete pain in the ass, but the adjustments are pretty easy and I believe they have very stable balance.  I checked balance after the valve adjustment done right after that picture and it was still great...  think I set it last a couple of years ago.

Frank

I have synched FCR and CR carbs on bikes (I have 39 FCR's) and....if I remember correctly... turning the hex head under the carb top controls up or down movement of the slide. Raising the slide (turning the hex clockwise) decreases vacuum...lowering it (turning counterclockwise) increases vacuum. The center slotted screw locks down the hex head adjustment nut (the adjustment nut is eccentric on the bottom allowing for up or down movement of the slide while turning it.) Same with CR's and Mikuni RS's. Mikuni TMR's are different.
All these can be synched while running....you need vacuum restrictors in your vacuum lines otherwise the pulses are to strong your synch fluid or rods will bounce a lot.
And despite what people say FCR's and RS's can run perfect on the street....you need to know carb circuits, how each effects the other, float height, needle tapers etc. RS's have a strong return spring but this can be lightened up a bit by taking a turn out of the return spring (pull the spring end off the post, let it unwind a turn and set it back on the post.) I highly recommend using a push/pull set up if you do this.
I removed the part of the the FCR throttle cable bracket that holds the cable ends and welded it to a more horizontal position. This allowed for use of both throttle cables. I use custom Motion Pro cable as the stock cable set up wasn't compatible. Throttle return i instant with real snap. The RS' can use the stock cables set up.

[JMR]

i apologise for the hijack but, i would like to pick some of the brains here for my benefit
could y"all take a look at these pics and throw any opinion on trying to sync them?
i'm sure i can get the sticks onto the nipples on the manifolds, but its adjusting the slides
as you can see the caps are not accessible when installed and running
-i do think i could free the coils from the mounts if that looks like it would help
 

Yes...moving coils will help. You will probably have to modify a wrench to get to the slide adjustment hex heads....I believe Motion Pro makes offset wrenches that work well. You will also need a stubby slotted screwdriver with a narrow head for the hold down screw. Once again you may have to modify a tool. I have a set of Kowa synch wrenches that I think are discontinued.