When the builder sent me my engine he sent me soem plugs that came with it before rebuild. The plugs are NGK R5649-9 and look like they should be used in a ROTARY engine. The electrode sits flush with the bottom...nothing sticks out. Should I use these or go with a a better plug for my application. It is a NA engine with custom JE pistons. 10 to 1 CR.

Regards.

I don't know that plug in it particlur ( I cannot be bothered walking out side to look at my car) but my plugs are level at the base because there racing style plugs,
go to a auto store and ask them to look it up the part number.

I would imagine it's equivilent to the NGK BP9ES.
Might have trouble in traffic with a plug that hot fouling, but you could try. I am running the BP8ES but haven't tried anything else.

NGK plugs get cooler as the number increases, therefore 8 in hotter than 9.

check line 16 for your plug in NGK racing cat.

http://www.ngksparkplugs.com/images/pdfs/racing_catalog.pdf

Sorry,
I don't know what plug you should start with...You need to check the clearence at TCD for extended tip plugs (BP).....I would start with B7ES and then go to B8ES if you need a cooler plug.
Phil