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fuel screw settings

  • Thread starter Thread starter Anonymous
  • Start date Start date
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Anonymous

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Hello all,

Can someone tell me the ball bark settings for the fuel metering screw that is located on the underside of the fuelbowls on a mikuni vm 26 carb.
These are the screws that either have a cap on them or a paint mark. Yes i did touch them (I know the manual says not to under penalty of death). I moved them because I have an overly rich condition. (turns out that it may have been the new wrong plugs that I put in!) :roll: The bike is a 79 gs 850 running with pods and rejetting. The bike ran great before I had the wrong plugs in it, but I attributted it to everything else but that! I would assume that these screws were set to the "stock" position.

Thanks
 
They are set at the factory and cannot be re-set exactly, but they can be set close enough. Never tighten them down hard, just until they seat.
They are commonly set at different points because of differences in each cylinder. You may have to tinker with them a bit and get low speed plug reads to help you with final settings. On stock bikes they are generally 1 1/4 turns out. If you have pods, an additional 1/2 turn usually gets you close.
The final settings on my '79 GS1000 with the stock carbs/pipe/pods is 1 7/8, 1 3/4, 1 5/8, 1 3/4. Like I said, it's common to set them at different points for each cylinder.
 
KEITH KRAUSE said:
They are set at the factory and cannot be re-set exactly, but they can be set close enough. Never tighten them down hard, just until they seat.
They are commonly set at different points because of differences in each cylinder. You may have to tinker with them a bit and get low speed plug reads to help you with final settings. On stock bikes they are generally 1 1/4 turns out. If you have pods, an additional 1/2 turn usually gets you close.
The final settings on my '79 GS1000 with the stock carbs/pipe/pods is 1 7/8, 1 3/4, 1 5/8, 1 3/4. Like I said, it's common to set them at different points for each cylinder.
Click to expand...

Hello Keith,

How did you get this fine final setting on each carb?
I want to set my BS32SS correctly.
Thanks
 
Lots of plug reads! :) I'm lucky to have a good place to ride and test. For the pilot circuit, I ride a steady low speed. On a bike like my 1000, I go about 40 mph steady in 4th/5th gear for several miles. Sooner or later I get it right. Once the plugs are a good color, I don't have any real performance problems.
You have to start with a very good carb synch first and of course everything else has to be set correctly, valves, ignition timing...
 
Little off topic but I noticed now dyno jet has a PC3 that lets you change the tuning on each individual cylinder now on a hayabusa. Amazing at some of the new technology.
 
The factory settings on my '83 gs850L (cv carbs) were 2 1/4 turns on the inboard cylinders, and on the outboard cylinders the screws were all the way in. These were original factoy, 'cause I checked them as soon as I drilled the cover plugs out. I still marvel that it ran so well..I left the inboard the same, and the outboard at 1 1/2.
 
Getting back to the VM26 for a 79 GS 850
The factory service manuel gives the specs as
Vis d'air de ralenti ---- 1-1/4 de toursen arriere ///this would be the screw on the side of the carb
Vis de reglage de ralenti-- 5/8 tour en arriere /// this would be the fuel screw on the underside
OK it's in french, I have no knowledge of french but the pictures look good in the manuel
 
KEITH KRAUSE said:
Lots of plug reads! :) I'm lucky to have a good place to ride and test. For the pilot circuit, I ride a steady low speed. On a bike like my 1000, I go about 40 mph steady in 4th/5th gear for several miles. Sooner or later I get it right. Once the plugs are a good color, I don't have any real performance problems.
You have to start with a very good carb synch first and of course everything else has to be set correctly, valves, ignition timing...
Click to expand...

Thanks Keith :!:
 
As an aside, anyone know where to get replacement o-rings for these fuel metering screws? Needless to say, mine have died.

I studied a carb blow-up diagram recently and it didn't even show the screws, nevermind the o-rings!

Local Suzuki parts dealer didn't know what I was talking about, of course.

Suppose I could bodge 'em with red Hermatite, but it's always nice to do a proper job.
 
Kirk said:
As an aside, anyone know where to get replacement o-rings for these fuel metering screws? Needless to say, mine have died.

I studied a carb blow-up diagram recently and it didn't even show the screws, nevermind the o-rings!

Local Suzuki parts dealer didn't know what I was talking about, of course.

Suppose I could bodge 'em with red Hermatite, but it's always nice to do a proper job.
Click to expand...

Try here http://home.att.net/~Robert.Barr/
or here http://www.motorcyclecarbs.com/
 
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