BannedCR500Riders.com

Ok, don't blame me, it's all Jack Daniels fault . . . . . Just fitting the Roosty decomp head on my 90 CR500, and notice the different casting numbers, ML3R and ML3N . . . . I KNOW I've read this somewhere before, but for the life of me I can't remember what the difference was . . . . Experts step up to the plate now !
OK, rip the piss out of me for my ignorance now . . . . . . . Oh, and thanks for your help in advance !

HF,HF-1,ML3,ML3-N heads share the same narrow squish, ML3-R heads came out in 1992 with a wider squish, likely compensating for running pump gas.

R head chamber on the right, alll previous versions left

the narrower squish head was better, it also let the boost port charge reach the sparkplug instead of deflecting out the exhaust port. the narrow squish head had lower wider dome, both were the same cc if measured without the shelf thickness.

Thanks Adam. Guru of all things CR5, as usual ! Any sign of billet covers or Fedex price yet mate ?