1980 GS750E - CV Carb Idle Adjustment Question

[dcb]

I have a 1980 GS750E with the CV carbs. I have noticed there are only three adjustments to synchronize the carbs. Is there any way to adjust all four? If not which carb can not be adjusted?

Thanks,
David
1980 GS750E
1968 YR2

[Scud]

Number three cannot be adjusted, you must adjust all carbs to that one. That is the carb that your throttle cable is attached to.

Scud

[wiredgeorge]

David, the title to your post makes me wonder what you are trying to accomplish. The idle adjustment is done by opening the vacuum slides via the idle adjust knob. The three screws you mention are used to ensure that these same slides open at the same time by making sure the throttle butterflies open simultaneously. They don't control idle speed directly.

OK... if your question was about the function of the sync screws, all four carbs ARE adjusted using these three screws. First, loosen all three locknuts. There is a special tool to do this while the carbs are on the bike. It is made by Motion Pro and is essentially a long tube with an 8mm socket on the end with a flat blade screwdriver in the middle. It also allows you to tighten the locknuts with the carbs on the bike by holding the screw while tightening.

The way you adjust the synchronization (getting slides to open simulaneously) is hook up a manometer (vacuum gauges w/four hoses). With the bike warmed and idling, FIRST use a long screwdriver and adjust the screw between #1 and #2 carbs so that the mercury (vacuum) level on these two carbs are the same. Then you adjust the #3 screw between carbs #3 & #4 so they are the same level vacuum/mercury. Last, you adjust the middle adjustment screw to level 1&2 and 3&4. When you have them all at the same level, shut the bike off. Use the special tool I noted OR remove the carbs and carefully tighten the locknuts on the adjuster screws while holding those screws with a screwdriver so they don't turn any as you do your tightening.

[dcb]

I need to get a mercury refill for my manometer so until then I am just trying to get it close. I will look into that Motion Pro tool, it sounds like one of those tools that can save you a lot of frustration.

I am also thinking about getting a Colortune, any thoughts there?

Thanks,
David
1980 GS750E
1968 YR2