sticking throttle,,

Fella, folks are trying to help and you are getting a lot of advice... the air screws won't change the high idle in all liklihood. They really don't have a huge effect one way or the other... except if they are grossly out of adjustment. If you turn them in till lightly seated and then turn them out 1 1/2 turns, they will be GOOD ENUF... If anyone could take an XRAY of the innards and see what a 1/2 turn does, they would understand why moving the needle up in the air passageway about an eyelash doesn't have much effect on idle. You can affect idle speed if you adjust them correctly but your idle is hanging and not just a 50-100 rpm so...

OK, your cables have slack. Next step is to pinpoint whether it is a mechanical issue or an air leak. Most of the time, I would have you check for air leaks... the carb holders SHOULD be changed every few years. The rubber hardens as the rubber sits in a place where it gets warm then cold a lot. Once it hardens some, the seal between the head and carb holders can be lost and air can leak. A bead of silicon sealer will fix this problem; if the you see even one small crack on the outside of a carb holder, REPLACE IMMEDIATELY...

I am sure somebody has had you spray WD40 on the carb holders with the bike idling. A leak will cause the bike to stall or spew white smoke. If there is no leak, the problem just may be MECHANICAL. The main cause for a mechanical sticking is:
1. weak throttle return spring
2. damaged main jet holder tube

In my business, I see both issues frequently. The first is not quite as common on a VM24 assembly as a VM26/28/29. You can usually figure out the spring issue by starting the bike with the throttle cable removed... the idle will hang and if you push down on the bellcrank at the rear the slides will close all the way... the spring will just not be strong enough to close the slides easily.

Second is the damaged main jet holder. To find this problem, remove the carbs from the bike and remove the throttle return spring. Open the slides with the bell crank by rotating it. If you feel a binding, one of the four main jet holder tubes (or more) are damaged. They get damaged by overtightening the main jet and the tube is pressed down into the needle jet which is the little jet that is press fit into the bottom/center of carb venturi. If you pull out the main jet holder tube and look at its end, it will be slightly distorted to one side. You can't fix this problem... you have to replace the tube.

There is also a very small possibility that one of the slide actuating mechanisms (the part that raises the slide and is attached to the shaft that raises the slides) is messed up. There are springs with stops that sit under and over a ball that allow the mechanism to pivot freely... if a part is damaged or missing here, the slide could stick.... I don't see this much but it CAN happen.

You might also get your manual out and BENCH SYNC the carbs per factory recommendations. The PURPOSE of a bench sync is to ensure the slide openings are in the MIDDLE OF THE ADJUSTMENT RANGE for the idle adjust knob... If you bench sync using a LARGE object... like a 1/4" drill bit, the slide openings will be open too far and you won't ever get the bike to idle down under 1500 rpm.

That's all I can think of. I do this stuff quite a bit so would actually have to see the carbs to be able to fix the problem if it is something else that I haven't thought of.

me109g4 wrote:

hi all, I have a 1980 kz1000 LTD, completely bone stock, I am having an issue with the carbs,, above 3000 rpm the throttle sticks open, like having cruise control, I thought it might have been the cables, but if i shut the bike off and restart, the bike is at idle. U can even see the throttle snap closed when u shut the key off, so is the passage of air through the carbs holding them open? and how do i fix it?

So you can actually see the throttle snap close after shutting off the engine. Take the cables off and actuate the throttle by hand. Feel for any resistance. You may have a out of round bore for your slides. This can happen if you have cold winters in which the fuel or condensation in carbs freezes and expandes the bore in one dirrection.
Also you my have a broken main needle and it is getting hung up on something.
You say that you actually see the throttle snap close so either you have cables fraying on the inside or something is wrong with your linkage and or slides.

A couple of questions:
Do you have a double cable one push one pull?
Did you take apart the carbs to make sure there was no bent or broken needles?
Is there any debris or rust on the linkage or inside the carb?
Do you run a fuel filter?
Is the spring strong enought on the carb body to close the throttle with moderate force?

About the only way you could see the carbs slides
snap shut when you turn off the motor is if
you have CV type carbs, cause they are vacuum
operated....

Bob

think we got it,, seems the slide in the #1 throttle is binding,, just enough it seems to make the throttle hang up. the drag could be felt by raising the slide, other 3 moved freely. fixing this is beyond my carb skills level so they were returned to the business that went through them and they are fixing it N/C. I wish to thank everyone who threw out ideas, I learned a lot just reading them. Regards to all. JT

Ok let me throw in my problem:laugh:

If I ride for a long way, and I pull up to a stop, sometimes the engine won't idle down. Sometimes 2000 or even higher rpms.So I reach down and adjust it down with the knob if it is really high. After it cools off it is ok, I have to readjust it because its too low.

Synce your carbs.