Carb rejetting odyssey .... No pods involved

[Guest]

I've been getting advice from different people, which is appreciated. But it's all apples and oranges.

The only mod to the bike is the air filter and lid, neither of which made the 33 year trip. Paper filter and improvised lid. Runs better w/o the lid currently. Carbs are sync'd and float levels are good.

Even 2 sizes out on the pilots with out the pilot screws out 2.5 it'll hunt and surge. (Lean)

So far I'm up 2 on the pilots, back to stock mains, and I think I might need to go down one on the mains.

One size up on the mains it wouldn't rev past 6k under load. Back on stock mains, up to 8, but still rich misfiring. (Rich misfiring)+

On stock jets, it hunts and surges at low and steady throttle and pings but is awesome up top.

Mid range might be slightly rich but haven't messed with it yet.

Might be able to add spacers to the needles and bring them down.

Just kinda putting this out there as a guide for other people with gs650GLs, because air box lids disappear and most people with a dialed jetting scheme are on different bikes.



No clue on fuel mileage because I haven't been able to/willing to really ride it.

[GSX1000E]

Return the pilot jets to stock. Increase the main jets ONE size if you are riding OVER 4,500' at all times or TWO sizes up from stock below 5,000'.
Adjust fuel screws to suite.
That is IF you have thoroughly cleaned the carbs otherwise all bets are off.

[Old guy]

I took your advice. I went back to stock pilot and 1 over on the main because it's all I had. You are right on the money sir.

Hunting is gone a steady throttle, but it leans out mid at up top. One jump in main should set it right.

The internet is wrong, mains do affect low throttle. Best guess is that the fuel rides higher in the pilot, and fueling is happening from the main at low throttle.

Shot a little video that shows the slide movement at low throttle opening.

http://youtu.be/qbDweEOs1xw

[Steve]

You tune the BS series carbs (also called "CV", but that is a type, not a model name) from the top down. Get the mains correct first, then do the needles, then finally, do the pilot. Also keep in mind that 99% of the time, you don't need to change the pilot jets.

Think about it. You need to add more fuel to an increased amount of air that is possible when you remove some restriction. That restriction could be removing the lid to the stock airbox or ditching the airbox for pods.

At half-throttle, the throttle blades are your restriction, not the airbox, so the needles don't usually need too much adjustment, but they do ease the transition to the larger mains.

At idle, your throttle blades are ALL restriction. It won't matter if you have airbox, pods, velocity stacks, whatever. You are simply NOT going to flow any more air at idle that will require larger pilot jets.

.

[Old guy]

It's a tad more complicated than that. The pilot circuit has 4 holes it feeds through. 1 in front of the throttle plate that is adjusted with the pilot screw, at idle, and 3 behind it.

The more air moving through the throat of the carb the lower the pressure in it. But the area at the back of the carbs with the air jets are is an area whee pressure changed too.

The air and fuel level in the emulsion tubes fight for space based on pressure. Less pressure at the back of the carbs, like with a stock filter, let's the fuel level in the emulsion tubes come up. More pressure, pushes the fuel lower.

My guess with the larger mains, since the pilot and main are connected, it brings the fuel in the pilot circuit up, and riches the mixture, as well as more fuel feeding from the main at low throttle. Since the air feed at the back of the carbs pushes up on the diaphragm and the hole in the slide is in the low pressure area of the throat and acts on the top of the diaphragm, the slide moves more per a given air flow.

IDK, I'm just glad the bike is rideable. I did drag the kick stand in a curve though.

[GSX1000E]

Just something that a major motorcycle manufacturer printed in the '70's