1985-1986 Honda ATC250R Shop Manual, Page 235Get this manual
TROUBLESHOOTING
POOR PERFORMANCE AT HIGH SPEEDS
CHECK 1Check ignition timing PROPER SYMPTOM INCORRECT PROBABLE CAUSE
(1) Faulty CDI unit (2) Faulty pulse generator
2Disconnect fuel tube at carburetor FUEL FLOWS OUT FREELY
3Remove air cleaner AIR CLEANER NOT FOULED
FUEL FLOW RESTRICTEDi (1) (2) (3) (4) FOULED
Lack of Clogged Clogged Clogged
fuel fuel fuel fuel
in tank line tank breather tube valve
Not cleaned frequently enough