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Quick question for those that have had it done - well actually two questions
Do you need race gas or will you standard 91 or 93 octane work?
And does the head just get milled/planed down to get a more ideal squish band, or does the actual internal profile of the combustion chamber get modified as well? As RB isn't doing a lot of them anymore, if I had the profile I'd be tempted to try do my own head at work here......

Thanks!

Scratch that............ I just found a post by RB on "everything two stroke"........ he modifies the profile as well to do it correctly. Time to read some Bell and Jennings books......

"Summary

The above measurements are needed so I can reduce the squish clearance. This is where the power, torque, gas mileage and reliability is to be found. I don't just go with more compression. I also re-do the combustion chamber to maintain the proper trapped combustion volume. You will not give up any reliability or shorten engine life with this mod.

The cost for the modification is $75 (U.S.) not including shipping and handling to Portland, Oregon, U.S.A. For more information, please visit our website at www.rb-designs.com .

About the Author :
Ron Black of RB-Designs has been building race engines of all kinds and his own custom race parts since 1970. He gained experience working side by side with many “old school engineers”. He has built 3 dyno's and has been running them since the early 70's. He has one of these dynos in his shop.

Over the years, he designed a number of motorcycle service departments and managed many of these. He designed his brother’s shop and worked with him for about 12 years prior to starting his own shop 10 years ago.

He has worked with both the Yamaha Road Racing Team and with Kawasaki’s motocross R&D department. He has spent the majority of his life designing reliable high performance parts."

There is definitely a lot to it when modifying the chamber of a head to get proper squish. It's one of those essential mods IMO.

I just got mine back, it looks like he faced off a bit but also changed the taper on a lathe. i think he ground a small channel between some coolant ports as well. To get the shape you can use clay or playdough and stuff it in there, then trim a piece of construction paper with scissor to fit the shape pretty tight. outline the paper with sharpy then scan it with a flat ruler into computer then scale and trace using scanned picture as a canvas. that'll probably be close enough but I could be wrong. At that point it would be worth making a head like Phathead does with the insert so u dont risk scrapping an oem head on setup