With a UFO installed you WILL need to go down to a #15 pilot AND drill a hole in the little top section of the needle jet that sticks up into the carb throat. I am away from home on a trip right now and don't have my tech info with me so cannot remember the exact size but perhaps someone else will. I am thinking that it is a #45 drill bit...may be something close to 3/32" ? ? Not sure though.
I went to the "Thunder Products" website and this is their brief intro into how to start the process. The material you get when ordering a UFO goes into more detail.
They start with a #55 drill bit in this section, but for the Savage a larger hole is needed. Just going on memory I am pretty sure that it is a #40 or #42 drill bit that I use when setting up a carb with a UFO.
** Remember ... do not go smaller than a #15 pilot; the guy who created it was pretty emphatic about that for some reason. Just drill the hole and
turn the pilot adjusting screw out for lean; 3 turns out is pretty much the limit without endangering the loss of the screw for lack of the spring holding power.
Please do remove the needle jet when doing the drilling. I have been tempted to drill with it in the carb but just the thought of tiny metal filings getting stuck in some passageway and screwing up jetting/tuning adjustments causes me all sorts of frustration.
Do not worry about getting the hole to large, go straight for the #40 or 42 size drill bit and adjust the pilot screw according to what the engine wants. If it is too lean then you just go back to a #17.5 pilot.
I believe that my 36mm VM carb (with UFO and DAJ) ended up with the pilot screw at about 2 turns out +/-.
U.F.O.
(Ultimate Flow Optimizer) PATENTED
AIR BLEED CIRCUIT
ONLY use air bleed when a 15 pilot jet is still too rich!
The air bleed circuit allows you to lean the pilot circuit without leaning the midrange and top end.
When your engine is running properly and your only concern is excessive fuel consumption or when you need to go leaner than a 15 pilot jet, the following drawing will show you how to improve your fuel mileage or lean out the idle circuit further by installing a small air bleed. This is an extremely simple modification. The size of the air bleed hole will determine to some degree what size pilot jet you run. The #55 air bleed is installed in the needle jet only (not the needle) right next to the floor of the carburetor as illustrated in the drawing. If you want to increase the size of your pilot slightly to throw more fuel across midrange, you may do this and still have the ability to lean out the idle circuit by enlarging the air bleed hole further than the #55 size. We recommend that this be done cautiously in increments not exceeding 5 per time (example: #55 air bleed enlarged to #50). Numbered drill bits get larger as the number decreases. NEVER exceed #40 in size.
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