very slight black smoke under fast throttle

[78GS1KNH]

Hello all! Fixed my transmission issue, but now im finishing up my tuning on my GS1000C. Seems all the needles are in the correct spots at 1 notch from the top. It keeps the "blue" gas smoke to a minimum... herein lies my problem... she bogs just a little bit at about 2krpm, but after that she'll open right up. I notice a small amount of black smoke comming from the 3-4 cyls side. This means too lean of a mixture right? I'll be posting pics of the beast soon...
Thanks!

 

[hampshirehog]

Black smoke usually means too rich. Time to do some plug chops methinks.

 

[Flyboy]

Hampshirehog is spot on, black smoke is excess fuel, blue smoke is oil, sounds like the carbs are running a wee bit rich at the bottom end.
Those in the know should be able to give you some advise on what jets and tubes should be in the slow running circuit, I have no doubt someone will pop in with the answers shortly.

 

[hampshirehog]

If you're running with the standard exhaust and airbox make sure you have got a clean air filter and your fuel and air screws / slide needle are set up near to the factory specs - see carb sticky for details: http://www.thegsresources.com/_forum/showthread.php?t=73723

Also check your float height as per specs.

If this doesn't cure it check that your choke plungers are ok, the springs are strong and the seating rubbers aren't perished / hardened.

 

[78GS1KNH]

If this doesn't cure it check that your choke plungers are ok, the springs are strong and the seating rubbers aren't perished / hardened.

The plungers are in excellent condition. I just reinstalled them with all new jets, air mixture screws pilots, needles etc. All of the springs will pull the plungers back down into the carbs, and the rubber is all in great condition too.
The blue smoke had to be from unburned gas as #1 cyl was the only one not to have the little spacer (small metal one that was installed when i had someone put in the dynojet kit before i went back to stock specs and forgot to remove them before i reinstalled stock) all the fuel levels are correct that i can tell with the gauge... could it be the air screw is too far out?
I'm not in front of the bike currently to look at it, but I'll see it later.

 

[78GS1KNH]

Seems i cant find the factory specs on that link for the 1978 GS1000C VM26SS carbs... i found a 1979, and i assume they are the same...

 

[hampshirehog]

Moving the airscrew out weakens the mixture and vice versa. For the fuel screw (underneath at the front) it's the opposite. The settings should be about 2 turns (airscrew) and 3/4 turns (fuel screw) out from lightly seated.

 

[Guest]

Check the plungers aren't being held open slightly when the choke is in the off position.

Then check the fuel and airscrews as suggested.

 

[78GS1KNH]

Not sure if this was the reason why but i found that the new air mixture screws that came with the carb rebuild kits were much larger tipped than the ones i pulled out. I moved the new orings to the old screws and it seemed to take care of the issue. Although it bogs bad at 2-3k. I'm thinking the timing is just a tad off. i checked it with an ohm meter, just havent hooked up a dynamic light to it.