OK, I'm new to this forum. I'm asking for help. My buddy and I bought '02 Grizzly 660's together. We ride them aggresively. Trail, swamp, small jumps/x-cross, and lots of water/mud. I have a K&N jet kit (running one jet leaner) with the replacement slide spring, etc. I also (was) running a K&N filter. My buddies bike is completely stock. Our bikes got progressively more difficult to start. They now won't start at all unless you have a jump and 20 minutes to play with. Once running, it runs perfectly (it seems). Same top end as before. Same mileage as before. No engine noises. I thought maybe the float bowl was needing cleaned (1800 miles) so I removed, soaked, sprayed and air sprayed clean/dry. Needle seat SEEMED to be moving freely and floats moving correctly. I now think my intake valve(s) are tight. Not getting enough cylinder fill to start? That's why it takes choke and throttle to start?? The airbox will be full of fuel when turning over like there's no place for it to go!! Am I on the right page?? If so, how do I find out how to check these? What are tolerances? Thanks for any help you can offer as we are now fixing two bikes as my buddies won't start either. Same exact problem/symptoms. We recently went on a 2-day 360mile run from Searchmont, Canada to Wawa, Canada through the snowmobile trails. Unbelievable. Had to struggle to get both started, however so fear was there upon awakening on day 2 in the bush. I desperately need this running for deer season as I am now relying on my Polaris. Yuck!!!!