Ok first I'm new to the 2 stroke world. Always been a 4 stroke guy until my brother bought a banshee then I rode it. I went out and bought one and being a car guy this is all new to me. The guy I bought it from said it just needed to be jetted for the big bore kit. It runs great until you go full throttle then it seems to fall flat. Plugs are gray and dry.
a little about the Banshee
Its a 1999, suppose to be a 421 ( but I'm not sure if it isn't a 392) Athena Jugs and heads Not sure how to tell the difference between the 421 and 392 without taking it apart.
It has the stock Mikuni carbs with a 280 main jet (this is where it runs best).
The sprocket is a 13 tooth on the engine
Exhaust is FMF Fatty Gold's
It has carbon fiber reeds on stock cages and new carb boots
K&N air filter with stock air box with vents and drilled lid.
Ok so I changed the main jet out from a 270 to a 280 no difference in plug color but it did seem to run a little better. So I went up to a 290 main jet, now if I go wide open it bogs down and damn near dies. Plugs are still gray and dry. At 1/2 to 3/4 throttle the pipes seem to ping or gargle on and off. I really don't want to blow this thing up and could use the help. I do have some Mikuni 44 carbs with 240 jets but wasn't sure if those would work, they came with a parts banshee.
Thanks