Hi, I am new to this forum. I am also sort of new to Polaris. I've been with Arctic Cat since 1970 except I bought one Polaris in 1972, a TX Starfire 340 that I still have. I bought a new 03 Pro X 600 last season and ran it stock except for Studs. I put 3,400 miles on last season. I am very happy with the sled. I did some mods this fall (SLP Air Horn, SLP Can) And a lot blue print time on the chassis/suspension. I was looking at the posts for some info on SLP's Air Horn Kit. I am trying to figure out just what does the shelf do that's in the stock airbox? SLP's instructions says to disgard it. Which I did. Does anyone know why it was there in the first place?
I went through both clutches and re-shimed the spyder in the primary. I cleaned and inspected the secondary. However I did not notice any abnormal wear in the Team clutch bushings as I have been reading in quite a few posts here. Now I am wondering if I should try and get this covered under warranty when it has not failed yet.
There were two reasons I switched to Polaris from AC. The first was durability. Cats have always been High Maintinace and my ZR has had 3 complete engines in 14,000 miles. Second Cat quit making their best sled ZR600 and started building single purpose F chassis which are not what snowmobiling is for me.
I'd like to improve the mid range with some clutching changes any suggestions please..

The airbox shelf/horns is there for one reason only...noise reduction. You'll be suprised how much intake noise you'll pick up. I ran a 70/44.46 helix with 62gm weights last year with great success. I was also using an almond/blue primary spring to up the engagement rpm slightly. Midway through the year, I switched to an SLP helix grind. It was a combo 66/44.56 and a 54/42F. The full cut side pulls harder in the midrange and was a good lake running setup.

I am not sure if there are any real HP gains to be had with a small block 600 by removeing the shelf! Even in a 7~800 your only talking 3HP..... One thing the shelf does do is keep snow out of the motor! if you get enough powder threw the carbs you will scuff your pistons ! the snow washes the oil off the skirts. I am going to try mine with out the shelf but I am getting a prefilter to make sure I dont hurt it!