UFO Mikuni slide optimizer

[John Orchard]

I just got a UFO slide optimizer from DC Plastics, it goes in the bottom of the slide of VM Mikuni carbs.  It reduces the area under the slide to increase the air-flow over the pilot jet outlet, giving much improved throttle response at part throttle; something my RM125B might like?  :-) .  It seems to make sense to me but I guess I'll soon find out.

Has anyone else fitted one of these?

[cappra]

We have been using these on the Mikuni's for a number of years. They do work. Seems to smooth out the revs, and adds a couple of horsepower.
The snowmobile guy's started using them sometime ago. It's best to establish a base line jetting without the UFO. When the jetting is correct, install
the "puck" and then cut your pilot jet size in 1/2. Might also have to increase your main jet size, but not all the time. Make sure you install your throttle cable
before tightning the screw that holds the puck in place. Almost impossible to slip the cable in afterwards!

[John Orchard]

Nice, thanks.

[VMX60]

John

Been using the UFO on my Ossa roadracer 38mm mikuni plus all VMX bikes CZ/Ossa for over 10 years

Bit of stuffing around to setup jetting once sorted  Great  overall improvement

Never had a motor lockup in all those years


Cheers

[Tahitian_Red]

I run one on my lead CR480 w/38mm Mikuni.  The pilot jet is actually plugged.  It runs great, but it makes an already hard to start bike even tougher to start.

[Sorelegs11]

I have run  the UFO in my it490 and found mixed results.
Following the jetting guide to cut the int jet by half the bike was easy to start but ran on a lot, I am almost back at the standard jet size and I am finding improvement at the bottom but not so much at the top.

[John Orchard]

Hmmm interesting

[dkupf]

A lot of the Hodaka riders in the US use them