Motorcycle Repair: Thundercat bogs at lowish rpm, micron exhaust, yzf600r

Question
Hi,
I have a 1997 YZF600R Thundercat which apart from a legal looking Micron exhaust is standard.  I have noticed that once the engine has warmed up it is very susecptible to totally bogging down when accelerating from lowish RPM (around 2750 - 3500).  Sometimes it stalls pulling away from the lights unless I push up the revs.  Im wondering if there is a carb problem or whether its due to the exhaust being non std and requiring air correction.  It feels pretty sweet on half choke and its ok if i keep the throttle at a gentle setting. Its annoying sure but more its dangerous!  My email is [email protected].. Many thanks.. Martin.

Answer
Hi Martin,

Changes to the air intake, carburetors, engine, and exhaust requires correcting the air-fuel mixtures.

Providing the carbs are clean and clear of varnished fuel, adding a bit of choke improves engine performance indicates the A/F mix needs to be a tad richer.  

Respectfully,
Mark Shively