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Throttle won't close all the way

  • Thread starter Thread starter giganticflying
  • Start date Start date
G

giganticflying

Guest
This is my first time tearing down the carbs, but I noticed this immediately after I got the carbs off of the head. Is that as far down as the throttle valves go, or are they supposed to go all the way down? This is a 79 GS850 that has been sitting in a backyard under tarp for four years.

The throttle shaft was really snappy when I opened it manually. The actual throttle mechanism that controls the cables seems to be completely frozen but that's a different issue I'll address later. I can't even manually push the throttle valves down to the correct closed position with the cable holder on the shaft. I unscrewed the two throttle cable adjuster screw so that they would have full freedom of movement opening and closing but still nothing.

I'm going ahead and break the carbs down, but should the throttle not fully close after cleaning and reassembling them, what should I do?

H9H3zlo.jpg
 
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Just making sure since your carbs are different, those are the bowls on the bottom, right?

I thought i saw somewhere (read: imagined) that the throttle valves close completely but if how they're supposed to be then I'm happy I'm on the right track.

Thanks!
 
yup bowls are on the bottom....

you should be good to go....

clean them up really well get new O-rings and you will be flying in no time....

Have you been here

http://members.dslextreme.com/users/bikecliff/

it will tell you all you need to know, including the proper way to strip, clean and put your carbs back together....

part way down the page on the right hand side....

.
 
GateKeeper said:
look to be about the same as mine.....

P1060188.jpg


.
Click to expand...

Not the same at all, those are CV carbs, they operate completely differently.
On the VM carbs that is the actual throttle, the slides need to go down all the way but a tiny sliver at the bottom.
There are several adjustments, take it apart and grok it until you figure them out.
 
Oh yeah. between bikecliffs site (thanks bikecliff!) and the workshop manual, I'm feeling pretty confident. I've already got them all taken apart, just waiting for the o-rings and gaskets to put them back together.
 
tkent02 said:
Not the same at all, those are CV carbs, they operate completely differently.
On the VM carbs that is the actual throttle, the slides need to go down all the way but a tiny sliver at the bottom.
There are several adjustments, take it apart and grok it until you figure them out.
Click to expand...

I did not mean that the carbs are the same, but that the slides are down about the same in mine as they are in his

as in this pic

vm26-01.jpg


and

1618d1360817210-1979-gs-550-carburetor-130213_0005.jpg
 
That's about as far as they close on the air box side. They close tighter on the intake boot side.
 
giganticflying said:
Oh yeah. between bikecliffs site (thanks bikecliff!) and the workshop manual, I'm feeling pretty confident. I've already got them all taken apart, just waiting for the o-rings and gaskets to put them back together.
Click to expand...

So, a carb body is in your can of Berryman's?
 
No, they're just sitting there, un-berryman'd, mostly disassembled, waiting patiently, unlike me. I can't wait to get this thing up back together. Still got a lot more work to do, though.
 
waiting for Berryman ? at least get them soaking while your waiting....if no Berryman at the moment get some PineSol

,
 
CV ( BS carbs) slides only go down as far as they go and that's that because they just float with the diaphrams. You bench sync with the butterflies and the screws on the rear linkages.

VMs however can be held open by having the sync screws way to tight. Loosen all he sync nuts and screws on VMs and be dure they are all the way diown first. THEN you open them till theres just a sliver at the engine side and make all 4 look the same.
 
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One other side note. When benching a set of carbs...VM or CV..you do it with the idle knob backede off so it is not toughing the throttle linkage. Once benched, turn the idle knob in about 1 1/2 to 2 turn after it just touches off on the linkage. The RPMs may be a bit high when you start the bike so be ready to adjust the knob.
 
Gatekeeper - I saw in a few other posts that letting them sit in there for too long can be bad for them and the parts aren't going to be here until tuesday next week.

Chuck - Where is the idle knob?
 
Well I didn't mean you let them sit in there that long, I thought you could strip them down, and dip them for 24 to 48 hours, pull them out, dry them off and have them ready for when your parts come in and then assemble. Since your waiting on parts anyways might as well get something done...

idle knob, is that not the knob you can see in the 2 pics I posted, near the top of the carbs...?

.
 
Good point. I've got them mostly disassembled so I'll pull off the old o-rings, scrap off the old gaskets and dip them this weekend.

Since the throttle was frozen I checked the knobs (I think there are two of them on VM carbs?) and neither one of them were even touching the the throttle cable shaft thing. I'll fuss around with it when I get everything else done and start her up for the first time.

But that brings up the other problem I found. I can't move the throttle at all. My buddy said I should try to take the cables off and lube them and try it again. It just feels like the handle itself isn't moving. Any other suggestions? Should I start a new thread for that?
 
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Yes idle knob is the big one between 2 and 3. And as I said before, if you have VM carbs and the idle knob ISNT touching the throttle linkage, you need to loosen the 8 MM nut under the top covers and turn the snyc screw and observe the slides from the engine side. Once they are all the way down, THEN you start turning the crews till theres maybe a 10/1000 to 15/1000 sliver at the BOTTOM of the slides at the throats. Make all 4 look the same. That's the basic bench sync for VM carbs.

On CV carbs, you do the same thing with the nut and screws at the back of the carbs where they are all linked together except you are adjusting the bottom of the butterflies. Follow me?
 
You can't get all 4 carb bodies in the dip at one time

Best be off to O'Reillys and get started on one carb at a time -that will take 4 days right there
 
giganticflying said:
Good point. I've got them mostly disassembled so I'll pull off the old o-rings, scrap off the old gaskets and dip them this weekend.

Since the throttle was frozen I checked the knobs (I think there are two of them on VM carbs?) and neither one of them were even touching the the throttle cable shaft thing. I'll fuss around with it when I get everything else done and start her up for the first time.

But that brings up the other problem I found. I can't move the throttle at all. My buddy said I should try to take the cables off and lube them and try it again. It just feels like the handle itself isn't moving. Any other suggestions? Should I start a new thread for that?
Click to expand...

I'm doing mine right now as well -- I'm just a day or so ahead of you and things are going well so far. Just got them all ganged back up and re-installed the choke actuator and bench synced them. :D

I leave the old O-rings until until I have the new ones...otherwise I forget where they go.:o

And I only dip the carb body in Berrymans for and hour or two. But I agitate/shake the can every 15 minutes or so.

Then wash them in the sink with hot water, dish soap and a toothbrush. That way, all the dirt and grime comes off and the finish remains intact.

Tip: If you have access to old guitar strings, cut them down to 5 inch pieces -- they make great carb cleaning tools.

You can't move the throttle on the carbs or on the handlebars?

:confused:
 
OriginalOwner said:
And I only dip the carb body in Berrymans for and hour or two. But I agitate/shake the can every 15 minutes or so.
Click to expand...

Not long enough....if you ask me....

it's not going to break down any of the crap that might be inside the smaller passages etc....

.
 
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