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96 Ultra. I ditched the airbox when I put it in the new chassis and went to filters. Now the vent lines are attached to nothing. Where should I run them to now?? I'd do a search but yea, that button is nowhere to be found.
 

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96 Ultra. I ditched the airbox when I put it in the new chassis and went to filters. Now the vent lines are attached to nothing. Where should I run them to now?? I'd do a search but yea, that button is nowhere to be found.[/b]
Attach them to a variflow :div20:
Or underhood or up into the handlebars, footwell etc
 

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Discussion Starter · #3 ·
Attach them to a variflow :div20:[/b]
That involves a decent lightening of the wallet. Was more looking at where to route the $4 worth of tubing I'll buy from Fleet Farm. I'm thinking I want those vents to be with the same air at what the filters are getting?? So if I'm lazy and let them take hot under hood air just leave them, but if they're getting fresh outside air to route the vents up the bars or something like that?? The machZ racks I've got just vent to the engine compartment. Really dont know the disadvantages to that.....
 

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That involves a decent lightening of the wallet. Was more looking at where to route the $4 worth of tubing I'll buy from Fleet Farm. I'm thinking I want those vents to be with the same air at what the filters are getting?? So if I'm lazy and let them take hot under hood air just leave them, but if they're getting fresh outside air to route the vents up the bars or something like that?? The machZ racks I've got just vent to the engine compartment. Really dont know the disadvantages to that.....[/b]
The temperature of the air entering the carb bowl vents is not an issue. Instead, the location of the vent lines determines whether the carbs run richer or leaner. Carb fuel flow is VERY sensitive to vent pressure. Slight pressure increases can make a big difference.

Atmospheric pressure applied to the vent lines is what forces fuel from the float bowl to enter the carb bore as air flows through it. The most consistent/reliable source of atmospheric air pressure is inside the stock airbox. This is the same air pressure seen by the carb. Most carbureted autos have the bowl vents inside the air filter at the mouth of the carb. That's why the Polaris vents were attached into the airbox from the factory. But, not too close to the mouth of the carb where it will see too large of a pressure drop.

By removing the stock airbox, disconnecting vents and installing filters, you've provided warm underhood air to what was originally colder airbox air from behind the windshield. The first effect will be a loss of potential hp and more detonation sensitivity just due to hotter air going into the engine.

The second effect will depend on where you place the carbs vent lines.

If you run them into the handlebars, they will experience reduced air pressure behind the windshield as sled speed increases. This will lean the mixture down more and more as speed climbs. Not an ideal situation.

If you run them down behind the engine as the Skidoo does, you will see increased air pressure as speed climbs. This causes an ever increasing enrichment. Slower acceleration and top speed, but much safer. Unless you are running away from the wind or going uphill slowly at WOT.

If you attach them to the ends of the filters so they see slightly reduced air pressure as air flow into the carbs increases with engine rpm, you will provide a setup similar to the factory one.

Depending on current jetting and where you decide to place the vents, you can be dangerously lean, just right, or very rich.

Take your pick. Then watch your plug color, fuel wash and EGTs.

:div20:
 

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Discussion Starter · #5 ·
If you attach them to the ends of the filters so they see slightly reduced air pressure as air flow into the carbs increases with engine rpm, you will provide a setup similar to the factory one.

Take your pick. Then watch your plug color, fuel wash and EGTs.[/b]
Ask and thee shall receive, thanks :beerchug: I knew that where the vents are had an effect of rich/lean but I wasn't sure how. I know it isn't ideal to not have an airbox but that was just one more thing that wasn't going to fit. My plan is to get a vent ducting cold air in, with something similar to prefilter material on the entrance to help keep snow out. It should work pretty decent, hopefully!
 
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