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Discussion Starter · #1 ·
Hello all,

    Thinking of buying a set of UFO's for my 98 xcr 600. Does anybody have a good start point for these on my VM38's?
I am currently running the Snowtech magazine mods (96 issue ?)on this sled for trail running. (reed spacers, carbon tech reeds mid tension 275's). Jetting is same as stock except pilot is 45 unstead of 40.
I would like to know your opinions on jetting with the ufo's for 2 set-ups. one for +20 deg C, and one for -15 Deg C.

BTW, I posted several times about a flat spot on the Ultra based XCR(5100-5500) and recieved alot of good comments. Unfortunetly I never got around to posting more test results.

Here are my conclusions for anybody with an ultra based XCR that runs poor at mid range. These tests were expensive but worth every penny

1.  Reed tension is too high, use a lighter reed like Carbon tech mid tensions. (have not tried the low tension but result are perfect know and there is no need)
2.  Boyesen has a good reed for this xcr and it is cheaper. Works great at low to mid but seems to trip at anything over 8200 RPM
3.  Since there is no way to get a leaner needle at the area that I need, I increase the mid range air flow by installing reed spacers for fett bros. This mod itself bumped my EGT from 1090 to 1150F
4.  Bump up the timing 2 deg if you don't have reed spacers. Brings EGT from 1090 to 1120. But expect to lose some RPM on top.
4.  heat shield your pipes with good tape

These 2 mods bring the mid burn hotter and the throttle responce is explosive.


Hope someone else has tried UFO's on this sled,
Thanks in advance
 

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On the front page of this website, there is an article on UFO's...you might want to check that out if you haven't already.
 

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Discussion Starter · #4 ·
Thanks - but I read those articles and they are too generic.

This article deals with pilot stage and main stage. But no jet needles or needle jets.

Most people already know the xcr's are "iffy" to jet in the middle. I spent alot of hours tuning mine.

I am wishing someone can share some data to help me save a few hours of tuning. Not to mention it's too hot to test a winter set-up and I will have to ruin a few weeks next season tuning.

Thanks anyways
 
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I sent a fax to the UFO factory (thunder Products) on the sled, carb size, average temp I ride, elevation I ride and they gave me the spec's they want me to run.
This set-up worked for me right out of the box. I later changed the main jet to one lower but it was a warm winter.
 
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