[Thumper]

Kind of a complex question. I hope I can pose the question so that it's understandable.

There are two suction nipples at AFTER the butterfly flaps and fuel injection, one for each cylinder. These nipples suck in air AFTER the ECU sets the mapped air/fuel ratio for each cylinder.

Air and fuel enter through the intake at a specified ratio, according to the stock mapping. AFTER that ratio is sent past the intake, the small nipple (that's normally connected to the Evap canister) sucks quite a bit of air in. I believe that may be part of the ECU's air/fuel ratio calculation.

If we remove the Evap canister and o2 sensor, the ECU runs on its stock mapping.

However, once the Evap canister is removed, we block off the nipple.....hence....allowing less air to enter into the cylinder, thus creating a greater fuel to air ratio.....perhaps making the bike run a bit rich.

Normally, the nipple sucks fuel fumes through the canister and directs it into the cylinder to be combusted.

By blocking off the nipple, are we causing the bike to run slightly rich? Because, the stock ECU mapping is taking into consideration the amount of air that the nipple sucks in and injects extra fuel to compensate.

But, if we block that nipple off, then the ECU is STILL telling the injector to put the same amount of fuel through the intake.

So, the same amount of fuel...........but less air.

Does this make sense, that it's possibly running slightly rich as a result?

How about, instead of blocking off the nipple, installing a small K&N crankcase filter on each one. Hence, allowing the nipple to continue to suck the amount of air it was used to sucking.

I tried sucking on the Evap canister to see if it had a one way valve on it, even with my finger over the fuel evap line, and there is no one way valve. It easily allows me to suck air through. Therefore, with the Evap canister installed, the nipples freely suck air into the cylinders.

Is blocking them off creating a slightly rich scenario?

I hope I'm making sense.

Thanks,

Tom

 

[Speeddog]

Ducs without O2 sensors will likely run a bit richer at small throttle openings, but IMO that's a good thing, as they're usually kinda lean from the factory.
From what I remember, it didn't really make much difference on my bike, but it was quite a while ago when I took the evap off.

Those with operational O2 sensors will likely correct for it when the ECU is running closed-loop.

 

[Mac900]

I think your basic premise is a bit off. Any air that gets in past the throttles would have to be tightly controlled and the stock system is closed off (self contained and sealed). I doubt that what you are getting when you suck on the tube is outside air. You could simply block off the "nipple" and seal it but to put mini air filters on it would introduce a vacuum leak which should make it idle and run like ****. Theoretically.

 

[Thumper]

A vacuum leak, after the throttle body and injection. A definite good thought. Perhaps the motor sucking in carbon air and gas fumes isn't acknowledged as a vacuum leak?

I just went down and sucked on the evap canister again. It doesn't suck that easily. I mean, you can suck air through it, but not that easy. The only time you can completely prevent any sucking, is if you put your finger over the bottom drainage tube.

I wonder if I'd get a check engine light if I took the bike outside and took off the rubber nipple caps. I guess the only answer would be to try it right? Popping the rubber nipple caps is only a 5 second ordeal. I guess I could just try it and see, without buying any K&N filters or anything yet.

UPDATE: Okay, I just went down and checked the stock set up. When it was stock, the vacuum seal was not closed. At the bottom of the Evap canister, is an overflow hose. This hose is left open with no plug. Even with the fuel fume hose capped, you can still suck and blow through the vacuum hoses as long as the bottom overflow hose is not blocked......which it's not from the factory. So, with the stock setup, the vacuum lines are not closed and can suck and blow all they want. As I'm typing this, I've got the canister in front of me. I've got one finger over the gas fume line and am sucking and blowing through the vacuum lines. The only time I can't do that is if I put my finger over the bottom overflow hose, which is not blocked on the stock setup.

I'll take it out tomorrow and pop off the vacuum caps and see what changes occur.

Any other ideas? Do you guys think that this bottom overflow hose was supposed to be plugged?

Thanks,

Tom

 

[Speeddog]

I haven't closely inspected one of the plastic-tanked bikes, but ...

There are 2 hoses from the tank, one is the vent to the inside of the tank, and the other is the drain for the filler recess.
Neither should be plugged.

 

[Thumper]

There are 3 hoses connected to the Evap.

On the bottom is an overflow hose that is open ended and just hangs to the underside of the bike. It doesn't go anywhere. It's open ended and you can suck and blow through it freely.

At the top of the canister are two inlet hoses. One from the gas tank and one from the intakes. The two lines from the intakes join together via T-connector and lead into the evap canister.

The two hoses that come from the tank? One goes to the evap canister and one is just an spill line that runs out the rear side of the bike.

I didn't start it up and play with it yet. Today I was to busy. But, I will when I can. I mean, it's running great the way it is, no complaints. I'm just wondering if it could run.............BETTER ??

Perhaps it's a little over rich and it could be leaned out a bit to produce a few extra ponies. Of course, this is all by the seat of my pants.........no dyno, so it's hard to tell.

Tom