Almost a decade ago, during the development of the Tillotson 196, 212, and 225 engines, we experimented with inexpensive stock-style rev limited coils. A couple of years ago, we sold off the small inventory of those coils, not expecting the demand they would create not only for our non-karting customers but also for many who wanted to build a program at their local tracks.
Since then, we have considered the greater need for kart racing as a whole, which could utilize these coils to reduce the cost of karting and better regulate the classes, especially when it comes to the speeds in the junior classes.
Recently, WKA introduced more restrictor plates to reduce junior class speeds. Restrictor plates help reduce the engine's power output, which works well for low-torque engines like a flathead. However, OHVs make much more low-end torque even when restricted, to the point that a restricted OHV makes more power than an unrestricted flathead.
Restricted class engines have been undermined over the years by rule changes that have allowed more power and higher rpms. The point is that restrictor plates are not the answer to controlling kart speeds. Other engines, both 2-cycle and 4-cycle engines, have used rev-limited coils to help control kart speeds.
Here are the range of coils we've brought in and our class recommendations
- Rookie/Red Plate: 4200rpms
- Junior 1 & 2 Green/Black & Purple/Yellow Plate: 5200rpms
- Junior 3 Blue Plate/Amateur Adult Stock: 6200rpms
- Pro Adult Stock/Builder Prepared/Super Stock: 7200rpms
Rookie Classes and Junior Classes can further control speeds with a gear ratio and tire circumference rule.
(In our option, the plate can be simplified in conjunction with the rev limited coils to back to the original red, green, purple, and blue, or preferably to black, yellow, & blue plates so each class increases in .75" increments along with 1000rpms)
The only drawback is with the billet flywheels or flywheels with high-strength magnets(Neodymium); the high-strength magnets may cause the coils to overheat when hitting the rev limited hard over extended periods of time and fail, so we recommend using our cast aluminum flywheels https://www.eccarburetors.com/tillotson-212r-bsp-cast-aluminum-flywheel
These flywheels fit:
- 196cc Clones
- All Tillotson Engines
- All Ducar Engines
- All Wildcat Engines
- Ghost 212 and Predator 224 Non-Hemi
- Most other clone-based engine except the Predator 212 Hemi and Non-Hemi Engines
The flywheel and coil together are less expensive than a billet flywheel, and the rev-limited coils 6200 and below will keep the rpms low enough for cast rods.
Rev Limited Coils have helped classes like the Briggs LO206 by keeping the tech at a minimum and a relatively level playing field, where most local tracks struggle the most. The rev-limited coil provides a low-hanging ceiling that limits the engine's power potential. It helps to meditate the advantages of lightweight valve trains, stiffer springs, and modifications that would, in turn, see more gains from improved volumetric efficiency (heads, cams, carbs, etc). In other words, you have fewer rpms where volumetric and mechanical efficiency is beneficial, making it easier and less expensive to build competitive engines.
Most importantly, tech can be simplified with less worry that a gray area or out-of-tolerance part determines the outcome of a race.
These flywheels and coils can be adapted to the current 196cc clone classes. However, we are not asking AKRA, NKA, or WKA to approve these parts for competition immediately. There have been too many last-minute rule changes, and there should be open dialog and testing done before any approval is made. We want to ensure enough time for racers to make the change without impacting investments and competition.
Ideally, we are looking at tracks that have created alternative rules to accommodate their needs and capabilities, which may be using engines other than 196cc and programs using a 212cc or 224cc engine.
