Wordet11, To start whatever you have for pilot cut that in half. Mine was a 20 so I am using a 10. You can buy them on eBay. I am still messin with it but I will wind up with a 10 or a 12.5 but my carb also has a quad wing and a Intelajet. I would recommend the Quad wing as well. And skip the Dialajet , just spend the extra $ and get the Intelajet it's much easier to adjust ! All 3 really gives it a good punch. I had to dremel the UFO so I could get the throttle cable in & out easily,once it's ready and fitted to your slide I used some gel superglue installed it quickly and put the screw in it,
Superglue is gasoline resistant some added security to keep it in place !

Follow instructions it's easy and you can always call Thunder Products to ask question he is glad to help !

kojones wrote on 01/27/18 at 05:33:24:



It does not go by that number.
The UFO's are sized for a particular slide type.  For most VM carbs, it is for a 38mm or a 36mm (2 types for this one depending on whether it is a snowmobile or a motorcycle 36mm), 34mm, 32mm etc.  
So for the 38mm there is one size, and for the 36mm there are two but we use just one of those since we use the 36mm made for motorcycles.
When the UFO is installed the cut-a-way is carefully ground down to match the shape of the UFO, and that just on the intake side of the slide, the back side is not touched.
I also drill a small hole in the hood of the needle jet, that part that sticks up in the carb throat, to help effectively lean the pilot system.  When using a UFO the air flow in the throat of the carb is increased so much that much more fuel is pulled up, and that is even after reducing the size of the pilot by about half of what is used in the carb without the UFO.  So  leaning is necessary.  
This effect of the UFO, this tremendous increase in efficiency most notably in the low-mid range, is why/how  it can increase power by as much as 1hp/100cc of engine volume, and with a 650cc engine that makes it about a 6hp gain.  
The BEST BANG FOR YOU BUCK anywhere.

kojones wrote on 01/27/18 at 05:33:24:


Did you get your UFO's from Thunder Products ?

My VM 36 has the UFO, Quad wingy thingy & Intelajet. It really gets up and goes ,still sorting out a off idle stumble/lag. I figure at least a 8 H/P bump with screamin midrange. Really shines on the twistiestwisties then when the road straightens out , I just tuck in and I'm gone ! The kind of bike that just makes you grin and grin the rest of the day as that ride plays over & over in your head.

Got my bike running, thought it was running rich as it didn't pull smoothly when cruising and hesitated heavily when twisting the throttle, but lifting the needle one slot cured most of it. Still hesitates a little just off the idle, how did you cure that? Running a 3.0 slide with a 3.5 UFO. Maybe I should try the 2.5 slide with a 3.0 UFO?

OK, found this: http://3cyl.com/mraxl/ufo/ufo.htm

"*Addition of UFOs into a VM really re-writes the tuning rules. One such thing is the pilot circuit. As such if an air screw is set to give the normal "highest idle" (provided the pilot jet is approximately the right size) the immediate off idle throttle response will be lethargic, possibly making the bike hard to launch at 1500/2000 rpms off the line in traffic."

Update on my progress, I did drill a 2 mm air bleed hole to the needle jet nozzle and largened the hole in the middle of the UFO to 8 mm. Pilot soldered shut. Now I can adjust the idle mixture with the air screw, we’ll see how it runs. Needle back to 2nd slot from the top.

Ruttly wrote on 04/29/18 at 18:06:33:


I think I soldered all the holes shut.

Mine runs very well now with just a small hesitation sometimes, requires a really tight grip of the bars  
Current setup is 2mm hole in needle jet hood, 8mm hole in the UFO and needle in the middle slot. Think I'll have to test and lift the needle one slot higher since my mileage is 56 mpg and that seems way too high  

Update on my setup, I replaced the needle jet with a new one without drilling any holes, needle clip on the fourth slot. Runs very well, but I will try to lift the needle. 54 mpg.