Throttle (Cable) Sticking

[RandallIsland]

I just replaced the shortblock in my 85 K.

I've replaced the entire clutch, the throttle cable, clutch cable, air filter and rubber doo-dads/gaskets all around.

The throttle was working O.K before I took it apart, or at least, it had this infrequent tendency to want me to push the grip IN to the handlebars to work right. I thought the metal plate on top, next to the master brake reservoir, was not seated well.
So I torqued it and the symptom got better, so I just figured it was the throttle cable there, rather than something else.

Yesterday, I took it for its test ride, with the just the old throttle cable. It was dusk, I was exited, what can I say?
The motor started and idled fine. Then I took it up the hill and could not get too high an rpm, but then the motor really raced and would not come down, so I killed it, backed into the curb and ended up having to manually push the throttle down on the intake housing. Hummm.

I said to self; "Self, just replace the throttle cable, and you're gold", right?

This morning I did just that. This evening I took it on it's second test drive.
Again, the rpm just wouldn't come up on the short trip around the block.
So I parked it, double checked my work and started it up again, just to see if anything changed. And guess what...
* it idles way high.
* the throttle still won't back down unless manually pushing by the intake

What am I doing here?

A) Do I need to reset the idle speed? The book says that has to be correct before I can adjust the throttle cable. If so, fine, I've never done that so I'll learn and hope I don't need something I don't have, or something I do but have forgotten how to use.

But I hadn't realized I had changed it with swapping out a shortblock. OR...

B) Am I now in search of some mechanical problem in my throttle assembly?

Any thoughts?

[j-budimlya]

Throttle cable return spring?? wild guess....

[PGlaves]

I would disconnect the cable at the bottom end. Then determine if the cable is binding or the throttle body assembly is binding.

Then go from there to find where it is binding.

With the cable disconnected the throttle bodies should snap closed cleanly without any sign of resistance.

With one hand pulling on the lower end of the cable and the other hand working the twistgrip you should be able to feel whether the cable is movoing smoothly.

From there - if the cable isn't moving smoothly you have two things to look at. The routing of the cable itself,and the twistgrip assembly.

[RandallIsland]

Thanks Paul.
I'll post when I get there. Maybe tomorrow but possibly next weekend.

[RandallIsland]

Throttle cable return spring?? wild guess....

And a good one.
You were close.

I got sick of waiting for the weekend when I would have had time, so I cracked my throttle cable assembly (again) and put it back together. Same problem.

So, I started looking at the throttle return spring and guess what?
The fourth cylinder circle clamp screw on the intake gaskets to the throttle body assembly was interfering with the return of the throttle. Not by much, but just enough to make a millimeter of a huge difference, you may say.

Thanks for the help ya'll! I'm officially back on the road. :thumb
Best,
-Randall

[mjanulis]

For what it is worth, I had a very similar throttle return problem with my '87 k75. I had just washed & degreased the entire bike and engine. It was very very clean. Actually too clean.

My throttle cable was not sliding in the cable guide just above the return spring. I sprayed some WD and a little lube in the guide and everything when back working fine. I had really degreased the throttle body area way too much.

Just a thought for others to consider......MJ