Random idle speeds

[Mickeymoe]

This section of the forum seemed the place for this post. My GS1000G is almost complete and I'm looking forward to regular riding. I noticed when I test drove the bike late last year, that when you turned the handlebars to the left the idle would increase. Didn't pay it much mind because I knew I'd be going through the whole machine, and converting it to a full dress Vetter bike.

Well, I'm about all done and on my last test drive before some serious riding, I've come to accept that there is some type of idle speed issue. The bike runs like new, (17k / bought from original owner/ purchaser) and after it warms up it idles at ~1400 and would do so all day.

However, in between shifts, the idle does not seem to drop down but rather "sticks" at about 2000rpm. While this could be lived with, when I come to a stop the bike is then idling at that same speed. It may calm down, or it may not.

When I was talking to the owner before I made the purchase, he casually mentioned that he has occasionally "lubed" the control cables. This leads me to believe he knew he had a throttle cable sticking problem and was trying to fix it by forcing oil down the sheath.

I guess I could take off the tank, disconnect the throttle linkage, tie a string to the carb throttle rod, pull it manually and see if it "snaps" back to idle.

My theory is that the throttle cable is sticking or binding internally at random times and that's why the guy brought up the cable lube thing.

Unless someone has a better explanation I'll probably just buy an OEM cable and replace it and be done with it.

Any thoughts?

Again, it does not do it all the time....

Mark

 

[BigD_83]

A couple of thoughts:

First, it seems like the throttle cable is too short/tight. You really shouldn't have any changes to engine speed just by turning the handlebars so check the cable routing and the bracket that holds the cable at the carburetor. That can get bent and cause the kind of binding you are describing.

Second, your idle is set a little high. I believe you should be around 1000 rpm, not 1400.


Third, if that is the original throttle cable, getting a new one wouldn't hurt the situation. I've used some of the aftermarket (i.e. MotionPro) cables, and have been less than impressed with them. They are good in a pinch, but they are not as robust as the original and routing them is critical. I'd try to find an OEM cable for the extra $5.00-8.00 it'll cost. Parts Outlaw still carried them this time last year.

 

[Steve]

1. For the "increasing engine speed when turning the bars" situation, turn the adjuster IN at the throttle grip to give it just a bit more play. Verify that there is no change when you turn the bars to full lock in either direction.

2. For the "hanging idle" situation, your carbs are running a bit lean. Might be because they are dirty, might be because the intake boots have a leak. If you have not changed the o-rings that seal the intake boots to the cylinder head, get some new ones from cycleorings.com. While you are on that site, be sure to also get the stainless bolts that hold the boots to the head. The OEM bolts seem to be made of aged Cheddar cheese and removing them also tends to destroy them, so put the boots back on with better bolts.

3. Lubricating the cable is a good thing to do, but that is likely not your problem, it's more likely what I show as item #2. As BigD mentioned, aftermarket cables feel great and do a decent job, but the plastic liner in the OEM cables is a better quality and will last longer, so they are worth the extra expense. Lube the new cable before you install it.

.

 

[Mickeymoe]

BigD and Steve thanks for the input. Seems like the easiest way to start would be to go with a replacement throttle cable, will make sure it's NOS. Steve, I've recently had the carbs apart and they are as clean as when the came from the factory. I've also had the jets out and made sure the holes were perfectly clean. The boots look as new as the bike, and at this point there's no reason to suspect a vacuum leak. The owner drained all the fluids yearly and stored the bike is a big zip-up bag with descant inside. BTW, the hole bike now has LED lighting, the Vetter trunk has running AND brake lights too and with a turn signal on (and the bike off) the headlight does not even modulate. I took a measurement and with the old incandescent bulbs it was drawing ~7 to 8 amps with this arrangement. (When stepping on the brakes)

arm

 

[mnferwerda]

I think Steve was referring to the o-rings between the intake boots and the engine. The o-rings are not part of the carbs. They can cause the problems you described.

 

[Mickeymoe]

Thanks for the clarification Steve, that makes sense. I forgot about the O rings....

 

[850 Combat]

As far as the handlebars go, that is routing of the cable, whenever I've had the problem. If the hanging idle is unrelated to that, then the probably air leaks.