Trouble tuning my Super G

[BMFC]

I cant seem to get it right. Or close enough to make me happy for that matter. Maybe someone can help me out. The engine is an evo with twin cam heads. It has an S&S 520 cam. BUB steel baffled 2:2 exhaust. Teardrop aircleaner and filter. I think I have a 72 main and 295 intermediate and its not bad. I cant get the accelerator pump dialed in and wide open is shit. Either way I go with the jets seems wrong and trying to read the plugs isn't getting me anywhere. Any help is appreciated

[BrokenSprocketGarage]

What ignition are you using? Many "fuel" problems are ignition and vise versa.
Only make one change at a time, test ride and observe the results.
Have you cleaned/inspected the acell. pump diaphragm?

[Guest]

Make sure your float is set correctly, that issue can come up when doing WOT.

[Loffer]

What size motor ? Carb might be a little large ...

[SSCycle]

What size motor ? Carb might be a little large ...

We don't usually reccommend a G carb for anything under 100". Give our tech guys a call at 866-244-2673.

[BMFC]

Its 100 inch, dyna S ignition. The float might is something I should look at.

I gave S&S a call. They said to try the jets I am currently running as a starting point but thats about it. I understand its hard to trouble shoot something without being in front of it.

If the G is big would jetting it down make sense?

[Sky]

Whats the stroke bore and displacement. More importantly, what's the compression ratio? Static first and dynamic if you do the math
Where is the mix screw set? What air bleed jet? What do the plugs look like? What springs are you using with your advance assembly?
Who did the motor work?

[SSCycle]

There is a downward facing fitting on the side of the carb toward the front of the bike. It is the float bowl vent. From the pics it does not look like there is a tube attached. is there? Without it the float bowl can pressurize from the wind moving past that fitting. Make there is a hose in place and the end is out of the wind.

[farmall]

That's interesting.

Out of curiosity has S&S had a manometer on a sample fitting to verify pressure buildup? How many inches of water did it move?

I can see it adding some pressure at speed if it has a slight forward-facing angle but that should be measurable.

[Sky]

I thought the float bowl vent was at the face of the carb same plane as the backing plate mount screw holes.
The downward facing fitting referred to is the overflow fitting as I understood it.

And seriously what speed is "at speed" . Like farmall, i'd like to see some numbers to back up this claim of pressure
Negative-pressure would be the result of air rushing past perpendicular here, also called vacuum. Not really adding press.

[SSCycle]

I'll start with a correction. It is in fact the drain, not the vent. Sorry about that, I don't spend a lot of time troubleshooting carbs anymore. As far as a manometer, possibly, at some point, but not in the recent past. My statement is based on history. There is a statement in the instruction sheet for the carb about this very issue.

[boomboomthump]

I think you guys may be getting into semantics about verbiage. The point is, as SScycle said, not having a hose there can cause problems.

You have a vent that has virtually no pressure coming out of it and when you're riding the air moving across it would be substantially stronger pressure, effectively blocking the vent. Pressure buildup at the vent, pressure differential or vacuum in the float, whatever you want to call it with relation to where you're looking at the problem from, its the same thing. At what speed? Probably anything greater than stopped as there's barely any pressure coming out of that vent.

Do people run the carbs with out the vent hoses? Yeah. Are they running optimally? No.

[BrokenSprocketGarage]

Verify advance timing weights are in good working order.
Check the VOES for proper operation.
Did you check the accell, pump diaphragm?

[Sky]

Dude, semantics are all we got on a text based forum!
BFMC hard to say if its too big, we don't know displacement even. how big are the ports? Did the engine builder build a street motor? Or something that is only happy at higher revs?

[BrokenSprocketGarage]

Displacement was posted by the OP as 100ci. I am presuming stock TC88 heads?