Comments on the Last Vetter Fairing March - April 10 Page 1
This is where I post the more interesting comments and questions. My comments in blue.
From Joe, Mar 1, 2008: Single track is two-wheeler, right?


We're wired to believe that two-wheelers are unenclosable because of the need to balance and put feet down at stops.

Well, I am working on a solution that probably will render that untrue.

Your work with streamlining definitely proves it is possible at least, and people will do a double-take at that vehicle for sure. Is there another reason for your focus on single track besides the lane-splitting and reduced friction?

Stay narrow so we can slip thru traffic.

Stay simple

Stay light

Stay a motorcycle

I think a good solution might take the best from various designs -- for instance your streamlined fairing around a geometry that can be loaded up without concern for balance and actively stays upright even without traction. Three points of contact are safer and more usable than two. Do you agree?

I put thousands of miles on bikes with a sidecar. There are times when they have an advantage, but those times are for when I am not able to or do not want to balance a single track machine. Remember, a bike with a sidecar has great virtue on icey roads in the winter because it is asymmetrical, thus, predictable. Of little value on dry roads.

At the moment, I am not old or infirmed enough to want three wheels... yet.

Look around... 3 wheelers are attractive to non seasoned riders.

I have best success designing for myself.

From Clive Feb 23: Consider 95% ergo fit? Make wider at the top (looking at the front view, shell would slope outward) for the MANY large riders of Helixii (sp?). Was just reading the HH discussion group, and realized that a lot of the riders are big people. Got me to thinking of my rides in a Lambo years ago - made for Italians, the door hit my head, had to ride slouched to the left the whole time. Also got a ride in a tadpole trike (2 wh in ft) kit car built by a fellow who worked in the CA Nissan design studios, Pasadena Design grad who should have known better, same prob; he was 5'7" 150lbs, cockpit fit him fine. I'm 6'2" and at the time weighed 200lbs, was wedged and scrunched so tight I had to beg off after 10 miles, even tho the ride was a total blast.

This being said, must also add that there are several very short people who select the HH because it's so easy for them to get their feet on the ground. Some have even cut down the foam in the saddle.

Tough equation. Good thing to bring up Clive and I think I know what to do about making the shell fit a variety of riders.

Oh, dunno if I mentioned this before: The windshield on "NotBent" led to an accidental discovery that high-pressure laminar airflow BEHIND the shield gives a nice boost upward of the flow coming from the front. I made the shield from an existing one, and missed on the base dimension, resulting in a .5" slot across the bottom in the middle. I taped it up, got buffeting of face shield. Tape was ugly so I took it off, opened up the slot, voila, no more buffeting. Suppose I should do tuft tests to see what's really happening, maybe opitimize it more, but works plenty good.

Letting air into the center works to help fill in the envelope we sit in. Snap Vents in Windjammers did that. Rifle Fairings has a nice vent that they have engineered.

I get airflow over my helmet beginning at 35-40mph, very nice still-air pocket. The only areas that are less than perfect are the edges; in some wind conditions I get a bit of turbulence coming in from the sides, so I need to add deflector tabs on the outside OR maybe a redirector splitter on the inside.

I have a wonderful, never been seen before solution to the problem of not falling over when we stop. Let me try it first before I tip my hand.

Dunno whut yr planning for stopping, but can add that I've done some work on auto-leveling center stands with roller feet and over-center action operated from the cockpit. That's what Royce does on the Voyager - one big honking lever that lets you deploy CS from the saddle (I suspect you kinda stand up at the same time as you pull, but have not verified that.) The auto-leveling work was done for a wealthy local BMW owner whose bike tipped over on a sloped street.

From Richard Feb 23: What is your plan for entering and exiting the bike?

Ah! You ask the good question. I must defer and not answer right now. Suffice it to say I believe I have a way. Remember one of the Vetter Design Truths: "A good design must not be more trouble than it is worth"

How do you stabilize while stopped?

Same answer as above

Are you limited by the lower envelope of the fairing by suspension travel and speed bumps?

It is best to stay away from the ground. I use the Helix bottom because it is already there

Why tilt the rear up?

Look how high I sit. I am trying to smooth the air around me. I am up high so the fairing has to be up high with me.

April 5, 2006 Roy wrote: I'm really enjoying your website. As I'm presently in the market for a 250cc scooter, the use of a Helix is of particular interest to me. I hope that you will entertain a question regarding your project. Wouldn't the use of a Yamaha CP250 scooter (Morphous) provide a more efficient basis for your streamliner? I believe that it is lower than the Helix, and with fuel injection, presumably the engine efficiency would be superior. In any event, what are the prospects of a kit becoming available for simple "bolt-on" reproduction? I'm afraid that a realistic assessment of my skills precludes me using your currently available streamliner body kit. I look forward to your reply, and once again, your webpage is GREAT!

It is all about horsepower. The Helix has about 18 I don't see what the Morphous horsepower is. do you know?

I do not know with certainty, but I've read that a Japanese web site lists the output at 15kw@7500 RPM, torque as 2.1 kgf@5000 RPM. It said that converted to 20.12 hp and 15.19 ft/lbs. Once again, I don't know if these numbers are accurate, or if the conversions are correct.

A Morphous may do just fine. You are great! 20 hp is at the high end of what is needed. Can you find out the same numbers for the Helix?

The only numbers I've seen for the Helix are 17 flywheel, 13 rear wheel horsepower. I don't know the original source of the first number, but the second came from a chassis dyno test of an Iron Butt Rally entrant. Additionally, it seems that there was some modification to the engine's evaporative system in the late eighties or early nineties which may have had some minor effect.

Sounds correct to me. This is the most powerful reason to choose a Helix over a Morphous. 17 hp is more than enough. 13 hp is better if we are streamlined.

But I must confess that popular culture does not necessarily agree with me.

Well, either way, from my perspective they both have advantages and disadvantages. If there is ever a streamliner kit available, I'd be happy to accommodate its requirements.

April 6, 2008, Mike wrote: On the streamlined Helix, I will be very interested in what your new top speed is (standard ones, from what I have read, top out at 70mph). I currently have a Suzuki Burgman 400, which gets around 65mpg, with lots of pep – besides being very quick on the update, that bike will do over 90mph, and has an awesome lighting system to boot. As a result, I feel comfortable using it on any of our Georgia roads/interstates, and the reason I went to a 400cc scooter instead of a smaller one. But, I love the idea of 100+ mpg, and look forward to your final analysis (and cost) for the modified Helix. The plan is to then sell the Burgman, go for your modified Helix, paint it green along with big letters on the side saying 100+ mpg, and drive it everywhere, including cross country J Also, as I mentioned, I be happy to enter one in the Iron Butt competition, could be a great way to generate more publicity for the bike (one guy did it on an unmodified Helix, click here).

Helix vs Burgman: My (Vetter) take is this: More horsepower burns more fuel. The Burgman has more horsepower. It will probably burn more fuel. Streamlining favors engines with less horsepower, allowing fewer horses do more work. So, the Helix with less power should respond to streamlining much better than a Burgman. It is nice the Burgman will do 90. Streamlined, it may go 120. I don't want to go 90 or 120. But I do want to go 70 into a 20 mph headwind, and it is not the same thing, is it?

Nobody knows these things for sure. We are learning here. My cardboard fairing in not streamlined at all. It is full of gaps and scoops... I am getting my normal 64 mpg with the tail and without the tail, used in errand running, half at 65 mph.

Also, in thinking it over, I would also consider looking into the following possible mods:

- put a safety bar underneath the fairing on at least one side, maybe both (would need to fashion a mini door of some kind). That would make the bike much safer, no?
- to complete the full streamlined shape near the bottom, how about some forward hinged panels where the feet go (e.g. would blow “closed” once the bike got moving)?
- Maybe rig an auxilarily gas tank somewhere under the fairing, and of course, use all available extra space for storage.
- Finally, for the option of the ultimate streamlined shape and weather protection, rig a jet style canopy that can slide forward in bad weather, as well as put a small windshield wiper on the front.

I believe you will be astonished at how I deal with these issues. It is too early to show right now. suffice it to say, it is nothing remotely like anything you have ever seen.

Anyway, thanks again for the DVD, and I will continue to check for updates on your web site – Mike

P.S. I would love to see you set up a forum; I assume you are familiar with the “Feet Forward” web site, at

On Apr 7, 2008, Gildardo wrote:

Hey MR.Vetter, i am following your Helix aero mod and I am inpressed. Its quite interesting how a design evolves from imagination to the actual 3D shape. I also like how u are doing it with a low budget in mind, it encoreges me of actually doing something like it in the future.

Thanks for the insight.

P.S, I check your site 3 times a weeks for any updates.

It pleases me that somebody is watching. I want this to be encouraging. You can do this. It is not rocket science.

On Apr 7, 2008, Jerry wrote: Craig - I like the shape so far but I'm finding myself impatient about your thoughts in a couple of areas like stability at stops and getting on and off the bike without destroying the laminar flow around the body.

Jerry: I have a plan for a way of staying upright and smooth with a solution that is "Not more trouble than it is worth". We will not be needing outriggers or 3 wheels. Please be patient.

I'm going to test drive a Helix on Wed if it's not snowing too much in Denver. If you do end up riding out to your brother's you can have a place to stay in Boulder or I'll at least buy you a cup of coffee.

Boulder? Well, see, I like to come from California up thru Durango, Montrose, Monarch Pass, South Park and Colorado Springs. Then east to Illinois. Lets stay in touch. There are good coffee shops in the Springs and maybe you can ride your Helix down. We used to live in Manitou Springs. I am pleased that folks are actually watching the development. I want you to understand that it is important to make our fuel go farther and that you indeed can be doing this kind of thing yourself

Keep up the good work (fun?). I'm enjoying watching the process as much as the result.


April 7, 2008 From Clive: Actually Variator Sliders of a new design. OEM is cylindrical, which over time wear flats at an angle, reducing top speed. The Dr. Sliders make great sense, I'm still looking at price and where I can buy a set.

I had a small business making these 'rollers' for Yam scooters when Yam was charging too much for a set, and had even thought about making angular pcs based on the wear pattern we were seeing.

Scroll far down to see the spec on Helix (CN 250) sliders.

BTW, the best top speed I have ever heard of for a stock Helix is around 87mph wound to the max witha well-broken-in engine and new weights, so to get any more that that, we'll really need to get anew set of final drive gears. I'll get started on that, as I think you'll have customers who will want them when they buy the shell kit.

You may want to talk with Blez about this, and the other v. simple speed tuning steps you'll want to take, including a new exhaust (stock is very heavy & prone to internal breakage/rattling. The very short header section at the head needs to be opened up from 24mm to 27mm, and have the internal welds smoothed out. Carb will need to be rejetted at least one and probably 2 and maybe even 3 steps with you at sea-level, Blez knows where to find this info. Some owners also bore the carb throat 1mm. If you learn anything about aftermarket exhausts, I'm all ears, may make something myself. Remember the muffler pivots with the engine unless we come up with a trick pivot and mt arrangement.

Oh, the trick variator is called "J. Costa", I presume this is the guy who makes them? Just now
learned this.

Oh, can you say what role you have in Legend event, in May? Have a friend, Larry Pearson, who got a bike accepted, he's very excited to be there, of course. And me too, as I did the final metal fabrication work after the original builder stopped work on it.


Here is the thing, Clive. I don't want more horsepower. More horsepower burns more fuel. The Helix' 17 hp or so is totally adequate. I want the best streamlining. The only difficulty I anticipate may be trying to gear the Helix up. From your note, it sounds as if the thing gears itself down as it wears...

Wrong way.

If anything, we may want to gear it up.

I know... We have been hot rodders all our life. It is built into us to open up ports, etc. to make more horsepower. More horsepower is now the enemy. Streamlining is our friend. The ONLY mod that may work is to raise the compression. But then, we'd have to buy more expensive fuel.

This page updated April 7, 2008