After warm-up idle hangs at ~ 2k

[rpickle]

Hi.

Wondering if someone has seen this before.  I own a '92 FJ w/ABS.  It starts and runs great.  However, once warm, the idle will "hang" at 2k unless I pull it below 2k with the engine.  It will then stay at the idle I have set (11k).  Last weekend I pulled the tank back, warmed it up and then by spraying WD-40 all around the carb/intake connections I was hoping to get an RPM rise.  I didn't.

Any ideas?

Thanks

Rick

[Marsh White]

Rick, please clarify for me: how do you "pull it below 2k with the engine"?

It's not a stuck choke right?

[pdxfj]

Also check to see if there is any slack in the throttle cables.  I have seen several bikes I've worked on where the cables are adjusted too tight and they were actually holding the throttle open.  There should be a couple millimeters slack on the throttle.

Also the idle adjustment is located directly behind the engine.  You should be able to hear the carbs "snap" back when you release the throttle.  What you are hearing is the pin that is connected to the carbs coming to rest on the idle adjuster.

Sorry if that doesn't make much sense.  Too much caffeine today...   

[rpickle]

Thanks for the replies.

What I meant, is if by letting the clutch out with the bike in gear results in a lower RPM than 2k, then the idle will drop down to normal.  If I am in 1st gear then letting the clutch out (of course depending on ground speed) will usually result in RPMs higher than 2k unless I am barely moving.

Hard to explain....

I can check the throttle cables closer.   It will stay at 2k whether or not my hand is on the throttle.

Rick

[Harvy]

Would a sticking vacuum slide do this?

Harvy

[andyb]

Stuck slide will make it boggy and fat, mostly.

Give it a very careful synch and tighten down things carefully so make sure you're not getting a tiny air leak.

[rpickle]

Will give it a closer look.

Thanks for the help.


Rick

[Harvy]

true....I was just thinking that its only after it warms up....pointing to something expanding and binding.
But it is also fixed by changing the rpm by dragging the clutch a little while in gear and at idle throttle setting?
So is a change in vacuum or something like that causing it to fix itself like this?

Harvy

[rpickle]

Harvy,

That is what I thought may be happening.  I'm no mechanical super-genius, but my limited experience was pushing me in that direction.  My GS850g Suzuki would increase RPM's from idle up to about 2000-2500 rpm.  Very similar carbs.  The issue I found with them was the o-rings between the engine intake and the carb boots were total crap.  Chunks were missing.  Anyway, a new set cured the issue.  That is where I was going to look.  Not too difficult to get at these carbs, so pulling them off and looking them over will be done soon.

Appreciate the help.

Rick

[fjrider1]

Did the "O" rings do the trick? I'm having the same issue on my 86 but need do to the leaking head gasket and full synch....

[rpickle]

Well, I finally had a bit of time on my hands and decided to dig into it.  Pulled the rack of carbs.  Pulled the intake boots.  O-rings were in like-new condition, very plyable and no damages.  Checked the boots over real well, they too appeared to not have any leaks.  Stucked them back on the bike.  Visually inspected the rack of carbs.  Yikes!!!  There was crud everywhere!  Red stuff, black stuff...  Tore rack down individually to the bodies (one at a time) and boiled them.  They cleaned up like new.  Did 2 yesterday and then finshed the other 2 today.  Reassembled, cranked it up and took it for spin around the block.  Much less hesitation.  Idle works like a champ.  I will post back if it comes back, but I think I got lucky.  Not sure what the cause of the contamination was at least the red.  Tank inside in very clean.  The black crap I think came from the black foam that seals the top of the air filter.  When I changed it out after buying the bike, the old filter was missing most of that foam seal.  I think it dry-rotted and then was promptly suck into the carbs....

Anyway, thanks for the help. 

Rick

[Harvy]

Hey...well done Rick. Yep, my sons RM125 air filter was in a similar condition when we picked it up........thus so was the carby and even some in the crankcase. Would not even run.
I had a feeling something was causing one of the carbs to be sticking open.

Glad you got it sorted mate
Harvy

[rpickle]

Thanks.

I can't believe it ran as well as it did.  One jaunts around the state, I average around 48-55MPG!  I don't ride it like it is a rocketship and that I am indestructible either, but I do get on it at times.....

I need to find a set of luggage for it.  Stuff on e-bay goes for a pretty penny....

Later.

Rick