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how do u rejet a carb with ufos, bigger or smaller, and do u have to rejet with vforce reed valves, if so bigger or smaller?
 

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how do u rejet a carb with ufos, bigger or smaller, and do u have to rejet with vforce reed valves, if so bigger or smaller?[/b]
well I would say to richen the pilot with the reeds. I have not used ufo's and so I will not say what to do there. I will say this no person on a computer can tell you what to do to jetting without pics of piston wash and plugs. there are more variables to jetting than that re: temps, altitude.
 

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I have used UFOs in the past.

TPI (the people who make them) would be the best source for a starting point on the UFOs. They do exactly what is advertised, increase air flow, especially at lower throttle positions.

If I remember right one needs to jet up on the pilot actually.
 

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It totally depends on the sled. Friends of mine have put UFO's in their carbs, every single one of them has melted a piston and took the UFOs back out.

For my sled, with stock 50 pilots, with UFO's, you need to drop down to a 10 pilot jet, you also need to change out each and every single component of the carbs as well (different needle, needle jet, main jet, and carb slide than stock).

If you get them dialed in, you'll get a bunch more performance, but expect much, much worse mileage. The one guy I know that successfully jetted his 98 MXZ 583 gets about 6 or 7 mpg, although he has burned the motor down twice and spent about $500 in carb tuning parts.
 
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