Need help with Idle problem 85' FJ600

Cbraun · September 14, 2015, 07:16:38 PM

Hi all
I'm having a issue with It not wanting to idle. It starts and runs after a little bit of ether when cold and starts like it should when warm but it wants to idle at between 3500 and 5000 RPMS!!! And when it does idle at a lower rpm its slow to return. I've had the manifolds off and sanded them back to flat using a 800 Grit belt sander and then touching it up with 1000 Grit cleaned them up and got some Permatex Motoseal Gasket Maker cleaned both sides up with lacquer thinner and let it dry and applied the sealer as directed. Carbs have been rebuilt. I have had it drivable before this and it has idled around 1600 with a smaller vacuum leak. but a manifold gasket broke and had to remove the manifolds only to find that they were warped. I have a new front tire on the way and this is the only problem i have left to deal with but I'm running around in circles with the same problem over and over again.

Any Advice would be greatly appreciated. I'm hoping to be able to get this bike running good enough so i can go take my licence tests before the weather turns too cold.

Thanks
Cbraun

movenon · September 14, 2015, 08:17:47 PM

Welcome. First IMO ditch the "Permatex Motoseal Gasket Maker" not needed and may do more harm than good. Replace all the manifold "O" rings (assumption that the 600 has O rings) with new one's they are inexpensive. Do not over TQ the manifolds.

Rebuilt carbs, the term "rebuilt" means different things to different people. But to start with check your choke cable and choke plungers. Do they all seat in equally and all in with no choke? Have faith it is fixable.

Have your carbs been balanced ? Probably not the cause but check the throttle cable and grip for any binding or slowness to return. Simple things to start with first.

George

Cbraun · September 14, 2015, 09:17:16 PM

The manifolds use paper or Graphite gaskets I forget which. What are the torque specs for the manifolds I cant seem to find them :/. The carbs were torn down and cleaned in a parts washer and reassembled with new seals and O-rings. Didn't sync the carbs because of the vacuum leak. it idled around 1200 before one of the manifold gaskets completely went and I found the warp in the manifolds. Ill check the throttle cable tomorrow.

JPaganel · September 14, 2015, 10:08:33 PM

Did you synchronize the carbs?

Cbraun · September 15, 2015, 07:53:49 AM

No they have not been synchronized the shop wouldn't even try because the manifolds had a small vacuum leak.

JPaganel · September 15, 2015, 10:31:57 AM

High hanging idle can be a symptom of out of sync carbs.

Could be an air leak. Have you tried using propane or starting fluid to find it?

I should mention that there is a particularly pain in the hind quarters place for an air leak - around the throttle shafts. Hopefully it's not that.

Cbraun · September 15, 2015, 10:21:11 PM

So I checked my throttle cable and it is a little stiff. And I was told by another motorcycle mechanic that the cable should have very little slack in it at full rest. Well mine was tight so just to see what it does I pulled the cable out of its mount and held it up just to where the the slack was out of it and was about 1/8" to short it was pulling the throttle plates open when in the bracket. Now with the cable detached it will idle but only in choke at 1600 rims and I guess I need to readjust the idle set screw because it dies when I let off of the choke. The cable has no adjustment left in it is all the way out and it's a little stiff

Cbraun · September 15, 2015, 10:26:08 PM

Oh and I found the sticker on the side fairing under some dirt and grime apperantly stock idle is 1200
Rpms. The sticker is still completely legible

JMR · September 16, 2015, 06:31:09 AM

You cannot tune around vacuum leaks. Replace the manifolds and associated gasket/orings. As someone mentioned check the enrichment plunger seals too.

Flynt · September 16, 2015, 08:28:39 AM

Quote from: Cbraun on September 15, 2015, 10:21:11 PM
it is all the way out...

Just to confirm... "all the way out" on the adjuster at the throttle is adjusting the cable housing to max length, effectively making the cable itself as short as possible. To fix the issue you describe you want to shorten the housing by screwing the adjuster at the throttle inward. Forgive if I'm stating the obvious.

Frank

Cbraun · September 16, 2015, 05:11:37 PM

so i start playing with the throttle cable and just decide to completely remove it and test run it. It finally starts by itself with no help from ether. no vacuum leaks around manifolds. it was idling around 1200 choked. My cable sheathing is stretched so i'm just going to replace it. but it wont stay running when taking it off of choke. and now i messed with the throttle plate adjustments(which i probably shouldn't have messed with :/) because it wouldn't shut all the way. And i have no idea what the idle mixture screws are set to. And now its up to around 2700. How do i adjust the carbs? I have a single vacuum gauge but i have no idea how to tune the carbs. I've never messed with a multi carb vehicle until i got my bikes so i'm still learning how to work on these things lol.

great white · September 16, 2015, 05:44:03 PM

Quote from: Cbraun on September 16, 2015, 05:11:37 PM
so i start playing with the throttle cable and just decide to completely remove it and test run it. It finally starts by itself with no help from ether. no vacuum leaks around manifolds. it was idling around 1200 choked. My cable sheathing is stretched so i'm just going to replace it. but it wont stay running when taking it off of choke. and now i messed with the throttle plate adjustments(which i probably shouldn't have messed with :/) because it wouldn't shut all the way. And i have no idea what the idle mixture screws are set to. And now its up to around 2700. How do i adjust the carbs? I have a single vacuum gauge but i have no idea how to tune the carbs. I've never messed with a multi carb vehicle until i got my bikes so i'm still learning how to work on these things lol.

Should be everything you need here: http://www.mediafire.com/?k0z54wr8zma9us3

Thats a haynes service manual. Im not a big fan of haynes and clymers, but it will do for what youre asking for.

great white · September 16, 2015, 06:00:17 PM

Actually, you might have to use this link to get to the downloadable manual: http://online-manuals.blogspot.ca/2013/12/yamaha-fj600-fz600-xj600-yx600-84-92.html?m=1

Mark Olson · September 17, 2015, 03:26:45 PM

Get back to a base setting..
Find the main carb which is the one the idle screw opens.
Use a drill bit as a feeler guage and put it under the throttle blade of the main carb..use a 1/8 bit and turn the idle screw in or out so the drill bit just slides under the throttle blade of the main carb.
Once you have that set ,now adjust the other carb balance screws so they all have the same gap as the main carb.
Turn the idle screw to close down the throttle gap and all the carbs should now move together . turn until there is just a little gap but not fully closed.....This will give you a starting point for a later carb balance.
As for the idle mixture screws , turn them in until lightly seated and turn back out 3 turns..this will be a baseline for tuning.
A vaccum guage is useless on carb sync , unless it has four guages.
This should get you running again..
Have you set the float level?
Are the carbs clean?
Is it running on all four cylinders?

Report back on progress.

Cbraun · September 17, 2015, 04:53:19 PM

Thanks for the link to the manual and all the help everyone

Float levels were set when they were reassembled and they were stripped down and cleaned. And it running oon all 4 cylinders too.
Ill follow the instructions you gave me Mark and let you know what happens after i set it all

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Need help with Idle problem 85' FJ600