Originally Posted by needtransportation
I cut the muffler off like an idiot, instead of more power it feels like less. I drilled holes in the air filter cover but havent ridden it since to assess the change.
Reducing back pressure is usually a good thing on these engines but remember you need to up the main jet most likely since it can flow more air through the engine with added flow from openint up the exhaust.
Clean the spark plug real good with a wire brush and a solvent like spray carb cleaner or brake cleaner, dry it off, put it back in engine and then go for a couple mile road trip, after you get back let it sit for 10-15 minutes and then pull the plug out and look to see what color it is, if its very light tan or white looking its for sure you need a larger main jet.