ATC250R

The ATC 250R is a high-performance ATV produced by Honda from 1981 to 1986. Early models (1981-1984) used an air-cooled, 248cc single-cylinder 2-stroke engine. Fuel was fed through a 27 mm ('81-'82) or 30 mm ('83-'84) round-slide carburetor. Power was accessed through a close-ratio 5-speed transmission with a manual clutch. Later models ('85-'86) used a liquid-cooled, 246cc single-cylinder 2-stroke engine with a 34 mm round ('85) or flat ('86) slide carburetor. The biggest engine downfall was the lack of a power valve. The 85-86 models were upgraded with a close-ratio six speed transmission with a manual clutch.

All model years were fully suspended, using air-assisted front forks and a single, remote reservoir gas-charged rear shock. '81-'82 models offered 6.7 inches of front suspension travel and 4.3 inches in the rear, '83-'84 offered 8.7 inches in front and 8.1 inches rear, while '85-'86 gave 9.8 inches of travel. All model years also used a gear-driven counter-balancer to reduce engine vibration. Dual disc brakes were used on all model years, with the exception of the '81, which used a front disc and a rear drum.

The 1981 ATC 250R marked a milestone in off-road history, as it was the first 2-stroke ATV designed specifically for racing. While ATV racing was in its infancy, racers had to rely on Honda's ATC110 and ATC185 models on the racetrack. Both of these 4-stroke models were sluggish and poorly suspended when compared to the 2-stroke ATC250R.

The 1983 ATC 250R incorporated many improvements over the prior 1982 model, mainly with the introduction of Pro-Link suspension, folding foot pegs, a larger fuel tank, longer travel suspension in front and rear, and other improvements.

The 1986 ATC 250R was the last model year offered for sale in the United States, after an agreement between manufacturers and the Consumer Product Safety Commission to cease production on all 3-wheeled ATVs. This was the result of thousands of legal battles regarding safety issues and high accident rates. The agreement stated that production would cease for ten years, although no major manufacturer has resumed production since the ban ended in 1997.

The 1986 Honda TRX250R Fourtrax was the 4 wheeled brother of the ATC250R, with an engine that was virtually the same (with slightly less horsepower). This machine also has a very large following and is still being used today for various forms of ATV racing.

Trike Fest is the world's largest annual gathering of three-wheelers at Haspin Acres Park in Laurel Indiana.

Comparable models of high performance 3 wheeled ATVs would include the Kawasaki KXT 250 Tecate, the Yamaha YTZ 250 TRI-Z, the Tiger 250 and Cagiva 250.

Engine Specifications

General
Engine type - Air-cooled (1981-1984), 2-stroke, single-cylinder
Bore & Stroke - 70 x 64.4 mm
Displacement - 248cc
Compression ratio - 6.6 to 1
Lubrication - Fuel:oil mixture
Air filtration - Foam element type

Engine type - Water-cooled 1985-1986, 2-stroke,single-cylinder
Bore & Stroke - 66 x 72  mm
Displacement - 246cc
Compression ratio - 8.0 to 1

Lubrication - fuel:oil mixture
Air filtration - foam element

Cylinder Bore - 66.020 - 66.040
Piston/cylinder clearance - 0.060 - 0.080
Piston Diameter - 65.94 - 65.96 mm
Pison pin bore - 18.007 - 18.013 mm
Piston pin outer diameter - 17.994 - 18.000 mm
Piston-to-piston pin clearance - .007 - .019 mm
Piston rings per piston compression - 2
Ring end gap - .20 - .40 mm
Ring side clearance - .045 - .075 mm
Connecting rod (sm end inner diameter) - 21.997 - 22.009 mm