Cam Grind Method

Cam Grind Background, By David Wallis

“In 2013, one of the guys who got involved in this, Dan Coats, had an idea for an alternative to our original build, using the theory of how a jake brake works on a diesel engine. At the same time, Ricky Corey of RCR Performance and I were talking and he brought up the same concept. Given that Dan is an engineer and Ricky a professional engine builder and I am better at pointing than comprehending foreign languages, I introduced them and they began to work on this new idea together. Ian Smith, an engineer, jumped in and this build came together and become one of the more popular methods.”

The cam grind method is more simple than the original valve removal method.  The engine does not have to be removed because, essentially, you’re performing a cam swap and valve adjustment.  However, given the closed system we highly recommend a “pop off” valve for the disabled cylinder.  Ian Smith has been making them for the past few years – contact  We recommend you buy a spare set of cams and have them modified so your original cams can be reinstalled at some later date.

The cam grind method — and our 2015 AFM rules — requires disabling the fuel either via software or by using dummy primary and secondary injectors.  The injector(s) tricks the ECU into thinking everything is all right.  See Secondary Injector Hack.



  1. Get a spare set of cams
  2. Remove – grind off – the lobes for the cylinder you are disabling using an angle grinder or a bench grinder if you are very careful.  Or ask your local machinist.  The newly ground surfaces won’t be rubbing on anything so they don’t need to be perfect.The following “Cam Swap” steps are critical and should be done correctly.  Ask your local engine builder for help if you are not comfortable and confident.
  3. Remove your existing cams following the  manufacturers directions.  Obviously, bad things can happen if you do this wrong!
  4. Install your modified cams, again, be sure you follow the directions.  Don’t forget to check valve clearances.
  5. Once the engine is buttoned up, install the “pop off” valve.   We suggest running the relief hose to catch bottle or down to the lower fairing.  Check your racing organization’s rules for any specific requirements.
  6. Modify the disabled cylinder’s spark plug.  One option is to strip back about an inch of insulation, wrap the bare wire around the threaded base of the plug and solder it onto the plug base.  Attach the other end of the wire in a secure fashion to a good ground.
  7. Insert the plug into the disabled cylinders respective coil and secure the plug/cap.  For the R6, the radiator fan mounts work nicely. See Spark Plug Modification.
  8. Install you dummy primary injector and secondary injector, if applicable.  See R6 Secondary Injector Hack.
  9. Tune.  The fuel maps will likely be very different from your 4 cylinder setup.
  10. Go Racing!

Pop-Off Valves

Made By Ian Smith

The purpose of these valves is to use the compressed air in the cylinder to blow out any accumulated oils that would normally be burned in the combustion process, preventing hydro-static lock.  If you’re interested in a valve or two, then contact for more information and availability.

The valves can be set to release from 20-125 psi (maybe bit higher but the gauge will not go higher reliably).

The spark plug tool is from a typical Honda tool set.  This tool, or one similar to the Yamaha tool, is needed as there is a tube (made from Tygon) that goes on the red fitting and passes threads through the hole in the spark plug tool upon installation. It’s a bit of juggle but doable if you take your time.  The crush washer pictured on the far left one isn’t being used anymore;  I now use a square O-ring instead

The valve just threads into the spark plug hole of the cylinder that you are disabling.