Weird carb sync problem

[Hoomgar]

Much better now, after correctly balancing the carbs, smoother operating throught the lower and mid ratges. Thanks guys.

Rock on 8)

Glad to hear it mate

[Einar J Skog]

Hi

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

[KEITH KRAUSE]

Hi

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, 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.

[ptm]

Hi

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, 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.

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...

[KEITH KRAUSE]

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.