[pockets]

Drill out the pilot air bypass (remove the pilot jet and drill straight down through where it threads into) to 1.0 mm (.040"). Start with 30 pilots, air screw at 1/2 turn, the slp 14-101 low elevation needles and stock 247 P-4 nozzles. 380/360/380 mains. Run BR10ES plugs, only good fuel, and if you are 1500ft. elevation, stock timing of 16 degrees at 8000 rpm. Take the weights out of the primary clutch and run the engine up to that rpm to check with a timing light. As said, belt to sheave clearance must not be more than .020", and deflection 1 1/8" to 1 1/4".

 

[pockets]

Pockets, if I have my flow paths correct this drill out modification will lessen an overfuelling/loading issue at low throttle openings with the sled under load? (heavy snow, 1/8 to 1/4 throttle opening). Or does this richen that circuit? I need leaner!

I have 30 pilots already but seems to load up if I creep along in heavy snow ie. maneuvering through the bush etc.

Yes, it makes that transition leaner. The 1997 and 1998 Ultra came this way.

 

[pockets]

You could try the SPX 6CEY06 needles, with Q2 247 nozzles.

 

[pockets]

PSI pipes do require different jetting. When changing heads, you actually should either put on aftermarket ones, or those from a Ultra SPX or 98 700 XCR. Polaris even came out with a team tips stating this when adding aftermarket triple pipes to the ultra engine to prevent deto.