Bonneville America Forums Forums Technical Forums Performance Mods Lean condition is back?

First let me give you a little history. My ’05 America didn’t run right since new. It had a flat spot during normal acceleration within about the first 1/4 throttle or so. Nothing serious but annoying. I installed long TOR’s and it got worse so I knew I had to rejet. I installed 130 mains and 45 pilots and the bike ran perfect. No flat spot and plenty of power all throughout the band. Now I pulled the TOR’s and installed my stocker’s with 2 baffles removed and the third drilled and my flat spot is back. Not as bad but it’s there. Would the partially gutted stockers have created a lean condition again? (I should add that I pulled the top snorkel and it got worse. I put it back in.)

Chances are this is more an attribute of the carb design. The carbs are vacuum actuated, so when you first hit the throttle, it must build vacuum before the slides will open- hence the lag or flat spot. Your stockers, even with the two baffles removed and the third drilled are going to have less flow than the TORs, so you will get less immediate performance (translating into less immediate vacuum to the carbs). You are only as efficient as your next bottleneck. If you are set on running the stockers as is, you could try lighter slide springs, but this is pretty much the norm with these carbs.

If you think this is hooey, remember:#1- The Pilot Circuit (also called the primary, low speed or idle circuit) consists of a brass fuel jet- called the pilot jet (in the float bowl), the pilot mixture screw (outside of, but adjacent to the float chamber), and the pilot air-correction jet (in perimeter of the “mouth” of the carb). The Pilot circuit delivers it’s air/fuel mixture through a small hole in the floor of the carb outlet, downstream of the throttle plate. It regulates the fuel mixture at idle and small throttle openings, typically under one-quarter throttle. The pilot air correction jet admits air to the pilot system, through a channel above the pilot jet, as a fuel/air ratio modifier and emulsion improver.

What about guys that have completely gutted there stockers? I've never heard anyone say that they've had to live with it.

Nope my bike runs like a scalded cat.I disagree on the TORs I have a set and they are not less restrictive than stock with baffles removed.

I did adjust the mixture screws out from 3 to 3 1/2 turns and it seemed to help a little. I have not synced the carbs recently. I did that after rejetting it when the TOR's were first put on.
So you think the stockers with 2 baffles removed and the third drilled have more restriction than the TOR's did? I was thinking the other way around.

It really depends on the version of TORs you have. From what I've read here, I think the consenus is there are at least five versions ranging from somewhat baffled to wide open.

Okay- down to the nuts and bolts of you issue and somebody help me here, but I think Going from 3 to 3 1/2 made it richer... Our air screws are engine side and meter fuel. Here is a break down of it from Dan's motorcycle Carb Theory web page. It is all good knowledge and well written, but look closely at #2:
1. Fuel level. The fuel level is controlled by the fuel floats and the fuel float valve. The floats are hollow or made of something that will float on gasoline, such as cork. Part of the float presses against the float valve, sometimes called a needle and seat. Most times the part of the float that touches the float valve needle is bendable so you can adjust the level of the fuel in the floatbowel. All plastic floats are not adjustable. If this level is way too high, gas can leak out the carb overflow tube or into the engine. If fuel gets into the engine it will thin out the engine oil, ruining it's ability to lubricate. This will, sooner or later, blow up your engine ! If a full tank of gas in the evening turns into a half tank by morning, check your oil. If it's thin and smells like gas, change it and replace your float valve and/or check your fuel level. If the oil is OK, check under the overflow tube. If it's OK, then check where you are parking your bike 'cuse someone is walking away with your gas !

If your fuel level is just a bit high, the mixture will tend to be a bit rich. If it's low, the mixture will tend to be a bit lean. This is because a high level takes less vacuum to suck fuel into the engine and a low level takes more vacuum to do the same.

2. Pilot or idle jet system. The idle jet controls the idle and on up to quarter throttle, give or take a bit. On some carbs, like Mikuni there is an air jet too. In conjunction with the idle jet there is an idle jet air screw. This screw leans or richens the fuel mixture for a smooth idle and on up to one quarter throttle. From the idle jet, there are little passages cast into the carb that lead to holes just in front of the throttle valve or plate. There can be just one hole or there can be several, depending on the carb design. They effect the mixture as long as the vacuum, in the venturi, is over them. As the throttle opens further, the vacuum moves to the needle jet and jet needle.
3. The Throttle Valve. The big slide that opens and closes your throttle has a bevel angle cut in one side of the big round (can be flat, too) slide, toward the air cleaner. This angle comes in several sizes and helps control the fuel mixture from idle to about 35% open throttle.
4. Needle Jet. This jet doesn't really even look like a jet, but it is ! It controls the fuel mixture from 15% to 60% open throttle. It sets in the center of the carb, right over the main jet.
5. Jet Needle. This is the needle that rides in the throttle slide and goes into the needle jet. This needle controls the fuel mixture from 20% to 80% open throttle. It can come in many different sized tapers. Sometimes, one needle can have several tapers on it. The top end of the needle has grooves cut in it, usually five, and you can move the little clip on the end up or down to lean (down) or richen (up) the mixture. Most late model bikes have needles with only one groove cut in them. This is so you can't richen the mixture, thereby keeping the EPA happy.
6. Main Jet. This jet controls the fuel mixture from 60% to 100% open throttle.

So, regardless, it would appear you are only dealing with the pilot and idle air jet (screw).

Hope this helps...

If it runs fine above and below the flatspot, a shim or 2 on the needles may help. Also, a bit bigger pilot jet will feed more fuel to the transition jets, and that may help.