Motorcycle Repair: ttr 90

Question
QUESTION: What is the best plug for my bike my engine is a ttr 5HN1 and can I cut the tip of my stock exhaust off and screw and aluminum silencer on? If yes, will I have to change my jetting or any other inquiries?

ANSWER: I think the  CR6HSA plug is Best and yes the re-jetting may need to be done
if the plugs burn white or there is popping through the exhaust.

---------- FOLLOW-UP ----------

QUESTION: What is the bestthing to do to make it faster and if the cam timing sprocket has the little notch in the center of it broken will it effect my timing

Answer
Don't take any Chances with the Cam Gear. Replace it.
Removing Restrictions from the Intake and Exhaust lets more air flow through
the carburetors and Increases Speed and Performance.
But these Modifications require the Carburetors to also be Modified. (Re-Jetted)
You might check to see if DynoJet make a Carb Kit for that Model and Year.
www.dynojet.com