Aye SRXweb,
I'm running an SRX600 with K&N filter, standard carbs and settings with a BSM exhaust sytem with a Futura 'short' stainless, road legal silencer on the end. No problems to report. 15 tooth gearbox sprocket and a 37 tooth rear sprocket (standard). Plenty of mid range, don't 'lug' the motor, let it spin.
My regards, Bill.