Bonneville America Forums Forums Technical Forums Exhaust Ideal exhaust size and length

Well... this is curious. I'll bet those megacycle cams made a BIG difference. I found the specs- they are in the front of the shop manual under general information. T100 and Thruxton are the same. AM abd SM are differentfrom T100 and Thrux, as well as each other. The specs for the SM are:


Intake:
open - 0º BTC
Close - 24º ABC

Duration - 204º


Exhaust
Open - 39º BBC
Close - 7º ATC

Duration - 212º

Which would make the steps 12"/15"/20". Not much change in the exhaust, but a lot of difference in the cams...