Adjusting the Idle Mixture on CV Carbs

[1948man]

Duh, I glanced at his post but didn't read the last paragraph.

[Kjpeter]

Sorry to bring up an old post.

I am following the directions and getting good results. One question I have is about the idle.

In the directions, it says to put the idle at 1300 during initial adjustments while on the stand. It doesnt specify if the idle should be set at 1300 during road tests and then dropped down to the factory 1050±100 after adjustments are completed. Or if it should be at the factory 1050±100 during adjustments.

Is it easier to tell if the adjustments are wrong with it set at 1300?

Kyle

Bone stock 1980 GS850G

[MechMessiah]

Sorry to bring up an old post.

I am following the directions and getting good results. One question I have is about the idle.

In the directions, it says to put the idle at 1300 during initial adjustments while on the stand. It doesnt specify if the idle should be set at 1300 during road tests and then dropped down to the factory 1050±100 after adjustments are completed. Or if it should be at the factory 1050±100 during adjustments.

Is it easier to tell if the adjustments are wrong with it set at 1300?

Kyle

Bone stock 1980 GS850G

1300 for adjustments and factory for riding. Yes it's generally easier with the higher idle and less likely to stall/stumble the engine while making the adjustments.

[Steve]

Actually, if you read the manual a little more carefully, a carb sync is done between 1500 and 2000.

One of the reasons for that is to minimize the bouncing of the balls in the Suzuki carb sync gauge.

For those of us that have other gauges at our disposal (I have several, including the Suzuki gauge), the fluctuations are not all that bad, even at 1100 RPM.

Will tuning differences be seen better? Not really.

.

[Kjpeter]

Steve, I was inquiring about the idle for adjusting the idle mixture screws not syncing. I did the carb sync at 1500rpms before and after adjusting the mixture screws.

[vuendox]

koolaid_kid! Thank you so so much for this thread and the write up. I have an 1981 GS650G (Shaft driven) bobber that I'm trying to get running reliably. I noticed some people advising to adjust valves before syncing carb and tuning. I wish that wasn't the case as I'm an inexperienced self mechanic who is anxious to get riding, but... I think I will go through it all. A big cheers, super helpful,

vuendox

[Tijmen]

Is it normal for it to run fine on 2 rotations out from bottom snug? Did that and it responded just fine, good throttle response and nice steady fallback to idle rpm when rolling off the throttle. Didn't bother experimenting more, as it was running a lot better with the carburettors synchronized and pilot fuel/air mixture back to stock (they were all different for some reason...). Thanks for your work though!

[MechMessiah]

Is it normal for it to run fine on 2 rotations out from bottom snug?

Yes, 2 turns from bottom is usually the factory setting if memory serves.

[Steve]

The "factory setting" is wherever their multi-thousand dollar tool told them that the mixture was "perfect", then they sealed it.

When I rebuild a set of carbs, I always check the setting and record it before I take anything apart. If the screws were still sealed, I make note of that, just for reference. I have found sealed screws to be anywhere from 1 3/4 to 2 1/4 turns out, so 2 turns is a good average, but that does not mean it's proper for your carbs. You are likely very close, but a little experimenting won't hurt.

It is easier for an engine to start and run when it is a bit rich. After all, that is the function of a "choke" on a carb, to provide a richer mixture. Because of that, when I rebuild carbs, I start with the mixture screws out three full turns, then adjust them in as necessary when the engine warms up. For example, if one particular carb required between 2 1/4 and 2 1/2 turns out for proper running, starting it at 2 turns out would be too lean. You would have some difficulty even getting it to run, but you won't know exactly what the problem is. Simply starting with a richer mixture at least lets it start.

.

[MechMessiah]

The "factory setting" is wherever their multi-thousand dollar tool told them that the mixture was "perfect", then they sealed it.

I stand corrected. Thanks for the knowledge, Steve.