Well I took my vforce out with my friend's banshee this week. He has a 91 banshee with a k and n proflow filter. Everything else was stock except he was running 22X12 spider track rear tires. The motor got a new top end last year. It feels about average for a stock banshee, maybe a little faster with the intake mods. I was surprised that my vforce would beat him until he hit 6th gear. On level ground racing in a field with a lot of grass (We both hooked up well) I would pull him from the start (At least when I could keep the front down!!) and jump out a couple quad lengths and he would slowly start reeling me in. Once he hit 6th he passed me and started walking away. I was really impressed with my vforce though. We even traded a couple times and it was basically the same result I would beat him until he hit his top end. We also raced the road and loose gravel, all the same results. I acutally was pulling further ahead on the loose gravel but the end result was always the same, 6th gear...see ya. Anyway the only mod I have done is the pink epi spring and I think it definately helped. After riding around for a while we went to a huge whooped out sand hill where everyone drag races. We both rode out there so we didn't want to risk airing down tires for traction. The banshee would catch me a little faster and was able to pull me on the hill but I'm thinking it was because he had better hook up with the spider tracks. But then it started happening...white smoke and tons of it! After looking, it seems that the overflow to the crank case is vented directly into the airbox? Granted it was around 85 degrees and we were running hard but it was ridiculous! At first I thought maybe the oil level was too high and that was the problem. But after riding for a couple hours (Not full out racing the whole time) it continued to blow out oil at full throttle when wide open for approx. 1/4 mile. So much for racing anymore evertime I tried I'd be ahead and then it would start spuddering and missing. I even noticed that my oil level had dropped down from full to in the middle of full and empty. Still kept doing it. I thought it may have been because I was climbing a large hill but it even did it on flat land. What's the deal? I was not very impressed!

 

I had the exact same problem with my '03 Prairie 650. It started when I had about 400 miles on it. At first, I thought that I had overfilled the oil. That wasn't the problem. I just got it back from the shop after it got to the point where it was blowing oil into the air box anytime I hammered on the throttle. Problem was that circlips were never put on the wrist pins at the factory. Bushings came out and wore grooves up the sides of the cylinders. Total repair included new pistons, rings, gaskets, and cylinders. Fortunately, Kawi picked up the tab even though quad was out of warranty. They acted as if I should have been incredibly greatful, when I complained that it took over 3 weeks to repair, because they were covering the cost. I told them (Kawasaki customer service) that I had nothing to be greatful for, as the problem was caused by incompetence at their manufacturing site. I hope that your problem is not due to the same thing. Only way to really tell is to do a leak down test and then tear down top end. If you are still under warranty, get it in to the dealer asap!