Bike is popping and spluttering i can get to 4 thou revs then it seems to halt and carry on revs will not go to red line and can not go above 20 mph uphill or down replaced jet and spark plug gave it oil change and the engine gets so hot it overheats tried what can i do pls help steve

Could be some dirt or moisture in the carberattor try loosening the drain screw on the bottom of the bowl. If this doesn't work the carb needs a good clean.

Check plugs, may be fouled> When storing bikes in my old mans garage, the plugs always foul

Specifications

The 1991 Honda CBR 1000F uses an in-line four cylinder, four-stroke engine that produces 36.5 cubic-inches of displacement. The engine uses a dual overhead camshaft system and has four valves per cylinder. The maximum power of the CBR 1000F is 93 horsepower at 11,000 rpm and the max torque is 45 ft-lb at 8,500 rpm. The motorcycle's compression ratio is11.3:1 while the bore by stroke ratio is 2.5 by 1.9 inches. The engine is liquid cooled. The transmission is a six speed and is chain driven. The top speed of the CBR 600F is 141 mph.
Dimensions and Features

The overall weight of the 1990 Honda CBR 600F is 460 pounds. The total fuel capacity is 4.36 gallons. The seat height is 32 inches, and the wheelbase is 55 inches. The front tire dimensions are 110/80-17 and the rear tire dimensions are 130/80-17. The front brakes are dual 276mm piston caliper disc brakes while the rear brake is a single 220mm pistol caliper disc brake. The suspension system uses a mono-shock swing arm design. The power to weight ratio is .44 hp/kg. This bike can go 0 to 60 mph in 3.8 seconds.
Appearance and Design

The 1990 Honda CBR 600F features a compact design. Close side mirrors flank a compact instrument panel and tight handlebars. This motorcycle sports a partial fairing that is designed for better aerodynamics. To reduce wind resistance, the legs and feet are fully positioned behind the motorcycle body. Like most sport bikes, when riding at fast speeds, the rider is intended to lie across the fuel tank to reduce drag. No chrome is visible on the bike, as the motorcycle body fully covers the chassis. The display panel features three gauges: a speedometer with built in odometer, a tachometer and a fuel gauge. The 1990 Honda CBR 600F is produced in various combination colors, including white, blue and red or black, purple and orange.

Sounds like either the bike is starving for gas at higher RPM's, or you're hitting the rev limiter.

Clearances about 4 and 5 thou.
But it sounds a bit more than that if its hard to start and is very loud, the cam and or rockers may be worn, very common after 20 years

sounds like the carb has blocked slow running jets in it

Either take the carbs off and clean them or add some fuel additive to clean the system. Sounds like you have a clogged jet.

my pit bike will not keep it revs for a long time so can some one help me it is my first pit bike