Help, help help the engine revs with the throttle closed

[Guest]

1978 gs1000E
stock, points, carbs cleaned last year.
2x times today on a 300 mi highway ride the engine revved up uncontrollably
Cruising 75 mph I had to kill the engine. Restarting the engine the revs took off. The throttle was closed.
how is it possible with the throttle closed for the engine to rev out of control
help
jim

 

[hampshirehog]

Either a sticking cable, sticking slides or somethings jamming in the throttle arm at the carb end.

 

[Steve]

Look at the clutch cable routing between carbs 1 and 2.

.

 

[Guest]

Yeah the VM carbs have quite a strong return spring, so something had to have gotten in there. Do you have a rodent problem?

 

[Guest]

Even a broken clock is right 2x a day

The cable closing the carbs came loose at the carbs. The spring would close the carbs below 4500 rpm. Above that rpm I guess vacuum or air flow or ? kept the carbs open.
Jim

 

[Guest]

Even a broken clock is right 2x a day

The cable closing the carbs came loose at the carbs. The spring would close the carbs below 4500 rpm. Above that rpm I guess vacuum or air flow or ? kept the carbs open.
Jim

I'm glad you found it, but I don't see the slides staying open with the spring in tact even with the return cable loose, vacuum does not open the slides on these carbs and the spring on these are like screen door springs, they snap back hard. My 78 1000 only has one cable and I've never had that problem. I see in your sig you are familiar with the 78 and 79 1000, but are you sure you have VM carbs and not CV carbs? The 80 1000 came with CV carbs, maybe someone did a head swap in the past.

VM

CV

 

[Guest]

I have the carbs in the top photo. Most of the time the spring did close the carbs but 2times it did not and the bike continued to accelerate. I have no explanation. I will check all the carbs and linkages. Is it ok to lubricate with wd40?
jim

 

[mnferwerda]

WD40 is NOT a lubricant, it is for displacing water.

 

[Peteortiz11]

I agree with GS Whisperer. I say this because the same thing happened to me

 

[Big T]

The throttle rod rides on rubber bushings, so silicone lube or Armor all would be appropriate

 

[850 Combat]

The VM carbs have a way harder throttle pull than the CVs do, which makes them more tiresome when touring. I've wondered if Suzuki didn't go light on return springs and use the return cable because of that. That said, If I were you, I would look hard at your throttle cable routing. I have seen them routed so close to the head that the vinyl jacket was cooked off, and no doubt any lube in that area was gone (clutch cables too, for that matter). Is your throttle action perfectly smooth in both direction? If not, it isn't right. It is important for your safety that you get this right. If it isn't right, it isn't safe. If it is sticky, it is probably well on its way to failure. The factory shop manual actually provides routing for cables and wiring.

 

[pandes]

interesting thread, I have the same problem