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Weird carb sync problem

  • Thread starter Thread starter ptm
  • Start date Start date
ptm, good luck with going over things again.
Let us know how the vacuum thing works out, and the other little problem.
If mixture related, the little problem you mentioned SHOULD change somewhat from cold to hot. Cold or hot should magnify any mixture problem, rich or lean.
You can still try removing the lid to see how that effects the problem.
But maybe your re-synch will fix this. Hope so. :)
 
OK, I'm confused. After I balanced my carbs to the same vacuum levels using a Motion Pro mercury manometer, I read the Suzuki GS1000 service manual. Alright, my wife tells me the same thing. The manual says I did it wrong, although the engine seems pretty smooth when compared to my previous bench sync. job. According to Suzuki, #1 & 4 should be the same and 2 & 3 the same, but lower by 1/2 diameter of the steel ball in the Suzuki balancer gauge. Is their any chance Suzuki may know more than I do? Could this be correct? If so, does anyone know what this difference whould be in cm's of mercury? Will this improve performance or is it too small to matter? Thanks for your help again. Confused Ray
 
Ghostgs1 said:
OK, I'm confused. After I balanced my carbs to the same vacuum levels using a Motion Pro mercury manometer, I read the Suzuki GS1000 service manual. Alright, my wife tells me the same thing. The manual says I did it wrong, although the engine seems pretty smooth when compared to my previous bench sync. job. According to Suzuki, #1 & 4 should be the same and 2 & 3 the same, but lower by 1/2 diameter of the steel ball in the Suzuki balancer gauge. Is their any chance Suzuki may know more than I do? Could this be correct? If so, does anyone know what this difference whould be in cm's of mercury? Will this improve performance or is it too small to matter? Thanks for your help again. Confused Ray
Click to expand...
I suppose it matters enough or Suzuki wouldn't call for it.
I've never seen the genuine Suzuki tool they picture in the factory manual close enough to see the scale. I would guess "half a ball" would equal 2 cm but could be as little as 1cm?? Hard to imagine anything less would really require a specific procedure? I couldn't tell any performance difference of just 1cm. Not always sure I can tell 2cm either but it does matter to the mixture.
IF YOU HAVE THE STOCK EXHAUST I suggest you follow the factory procedure. If a 4-1 pipe synch them evenly as possible.
 
Hi :lol: :lol: :lol:

The outer carbs should be higher by
ca: 2.5 cm (one inch.) of mercury
That is if you have the air filter box and filter..
If you have seperate filters, then you adjust all equally..
It has nothing to do with what kind of exhoust you have...


:roll: :roll: :roll: :idea: :idea:
 
KEITH KRAUSE said:
ptm, good luck with going over things again.
Let us know how the vacuum thing works out, and the other little problem.
If mixture related, the little problem you mentioned SHOULD change somewhat from cold to hot. Cold or hot should magnify any mixture problem, rich or lean.
You can still try removing the lid to see how that effects the problem.
But maybe your re-synch will fix this. Hope so. :)
Click to expand...

Thanks, Keith. I'll let you know what I find. If it were running poorly, or if the weather was bad, I'd be taking it apart now, but until then, I'd rather be riding every chance I get. There will be plenty of days this winter to dig into it deeper...
 
Einar J Skog said:
Hi :lol: :lol: :lol:

The outer carbs should be higher by
ca: 2.5 cm (one inch.) of mercury
That is if you have the air filter box and filter..
If you have seperate filters, then you adjust all equally..
It has nothing to do with what kind of exhoust you have...


:roll: :roll: :roll: :idea: :idea:
Click to expand...
Got me scratching my head here. :?
How could the airbox, which is designed to feed each cylinder equally, create the need to set the vacuum higher at 1/4?
I believe that because 2/3, due to exhaust design, has a little more back pressure. This would obviously create the need for less vacuum at 2/3 to compensate. If there's just a little less flowing out, then you need a little less coming in.
 
Thanks, Einar & Keith, My settings had been almost exactly backwards after many teardowns and tinkering. I guess that is why it ran so much better when I set them up all the same. Now I am anxious to try it again with the correct info. Suzuki and good folks on GS Resources do seem to know a lot about this. I'll let you know how this progresses. Thanks again, Ray
 
Hi :?: :?: :?:
How could the airbox, which is designed to feed each cylinder equally, create the need to set the vacuum higher at 1/4?
Click to expand...

Because they do not.
The carbs in the middle got more air.
If you have seperate filters, then all got the same amount of air.
And therefor adjust all equally..

Einar
 
Einar J Skog said:
Hi :?: :?: :?:
How could the airbox, which is designed to feed each cylinder equally, create the need to set the vacuum higher at 1/4?
Click to expand...

Because they do not.
The carbs in the middle got more air.
If you have seperate filters, then all got the same amount of air.
And therefor adjust all equally..

Einar
Click to expand...

Every air box I've seen sure looks like it feeds each cylinder equally.
Just a big box that feeds 4 equal sized openings. I can't see or imagine any difference in flow between them.
 
Much better now, after correctly balancing the carbs, smoother operating throught the lower and mid ratges. Thanks guys.
 
Ghostgs1 said:
Much better now, after correctly balancing the carbs, smoother operating throught the lower and mid ratges. Thanks guys.
Click to expand...

Rock on 8)

Glad to hear it mate :)
 
Hi :lol: :lol: :lol:

This is taken from Carbtune web....

On older Suzuki models with CV carbs (except GSX400F) the two outside carbs are set about 2.5 - 3.0cmHg higher than the inside pair. For specific model details consult your workshop manual or the Suzuki importer. (If the airbox has been removed set all the carbs the same).


Einar
 
Einar J Skog said:
Hi :lol: :lol: :lol:

This is taken from Carbtune web....

On older Suzuki models with CV carbs (except GSX400F) the two outside carbs are set about 2.5 - 3.0cmHg higher than the inside pair. For specific model details consult your workshop manual or the Suzuki importer. (If the airbox has been removed set all the carbs the same).


Einar
Click to expand...
Einar, both ptm and Ghostgs1 have VM carbs. I don't know how that factors into the carbtune website.
I also never believe something just because it's printed. Just like you don't believe what I'm printing. :) We all follow what we believe to be true. It would have to be proven to me. In this case, I see no evidence the air box will require setting the vacuum levels differently. I do see how exhaust design can cause a difference in backpressure. I've also tuned a lot of bikes and had no problems with my practices. So if it works for me, I pass it on.
 
KEITH KRAUSE said:
Einar J Skog said:
Hi :lol: :lol: :lol:

This is taken from Carbtune web....

On older Suzuki models with CV carbs (except GSX400F) the two outside carbs are set about 2.5 - 3.0cmHg higher than the inside pair. For specific model details consult your workshop manual or the Suzuki importer. (If the airbox has been removed set all the carbs the same).


Einar
Click to expand...
Einar, both ptm and Ghostgs1 have VM carbs. I don't know how that factors into the carbtune website.
I also never believe something just because it's printed. Just like you don't believe what I'm printing. :) We all follow what we believe to be true. It would have to be proven to me. In this case, I see no evidence the air box will require setting the vacuum levels differently. I do see how exhaust design can cause a difference in backpressure. I've also tuned a lot of bikes and had no problems with my practices. So if it works for me, I pass it on.
Click to expand...

I wonder if it has something to do with the position of the intake horns in the box. 1 and 4 are next to the side 'wall' of the airbox, while 2 and 3 are in the middle. The air intake into the box is in the middle as well. Maybe they get better flow... Don't know how that would translate into them needing to pull less vacuum. Could it have anything to do with 2 and 3 cylinders running hotter since they're in the middle and have less cooling air? Random thoughts, but no answers. There must be some reason for it, but it must have a pretty small effect since, as you say, Keith, you've been able to successfully tune a lot of bikes (some even over the internet without laying a hand on them :) ) without doing that... :-k
 
I agree it makes sense that 2/3 run hotter. Some models even run larger mains in 2/3, but not all.
Less vacuum will actually draw less fuel through the jets.
 
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