throttle cable

Hi:

I went to start my 1973 -850 ccCommando, and turned the throttle. It somehow lost its return resistence, like it may be stuck wide open.
Any suggestions on what this is and how to fix it- not much of a mechanic.
Thanks,
John

Maybe broken cable from twistgrip to the junction box, are the slides coming up? You'll need to remove the air filter to check this.
Although on second thoughts if the cable was broken the outer would easily pull out of the twistgrip, should be easy to identify this problem.

Hello John, and welcome to the forum,

If you can feel spring resistance when you pull up both left and right outer cables where they enter the carb tops then the upper cable could either have broken or one of its cable nipples has become unhooked, either inside the throttle junction box where the top cable splits into the two separate carb cables or inside the twistgrip housing on the handlebar?

If one of the two lower cables had broken then you should still feel some resistance when you opened the throttle?

Or the carb slides could have stuck open, in which case the lower cables should feel very loose when you pull on them?

Thanks daveparry and L.A.B.:

What I found is that there is a good pull on the cable until I can't access it under the gas tank. When I pullup on the cables as they enter the top of the carbs, they are quite loose, so if I 'm reading you correct, I should take off the air filter and see if the carb slides got stuck- right?
Thanks,
John

Yes John, remove the air filter and check the slides, sometimes they get suck up if the bikes been standing for a long time and then the throttle gets wound open. If they are stuck a squirt of wd40 might help.

hi slatebarn,if the slides are stuck open you will have excess slack in all the throttle cables,try shaking the cables or tapping the carb bodies with the handle of a plastic screwdriver,if the bikes been stood for a while you might need to dismantle and oil the cables and clean up the slides,when you open the throttle and let it go it should snap shut,with the air filter removed you will be able to see whats going

Thanks everyone. The next thing I was going to ask is- how do I get the slides to come back down. In the meantime, you posted to tap with a screwdriver handle. I did just that, and sure enough, the slides came down and it seems to work fine.
Appreciate all your help. I'm sure I will run into many other situations.
John

slatebarn said:

Hi:

I went to start my 1973 -850 ccCommando, and turned the throttle. It somehow lost its return resistence, like it may be stuck wide open.
Any suggestions on what this is and how to fix it- not much of a mechanic.
Thanks,
John

Click to expand...

Hi by not much of a mechanic do you mean you do not know how the cable is made up if so ...It runs from the throttle grip (single cable) to a 1 to 2 connector under the tank (It is a small cylindrical piece about 2 to 3 inches long ) from the other end of this 2 cables run to the carburetors (I am assuming you have 2 carbs )
1. If the carbs are stuck wide open you should be able to get hold of the cable going into the top of each carb and pull it up with no resistance. If there is resistance then when you let go it should snap back as the throttle slides are pushed back down by the springs.
2. If this is not the case then best bet is to remove the tank and check the complete cable it could have frayed or gummed up.
Depending on the length of your fuel hose you may not have to totally remove the tank but lift it up (after removing the tank bolts) and prop it off the frame with something soft.) This may enable you to get to the cable junction and carefully ease it out from under the tank to check it out.

One last thing to free it you may decide to use WD40 thats OK but after make sure you run some oil into the cable WD40 is not a lubricant .

slatebarn said:

Thanks everyone. The next thing I was going to ask is- how do I get the slides to come back down. In the meantime, you posted to tap with a screwdriver handle. I did just that, and sure enough, the slides came down and it seems to work fine.
Appreciate all your help. I'm sure I will run into many other situations.
John

Click to expand...

As you may guess this is an undesirable condition. You should really get the cabs checked and see exactly why they were sticking.

Seems like I've seen slides get dirt and corrosion that held them up after they sat awhile. I'd be tempted to check the whole thing, not just cables. Having had a stuck throttle on a couple of rigs it can add to your stress level.

Warped bodies are the most likely cause. If you are going to ride the bike like that, make sure you have a functioning kill button. It's pretty exciting trying to find the key while going down the road with the throttle stuck wide open. DAMHIK!

This would be an opportune time to get the carbs sleeved if they are not already. If they are, I have been able to remove the ovality from the carb body by inserting a socket that just barely fits and using a body hammer to restore the roundness. Test with the slide until it moves freely from top to bottom.

Then use a new o-ring and snug up the nuts to the manifolds but do NOT overtighten. It doesn't take much to distort the bodies.