Boule’tard wrote on 03/27/11 at 19:06:42:The UFO is more trouble than it's worth, IMO. But it can be made to work (and still have a small pilot jet) by enlarging the hole in the UFO (that the needle goes through) with a 5/16" drill bit. Also, there is the optional air bleed, outlined in the UFO instructions, that will lean out the idle mixture. It is an approximately 1/16" hole in the brass shroud just upstream of the needle. Drill it just above the "floor" of the throat. Those two mods should get the mixture in range to where you can control it with the air screw.
Prepare to curse, jan. Tuning is very very tedious. I had forgotten that I had at first, a very lean spot right off idle. I didnt enlarge the hole the needle went through but I did do the air bleed and it helped a lot. It helped enough that I could tune from that point. Start with a very small size and enlarge it one size at a time, and test it each time. You'll find that the popping and hesitation will lessen. Just for kick though, before you go drilling the needle jet...try a #10 pilot, needle on the 3rd slot, #200 main, airscrew out 2 turns. Thats where I'm at after a long tuning process last spring and should put you in the general ball park. You'll Probably be running rich as I have a more open muffler but give it a shot.
And you'll never be able to crack open the throttle from idle to main without it stalling. I dont know how to explain it well but someone will chime in.
PS - the off idle hesitation is far less pronounced under load. Even now, tuned as well as Im going to get without continuous dyno acess, if i crack the throttle wide open from idle while in nuetral if i try hard i can get it to stall. If im actually taking off in 1st and crack the throttle the same way I get a split second of slight hesitation and then I get launched forward like a rocket.
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