I was thinking of doing your exhaust mod in the near future. I was wondering what size holes that you drilled and will drilling the holes cause me to have to rejet the carbs as I would if I got a new pipe ?

Thanks, John

 

I drilled 7 3/8 holes (1 down center, six down sides). This caused me to need to rejet. It is exactly as loud as a stock 660, but the tone is deeper and sounds better IMO.

Some people have dilled 1" holes, and they have the most noise.

Other people seem to like to drill 7x 1/2" holes, for better perormance yet not so loud.

The bit I used was exactly 12 inches long, and it just barely made it through the furthest baffle.

 

Did you only have to go up one jet size or did it require more ?

John

 

I went up one size, but was on the verge of needing more. It needed the needle one notch richer too.

 

Thanks for the help nyroc.