Many thanks to members Bob M (Antioch) and Rhys Nolan (Rhysn) for writing this FAQ.
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Welcome to the wonderful world of CycleKarts. This Frequently Asked Questions (FAQ) page is provided to assist you in finding your way around CycleKartClub.com and the world of cyclekarts in general. There is much that could be posted here, but we have limited this to something to help you understand what you are seeing and being able to find popular areas of interest on this website.
What are CycleKarts?
While there are a number of differing descriptions, we will post the "Classic" Stevenson specification. Please remember while you can build it any way you want, you may want to keep in mind who you will be racing with... what do they use? It has been suggested elsewhere that Peter Stevenson kept their specs this way to foster a very even competitive racing class & much in the spirit of the period. Racing is the most fun and rewarding when there are many entrants with similar specs.
So... we return to the modern CycleKart: The most fun with the least machine, while still looking like a pre-war sporting machine!
This video by Steve Cameron is a great demonstration of the concept:
Cyclekarts are compact, lightweight, sports machines, home and hand made by their drivers for the pursuit of classic motoring sporting excitement. They're not built to be serious race machines or show cars. They're built purely for the personal satisfaction and fun and of driving a machine you've built yourself. As driving machine, the CycleKart formula loosely limits certain aspects of the machines to maintain good sporting performance without jeopardising the light-hearted nature of these machines and the people who build them.
CycleKarts and their builders don't like to take things too seriously, but do encourage good, sporting competitions for fun. The Cyclekart specifications allow for all the cars built being similar in performance, without strictly governing the rules.
Cyclekarts are generally not for sale, as they should be an expression of the owner's individual styling interests as well as sharing the pride in building one's own unique kart. Cyclekarts are built for the pleasure of the imagination, the design and the building of the kart. Cyclekats are based on the styling of 1920s and 1930s race cars to pre WWII. Making it look good is fundamental, performance is secondary in the Cyclekarting community.
Stevenson CycleKart Specification
A one-seat car using Honda 17" x 1-3/4" or 2" rims, 2.50" x 17" tires (2.75" have been used on the Alfa), a 38" track, wheelbase as close to 66" as the aesthetics of the car will allow (err on the shorter side for more abstract cuteness and general attractiveness), weight no more than 250 lbs, and powered by a 200cc, single cylinder, 6.5 hp Honda OHV engine (the GX200). A CycleKart should not cost more than $1,750 to build in 2001 dollars. This is to avoid "spending races" where people start hiring out parts and making things too nice; we're not making show cars, and an element of scrounging adds to the fun.
Measurements and Notes:
* Styling - 1920s and 1930s race cars, maximum pre WWII. Make it look good. Performance is secondary
* Overall Maximum Length - 98" (2490mm)
* Overall Maximum Width - 40" (1020mm)
* Wheel Base - 66" (1675mm)
* Track - 38" (965mm)
* Chassis Frame Rails – (2) 1" x 3" (25mm x 75mm) steel (1/16" thickness is sufficient)
* Body Work – 1/4" (6mm) plywood and 3/4" (18mm) plywood monocoque box, or metal work
* Body Width - 14" (355mm) wide at front axle, 20" (510mm) wide at seat back
* Front Axle – 1-5/8" (41.5mm) O.D. tubing, dropped to accommodate the leaf springs
* Rear Axle - 1" x 36" (25mm x 915mm) long axle
* Front springs - 24" x 1-1/4" (610mm x 38mm), 2 leaf, 1/2 elliptic
* Wheels and tyres – Honda 17" x 1-3/4" (177mm x 44.5mm)
* Minimum Weight – N/A
* Maximum Weight - 250 lbs (113.6 kg)
* Engine - 200cc, single cylinder 6.5 hp Honda OHV engine (GX200)
* Engine Location – Rear
* Drive - Comet TAV-30 (or similar) unit to one wheel only
* Drive Chain - #40 chain, 72 tooth main sprocket
* Braking – Single rear wheel by mechanical disc. No front brakes allowed
* Variation – Adjust all or any specifications above as required or desired
There is no lower weight limit, as we feel that this is a perfect place to "cheat". Lighter cars will perform better, will also have better braking (using the same brakes) and the structure will be loaded less heavily: All good things. There's a natural lower weight imposed by the strength of materials used, but it would be fun to see what could be done. Lighter machines are more prone to breaking, so please make safety your priority, and keep in mind that you'll spend more time fixing things than others might. It's all part of the fun of CycleKart design.
Some very important engineering points:
* Power is transmitted via a Comet TAV-30 unit to one wheel only.
* Braking is also on this same rear wheel by mechanical Comet disc.
* There are NO front brakes, due to the light vehicle weight, added complexity, and the loss of steering control under braking.
* No rear suspension (weight gain not worth it).
* All of the cars have the same front and rear axle dimensions.
* The front axle is made up from 1-5/8" O.D. tubing, and is dropped to accommodate the leaf springs, Azusa spindles and brackets are welded on.
* Front axle angles are taken from an old Amilcar blueprint; they're not our own, but they work well.
* The steering columns and steering wheel hubs are also Azusa, lengthened to suit each car.
* The rear axle, drive sprocket, and hubs are also Azusa: 1" x 36" long axle, 72 tooth main sprocket, #40 chain.
* Front springs are buggy seat springs, half-elliptic.
* The fixed end has been mounted at both the front and rear ends, depending on the car. It hasn't seemed to matter which end gets the shackles.
* The wheels are Honda Super Cub, Passport, or Trail 90.
* Azusa rear wheel hubs are used on their 1" axles, and the lug bolts are ground to fit inside the Honda motorcycle hubs.
* New through-bolts are located near the hub-reinforcing webs in the motorcycle wheels.
* Only one hub is keyed (the right for all our cars, and the tracks are designed with this bias in mind).
* Be sure to grease the freewheeling hub.
An important weakness in the drivetrain showed up after a few seasons: The Honda GX200 has a lot of torque for its size, and we're driving into a large diameter wheel. What happens is the keys in the sprocket hub and wheel hub begin to rock in the axle keyway and mess up the axle. We have now installed extra-long keys (3" or longer, with keyed locking collars on either side of the sprocket hub) in an attempt to spread the load a bit and increase the resistance to rocking. We're still testing this, but it seems like a workable solution.
The main structure of our cars is the monococque plywood box which forms the core structure. This is strong and light. The side framerails are rectangular steel tubing and are primarily for locating the axles fore-and-aft. The "exhaust pipes" on all of the cars are a necessary part of the structure; they add torsional stiffness to the box structure around the cockpit.
Many of these issues and more are addressed in the CycleKart FAQ at: http://www.cyclekarts.com/CycleKartFAQ.html
Additional build notes:
Is there any reason to use a bigger engine? Probably this is one of the first questions a potential person asks in some way. Not really, you will lose the character that makes a CK so great. The 6.5 hp engine, either Honda or one of the many "clones" is all that is needed, and with "Stage 1" modifications (see info at NR Racing) is more than adequate. NR are at the forefront of what works. Don't be tempted to go any further than Stage 1.
What clutches or transmissions are used? Most things have been tried. With the bigger wheels the centrifugal clutches have been found to not last well. The range of torque convertors from Max Torque, GTC and Comet are the ones to use. The Asian copies, while cheaper have shown many problems in active use. You can use either the 35 series or 40 series chain, both hold up well.
What gear ratio should I use? The originators of the whole concept (Thanks so much) were the Stevensons and they found approx. 6:1 to be the best compromise when used with a torque convertor. For example, 10 tooth on the trans, 60 on the axle.
Wheels are a problem, where do I get them? Ebay is always worth a shot, there are a few new suppliers also on Ebay, or do a bit of research on motorcycle wreckers. The parent bike is generically known as a C90, variants are CT110, CT90 etc. It is one of the most produced motor vehicles EVER, so you may be surprised.
Why not? This one comes down to experience. They have been found to be troublesome at best, and probably totally unneeded. If you are "parade" driving, one wheel drive is fine. On any loose surface both wheels fixed is just great, it does not give the problems many perceive. Many budget rally car drivers have used welded diffs in the past to the same effect.
FRONT END GEOMETRY:
Again theory will throw all sorts of problems, which don't exist in practice. They do need castor, about 10 to 12 degrees is a good start (kingpin further back at the top than bottom), Camber doesn't seem to make any difference (perhaps the very thin wheels) and should be based on your inspiration car more than anything, toe in or out, make this adjustable and play to see what happens. Start with a little toe in. Kingpin angle and centre patch steering, scrub radius etc don't seem to make any difference at all! (Thin wheels again?) There are more ideas about this than letters in the alphabet, don't stress about it.
There are cyclekarts which have been built with a hacksaw, cordless drill and a few handtools. Others have a full workshop. If you don't have all the tools you will cultivate a few people to do things for you. It's a great way to spread the word too. Cut things, clamp them together, use bolts or whatever and then take quite a lot to a welder if you need one. Offer cash or beers.
Where do I get axles, hubs and things like that? In the USA, Azusa Engineering is the preferred source, the rest of the world makes stuff too.
Do I need to use spindles as big as I see? 5/8" seems to be as small as you would want to go, smaller does bend!
The history of classic and vintage pre-war cyclekarts is found in many places on the web and in history books.
The CycleKart Inspiration Photos topic has lots of great photos to get started.
The history of the modern cycle kart starts with Peter Stevenson and his family, who built many of these wonderful little cars.
The link to their website can be found here - it is well worth reading:
The CycleKart Club - cyclekartclub.com
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Common Questions Regarding CycleKarts
Please give me a set of your plans?
Sorry, but no. This isn't intended to be rude but:
* There is no master plans list. Some builders design that way, many others do not.
* The main concept is a builder designs their own cycle kart. This follows the history of the period and was part of the design philosophy of the Stevensons who probably did more to start the 'modern era' of cyclekarting.
* It isn't that hard... honest! Have a look at the pictures & videos that surround you, and ask questions. There are pictures & diagrams on this site & others that while not plans, are full of detailed information that give you just about everything you could want.
Why don't you...?
Add a bigger engine, etc etc etc... Keep in mind the generic weight limits & other restrictions you will be trying to fit everything into.
Also remember that racing is the most fun and rewarding when there are many entrants with similar specs.
Well I am going to do it anyway!
You are welcome to. But do keep in mind that some people on this website have built quite a few of these vehicles, and their advice is as a result of hard & sometimes painful experience. Sometimes advice or hints may be as a result of trying to keep you safer!
Where do I find people or groups near me?
Try the CKC Members Map (you need to register a free account & sign in to view it, for privacy reasons)
This hobby is still in its infancy, so there are not a lot of organized groups yet. Perhaps the largest and best known is the Gittreville club, located in the Seattle, WA area in the USA (see links section for more info). Some of their members participate on this forum.
How Do I...?
Try a using the Forum Search.
In most cases you are not the first one to have though of the question, and you will find your answer in previous conversations.
If you can't find your answer by searching, click Start a New Topic in the appropriate forum section, eg the CycleKart Tech Forum.
Cool and Useful CycleKart Links
The Stevenson Website: Peter Stevenson & his family were among the pioneers in coming up with the modern version of cyclekarts.
Their web site is well worth a read. Many ideas and pictures for inspiration can be found here.
The Gittreville Group has been around for a number of years and have posted information and pictures on their events and cars. They freely share information and concepts in their posts and again it is a very good place to go look at when you are just starting out and also want to look at racing these karts. They also are known to publish their building guidelines document.
Gittreville Blog - CycleKart Build Series
Part 1: Rear Wheels and Hubs
Part 2: Rear axle and drive
Part 3: Front axle
Part 4: Frames (and tubs)
Part 5: Brakes
Part 6: Steering
Part 7: Engines
Part 8: Restoration
Part 9: Redemption
Part 10: Yellow Peril
Steve Cameron got involved in cyclekarting and was amongst the first to post videos on YouTube for how he was building his cyclekart & how to get things done. It has inspired many people on this forum & elsewhere. His videos are posted in the CycleKart Video Thread (as are many others) and can also be found on YouTube, with videos for each step of his building process.
Dennis Thomas is an active member of this forum and has built several cyclekarts. He has posted many videos and pictures as well. He has helped many through building cyclekarts... you will find him active in the forums. His video channel can be found on YouTube where he has many many videos. A great source of info.
Thanks for reading and welcome to the CycleKart Club!
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