Do you guys think that removing the drain screw on the bottom of the factory silencer reduces back presure?
With my recent jet change to 142 145, my plugs look a little dark, but I hate to go back to the 138 142's. I am thinking that by removing that screw it will relieve enough back presure to bring the plugs back into tan color. I have contemplated the NYROC muffler mod, but I really dont know any good welders and I am a hack with my stick welder.

BTW you should have seen how much dark sandy junk came out of the silencer after I broke the hard wall above the screw.

Thanks

Don

 

Bump

 

Sammy

Only good way to test jetting is by doing a full bore 1/4 mile+ throttle chop, keeping the throttle open, hitting kill switch & keeping throttle open till quad coast to a stop and check your plugs. Idling after highspeed pass will give false plug readings.
http://cochise.uia.net/pkelley2/sparkplugreading.html