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Old 04-03-2013, 09:40 PM   #3698
Zuber
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Joined: Sep 2004
Location: Main Street, Shedd, Oregon
Oddometer: 1,757
Yeah, there is a small air leak through the canister at idle. This is very minor, but enough to raise the idle. When you plug the vacuum hose at the intake manifold the idle will drop, so you need to open up the idle a little to make up for it.

This doesn't effect the mixture. It doesn't know if the air is coming past the idle speed screw or leaking in through a vacuum hose. This is an open loop system, it knows rpm, throttle position, temps, vacuum, calculates what the mix should be and throws it down the hole.

The reason to remove this canister is the erratic running when the canister gets over full with fuel. When you drop the bike or ride down a steep hill liquid fuel will get blow out the vent and fill up the canister. Then it dumps this liquid into the engine instead of a little vapor. It will soak the plug and in bad cases (BMW) it will hydro lock the motor and bend a rod. It does remove VOC's from the atmosphere.

The other control, the SAS (air valve in the exhust) just adds fresh air to the exhaust and fools the test to make it seem there is less pollution coming out. It doesn't change the amount of pollution created, just lowers the percent of total gas coming out. It makes the back fires, but doesn't effect the running.

Hope this helps. Most of the weird running and flame out's go away after 15 hours.
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