Throttle sticking bad routing?

thejet95

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Hoping someone has some ideas for me. I have professionally rebuilt and synced dual carbs from Murray's carbs. Had a previous thread about carb problems before I sent them off to Murray's. It now runs amazing other then the sticking problem. They came back with all new throttle cables as well. It is a single cable from the throttle tube then splits to 2 cables going to each carb.

When on center stand I can rev the engine, the throttle instantly snaps back, no sign of sticking at all. As soon as I ride it however it sticks consistently around 3k rpm and will only drop if I rev the engine. Downshifting won't really work to lower the rpms off throttle it just stays at 3k and pushes the bike forward, which is scary. Only way to stop it is to rev the engine in between shifts and when slowing down.

I have tried re routing the cables a myriad of different ways, no difference. Bought a motion pro cable luber and some cable spray and went to town. Made zero difference. I will attach photos of how the cable is currently routed, which is over the frame but under the tank, then through the left front fork and up to the right throttle grip. Does this seem correct?

Wondering if there is another possible problem other then the cables sticking. In other words can the cable be fine and the throttle be elevated by some other means either
by electrical (points?), or some other mechanical issue?
 

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Not a single idea? I have verified that the throttle cable is not sticking and is fully closed, but the RPM's will stay at 3k or so after driving a short distance. If I hit the kill switch with the RPM at 3k and don't touch the throttle, on restart it idles normally.
No ideas on other reasons throttle would stay elevated? I tightened up all the boots on the carbs to make sure no air leaks. Could back pressure in the
engine keep the throttle high? Maybe my oil hose routing is wrong? Got to be someone that has seen this before? The bike is un rideable like this.
 
It sounds to me like your carbs might not be synced 100%. I don't know if Murray syncs them on the bench before sending them to you, but it might be worthwhile to sync them while on the bike.
 
The single cable (pull only) does not allow closing the throttle with a twist of the wrist. I know the later 750's used a dual cable "push pull" setup so if the throttle did hang up you could pull it closed. I'm wondering if the throttle return spring is either weak or missing? Maybe add a supplemental spring to improve the return to idle position? I would try that first before undoing the synchronization that you put so much effort into getting done.
 
The single cable (pull only) does not allow closing the throttle with a twist of the wrist. I know the later 750's used a dual cable "push pull" setup so if the throttle did hang up you could pull it closed. I'm wondering if the throttle return spring is either weak or missing? Maybe add a supplemental spring to improve the return to idle position? I would try that first before undoing the synchronization that you put so much effort into getting done.
Yes there is a single cable on the throttle that then splits into the two going to each carb. When turned off and I twist the throttle it seems to snap closed nicely, but once running and under load it doesn't. I'll look into the spring for sure. Thanks for your input!
 
I just had the tank off my '79 and my stock throttle cables are routed lower than yours. They run under the front mounting tabs for the tank and underneath the upper frame tube. I wonder if the weight of the tank on that splice where the cable splits in two is causing them to stick?
 
I just had the tank off my '79 and my stock throttle cables are routed lower than yours. They run under the front mounting tabs for the tank and underneath the upper frame tube. I wonder if the weight of the tank on that splice where the cable splits in two is causing them to stick?
I’ll check and see but I’ve tried about 6 different ways to route it and makes no difference so far.
 
Hoping someone has some ideas for me. I have professionally rebuilt and synced dual carbs from Murray's carbs. Had a previous thread about carb problems before I sent them off to Murray's. It now runs amazing other then the sticking problem. They came back with all new throttle cables as well. It is a single cable from the throttle tube then splits to 2 cables going to each carb.

When on center stand I can rev the engine, the throttle instantly snaps back, no sign of sticking at all. As soon as I ride it however it sticks consistently around 3k rpm and will only drop if I rev the engine. Downshifting won't really work to lower the rpms off throttle it just stays at 3k and pushes the bike forward, which is scary. Only way to stop it is to rev the engine in between shifts and when slowing down.

I have tried re routing the cables a myriad of different ways, no difference. Bought a motion pro cable luber and some cable spray and went to town. Made zero difference. I will attach photos of how the cable is currently routed, which is over the frame but under the tank, then through the left front fork and up to the right throttle grip. Does this seem correct?

Wondering if there is another possible problem other then the cables sticking. In other words can the cable be fine and the throttle be elevated by some other means either
by electrical (points?), or some other mechanical issue?
 
I suggest loosening your throttle connections at the carb and manually lift the part of the carb where the cables were to see if it springs back on its own
 
Suggest to install new right throttel grip including the plastic pipe system.
I was thinking about this as well. I have a NIBBI aluminum throttle currently. Do you happen to have a specific model or website where I could buy? The single cable style is not as easy to find.
 
I have an aftermarket throttle housing on my 1981 cb750. After tinkering with the carbs and having to put the cables back on the carbs I always have to loosen the housing to let things relax (best way to describe it) and retighten.
 
I have an aftermarket throttle housing on my 1981 cb750. After tinkering with the carbs and having to put the cables back on the carbs I always have to loosen the housing to let things relax (best way to describe it) and retighten.
When I get home this weekend I will give this and other suggestions a try!
 
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