Doc wrote:
The motor runs lean to meet EPA emission standards but the carb is set up rich.
I know you explained this before but it was more than 15 minutes ago so I have no recollection. How can the carb be rich but the motor lean? If that's the case why do we need to lean out the jetting? Doesn't the jetting control how rich the motor runs? I'm so confused This is gonna be a real simple answer ain't it?. I'm gonna feel like a real dummy when your done with me ain't I?

I can't wait to hear this answer.

I'll throw my thoughts in and then I can feel dumb too... carb is rich, but the ais compensates for it as far as emmisions go..any unburned mix gets burned in the pipe....

Bingo!

Trying to watch the SENS so I'll be brief (Ohhhh a goal )

The bike must meet current EPA exhaust emission standards.

The bike is choked by the air cleaner.

Why is it that when you put on an aftermarket air cleaner but run stock jetting you're much to rich (Ohhh another goal ) and have to lean the main jet out.

I'll leave you with that and get back later. Gotta watch the game.

Doc

OK. The motor isn't running lean. It's running rich because of the rich jetting in the carb. But the AIS is burning it up in the pipes. That's cheating

Yea I agree, I had a 1989 olds, that burned more gas and gave less HP and torque than a lawnmower..

3 - 1

As we know there are 3 circuits - pilot, needle and main

The stock needle is fatter than after market ones and helps to maintain lean condition at midrange for the stock setup. So in the midrange the carb may be jetted where it should be.

When you put on an after market air box you are leaning the motor out by increasing the amount of air that the motor gets.

We have found that the stock pilot seems to be adequate when the air flow is increased (new air box), which by extrapolation would make the stock setup too rich. We have also found that the stock main is too rich when adding a new air box .... which would mean that it's even richer for the stock choked engine.

I believe the stock jettings are a bit too rich on the pilot and main circuits. The AIS helps meet the EPA emission standards by 'injecting' fresh air into the system which reacts with the unburned gases.

Doc

Okay, here's a definite dumb question. If the stock settings with an AIS bike are too rich, is the Mikuni normally set as rich for a bike without AIS?

Well, Pop, the Corp wants to cover their a$$, so they would rather your bike run a little rich rather than lean..the carb comes sealed with a plug over the pilot screw, so that screw is set by someone at mikuni, at yami's specs,,can you trust them..? that carb has never been on anything alive until it was bolted onto your bike and the techs at yami usually would not take the plug out and adjust anything,,IMHO

AIS is irrelevant .... it's only there to meet emission standards.

For a OEM bike without the AIS the carb would need to be jetted differently or some other emission control device would need to be used to meet emission standards.

Doc