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Apexcarver UltimaDork
1/4/19 5:37 p.m.

Back in college, circa 2005, I participated in FSAE and got to do some test driving.  I NEVER forgot how fun open wheels were and wanted to do it again ever since.


Life happened for awhile.  Graduated.  Moved in with an amazing woman (more on this later). Launched a career. Married. 99% finished a restoration on a Bugeye Sprite.  Had a kid. 


Was contemplating what was next.  I had gotten a Spitfire and had intentions of building it into a Miata suspended, motorcycle powered beast. Then realized that being a parent, time to build it was unlikely.  At least if I didnt give up driving for quite awhile.  Was offered another Bugeye that had been a racecar and would need a total resto to be a vintage racer.  Again.  Time.   


Talked about it with my wife, while we were feeding our 3 month old (at the time) baby.  What did I really want to do? I wanted to be able to autocross somewhat competitively, but also be able to do track things.  I wanted open wheels.  She told me to do it.  Seriously.  Lucky doesnt begin...  I married well.



Bought it in early November and was going to surprise people at the first event of the year.  I decided that the off season was boring and spilled the beans.


Its a 1994 KBS MK7 with a Rotax 494 and an updated suspension.   Its in roadrace trim, but I am slowly working it to go both ways.


So far:

  • Added electric start
  • Upgraded cutoff switch to handle additional power demands
  • Added cooling fans
  • Added muffler
  • mild rework of cockpit to better fit (padding, steering wheel spacer, etc)


To do Items

  • Regear for autocross and convert final drive from belt to chain. 
  • Shore power for cooling with engine off
  • electric water pump for cooling with engine off. 
  • Wider wheels for front to run wider tires in front. May require new a arms.


Its gonna be a good year.


Box4VIR New Reader
1/4/19 6:06 p.m.

Congrats!  I’ve been combing craigslist for something like this forever, can’t tell you how jealous I am! Keep us updated


Apexcarver UltimaDork
1/4/19 6:14 p.m.

In reply to Box4VIR :



Racecars like this are a bit too specialized for craigslist.

I found mine on Apexspeed, which is a good hub for all things formula car and sportsracer.


Other good places for F500 are F500.us and Formula500.org  


If you want to go autocross only, you can seriously do it for close to a challenge budget with an earlier car that wont pass roadrace tech due to a change in rollbar rules. 

B13Birk Reader
1/4/19 6:33 p.m.

I have had the privilege to drive some epic cars over the years. From super cars, vintage racers to Porsche Cup cars.... 

The F500 is one of my most favorite. It’s of the most enjoyable driving machines around! Great buy! Enjoy and have a blast. 

Pete Gossett
Pete Gossett MegaDork
1/4/19 6:49 p.m.

From what I’ve witnessed, the key to success & happiness in owning a racecar like this is having someplace relatively convenient to test it before/between events. 

gumby Reader
1/4/19 9:22 p.m.


I've got one as well. It has been neglected in the corner of my storage garage for a few years, but with the allowance for aluminum rear axles and a Thanksgiving delivery of the MC drivetrain to swap in, the car has come out of the corner and I am excited to work on it again.

Congrats on the purchase, I look forward to following along.

Woody MegaDork
1/4/19 9:32 p.m.
Apexcarver said:




If you want to go autocross only, you can seriously do it for close to a challenge budget with an earlier car that wont pass roadrace tech due to a change in rollbar rules. 

Please tell me more about this.

Apexcarver UltimaDork
1/5/19 12:04 a.m.

In reply to Woody :

In the early 90's scca increased the required diameter for the main roll hoop for road racing. This made many cars obsolete pending replacement of the main hoop, which means cut the car in half. Many cars weren't updated. They are only able to be used for autocross. 


Engines, they have brought in new motors over time. 440s were what to have about that time. In the 90s it was 494 or 493. Now, you can run a 593 or a 600CD bike motor (snowmobile two strokes will be faster for autocross though).


Older car with older motor? They can be had pretty cheap. 


Here's a fixer upper for sale now. That (tires aside, but shop used) could likely run for challenge money. http://f500.us/forum/viewtopic.php?f=21&t=2353

The cars are a lot simpler than you may think. The 2 strokes easier to work on. I have heard of people rebuilding a top end (piston replacement) of a motor in car in an hour or two. The bodies come off and it's more like working on a big go kart. My body comes off in a few minutes with 20ish dzeus clips.

Would it be most competitive at that price? Not at nationals, but locally... major shot at ftd.  5th fastest pax after am, bm, fsae, and kart mod.


Apexcarver UltimaDork
1/5/19 12:16 a.m.

Another bonus for the class. My cars weight should be about 800lbs with me in it. You really don't need much trailer or tow rig. Mine came with an enclosed trailer and I have an expedition, total overkill. Small open trailer and you could tow with just about anything.

Brett_Murphy UltimaDork
1/5/19 12:36 a.m.

This is badass. Would it count as a production car for the 2000 Challenge, I wonder?

Akbarratt None
1/5/19 1:08 a.m.

I bought mine off the Facebook f500 forum last August. Drove 4000miles  round trip to get it just in time for our last season event in October. That shakedown event I spun it like three times, though one was on slicks in the rain. Posted 5th fastest raw for the two day event behind some very serious race cars. Worth every penny. 


Congrats on the purchase! 

GTXVette SuperDork
1/5/19 7:32 a.m.

All it needs is a Factory Produced Body For The Challenge,  Not like a Myers Manx Though they made more than some Factory's. But an old Fiat or Renault or Subaroo

Woody MegaDork
1/5/19 8:27 a.m.

Would someone who is, say 6' tall, 225 lbs fit into one of these things?

Apexcarver UltimaDork
1/5/19 9:17 a.m.

In reply to Woody :

Depends on which chassis.  I'm 6'2" and 155 and it's a tight fit, but not in the butt/waist. Feet knees and shoulders moreso. Then again, you can modify a lit for fit. The GRM f500 is basically the same chassis and JG fits (sorry to put it that way JG). Mine is roadrace legal and tighter though.


Shopping formula cars is like shopping for pants, you have to try them on and understand that some tailoring is needed.


Test sitting a car for fit is a very normal part of buying one of these.

914Driver MegaDork
1/5/19 9:17 a.m.
Ian F
Ian F MegaDork
1/5/19 9:58 a.m.
Apexcarver said:

Another bonus for the class. My cars weight should be about 800lbs with me in it. You really don't need much trailer or tow rig. Mine came with an enclosed trailer and I have an expedition, total overkill. Small open trailer and you could tow with just about anything.

One of the local guys used to tow his F-Mod on a slightly modified single-axle landscape trailer with his STX prepped WRX wagon. A family (dad, mom and daughter) are running one as well for cheap, towed behind a similar small vehicle (an older minivan, I think).

At the other end of the spectrum, we have another guy who tows his F-Mod in a toy-hauler and diesel pick-up, but he uses it to travel to National events.

Woody said:

Would someone who is, say 6' tall, 225 lbs fit into one of these things?

Absolutely. The cockpit is typically quite roomy and a seat custom fitted to the driver is used. There was a GRM article about making a poured foam seat when JG had one, but I've seen more basic seats as well. 

Patrick MegaDork
1/5/19 10:01 a.m.

So can i have the cobra?  Because you’re clearly not mustangboy anymore 

Apexcarver UltimaDork
1/5/19 10:15 a.m.

In reply to Patrick :

Mustangs not going anywhere. Jenn would kill me if I sold that, I've had it since highschool. Probably going to pull the race seats and use it for rain and bumpy lots.


I tried to give you a spitfire though cheeky


Want a miata?



Patrick MegaDork
1/5/19 10:49 a.m.

Kinda do want a miata, but also kinda have 9 cars, and only one of those is scheduled to go away.

Apexcarver UltimaDork
1/5/19 11:01 a.m.





Should give an idea of fit.


Again, there are a number of different chassis in the class and many have more room than this. 

Apexcarver UltimaDork
1/5/19 6:04 p.m.

So one of the things the car needed for me to be able to autocross it locally is a muffler. 



The expansion pipe is from AAEN and this is the silencer they sell for it. This setup is a common one and should pass sound for SCCA as well as other venues. I have heard 92db as what to roughly expect.  It is quieter with it, but I havent really run it beyond the stand with it. 


To install I had to modify the tail of the car and cut away some of the rearmost plate that the body attaches to for clearance.   I had thought it was aluminum, but turns out its stainless steel. may be an area for weight reduction in the future if necessary.  


Before Muffler installation 


Will get an after soon.




Apexcarver UltimaDork
1/5/19 6:12 p.m.

For those interested in the CVT and how it works, here is a picture of the setup.


The bottom is the rear of the car and that is the primary clutch. That is attached to the engine crankshaft.   Towards the front of the car is the secondary clutch, which is on a jackshaft. As the engine RPM increases, the primary squeezes the two cones together on the belt and the effective pully diameter becomes larger. The secondary spreads apart to compensate and the effective diameter goes smaller. This is all mechanically controlled by ramps, weights, and springs. 


At idle, the clutch belt is slack and doesnt apply much of any motive power for the car. (think an automatic at idle in drive). This is also why the rulebook spells out that you cannot start one of these unless there is someone in the car OR the rear tires are off the ground.  Hit the gas and the engine runs at a steady ~8000rpm which does not vary with vehicle speed. Its all done with the CVT.

adam525i Reader
1/5/19 7:13 p.m.

Would the Rotax 494 have started life in a Ski-doo or bought specifically for the purpose? For autocross does it have to stay a 500 or could an 800 twin find it way into the back of the car? Solid rear axle? Some pictures without the bodywork on would be cool to see.

Looks like a lot of fun and a clean car, congrats!


Apexcarver UltimaDork
1/5/19 7:34 p.m.

Will try to get some nookid pics in the next few days.  


Yes, it was a skidoo motor.  If I want to stay in FM/F500 I have only a few motor options. I could upgrade to a rotax 593 and get 5-7hp, but it would carry a weight penalty. There are also 600cc bike motor options, but no CVT which would be a disadvantage for autocross with such a peaky engine.  For me, keeping the 494 makes the most sense as a change wouldnt give much cost-benefit. 

An 800 would land the car in AM, which could be fun, but harder to be competitive. If it fits without frame mods is another question.

Yes, the rear axle is solid. No differential, it is one solid bar with a keyway and threads on each end for the wheels.  The car came with a spare axle. 


Woody MegaDork
1/5/19 7:59 p.m.

In reply to Apexcarver :

FYI, I have contacted the guy with the fixer-upper.

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