Hi, I bought a 1983 Heritage special around the 1st. of june and have been tinkering with it as time allows on the farm. My plans are to do a street tracker type build this winter. The bike was missing one air cleaner and had leaking carbs so I put on a Joe-Wiseguy two into one tracker intake and jetted up a 36mm Mikuni VM I had for a TT500 Yam[special thanks to Tee-Cat on this site for answering my e-mails about his set-up] and the bike really runs great with the single Mikuni. Starts first kick, idles smooth and pulls strong. I saw on the Australia XS650 site there was mention of a company in Minn. called Thunderproducts that sells a tuning piece for the Vm's called Ultimate Port Optimizer, appears to be a plastic piece that you attach to the bottom of the slide and it fills the slide cavity to cut out rolling air turbulance to give better fuel atomization. Claim three/forths to 1 h.p. gain per 100cc of engine disp. Wondering if any one here running VM's had any experiance with this product on their 650's? It's Thunderproducts.com if any one is interested. Mitch
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U.F.O. for Mikuni V.M carbs
- Thread starter plowboy1
- Start date
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- Tags
- carburetors
pregrid
XS650 Guru
looks like it goes on top of the slide, not sure what advantage that would be.
dwyatt
XS650 Addict
Mounts on the bottom to reduce the turbulence in the flow as it goes past the slide, giving you much of the advantage you'd get with a newer flast slide carb. Should be a small performance boost.
Well, it has been over 10 years but I'm wondering how it worked out.
Gee, it sure is great that the owner of an obscure snowmobile shop and an unknown engineering genius got together and came up with a product that corrects defects that the knownothings at Mikuni, Keihin, Amal, and Dellorto weren't even aware of! I smell the reek of snake oil, old, rancid snake oil.
I'm thinking that "turbulence" is what helps atomize the fuel as it exits the needle jet.
Not that you're wrong necessarily, but Mikuni stopped development if their VM line many years ago, preferring instead that you buy their new line of carbs which all incorporate the very features claimed by the UFO. Add to that, there have been many advancements since the development of the VM over 40 years ago. "The knownothings at Mikuni, Keihin, Amal, and Dellorto," and many others have all changed slide designs since then to do the very thing the UFO claims to do.
Modern Mikuni carbs have slide designs that approximate the UFO.
Would you make the same nonsense claim had someone asked about replacing one brand of carb with another?
Add to that, the snowmobile forums are full of praise for the very product you so snobbishly believe not to work.
But alas, you simply insert your uninformed opinion simply because you want to sound smart.
Have you tried the product for yourself? If not then you've really nothing to add but more BS.
Newer carbs have slides that incorporate the same changes as the UFO.
As a matter of fact back when I was running VMs I did buy a pair of UFOs just to have a look. Instructions which come with the UFOs but are not posted on the Thunder Products site direct the installer to modify the slides to a one-size-fits-all cutaway, which is emphatically not what is done in newer carburetor designs. I shook my head, stopped right there, and gave that stuff away. It might do something for 2-stroke snowmobile motors, but I'd think more than twice before I'd tear up an expensive pair of slides. In my uninformed and snobbish opinion any product that is promoted with claims of extreme power gains and a Mystery Expert story should be viewed with extreme skepticism. You've already decided you know what's what, so buy a pair and prove me wrong.
But you never actually tried them so you are unable to say how well they may or may not work.
And you're wrong about the instructions no being posted online. How are we to believe anything you have to say? https://thunderproducts.com/wp-content/uploads/2019/08/UFO-Instructions-0719.pdf
"Thunder Products in the USA make these things called UFO's for Mikuni VM roundslide carbies and from all accounts they do what they are claimed to." http://old.xs650.org.au/Racers.htm
"anyone else?main reason taking this serious is a highly respected xs650 road racer in oz got a set of ufo conversions back in 2008 from mmm and has been using them ever since, he reckons they do work well but would like some comments off any body that has tried their products (4 stroke),especially the ufos.sorry grizld but as the xs has proven there are a lot of upgrades to parts the exspurt/manufactures have made perfectly as well as some shonky upgrades" https://www.xs650.com/threads/ufo-carb-conversion.32578/#post-330605
"anyone else?main reason taking this serious is a highly respected xs650 road racer in oz got a set of ufo conversions back in 2008 from mmm and has been using them ever since, he reckons they do work well but would like some comments off any body that has tried their products (4 stroke),especially the ufos.sorry grizld but as the xs has proven there are a lot of upgrades to parts the exspurt/manufactures have made perfectly as well as some shonky upgrades" https://www.xs650.com/threads/ufo-carb-conversion.32578/#post-330605
They must have added instructions to the site at some point after I bought a pair of those things 15 years back. You're good at slinging insults, but I'm not going to reply in kind. I'll just offer this one more time: put your money where your mouth is.
What is the difference between 2 stroke carbs and 4 stroke carbs? Jets, needles, emulsion tubes? All those things differ when comparing one 4 stroke carb to another 4 stroke carb. It is a myth that the carbs are actually different.
You began with, "Gee, it sure is great that the owner of an obscure snowmobile shop and an unknown engineering genius got together and came up with a product that corrects defects that the knownothings at Mikuni, Keihin, Amal, and Dellorto weren't even aware of! I smell the reek of snake oil, old, rancid snake oil."
Thus insulting the intelligence of every member of this forum. The very idea that no advancements have been made in over 40 years is absurd.
PS. I'm currently working out the jetting after having installed a UFO. Already I'm seeing improvements without actually having it dialed in exactly as I like it. Jetting must be reduced by half or more to stop plug fouling. I'm close but not quite there. But alas, I ask a simple question in the hopes of learning what others might know and I get a smart-assed answer from you.
People used to think the Earth is flat.
Here's the slide on a VM36 showing the bottom https://www.mikesxs.net/yamaha-xs65...9PVMTNkvQmUO0onPVXYqGADyRUYrQ0lRoClY4QAvD_BwE
Here's the slide on a BS 38 showing the bottom https://www.dimecitycycles.com/yama...70-77-bs38-oem-256-14940-00-256-14940-01.html
See the difference? The UFO approximates the difference.
Here's the slide on a BS 38 showing the bottom https://www.dimecitycycles.com/yama...70-77-bs38-oem-256-14940-00-256-14940-01.html
See the difference? The UFO approximates the difference.
You're comparing apples to pears. In the BS and other vacuum diaphragm carburetors the throttle plate cutaway performs the same tuning function as the slide cutaway in a carb with a mechanically lifted slide. With a mechanically lifted slide, less cutaway richens the mixture just off idle, and secondary effects at closed throttle are strong enough that a change of pilot jets is always forced, no exceptions. Ditto a change in throttle plate cutaway.
I gave an opinion of a product, the claims made for it, and the advertising narrative used to promote it. If you feel personally insulted by my views I would respectfully suggest that you consult a dermatologist about growing a thicker skin.
I gave an opinion of a product, the claims made for it, and the advertising narrative used to promote it. If you feel personally insulted by my views I would respectfully suggest that you consult a dermatologist about growing a thicker skin.
That said, you have not addressed the subject at hand, that being, "Well, it has been over 10 years but I'm wondering how it worked out." and obviously you've no experience with the device or if it may or may not work.
I lurk a lot. I don't usually talk because I tend to piss people off. Good to hear from you.
