Here's a Jetting / EGT report from this past weekend. Temps around 20 degrees - running in 6 inches of fresh pow on a 40 mile river system - sled 800PT Gade - avenger1 EGT - probes 100mm from pistons.
Jetting 430 Mains (down 1 size from stock - this increased WOT EGTs by around 20 - 30 degrees from stock)
Needles - .010 shim (didn't notice any change in mid EGTs)
Reed Spacers - installed ¼ inch (stock 3/8 - didn't notice much difference in overall performance)
Off the line hesitation - none (never had it before these changes either)
Oil - Blue Marble
Max RPM - 8300
RPM at hard acceleration - 8100
Mag side EGT consitently running hotter than PTO
Max EGT readings at 6500 - 7000 RPM - 1409. Had my warning lamp programmed to flash at 1380…and it was flashing all the time. I didn't hold it at this range very long as I was too afraid. Never did see the knock sensor lamp kick. I did not get an accurate midrange plug reading
Full throttle EGT - held WOT at over one mile intervals in fresh pow and on existing tracks..... temps would drop to 1190 - 1235. Plugs looked good - tan in color - subtle white crest on electrode tip.
Final analysis - dropping a MJ appears to be safe - however I don't understand the incredibly high mid range temps. My theory is that the head design allows fuel to continue to burn in the exhaust pipe, especially in the Mids - which is giving an inflated EGT reading. At 1400 degrees, I should be melting aluminum rather quickly, but I never had a problem and my plugs never looked solid white on the electrode.
As an aside, this river run trip is notorious for burning down sleds…if you're off in jetting at any RPM range, you'll smear a piston. We had 2 Polaris's burn down on this very trip - one at WOT and one at mid range speeds. I also discovered this 800 Gade with the 1.75 track can go over open water pretty much indefinitely!
Had a chance to get 30 miles on yesterday and heres what I've found so far. Just doing some runs in my bean field at various speeds trying to pin down what this motor is doing. I had the head sent to Rk Tek to be re-done to enhance cooling cause these motors run warm anyway. Kelsey put 13 to 1 domes in it and it LOOKS great. Just a rough estimate on temp gauge it did drop maybe 20% runs right at the 1/4 mark on gauge. I believe these motors run so hot in the mids to make sure all the fuel gets burned, this is how they (BRP) have this sled 2006 compliant with emissions. With the carbs. I put in 20 pilot jets and dropped the mains. I never had the 5K stumble thats been mentioned on here before.I think my next investment will be EGT's so I can get a more accurate bead on things. This motor compensates for jet changes and the ECM won't let you get to carried away. I managed to get to .390 mains before the engine light came on and she was sounding a little rough in the low RPM's. Went back up to .410's and light has not come on yet. When I was at .390 the plugs looked the best but the motor didn't sound like it cared for it, now that I'm up to .410 the plugs are considerably black at the electrode and you can barely tell the porcelain was white, appears to be safe to me. Just a heads up, do NOT go this low on jets without the headjob!! My primary clutch is lacking about 1/4 inch or just a little more from being shifted all the way out and tach reads right on 8K. I think I can go up one click but I'm holding off on that for now. Still waiting for my hyperlite, then I'll start playing with clutches. Putting studs in this week but can't make up mind on what pattern. Alot of what I'm reading say don't put in outside windows cause of the push they create which I think this is where some of the precision bashing is coming from. Has anyone tried every other window of the outside with any success?
Interesting....I think we're both going to end up with similar engine mods. I'll be adding the Hyperlite next Fall and am still debating which head option I go with...I'm curious why you choose the stock head mod vs Kelsey's RKT? Did you notice any power gains?
I didn't realize you could jet down this far with the stock head mod. You're pretty ballsey putting in those 390s! When you drop mains this aggressively, I would think this should also lean the needle circuit - at what speed/rpm did the light come on? I would like to add adjustable needles to these carbs - but I'm not sure where to find them.
If you're making more power than stock, I would think you should be seeing higher Rs and needing to drop a clicker. Is this the first 30 miles you've put on the sled, or did you get to rider her stock?
Unfortunately, these are the first miles. A lack of snow allowed for alot of time sitting the garage. I chose the cheater head because to my understanding it's the same head for a little less coin. Kelsey machines out the stock head to accept the new domes. Can't really account for any power gain due to limited stock mileage about 5. The RK headjob accounts for a main jet drop of usually a couple sizes. The light came on 2 times with the 390's both times the sled was warmed up and slowly cruised about 1/4mile then once I made the turn to the run and brought it up to about 80 then slowly backed down the light came on and steadily flashed but no audible alarm. Light continued to flash until sled was shut off, I looked engine compartment over and started back up light was gone and I made a few more runs with no light but motor did sound a little off. I guessing that the timing was being changed. These Mods. don't add that much power without the port job and pipes to compliment it. I done it as a fix to the Series III motors heat problem. As for the clicker I'll wait awhile until I'm a little better broke in. A sponsor on this site had told me that with this dummyproof motor you could jet down until the dash light comes on and go back up 2 sizes, kinda makes sense to me. Thats how I ended up where I am.
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