Noob question: wandering idle

Hi all:

New to XJs, I just purchased an 81 XJ650. This is my first bike and I'm having a wandering idle issue.
I start the bike with the choke on (when cold), when its "warmed up" it revs to ~4000 rpm, so I shut the choke off. Problem is it doesn't want to idle. It starts to sit around 1200 and slowly dies (~800 rpm), so I crank in some idle speed with the thumb wheel for it to sit at 1200. Mind you this is after a minute or so after the choke is off and the bike is running on its own.

So I drive a mile or so, and after a bit the idle starts raising to ~2500-3000. I pull over and reset the idle and its fine. However, when I go to restart the bike after I shut it down for a few minutes, the bike can't idle because its so low.

Is the choke operation normal, and what do you think of the idle speed?

 

Carbs are probably out of sync, that or you have an air leak. The choke is normal. You can check for leaks when it is idling low with propane. If no leaks are found, then you need to check to see if your carbs are synced. There is a lot if info on this site about carbs. Do some searching and pretty soon you will feel like an expert.

 

The short answer is - - you're getting air in there somehow.
Most likely throttle shaft seals (8) , Pilot "O" rings (4) intake boots compromized, and throw in Pilot wells not perfectly clean.

 

Sounds just like mine was--followed th how to's and asked a few questions--
carb problems must be top of th list of things to fix/maintain on bikes of this
age.

These links will help, good luck with it.


http://www.xjbikes.com/Forums/viewtopic/t=14692.html

http://xjbikes.com/Forums/viewtopic/t=8 ... art=0.html

 

What they said. Plus, make sure the bike is WELL warmed up before you set the idle screw, otherwise you will just be changing your idle all the time. Trust me on this. At least a half hour of riding, or you are wasting valuable time.

Once you get your idle "right for now", find the air leaks. You have some.

Check the pilot screws. Turn them GENTLY all the way in, and count the turns while doing it, then out 2.5 turns. Just see what it does. That is just a start, though. I set mine to 3 out, but I'm not done yet.

You aren't the first with this problem, and you won't be the last. You will find the answer here. Use the search up at the top, or you can go to google and type in the format between the brackets:

["exact words" not exact words site:www.xjbikes.com]

In between the quote marks you will only return those exact results. Without the quotes your search will be less precise.

 

I adjusted it with the bike completely hot. Now it just randomly opens up to 3000 or so. I think my linkage may be sticking (OH NO TOYOTA made my bike? lol)

 

Sounds like a sticking needle or air leak

 

If th revs go up to 3000 or so, randomly as you said and you didn't touch th throttle.... it's air leaks...I'll betcha.

 

A sticking throttle doesn't suddenly rise. It just doesn't come down. Not on a mechanical linkage, anyway. The spring pulls it shut. If nothing else, a sticky linkage will keep it there.

There are LOTS of threads about air leaks. You have some. Your bike is old. You have to find them. There can be no stray air coming in to the engine that doesn't come from the air box, through the filter, the carb intake boots, the carb, and the intake manifold boots.

If you are missing pieces, or have cracked pieces, or don't have your pieces tightened down, or (insert possibility here)....you will experience these symptoms.

My air leaks were obvious, but if yours aren't search around for how to test for them. I haven't done it, so I can't tell you how.

 

Two ways to test for air leaks:

1.) Use an unlit propane torch, or
2.) Buy a can of ignition spray

Get your bike running steadily. If you use the torch move it around to areas of likely leaks. If the ignition spray, spray small puffs into possible areas of leakage. In either case when you find the leak the bike's idle will surge each time you add the "combustible" gas or spray.