Thunder Products (UFO)

Has anyone tried the UFO mikuni carb round slide insert yet? I also sand and file the UFO insert for a better fit on the wedge or ramp. If it sticks out above the slide. It's all about the smoother flow. It comes with a drill guide fixture. On the inside of the slide we just chamfer the holes we drilled for the flathead screws. I just use a larger drill to chamfer so the throttle cable retaining plate sits flush.

https://thunderproducts.com

Now rejetting is next. Since the UFO allows more of the mixture to enter into the engine it becomes on the rich side. So smaller leaner jets are needed. I put the clip on the needle in the middle slot for starters.

Yes, I have used them on many different bikes, but I dont have any right now. I need to put one in my 84 KTM125 that I just swapped out the stock 36mm Dellorto (its WAY too big for a 125) for a 34mm Mikuni. It runs much better but any improvement in the vacuum signal will help.

I installed the UFO's in all my husqvarnas. The last 390cr I built with the 40mm mikuni carb had one along with the needle jet change, with the rejetting. But I did pickup some 175cc Husqvarna 36mm mikuni carbs.
I need to figure out what mikuni carb would go with my Clinton 2 hp 2t go kart racing engine someday.

I have some KTM 125 new and used parts for 1984-1986. I have a pretty much complete 1986 roller. Let me know what you might need and maybe I can help you out.

I've got two 84 125s, one MX and one GS with a spare engine for each but I am always looking for more spares. I can't use any of the chassis parts but I would be interested in any engine parts you have.

So these UFO things actually work? I am not doubting them, they look like they should it's just that I've never heard of them before.
Tony.

My concern is do you really reduce your pilot jet to half its size ? That is a lot. I think the other product i will try the wing unit
that fits in the front of Carb.

Yes, the UFO works well, but no it is not that drastic a change. You will not go to half the size pilot jet, maybe one or two sizes leaner (like from a 40 to a 35 or maybe 30 at most) and that all depends on the intake tract of the bike you are installing it on. I dont remember ever going more than one size leaner, but it has been a while.

I'm skeptical of the "wing" but I have used the Thunder Jet power jet kit, along with the much cheaper Mikuni power jet kit. They both work the same once you get them dialed in, but the Thunder Jet is easier since its a knob adjustment where the Mikuni kit uses pilot jets to regulate the powerjet flow. I prefer the Mikuni kit because its 1/3rd the price of the Thunder Jet and unless you go from sea level to 12,000 ft you will never have to use the knob adjuster once you get it dialed in.

Be a good winter project for you to try them all?

does the mikuni kit works like the lectron's power jet? imho thats one of the key advantages of the lectron and one of the ways its so easy to get the lectron dialed perfect.

Now you said it. Thats what I really want is to install a Lectron. Of all things they are making them down the road from me about 90 min drive.

I think we would have everything in the Lectron we would ever need.

Used them on my 390 back in the 77 78 seasons. Now I just have to make sure they are Armha legal.

probably couuld be if you used a vintage lectron. i really like the one i installed on my 95, want to install one on a swede but other things get in the way. i know i will not invest money in carb stuff unless its a lectron, although i respect and like the mikuni vm.

Yes, the Thunder Jet, Mikuni and Lectron power jets all work the same, but the Thiunder Jet and Lectron have a knob to adjust the mixture, the Mikuni you have to use pilot jets, but its very easy to change.

Installing the UFO on the bottom of the slide is a big improvement. I was down to a 35 pilot jet and. 400/410 main jet on my '81 250cr Husqvarna. A big improvement on the lower to mid performance, besides the top end. The UFO guides the fuel mixture through the carb to the reeds much smoother. Without it the mixture hits the wall in the slide gets confused and turns around to head back. Plus it performs better and saves on fuel consumption.

imagine using a carb that doesnt have near that obstructions , is taper bored with a polished airbell, and dial adjusted main jet. plus a clear float bowl to instantly check fuel?

The UFO doesn't cost so much for a mikuni upgrade.

no doubt its an improvement. just depends on how much you want to spend.

Did you ever try one? It's proven snowmobile technology. It smooths out the gas delivery as the slide opens.
On the rear of the slide opposite the half round opening there's a flat wall the protrudes down.

Hint it comes with different sized wedges. I can't mount the larger wedge in the smaller cutout. Then file it or belt sand it carefully to the thickness it needs. Like 2 fear one.

With the mikuni 40mm round slide I installed the UFO, The leaner needle jet, the smaller pilot jet and main jet. After a few trials in changing jets she ran awesome. The 390cr ran.

It is an improvement, but it is not even in the same time zone as a Lectron, its best described as a band-aid for a Mikuni.