Ross650 wrote - Thanks Ross, I stole your quote from another thread.

I've suspected this for awhile and now have first-hand experience of the phenomenom. Last weekend I added one more 1" Univent to the airbox lid for a total of 6. The grills in the Univents seemed really restrictive so I then cut the grills out of all 6 vents. I didn't think the extra air would be too much as the 650 was running a little rich. It seemed to run good with a warm engine on a warm day after cutting out the grills.
The next day I went to a rally, it was cold and raining. Unloaded off the truck, drove around the parking lot a bit. The machine sucked badly, totally dead! I assumed that it was lean due to the airbox mods so added a little choke; no better. Got out the duct tape and covered the 3 vents I had put directly over the top of the carbs; no better. I took the tape off the 3 top vents and covered the 3 vents I had put on the side of the airbox lid, they were located so air flow was blowing sideways over the top of the carbs and from the opposite direction of the stock snorkle; the 650 woke up and ran like a top. The whole time it was running poorly you could hear the vacuum actuated slides in the carbs fluttering badly when trying to accelerate. The fluttering/fluctuation was gone after covering the side vents up.
I guess the best plan is to run an aftermarket or homemade snorkle with no extra vents in the lid, or block off the snorkle completely and fill the airbox lid with strategically located holes/vents. It appears that the two together have the possibility of being counter-productive.

 

BTT - anyone had a similar experience?

 

We have two bikes running 3 - 1" vents on the left side of the cover (right face of the small cavity in the cover) and the diamondg snorkles and have had no problems yet.

 

I'm thinking of doing the same - vents in the left-hand side on the vertical flat surface. This will put the airflow in the same direction as incoming air from the snorkle, which should work well. My problem was with vents I had installed on the far right-hand side. The air came in at the opposite direction of the snorkle air; thus my turbulance problem.
Oh yeah, you guys with '03 Prairies don't have a left vertical surface on the airbox lid.

 

Scott,

If we get to ride togeather sometime your welcome to try my airbox cover and see how it works before drilling some new holes in yours.

 

We have the Diamond G snorkel and if I remember right, 12 or 13 of the univents in our 02, the 4 across the front have the centers still in them but the rest have the vents cut out. I have even made a wire to hold the air filter in and ran with no air box lid at all. We have never had it give us any problems unless we hit water but now that you have mentioned this I think I may do some testing with some tape over different holes and see if it changes our performance. Thanks for the info!