Need help fast

[dave5.0]

Family is at a riding park and the boys viper 90 won't run right. We just recently put on a wrh pipe, 20mm (I think) mikuni carb, ported aluminum intake, and bigger reed cage. Also did some clutch work, rollers, and springs in the back. The thing ran great in the backyard now it feels like it's too rich or the plug is fouling. I put a foam filter on the carb and oiled it. Been running like crap since off and on. It sputters on top end and sounds like the plug is fouled.
I've changed the plug, checked the reeds, checked for airleaks, ran the fuel line straight from the bottom of the tank to the carb, cleaned the air filter again, checked some electrical connections and nothing. It'll run great for a minute then when he goes to climb a hill it sputters and won't pull.
I'm at a loss please help.

[nordic quad]

It could be a number of things,check for leaks around the intake,then check your jetting,check rollers,may be wrong torque spring,check only one thing at the time.This link may have some info for you.
Stein A

http://www.apexatv.com/2009%20Apex%20Site%20by%20488/Tech%20Suport.htm

[TeamNeilson]

First thing i'd do is swap the air filter for one without oil (AS A TEST).. If the engine starts behaving then you may have over oiled it..


I've done that a few times this year, stupidly... it cost my little guy a few races...



Also, clutching could do it.. or as I found out recently a bad ground or bad carb tuning... Pull the main jet and make sure nothing is blocking the orifices too.