GS1000 lacking low down punch

[Guest]

Just got the 1979 GS1000 back on the road this year. I have a Vance Hines 4 into 1 and carb bellmouths. Carbs are fitted with the dynojet kit. The bike seems a bit fluffy from 2k to 5K revs and then takes off strong. On checking the plugs they do seem black and sooty. At present the fuel screws are set at 1.25 turns out.

[Agemax]

i would turn the fuel screws in, running bellmouths actually causes the bike to run richer as the increased air flow draws in more fuel. you may need to drop the needles a notch as well

[gs79]

Thanks Adrian, I have dropped the needles already my friend. Will tweak the fuel screws and test.

[OldVet66]

Which DJ jets did you use? I just rebuilt my carburetors lately using the 142's I don't have a big bore kit so I don't have a clue how that will affect it. My pilot fuel screws started at 1/2 turn out and I believe the main jet needles have the clip on the third slot from the top. That was turned in a little too much on the pilot fuel screws. The air screws were almost closed for highest idle. I turned the pilot fuel screws out about another 1/8 turn and this brought the air screws near two turns out for highest idle. The bike has plenty of power off idle through red line, nice low speed characteristics and gets 44 MPG. I am using pods.

[gs79]

Yep, I am also running 142's, with clip on third slot, air screws 2 turns out for max idle, looks like my fuel screws want tweaking in a touch, as she is running very rich which I think is responsible for the fluffiness.

[OldVet66]

What is the shape of your pilot fuel air screw seats. Lightly seated, the tips of the needles are just visible below the tiny hole in the throat of the carburetor. If the tips stick up into the throat lightly seated, the seats have been ruined. It will still work, but it would mean your needle at 1/4 turn out might be equal to a good seat at 3/4 turns out. They would never meter properly, but you might get them close. Dynojet doesn't have a .pdf up for our jets for some reason. I called and they recommended starting the pilot fuel screws at 1/2 turn out. I found that caused a slight blubbering at 1,500-2,000 RPM like it was too rich, but tweaking them out slightly has cured most of that. Seems like that worked backward, but it did shift the air screw adjustment to a more normal setting, approximately 2 turns out for highest idle from almost closed and did clear up 99% of the low speed blubbering. Tweaking your fuel screws will require adjusting for highest idle again.

[gs79]

Many thanks for the info my friend