CV balancing question

[Paul_IOFJS]

Hi y'all,

I was looking through the carb balancing procedure in my factory service manual, and was a little confused by the "specs" the gave. In step #8 of the procedure, it states " When the balls in Nos. 1 and 4 carburetor balancers are on the same level and the other balls are on the lower position by one half of the ball diameter as shown below, all the four carburetors are well balanced."

Now the problem that I have is that they don't list a specification for what "one half of the ball diameter" is in in. HG or any other usable value. Since the balancing tool I'm going to be using is a guage type, all I can really do without a numerical value is guess and hope for the best. If anyone has come up with an acutal specification for this could you please post it?

Also, if someone could explain why the inner cylinders should be set at a lower vacuum than the outer ones anyway, I would really aperciate it. I'm an auto mechanic by training, but this doesn't make any sense to me. Of course it could have something to do with the fact that my class was the first to go through the program without any carburetor training whatsoever (all fuel injection), so my knowledge of carbs is limmited to what I have picked up while working on my own projects.

I realize that the Suzuki manual is going to assume you are using the Suzuki balancer tool, but I hope someone can clear this up for me. Thanks in advance for any light you can shed on this,

Paul

[Steve]

I have not actually seen one of those gauges, but by looking at the picture, it appears that the balls are just under 1 cm in diameter. The sad part is that even though they appear to be about 1 cm in diamter, it does not mean that a change in vacuum level of 1 cm of mercury will move the ball 1 cm.

I have never seen a difinitive answer as to why the difference, but I seen/heard others speculate that the lower vacuum level indicates that the two inner cylinders are getting a little more fuel, making them run a bit richer, therefore cooler. That does not make sense to me, as they are getting the same mixture ratio, but more of it, and would be running hotter, not cooler. I have also seen it speculated that the different vacuum levels should be used with stock exhaust, but not with a 4-into-1 pipe. Again, not sure why the difference.

.

[psyguy]

i have strugled with this myself...

the difference in the cmHg is 2,5-3
this is according to the morgan carbtune info sheet

as for the reasons, haynes sugest that this has to do with "slightly longer inlet tracts of the outer cylinders"
doesnt make sense to me...

i have synced an 850 and an 1100 and found both smoother running and higher idle (up to 150rpm) when all four carbs are synced equally!

1100 is completely stock
850 has k&n in-box and 4-1 pipe

[mac1170]

gday guys, don't worry about gauges, or balls, i prefer the suzi balls, but i digress, first off, run the motor, until warm, then plug each gauge singly into no.1, carb adjust the damper screw, on the gauge, till the whatever, isn't fluctuating as bad, then plug all four gauges in, turn it on, run it at 1500 revs, and check what it's reading, then adjust from no.3, which is fixed, slides inline balls, cv's 2 middle down, either end up, don't know why, suzuki spent millions, developing, who am i to argue, regards

[doctorgonzo]

"I have also seen it speculated that the different vacuum levels should be used with stock exhaust, but not with a 4-into-1 pipe."


That's what I was led to believe, that it's because of the crossover pipe between 2 and 3 on ther stock exhaust.

[Skyboy8950]

"I have also seen it speculated that the different vacuum levels should be used with stock exhaust, but not with a 4-into-1 pipe."


That's what I was led to believe, that it's because of the crossover pipe between 2 and 3 on ther stock exhaust.

I, too, have heard that it is the crossover. I have never been able to get a reading people have suggested. I always just balance them with a slight dip in the center. Even with a morgan carbtune, it is difficult to get it perfect. those screws are so touchy and hard to get at. Just get it as close as possible.

[twr1776]

The Carbtune directions note for the CV carbs and a stock airbox use a 2.5 - 3.0 cmHG difference between the inner two cylinders and the outer two cylinders. I have also seen the similar note in the Clymers manual. As others have mentioned I think it has something to do with the crossover pipe, what exactly I do not know. If you are running Pods or a 4 - 1 you should keep the air levels all the same. BWringer gave me the tutorial on my 1100 with a stock box and pipes and the carbs were pretty close to even but after adjusting them per the inner/outer method the motor did seem to smooth out a bit more.

[Killer2600]

From my understanding cyl 2 and 3 cool less efficiently than 1 and 4 and are thus hotter when run equal. The offset balance where the vacuum on 2 and 3 is less, flows less fuel/air mix and makes those cylinders run cooler and on par with 1 and 4 temp wise.

As far as exact numbers, I don't think suzuki has any so basically it's a "whatever looks right" type deal. That is unless you have their tool.

[Steve]

From my understanding cyl 2 and 3 cool less efficiently than 1 and 4 and are thus hotter when run equal. The offset balance where the vacuum on 2 and 3 is less, flows less fuel/air mix and makes those cylinders run cooler and on par with 1 and 4 temp wise.

The only problem I see with this logic is that, if the vacuum is lower, it's because the throttle is open a bit more, meaning you are getting more mixture in there, not less.

I have always adjusted them straight across on my wife's bike, but I might try the 'dip in the center' method next time I check them. My son's bike has a pipe on it, so they went straight across, too.

.

[Paul_IOFJS]

Well thanks for the input guys. I'll try the 2.5 - 3.0 cmHG spec you found. As for the vacuum differential between the inner and outer cylinders, it doesn't sound like we'll ever get a 100% solid answer on that. Oh well, "Ours is not to question why, ours is but to do and die." Thanks again guys.

Paul

[bwringer]

I've tried it both ways and never been able to detect the slightest difference, so I just make 'em all even nowadays.

If they happen to come out with the inner two a little below the others, then great. If it's easier to make them even, then that's what I do.

There are lots of more important things to worry about.