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whiskey_business New Reader
3/9/17 6:53 p.m.

Bang for buck, these things seem like a pretty solid option for a Solo/Time-Trial/Challenge? car. In my eyes, they have three key things going for them:

  • Obsolescence. This might seem like a bad thing, but only to those who race in the F500 series. Older, less competitive chassis and cars can be picked up surprisingly cheaply, especially compared to other vehicles with the same performance.

  • Parts Availability. Because of the long-running nature of the series, parts are easy to find and relatively inexpensive. Wheels and tires are shared between several formulas, and their elastomer puck suspension is cheap to replace.

  • Simplicity. For a race car, these things are stupidly simple. Stock snowmobile engine? Solid rear kart axle? Come on.

However, I have no firsthand experience with these. How are they to drive, are they quick, can they be setup well? If anyone has information on them, please share.

Robbie UberDork
3/9/17 6:57 p.m.

Doesn't JG have one for autox?

The issue with the custom foam seat right?

freetors New Reader
3/9/17 8:22 p.m.

Well everyone loves to watch them but simultaneously hate to hear them. A two stroke running through a cvt doesn't produce nice noises. I think they would be really fun to drive on a nice smooth lot, torturous to drive on a bumpy one. I also think they are quite heavy for what they are really...

David S. Wallens
David S. Wallens Editorial Director
3/9/17 8:35 p.m.

Yes, JG has one, although he's been campaigning the Mustang the past year. You can read a little about his F500 right here, though.

whiskey_business New Reader
3/9/17 9:05 p.m.

I've read the stuff that JG has written, and while they are great articles, I found them lacking on technical details. And my plan is a 600cc motorcycle engine swap, bored and high compression, so sound would be somewhat less of an issue.

jstand HalfDork
3/9/17 9:09 p.m.
freetors wrote: Well everyone loves to watch them but simultaneously hate to hear them. A two stroke running through a cvt doesn't produce nice noises.

As someone who rides snowmobiles, I would have to disagree with the statement about 2 stroke noise.

It is different than the sounds of a 4 stroke, but with the right pipe and intake they can and a very aggressive sound and not be buzzy.

Stefan MegaDork
3/9/17 9:29 p.m.

In reply to jstand:

You've never heard an F500 running on a road race circuit, then have you? Let alone more than one (there were only ever 4 running at one time at our local track, all owned by the same guy and rented out).

Yeah they just don't sound good. I'm sure there are options for snowmobiles that do, but the technology and rules the F500's ran under apparently limited them to sounding like angry Briggs and Stratton lawn mowers running at full tilt on old gas after a winter of sitting.

Needless to say almost all of the F500's have been scrapped or converted to F600's with slightly larger motors and a real sequential shifted transmission.

Tom1200 HalfDork
3/10/17 12:09 a.m.

I run a 1987 Novakar F500 as an autocross car.

@stefan not sure if you mean your local track or not but the vast majority of cars running are still in F500 configuration. There were only 2 bike motored cars at the 16 RunOffs. Thus far F600 as only won the RunOffs once. At Solo Nationals it's all 2 strokes. I'm a former motorcycle racer so I think the 600cc bike motor is a cool package but the fact is something like 90% of the cars are running 2 stroke CVTs.

Whiskey business there are a coupe of things to ponder; first the class is a spec class. The 4 cyl 600cc bike motors are stock expect the exhaust and they have to run a inlet restrictor. So now wild cams over bore etc. The 2 stokes are also stock except the pipe, the choices are Rotax 494, 494 reed valve and Rotax 583 with inlet restrictor. They all make around 100hp at the wheels. Weights are 800 or 850 with driver dependent on motor configuration.

I contemplated the bike motor swap but Jay Novak ( former Ford engineer & designer builder of Novakar) told me to stick with 2 stroke and CVT, especially for autocross.

The CVT is infinitely tunable, no need for $4000-$6000 close ratio box. You tune them by changing the springs, spring preload and flyweights. You can tune the engagement RPM, the upshift and what is called the back shift (down shift) $200 will buy all the parts you'll ever need to tune the primary clutch and the secondary. To service the units you need 4 special tools that will run you about $130.

The suspensions use rubber pucks and you make your own, you just order the sheet from McMaster car and then use a hole saw to cut them out.

Engines are cheap, as they are stock the retain the oil pump so you don't even need to premix oil and gas. I bought a Rotax 494 several months ago for $600. My car still has the no longer in production AMW motor. Autocrosses get something like 5 seasons on an engine. Road racers at the regional level will go 2 seasons.

There is only one tire, Hoosier R25 compound slick and the are $170 each. You can run 20 autocrosses on them. Not sure how much mileage road racers get out of them but I believe it's at least 3 weekends. For autocross you run 7.5 wide tires on all for corners to counter act not having any sort of differential (at low speeds it behaves like a car with a locked rearend)

I run a silencer on my pipe because, despite being raised on 2 stroke bikes, I find stingers annoying as well.

As for speed, they are equal to Formula Fords and at local autocross the only things faster are shifter karts.

4 years ago a friend let me drive his 06 Novakar, right after that I started shopping. If you look at autocross videos with telemetry you'll see they'll do 0-60 in just on 3 seconds. A coupe of guys have run them down the quarter and pulled high 12s to mid 13s. They pull 2gs in a corner and like most formula cars they everything right now.

I'd stopped going to local autocross for the most part. I have a Datsun I vintage race and use at track days but once I drove the F500 it was an instant this thing kicks butt, I need one of these.

The plus side of the CVT is you can let anyone drive it without worrying about them over revving the motor or abusing the gearbox. Last year we invited a friend of my son to drive it (he's a drift kid with a turbo 240SX) and he was blown away by the performance. The young man has a good bit of natural talent and he admitted he made himself nervous in a coupe of spots because he couldn't believe how far beyond a street car it was.

I've had my car for a little over 2 years, I paid $2000 for it $1400 to ship from Michigan to Vegas. I spent $300 upgrading the radiator, adding an electric fan and other bits to make it more autocross friendly. I've spent $400 on tires and will need to buy a fresh set ($750 mounted) this summer.

Check out F500.us as it as a lot of good info; keep in mind this site is the 2 stroke stalwarts who are still peeved about the bike motored cars (long history to much to explain here) they are super helpful and very welcoming.

Apexspeed is the other place and there is Formula500.org but that doesn't get much use anymore.


jstand HalfDork
3/10/17 7:20 a.m.

In reply to Stefan:

You are correct, I have not heard an F500 running.

It is disappointing to hear that the rules lead to them sounding the way you describe.

In a snowmobile those rotary valve engines have a healthy sound and meet noise requirements while still producing >100 HP from the factory.

whiskey_business New Reader
3/10/17 3:26 p.m.

In reply to Tom1200:

Excellent info. I am largely interested in a fun, autocross focused car with little regard to the spec series rules. Would a modified F500 still be eligible for F-Mod or any other SCCA class for Solo?

freetors New Reader
3/10/17 9:14 p.m.
whiskey_business wrote: In reply to Tom1200: Excellent info. I am largely interested in a fun, autocross focused car with little regard to the spec series rules. Would a modified F500 still be eligible for F-Mod or any other SCCA class for Solo?

I would suggest you look at building something for the FSAE class then. SCCA lets you choose any year FSAE rulebook that you have to meet the rules for. It's still rules, but compared to SCCA standards it's like having no rules. Basically you can use any engine you want as long as it runs a certain restrictor size (18mm for NA engines running gasoline iirc). There is no weight minimum. You could build a 300 pound car if you have the skills. Even active aero is legal. The only cars faster than a good FSAE car at autox are the A-Mods.

Tom1200 HalfDork
3/10/17 11:41 p.m.

Whiskey_Business There is post on F500.us I put up a out 4-5 months ago about modding a F500 beyond the F-Mod rules. Basically what your looking at is bumping up into A-Mod. At the regional level it won't really matter as very rarely does anyone run a actual A-mod car. You could run an unrestricted Rotax 583 or mod an existing 494.

My idea was to take my Rotax run twin pipes and mix and match standard Rotax parts which would up the horsepower to around 115 or so.

Another alternative is running one of the 150+ HP 850 2 stokes twins. The easiest route is using another twin cylinder snowmobile engine as that won't even invoke reconfiguring the entire drive line. Also the engine bays on the cars are a bit narrow so squeezing a triple or four cylinder motor may involve cutting the frame.

Much beyond 120HP your going to want to put some downforce in the car. The older cars like mine are 73" wheelbase and the newer ones are 80" so either way they are a really short wheelbase.

So basically there's nothing stopping you from picking up an F500 hopping it up and simply running it as an A-Mod.


whiskey_business New Reader
3/11/17 12:43 a.m.

In reply to freetors:

Oddly enough, I'm actually on a FSAE team at the moment at university! I'm looking to scratch that itch once I graduate, and a F500 or A-Mod seems to be the way to go.

whiskey_business New Reader
3/11/17 12:45 a.m.

In reply to Tom1200:

This is exactly what I was looking for. It's interesting to see that they fit into A-Mod, but it makes sense. Thanks for the info.

Robbie UberDork
3/11/17 7:32 a.m.

I think A-mod is the highest-end default. I don't think you can mod a car out of a-mod.

Robbie UberDork
3/11/17 7:32 a.m.

p.s. this thread is highly relevant to my interests.

XLR99 Dork
3/11/17 5:44 p.m.

Me driving my dad's KBS; I think this was at CART in Hartford, CT; which was definitely NOT a mod car friendly venue (the people were fine, site was kind of like a rallycross)


The car is an '87 KBS Mk3, 73" wheelbase. It's been repowered with a Rotax (can't remember if it's a 493 or 494). My dad did a ton of development on this car, including a lot of work to quiet it down enough to meet NER noise restrictions. It has a Quadrini 4 link rear suspension, and a fairly unique rocker arm front suspension that's completely different from the later KBS cars.

I also had my own 88 Red Devil back in the late 90s-early 00s. Much less developed and more primitive design, and still ran the original Kawasaki 440. (Someone did win Nationals with a very similar car, maybe 2005ish?)

Tom1200 HalfDork
3/11/17 5:51 p.m.

It may be possible to B-mod or C-mod but I think those required big changes. A-mod is simple; take a garage door bolt some end plates on it and then bolt that on top of the roll hoop. Fit some meaty slicks a 200 hp motor on a 900lb car point down course floor it and steer as fast as you can............simple enough.

I've run my friends Exocet in A-mod because that's where is lands, you'd get your clock cleaned at Nationals but at a local event it's fun to have something really capable FTD. Of course those pesky shifter karts will make you work for it.

I hope to switch over to the Rotax motor this summer if per chance I find a twin pipe manifold cheaply then I'll bump to A-Mod otherwise I'll stay in F-Mod. There are no other F-mod cars locally so it really doesn't matter to me which class sticker is on the side of the car.

Tom1200 HalfDork
3/11/17 5:58 p.m.

I was typing away while XLR99 added his post; my car is 73" wheelbase as well. These cars do take some development for the switch to autocross. The AMW motor in my car is probably down 10hp compared to the Rotax motor, so I'm looking forward to the upgrade.

jstand HalfDork
3/13/17 3:26 p.m.


There are different rotary valve disks available for the Rotax engines, which could possibly help move the powerband around depending on the final usage.

Rotax would use different disks depending on the sled model the engine was installed in. Also, the newer rotax engines had power valves on the exhaust that can be retrofitted on earlier engines by replacing the cylinders.

iceracer UltimaDork
3/13/17 5:47 p.m.

Way back when, the 500s had a single cylinder motor cycle ,Triumph I believe, engine.

They gave an annoying, throbbing noise when on track.

NickD SuperDork
3/14/17 7:55 a.m.
XLR99 wrote: I also had my own 88 Red Devil back in the late 90s-early 00s. Much less developed and more primitive design, and still ran the original Kawasaki 440. (Someone did win Nationals with a very similar car, maybe 2005ish?)

The gentleman's name was Brian Ciarlei, and he won in '08 in the Sharlay Machine/Pennon Composite Red Devil 440. The car got badly wrecked in '09, and it showed up at a local autocross (CNY SCCA, he's from the Syracuse region) fresh off of rebuild for a few shakedown runs back in '15, setting FTD at the event. It was going up for sale to pay for a new engine for his dad's '68 Camaro

chada75 Reader
5/25/20 3:55 p.m.

Apologies for the thread resurrection. Is thier an approval process to build a chassis for the Forumla600 Challenge or can anybody build thier own? Is the 600 legal in F-Mod? The more I read about The F500/600, the better it seems to get one conpare to a competitive Street Touring class car. Thanks.

Tom1200 Dork
5/25/20 6:15 p.m.

Anyone can build a chassis; you will need to get it inspected and certified / homologated by the SCCA. This isn't a big deal I did it with a D-sports racer back in the 90s. I took a bunch of photos and sent them to national.

F600 is legal for Solo but the 2 stroke CVT seems to be the way to go for Solo.

I'm assuming part of the fun for you is building a car, if it isn't just buy a car. 

Apexcarver UltimaDork
5/25/20 6:33 p.m.

If it's autocross only, I'm not sure what might be needed in regards to homologation. I could redo large amounts of the chassis and not have to do that, you just have to pass tech and possible protests I think, I say think because I don't know for sure.


600 has to weigh more than most of the two strokes and it's not just any 600 you can run. It's specific engines with restrictors. The rub is that the bike motors are peaky and you will be chasing the powerband bogging out of corners whereas the cvt two strokes are always peak powerband.


Join the Facebook group, it's the most active thing right now. https://www.facebook.com/groups/360619197459057/


There was someone working on an open source car awhile back, it's worth chasing them down for the knowledge dump on off the shelf components. I forget if it's mini or micro sprint dirt track cars that are a possible rear axle source. I was loosely eyeballing stuff in the Joe's racing, Smiley's, and speedway motors catalogs. 

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