My Gosh GS650 Woes! Engine revs to 9k after starting..

[Anonymous]

Ok.. This is not a good thing.
1982 GS 650 with mikuni cv 32mm carbs

I just cleaned out the the carbs top to bottom. New plugs, stock airbox installed. Throttle cable is not hanging up. With or without the choke this beast revs as soon as you start it up. Obviously i hit the killswitch as fast as possible. I tried adjusting the idle mixure screws from all the way in to 2.5 turns out.. no change.

Just prior to this I had it running (just to test the cleaned carbs) with the airbox off and it was idling fine but would stall if you turned off the choke or gave it fuel.

Looking for any suggestions. I am at a loss at this point.

 

[Anonymous]

I have this exact same problem with my 1985 Suzuki GS 700. I didn't understand how the idle screw worked, so I took the carburetor off and now I get that, so after I put it back on I hope it will work - any assistance on this would be greatly appreciated!

 

[earlfor]

Re: My Gosh GS650 Woes! Engine revs to 9k after starting..

Between your #2 and $3 carbs on the airbox side, you will find a knurled idle adjustment knob/screw. Look at your throttle linkage on the carbs as you turn the idle adjustment screw counterclockwise to reduce idle. You will see the carb linkage lower and lower and lower, until it is down all the way. Once the linkage is at the bottom of its travel, continue looking at it while turning the idle adjustment screw clockwise, As soon as you see any movement in the throttle linkage raising (on the side of any of the carbs)
turn the idle adjustment screw in about two turns. Start the bike, turn the adjustment screw to maintain a 1200 rpm idle. Once the bike is warmed up, you will need to reduce the idle setting to maintain a 1200 rpm idle.

Earl

Ok.. This is not a good thing.
1982 GS 650 with mikuni cv 32mm carbs

I just cleaned out the the carbs top to bottom. New plugs, stock airbox installed. Throttle cable is not hanging up. With or without the choke this beast revs as soon as you start it up. Obviously i hit the killswitch as fast as possible. I tried adjusting the idle mixure screws from all the way in to 2.5 turns out.. no change.

Just prior to this I had it running (just to test the cleaned carbs) with the airbox off and it was idling fine but would stall if you turned off the choke or gave it fuel.

Looking for any suggestions. I am at a loss at this point.

 

[Anonymous]

no luck

no luck

Thanks for the suggestion Earl. I tried that. With the knob backed all the way out it is still doing the same thing. Not sure how this is possibly happening. I soaked the carbs in carb-dip so i know they are clean....
I dont think a plugged jet or passage would cause this behavior anyhow

Richard

 

[earlfor]

Re: no luck

Re: no luck

For rpm to increase, the slides in the carbs MUST be raised. For that to happen, either the throttle linkage is being pulled, or the slides are installed incorrectly and jammed into the top of the carbs with no travel possible.

Have you looked into the airbox/intake side of the carbs to visually verify the slides are resting all the way down in the carbs?

Have you tried disconnecting the throttle cable and started the engine.
(Since you do not use throttle anyway when starting, this would verify that the problem is not something in the cable travel adjustment.)

When you start the bike with the choke, have you visually verified that returning the choke to the off position does return the choke linkages on the carbs to the off position?

The engine cannot rev to 9K if the carb slides are not raising.

Earl

Thanks for the suggestion Earl. I tried that. With the knob backed all the way out it is still doing the same thing. Not sure how this is possibly happening. I soaked the carbs in carb-dip so i know they are clean....
I dont think a plugged jet or passage would cause this behavior anyhow

Richard

 

[Anonymous]

makes no sense

makes no sense

The slides are free sliding and are down when the engine is not running. not sure exactly whats happening when it is running. I can push on the slides they move all the way up and when i release they come all the way down.

I have tried with no throttle cable attached still same.

When the choke is off the choke slides go all the way in.

I am not exactly sure how the slides themselves work i presume they are vacuum based?

Richard

 

[earlfor]

Re: makes no sense

Re: makes no sense

There is a vacuum relief port on the right side of carb 4 and on the left side of carb 1. The hoses on those ports/fittings should be vented to atomsphere. You dont have the two ports connected with a single hose by chance?

Earl

The slides are free sliding and are down when the engine is not running. not sure exactly whats happening when it is running. I can push on the slides they move all the way up and when i release they come all the way down.

I have tried with no throttle cable attached still same.

When the choke is off the choke slides go all the way in.

I am not exactly sure how the slides themselves work i presume they are vacuum based?

Richard

 

[earlfor]

Re: makes no sense

Re: makes no sense

There is an internal bypass/vacuum bleed channel in the carb body and vacuum is balanced by the spring located on top of the slide. You DID put the springs back in didnt you? LOL

Earl

I am not exactly sure how the slides themselves work i presume they are vacuum based?

Richard

 

[Anonymous]

hahaha yes the springs are back in! Now this vacuum port is not famillar to me. I do have two T's in between 1and2 and 3and4 of thats what your talking about. Those i thought we overflows but they are vented to atmosphere separatly. Perhaps they are pinched somehow..
i will check that in the morning

 

[earlfor]

Re: makes no sense

Re: makes no sense

I dont have a 650, so I can only say for a fact how my 750 is set up.
Carb 1 and 2 vacuums are TEE'd together to atomsphere. Carb 3 vacum operates the petcock. Carb 4 vacuum goes to atomsphere.

Earl

The slides are free sliding and are down when the engine is not running. not sure exactly whats happening when it is running. I can push on the slides they move all the way up and when i release they come all the way down.

I have tried with no throttle cable attached still same.

When the choke is off the choke slides go all the way in.

I am not exactly sure how the slides themselves work i presume they are vacuum based?

Richard

 

[Anonymous]

ahh

ahh

ahh ok.. on my carbs i only have one vacuum port for the petcock..
I am getting a second set of carbs soon so i am going to rebuild those and see if the problem still persists..

 

[earlfor]

Re: ahh

Re: ahh

I assume you have the boots tight, the airbox in place with a filter and have the float bowl floats set to the correct height? If the 650 carb rack only has the one vacuum port and that is used to operate the petcock, I dont think that could be the problem.

Earl

ahh ok.. on my carbs i only have one vacuum port for the petcock..
I am getting a second set of carbs soon so i am going to rebuild those and see if the problem still persists..

 

[Anonymous]

more info

more info

Yeah i spent a long time making sure it was all together good. I took all the boots off and inspected them, o-rings are good, i used RTV Silicone to hold the boots in the airbox, they were a little loose fitting previously.

 

[earlfor]

Re: more info

Re: more info

On the forward face of the carbs (the side between the carb rack and the cylinder head), you will see in each carb throat (when the carbs are removed from the induction boots) a round plate. That is the throttle plate. That plate is moved mechanically by the throttle position. If that plate is closed, it is not possible for the engine rpm to increase beyond what can be caused by leaning or richening the mixture screws. If the throttle cable is disconnected, then it is not possible to actuate the throttle plates. So.........for the idle to increase, either the throttle plates are well open when the linkage is in the return/off position, or the throttle plates are jammed in place and cannot move. Remove the carbs and check the throttle plate position on each carb. When the throttle linkage is in the idle position/off position, the throttle plates should be closed. There should beless than a 1/32" gap between the edge of the throttle plate and the surface of the carb throat.

Earl

Yeah i spent a long time making sure it was all together good. I took all the boots off and inspected them, o-rings are good, i used RTV Silicone to hold the boots in the airbox, they were a little loose fitting previously.

 

[Anonymous]

650

650

Ok, When i put them together it was not an issue but who knows now. I am going to have a look inside with a mirror through the airbox to see what the slides are doing and if they are up maybe i can see the throttle plates too..

Thanks for all your suggestions.

Richard

 

[earlfor]

Re: 650

Re: 650

The slides should be in the full down position when you look. You will need to push them up with your fingertip and hold them up to be able to see the throttle plate on the other side. I doubt you will be able to accurately see the required 1/32" or less throttle plate gap without removing the carbs. Besides that, you need to have all throttle plates set to the same minimal gap at rest. I would just pull the rack, set all the throttle plate positions and work the throttle linkage with my finger while observing throttle plate operation and return. Its is a fact that the rpm cannot increase if the throttle plates are closed at idle and return to the closed position after being opened. There is something mechanically wrong...gotta find it.

Earl

Ok, When i put them together it was not an issue but who knows now. I am going to have a look inside with a mirror through the airbox to see what the slides are doing and if they are up maybe i can see the throttle plates too..

Thanks for all your suggestions.

Richard

 

[Anonymous]

carbs

carbs

Ok I have the carbs on the bench.. I don't see any space between the plates and the carb body. I have a small wire i mic'd at about 1/64" and it does not go in anywhere. I however did notice on carb #1 and #3 the bores are not perfectly smooth where the throttle valve closes.. perhaps this can be my problem?

slides are all the way down..

 

[earlfor]

Re: carbs

Re: carbs

I dont think a slight roughness in the bore of two carbs would be the cause.
The part I cannot get past is that if the throttle cable is disconnected, then the springs on the carb linkages hold the throttle plates in the closed position.
Engine intake vacuum at startup would not be strong enough to suck the throttle plates open against the heavy spring tension of the carb linkage.

Do you have a manual for the bike and do you have the float bowl heights set to what the book specifies?

Do you have a 5/16" fuel line between the petcock and the carb fuel Tee?

If you have any kind of inline fuel filter between the petcock and the carbs, git rid of it.

How many turns out do you have your mixture screws set at?

Do you know what size main jets are in the bike?

When you put the carbs back on the bike, make sure you have all the rubber boots sealed on both sides of the carbs. Leave the throttle cable unconnected. When you start the bike, reach between the carbs and hold the linkage between the 2 and 3 carbs in the closed position. This will insure that the throttle plates are not opening. If rpm increases as it always has, then we at least know it is not the throttle part of the carbs that is the problem. Let me know what happens.

You havent installed an aftermarket 4 into 1 or pods??? right? stock?

Earl

I however did notice on carb #1 and #3 the bores are not perfectly smooth where the throttle valve closes.. perhaps this can be my problem?

slides are all the way down..

 

[JJ]

When I changed the handlebars on my '83 GS1100G, I inadvertently put the throttle cable into the wrong hole in the twist-grip assembly. There are two holes, and I chose the wrong one. When the engine started, the RPM's skyrocketed instantly. I changed hole locations in the throttle assembly, and all was well. It may not be your problem, but it's worth a look-see. Good luck!

 

[Anonymous]

I wish that was my problem I picked up another set of carbs off ebay for $10 and i am soaking them right now in carb-dip. Hopefully this will resolve my problem or at least eliminate carbs as my problem..