Thunder Products U.F.O. - anyone?
 

Anyone tried the UFO filler for the Mikuni slide? After I get mine tuned (still waiting on jet deliveries) I may give this a try.

https://thunderproducts.com/shop/u-f...low-optimizer/

Never heard of it, and I can't get the page to load properly. Does it replace the stock slide?

fills in the bottom of Mikuni slide
 

It uses the stock slide, you have to drill the slide for a screw using their jig piece and then you screw a plastic puck to the bottom side of slide. It contours the bottom into a more aerodynamic shape but by filling that void and shaping the flow it also increased the intake signal (e.g. vacuum pulse) and therefore pulls more suction/vacuum on the pilot and needle/main jets. You have to go to a much smaller pilot jet (1/2 or more) because of the increased signal that draws out much more fuel, so you either have to halve the pilot or more, else you'll be running super rich. I can see how it would really draw up the fuel into a better atomization from the main jet and needle let. I plan to give it a try. I think some people have had issues because they didn't tune it properly afterwards and got horrible fuel economy or 8-stroking misses from running too rich.

They may not offer the size we need for the little 23mm ID slide size in the VM26 PZ30 Mikuni carb. Also I think the Slide cut is a 2.0 and they provide 3.5 cut dimensions.

It sounds like you could accomplish something similar with a smaller carb.

This UFO is supposed to increase the efficiency of the Mikuni carbs, due to the "flawed" design of the bottom of the slide. Optimized by shaping it and filling in the volume under the slide, that decrease in empty void volume by filling it in transmits into a stronger pressure signal at the main and pilots, and distributes and atomizes the fuel more efficiently higher up into the air flow. No reason to go to a smaller carb and lose top end air flow, when it can be increased by making the flow more laminar through the venturi.

That makes sense, and it was a much more sophisticated answer than mine.

If the Mikuni had such a simple and easy to correct flawed design wouldn't it have been corrected 75 years ago or so?


/

make an epoxy puck using an old slide as the mold. and see if it makes it run pig rich.

that would tell you if they are on to something.

Example, for cars...People have sticking these things in their intakes for years
http://www.tornadoair.com/
Do they make a significant difference :shrug:. Is the customer happy, probably. Wouldn't have purchased it in the first place if they didn't have faith in it.

I think tweaking the carb jets is what is making the overall difference.

Hope it works for you!