fixing idle issue

[Striker]

Hey I have a 1985 FJ1100. It runs great and idles great at startup, right at 1000. Except for the fact that after it warms up and the idle jumps to 2000. And stays there at idle! I have done a little research and it seems the consensus is that one of the previous owners messed with mixture and got it where to much fuel gets past the bypass valves. I have the FJ manual on pdf and it says I might be able to fix things with the throttle stop screw for main idle. But picture is bad so can't tell exactly where it is. Any help with this issue would be much apreciated!

[rlucas]

The throttle stop screw is between the second and third carb, *under* the carb bowls. You can see it from the right side of the bike, it's a knurled wheel. You can usually reach it with your hand from the right side; if not, use a long flat-bladed screwdriver to turn the knob.

Be aware that adjusting the screw WILL NOT affect the current air/fuel mixture, just the idle speed. Changes to the air/fuel mixture gets a bit more complicated. I'd also pull the carbs and give them a thorough cleaning, then re-mount and balance the carbs. My '86 originally had a similar issue.

Welcome to the club...this is where all the cool kids hang out!

Rossi

[andyb]

If it absolutely idles at 2k when hot come hell or high water, let it get good and hot, then adjust it down to 1100 or so.  Then use the choke when it's cold to keep it from dying on you.



#31 is the idle stop screw.  It's a little hard to see, it just peeks out and you can see about half of it from the side of the bike.

It's shown clearly in a photo here.

[Arnie]

Hey guys!  At least tell him to wear a glove while making the adjustment.  It gets hot in there.

Arnie

[andyb]

My mitts don't fit in there.  I use a long flatbladed screwdriver.  Even if the motor's cold and I really cram my hand in (boy, that would sound bad out of context...) I can't hardly twist the thing (even worse..), so a screwdriver from one side to go up and the other side to go down (...).

[mikeholzer]

My mitts don't fit in there.  I use a long flatbladed screwdriver.

+1 on the long screwdriver. My hands aren't huge, but I still can't fit them in there. And, the tach usually lies; I hook up my timing light and use the idle feature to get a better reading.

[Striker]

Hey thanks a lot for the info!! I'll definitely be using it to see if I can get it to run a little better. In general I feel lucky I was able to get this bike for $1000 with no big problems.

[Striker]

Took the tank off to look at the carbs better and saw that some previous owner has exposed the 4 mixture screws in front of the carbs. I've heard that if those are opened to much it could cause the problem I have? If that is the issue what would be the best way to fix that? Thanks again for all the help!!!

[andyb]

If it's idling high, it's idling high.  Nothing to do with the mix screws.

If it's idling fat (read the plugs, for starters), then you're going to start looking at mix screws.  I don't know that I've ever seen a bike that had those plugs in place, ever, they're the first thing to be removed if someone has to clean carbs and do a decent job, or if they think they're "tuning" by doing silly things with them.

[Striker]

took out the spark plugs and it looks like it's running a little lean. I recently moved from 4500 ft above sea level in Utah to Phoenix a around 1000 ft. Wonder if that might have changed something?

[jack02]

I don't know that I've ever seen a bike that had those plugs in place, ever,

Mine has. Twenty one years old and there they still are... but when I dropped one once,it took days of searching and grovelling around in the dirt to find it. Would never have slept again had it not turned up !

[Arnie]

took out the spark plugs and it looks like it's running a little lean. I recently moved from 4500 ft above sea level in Utah to Phoenix a around 1000 ft. Wonder if that might have changed something?

Yeah, the move to 3500 ft lower would cause it to run a little lean, and that might also cause the idle to go up a bit. 
Normal for the mix screws is between 2-3 turns from seated, but Yamaha sets them with and Exhaust Gas Analyzer and then puts those caps on to keep our dirty fingers out. :-)
You could try seating the screws (lightly or you can damage the tips) and then back them out 2 1/2 turns.  Then do blip tests to get it right (see files section)
BTW  All 'wasted' spark engines' plugs will look a bit lean even when they are carburated correctly.

Cheers,
Arnie

[Firehawk068]

took out the spark plugs and it looks like it's running a little lean. I recently moved from 4500 ft above sea level in Utah to Phoenix a around 1000 ft. Wonder if that might have changed something?

Hey, where in Phoenix are you?
Erich lives in Chandler. He's got an '84
I live in Mesa. Mine's a '90
if you ever need any help, I've got plenty of tools, a garage, a set of vacuum gauges for carb sync.
We are all willing to help out usually 

[andyb]

Changing elevation also often changes temperature a bit (it's cold up there!) which helps balance things out a bit.

Sounds like you're dead set that they're wrong, and are going to fiddle with them no matter what, so you may as well fiddle with them correctly.

I personally like the way of adjusting them as described for the RC21 motors by honda, as seen here.

[Striker]

Well, I live in Scottsdale so any help is always greatly appreciated! I'm not dead set on changing them, I just thought it might be the most logical thing for the idle being a bit off. And thanks for the link on adjustment!