Before you remove the plastics to access the vent tube remove the gas cap to see if the problem is resolved. You will find two or three threads where several of us were having similar problems awhile back and it wasn't the vent tube. Problem we were having was regulator/rectifier related. Bike would idle fine but while reving would start backfiring and run very sluggish. I like you picked up a rectifier off of ebay for under $20 including s&h and it's been over a year now and no further problems.

Do you have a friend or acquantance nearby that has a DS that you could borrow the rectifier from for ten minutes and see if this resolves the problem? Let us know your outcome.

 

A little while back I was having a backfire problem and it was a simple fix that someone of the bomb forum suggested and it worked...my quad was backfiring everythime I would hit the gas and shut it off...well the suggestion was that my headers may be loose and causing cold air to enter the exhaust so I tightened the bolts and got new gasktes as my old ones were shot and it fixed half of the problem...I check ym plugs the other day and they were white so I was running lean and I rejetted today and my ventline was causing my quad to backfire when I shut it off so I cut the hose and its fine now...Try the simple stuff and if it doesn't work go and get yourself a new rectifier its under the airbox I believe

 

alright......so i cut the vent line and decided to check the carb one more time for anything and i found nothing.....checked the plugs which are very black and i will be getting a new set soon.....put it all back together and the same deal...i could actually get going as long as i didnt punch it...but once i did it would spit and sputter and sound like i hit the rev limiter

now what does the recitfier actually do and no i dont know anyone else that has a ds so i couldnt borrow theres.... does this sound like my next step....since the carbs clean, vent hose is short and uncrimped???? my headers are tight so thats not it either

 

so i just pulled it off to do an inspection of wires and what not....how essential is this to the wheeler because with it off i can start it.....its 11:30pm and alittle to late to go for a test ride but can i ride it without it??????