I rebuilt my carbs and rejetted etc. on a 1996 xcr 600 sp. I runs fast and clean now but i now noticed it has ufo's in it. will they put me in danger of burning this thing down? I have it jetting and rebuilt as pockets had suggested to improve this carb's on this thing.. it worked great but now i have no experience with these Ufo's how do they change the carbs... should i be concerned..

The main thing it alters is the pilot jet. If you changed pilot jets per a rec from pockets then you will be running pig rich. I used ufo's the first year they were out and had a hard time getting jetting right and had terrible mileage. I would not even think of running them unless the sled has an egt. Also if you decide to take them off usually the slide cut away gets changed 1 size when you run UFO so make sure you have the correct cut away. And don't go just by the stamped number they may have opened up the cut away.

if i leave them on will i chance a burn down .. or will my life just be full of screwing around to find a leaner setup...

They take some playing to run right. Starting point was 1/2 the pilot size it had stock, richen needle one clip, mains down one size usually. Also as mentioned, to use one cutaway leaner than stock, and cut the slides to match. If you take them out, the slides will be too lean. There was also something I remember about drilling the hole in the center of them larger, to improve fuel economy. I do not remember to what size. If you drilled the pilot bypass like I said, 350/370/370 mains, needle #4, or leaner for above -15C, P6-247 nozzles, and air screw to 1/2 turn (I believe), idle 1800 rpm, warm, you will not believe how much better it runs. No need for UFO's. The stock nozzles on the 96 were 6 or 8 sizes too rich!!

my current set up is exactly as you described and wow... but i do already have the ufo's .. they were there from when i bought it... I honestly have no idea how to tell what cutaway i have.. but i know right now it is rich but not too bad?,, i goes like @#$@# but i just concerned about if i have a world of hurt with the current setup and those ufo's... ? I think i need to get my hands on one of those installation manuals for the ufo's

I've been installing UFOs since they came out. In fact, the inventor from Thunder Products offered to sell me the patent years ago. I also own the patents on all the Boswell carb modifications. These UFOs work very well with the Boswell mods because the Boswell mods used fuel flowing through the needle jet to cause the Boswell-interconnected idle circuit to "reverse" as fuel flows into the needle jet and thereby flow air/fuel backwards from the idle circuit into the needle jet to better emulsify the mixture and aid in throttle response. Trust me, it works. Patent testing at a major sled manufacturer test site shows up to 6 times faster throttle response than a conventional circuit. The UFOs increase this reversing signal.

These UFO devices encapsulate the hood of the needle jet. In fact very much the way the latest TM flatslide Mikunis do. This creates a very strong siphoning effect on the needle jet even at idle. That's why you usually drop the pilot jet by half it's number size. I.E, #40 goes to #20. (Notice that the TM carbs have fuel screws to reduce fuel flow at idle, yet have large pilot jets). Some people even plugged the pilot jet completely with the UFOs. The increased siphon effect usually causes more flow and a much better atomization of air/fuel emerging from the needle jet, so the jetting goes richer. This is why the cutaway is usually increased. The original versions had too tight a hole around the needle jet hood, and too strong a suction, so it was recommended that the hole be made larger (about 1/16" I believe). Later versions had a larger hole already. As the slide is raised and the UFO lifts off the hood, it goes leaner quickly so that's why the needle needed raised. Yes, it's complicated, but you're sort of stuck with the UFOs unless you replace the slides.

As long as you raise the needle and lower the size of the pilot to about half it's normal size, you shouldn't burn it down w/Pockets other jetting recommendations.

Phil

I am certainly not saying that they don't work. I had a tremendous increase in throttle response. I would have had less frustration if I had not run them the first year and as pockets said drilling the center was supposed to help the fuel economy (second season trick). I would find out about the hole size in the center to see which version you have. My fuel economy only dropped on twisty trails where it went in about half. It is probably better with the center drilled. But I still would seriously be afraid to run them without egt until they are dialed in.

In other words, make sure it has 20 pilots, air screw 1/2 turn from lightly seated to start, needle 4th or 5th clip (5th first and see if it loads up at part throttle), mains to 340/360/360. P6-247 nozzles.

thats good info.. im am still waiting for my service manual for this sled so for now i do not have any stock specs to compare with.. i have no idea what the stock pilot would have been for this sled. NOTHING was stock on it when i picked it up.. i bought it for a 1000 bucks... its been a interesting adventure so far... the guy really had no mechanical skills and just kept throwing aftermarket parts at it till she stopped running.. then i bought it.. well it really runs now.. i hope it stays running? lol

does anyone have a manual for these ufo's . the sled came with no literature for the parts.

i will make those adjustments pockets... thanks.. i must ask, the needle jet(nozzle) 247-p6.. my dealer couldnt find that type.. he found a 247 and a p-6 but not both in a single unit? there was a 247 in it when i got it.. whats the difference between them?

Mikuni carbs have a variety of needle jet types used. 247 is one type. P6 is is the size.

Each type can flow differently, even in the same size. I wouldn't use any needle jet that doesn't have both numbers stamped on it.

Here's a website that sells/gives a complete listing of each type/size:
recleisure.com

Phil

Mikuni carbs have a variety of needle jet types used. 247 is one type. P6 is is the size.

Each type can flow differently, even in the same size. I wouldn't use any needle jet that doesn't have both numbers stamped on it.

Here's a website that sells/gives a complete listing of each type/size:
recleisure.com

Phil

Tell your dealer to look up the ones from a 1997 600XCR/SE. They had the 247 P-6 stock. They will be cheaper from someone such as Recreation Supply or Cycle Works though I would think. Did you drill out the pilot air bypass to .072" (1.8mm)?

yes i saw a big change... I will go pick up the nozzles and pilots. i will let you know when i get them in.

new info... i ripped the carbs apart and took a really close look . the pilots are 22.5, and the nj are 247 P-8's its seems to be working with the ufo's... its seems very responsive and doesnt seem to load up yet... has new needles , drilled out bypass. and currently sits with 350 370 370 mains...
I guess i will have to wait for the snow and cold to really know how it will do...

The P-8 are one step richer. You could still go to the 247 P-6 safely. That became stock in the 97/98 XCR. You still have the stock needles, 6CEY6, 4th clip from top?

yep stock needles and forth clip...

Had a set of UFO's in an Ultra SPX. The fuel mileage jumped up from 12 mpg to 16 mpg. And the throttle response was absolutely ridiculous. (good).

I have little in the way of sleds currently to compare with but i can tell you the throttle snap is no sluff, even compared to my YZ 250... the sled really pulls... i am little concerned about the high engagement.. i shotting for 4500 + but i seem to be hitting 4800-5000. I sure pulls away strong though.

48-5000 is what the engine likes best. You have the gearing and hot seat clutching in it?

I have the primary redone (polaris almond round, and 10 54 aggressive trail) and spent way too much time on the carbs(redone everything on them).. the gears were already done.. the secondary isnt changed out yet.. i wanted to start with a single clutch and see the change.. so far , biggggggg change
I see we live fairly close together, im from vermilion area.. are you right in lloyd

21/39 gears? That primary set-up was the stock 97-98 one, not bad but hot seat white spring with hot seat Z hypershift weights was much better. You could also use the 3211075 overdrive belt, and reshim the primary clutch for the proper .020" clearance. If not changing belts, make sure it is no more than .020" with the stock 3211066 belt.

gears yes.. as for the reshim on the primary to .20". I am not sure how to. I will have to take a really good look at the schematic.. currently i have a 1070 belt.. would the 1075 be a better choice?

Definately. I do not think the 3211070 will last long.Take the windage plates off the secondary clutch. The proper measurement is .020". You have to remove the spider from the primary, and add or remove shims/combination of shim thicknesses to obtain that measurement.

thanks I will get to that some time here on the primary.. as for the windage plates.. how do they affect the clutching...

on the secondary my spacer block on the outside of the clutch is too thick, giving to much free play.. should i trim it down or use the 1/8 shims (same as from the inside of the secondary on the jackshaft) to close up the free play?

If you have more than 1/8" float, be sure the alignment is good, then remove small washers from the mounting bolt to lessen the float. If there are not any washers, you could cut the spacer shorter. Be srue the alignment is good first though. Make sure the sled has had the jackshaft update done. On the jackshaft there should be a large aluminum ring/spacer on the outside of the tunnel, against the bearing. Look at my post under the 440 forum, suggestions for cross country set-up for info on proper alignment. The powerband on that sled is not very smooth, especially in the transition from low end to midrange. I found it causes more belt heat than other sleds, as well as having more jackshaft flex because of the wide engine, and corresponding longer jackshaft for proper alignment. Removing the plates helps greatly in keeping the clutches and belt cooler, especially if riding in deeper snow, off trail.

the ring spacer is there but it blows the alignment out of the water.. i will read your post and check it out. how do i know if the jack shaft update has been done.. is the spacer the update?

The large aluminum plate on the outside of the tunnel. All you shuold have to do in remove shims from behind the clutch for it to be properly aligned. Look here at a 97 XCR 600, and see what parts it shows on the jackshaft. It came stock what the update was on your 96.http://parts.polarisind.com/Assemblies.asp