Outboard cylinder carb synch

[wolfie]

I did a search but couldn't find what I was looking for. In my Clymer manuel, it says that I should be drawing slightly more vacuum on my outboard cylinders than my inboard ones. It shows a nice picture of what that looks like on a Suzuki synchronizer with steel ball type guages and no indication as to how much vacuum should be pulled. I know that it doesn't matter how much the cylinders are pulling, as much as the difference between them. My question is, how much difference in Hg should there be between my inboard and outboard cylinders. I have an 81 gs850L with the stock Mikuni BS series CV type carbs. I am using a Motion pro mercury manometer. Thanks.

[bwringer]

It's one of those mysteries of GS life -- the Suzuki gauge isn't marked or calibrated in any way, so who knows?

Whenever this comes up, the consensus seems to be that most of us just set the inner two cylinders about 1-2 centimeters below the outer cylinders (On a Motion Pro mercury gauge, 1 line = 2cm). A few don't even worry about it, set them all the same, and also report good results.

Setting the inner two cylinders differently only applies if you are using the stock airbox.

Sometimes it's so fiendishly difficult to get those carbs synced that you're just happy when they end up in the same ballpark after tightening those &^%$#@! locknuts.

[tfb]

For what it's worth, my Haynes manual says that if you balance the carbs with the air filter removed, then you can set them all at the same vacuum with your gauges. I'm not sure what the logic is on that idea , but that's what I do and the carbs seem to balance nicely every time (as evidenced by the fact that the clutch rattle disappears).

Mike.

[bwringer]

Good point -- balancing to the same spec with the airbox removed would work just fine. The difference in sync specs comes about because the airflow in the airbox is slightly different for the inner cylinders.

The problem is that a stock 850 will barely start and may not idle with the airbox removed. If you can keep it running reasonably smoothly without the airbox, then syncing without it would work great.

[tfb]

Thanks for your thoughts there Brian... but what my Haynes manual is proposing is not the removal of the airbox as such, but the removal of the air filter from inside the airbox.

So if we removed the air filter, I guess the question we need to be asking is, Would that even out the intake differences between the cylinders sufficiently for the purposes of carb balancing?

Cheers,
Mike.

[wolfie]

Thanks. Good info to chew on.