Odd behavior of carb. butterfly valve

[Droneh8tr]

83 Venture

Carbs rebuilt, idles nicely...except..

When I release the throttle the idle rises to about 2000 rpm. I removed the throttle to lube it etc., started the bike and the idle still floated up to 2000ish rpm. Hmmmm..

Manually pushed the arm on the carb. the throttle cable attaches to down to the throttle stop screw and the idle was fine. When I let it go, the arm raises off the screw. I saw no binding or tension on either throttle cable. The throttle was still disconnected. When the bike is off the arm will lay nicely on the throttle stop screw.

I HAVE NOT as of yet tried to sync the carbs.

What is causing the arm to raise up off the throttle stop screw? Could it be so far out of sync that vacuum in one or more carbs is pulling the throttle open?

[Black wing]

That could certainly be a possibility, one of the big symptoms of out of sync carbs is that the idle will rise on its own. If I were you before any digging begins check the sync

[Peder_y2k]

The throttle control uses two cables, one to open, the other to close. If one is slack, then the throttle plates can move. There is also a small return spring on the carb linkage that could be compromised.

-Pete, in Tacoma WA USA

[Droneh8tr]

That could certainly be a possibility, one of the big symptoms of out of sync carbs is that the idle will rise on its own. If I were you before any digging begins check the sync

 

Thanks, allright, maybe I'll go ahead and start the syncing job and see what happens..

 

The throttle control uses two cables, one to open, the other to close. If one is slack, then the throttle plates can move. There is also a small return spring on the carb linkage that could be compromised.

-Pete, in Tacoma WA USA

 

The spring on the carb. seems plenty strong. It works pretty well when the bike is off. It easily pulls the throttle to a closed position. Thanks for your insight..

[Venturous Randy]

Thanks, allright, maybe I'll go ahead and start the syncing job and see what happens.

 

With what you are describing, you may need to check for vacuum leaks before you try to sync. Get some starter fluid and spray around the base of the carbs and the manifolds with it running and if it speeds up, you have a leak. If you have a vacuum leak and try to sync, you will just include that into your readings.

RandyA

[Droneh8tr]

With what you are describing, you may need to check for vacuum leaks before you try to sync. Get some starter fluid and spray around the base of the carbs and the manifolds with it running and if it speeds up, you have a leak. If you have a vacuum leak and try to sync, you will just include that into your readings.

RandyA

Thanks for the reminder, I'll keep it in mind..

[FJ1200]

The leak will probably be the problem.

 

I had a similar problem but my carb vacuum membranes where incorrectly installed. So you might check that out also.

[Droneh8tr]

The leak will probably be the problem.

 

I had a similar problem but my carb vacuum membranes where incorrectly installed. So you might check that out also.

Well I did just do a rebuild, although I was very meticulous about installing the diaphragms.. But I'll definitely look closely at that..

[StarFan]

I would guess you are missing a small spring in the carburator assembly. When I did the carbs on my former 1998 Tour Classic I had the exactly same problem. The idle was high up but I could push the arm down and the idle would be fine - by realesing the idle went again up to 2000 to 2500 rpm´s. Took me a whole night to figure this out with a help of a friend. We found out that there was one little spring missing. It was d#%"$ difficult to get it in the right position but got it done with a lot of patience.

See photo. it was either one of these little buggers. Don´t get fooled by the size of the pictures. These guys are small.

 

 

http://i1281.photobucket.com/albums/a501/jonaslill/Yamaha%20Venture%20Millenium%202000/Untitled_zps47b2813a.jpg

[Droneh8tr]

I would guess you are missing a small spring in the carburator assembly. When I did the carbs on my former 1998 Tour Classic I had the exactly same problem. The idle was high up but I could push the arm down and the idle would be fine - by realesing the idle went again up to 2000 to 2500 rpm´s. Took me a whole night to figure this out with a help of a friend. We found out that there was one little spring missing. It was d#%"$ difficult to get it in the right position but got it done with a lot of patience.

See photo. it was either one of these little buggers. Don´t get fooled by the size of the pictures. These guys are small.

 

 

http://i1281.photobucket.com/albums/a501/jonaslill/Yamaha%20Venture%20Millenium%202000/Untitled_zps47b2813a.jpg

 

Thanks Starfan.... My springs are present... I'm gonna go with the springs not being anywhere near the right tension ( sync way out) and adjust accordingly.

But, thanks for the reply