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Discussion Starter · #1 ·
Alright well I was told that the 300ex 250x carb is a 28mm.Then in 2000 honda went with a 32mm carb.I was also told that 400ex carbs are 35.5mm and that in 2004 they went to a 38mm.Is this true and what would be the best setup for my 250x?In the near future there will be mods such as bigger valves,cams,biger bore,and maybe a stroker crank.
 

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Alright well I was told that the 300ex 250x carb is a 28mm.Then in 2000 honda went with a 32mm carb.I was also told that 400ex carbs are 35.5mm and that in 2004 they went to a 38mm.Is this true and what would be the best setup for my 250x?In the near future there will be mods such as bigger valves,cams,biger bore,and maybe a stroker crank.
Moose will be the man to talk to about that.
 

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Discussion Starter · #3 ·
Yeah but he's not on so I figured I'd ask you guys to.
 

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Discussion Starter · #5 ·
Alright thanks.I know that much is right.
 

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According to my 2001-2006 300EX manual, the carb bore is 29.0 mm.

According to my 1999-2002 400EX manual, the carb bore is 38.0 mm.

According to my 2005-2009 400EX manual, the carb bore is 38.0 mm.

Hope that helps. That's the only years I have.
 

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Sportrax 400EX

The 2003 Sportrax 400EX dominates the competition with superb performance and handling.

Features & Benefits

New for 2003

New Honda Racing-inspired graphics.

New Red seat on Red model.

Unique Features

The 397cc RFVC(tm) engine draws its breath from the same engine that powers the bulletproof XR400R.

The ultra-lightweight TRX400EX weighs only 375 pounds.

Long-travel suspension exceeds that of even Honda's legendary TRX250R.

Rugged steel frame with removable subframe for easy maintenance.

Beautiful one-piece cast aluminum swingarm offers exceptional rigidity.

Radial tires for exceptional handling.

Triple disc brakes provide superb stopping power.

Aggressive body style complements the all-sport appearance.

Engine/Drivetrain

High-performance 397cc dry-sump air-cooled four-stroke single-cylinder engine.

Radial Four-Valve Combustion Chamber (RFVC) for maximum combustion efficiency and horsepower.

Camshaft timing developed especially to meet ATV requirements for torque and useable horsepower.

Gear-driven counterbalancer minimizes engine vibration for smooth operation.

Dual intake and exhaust ports for maximum engine efficiency in sport operating conditions.

Maintenance-free automatic cam-chain tensioner.

Closed crankcase vent system safeguards against engine oil contamination.

35.5mm carburetor provides light throttle effort, superb air/fuel mixing and excellent driveability. An accelerator pump assures excellent throttle response for maximum power.

Stainless steel dual exhaust headpipes resist corrosion.

USDA-qualified muffler/spark arrester offers quiet operation and maximum power.

Solid-state CD ignition with electronic advance and 9100-rpm engine rev limiter.

Heavy-duty clutch has 2mm-thick plates designed to stand up to sport ATV demands.

High-efficiency oil cooler supplements the large-capacity oil tank for maximum engine cooling.

Five-speed transmission with gears designed and ratios selected specifically for sport ATV use.

Chassis/Suspension

Round-tube steel frame with removable subframe is lightweight, durable and very strong.

One-piece cast aluminum swingarm for maximum strength, rigidity and durability.

Independent double-wishbone front suspension offers 8.2 inches of travel from twin Showa(r) shock absorbers with five-position adjustable spring preload for superb ride quality over harsh terrain.

Pro-Link(r) rear suspension with a fully adjustable large-diameter aluminum-body piggyback Showa shock absorber provides 9.1 inches of travel.

Triple disc brakes for excellent stopping power and a weight-saving aluminum rear caliper stay.

All Pro-Link components are made of aluminum to further reduce vehicle weight.

Lightweight aluminum wheels reduce unsprung weight for even better handling.

Radial tires with knobby pattern provide superb traction and cornering ability.

Durable and lightweight heavy-duty O-ring-sealed drive chain.

Easy-to-use eccentric chain adjuster.

Additional Features

Engine design produces low emissions and meets California Air Resources Board (CARB) off-road emissions standards.

Convenient push-button electric starting.

Long, narrow seat provides excellent comfort and superb sport riding ergonomics.

Aggressive styling of front cowl, fuel tank and fenders complements pure-sport ATV design.

Plastic fuel tank is durable and won't rust.

Dual 30-watt headlights integrated into front cowl provide distinctive sport style and excellent function.

Snorkel-type airbox to avoid water and dirt contamination.

Washable, two-stage large-capacity foam air filter.

Oil tank features a dipstick for easy maintenance.

Comfortable dogleg levers; clutch lever has cable adjuster and dust cover.

Tough steel front skidplate.

Heavy-duty steel skidplate protects rear brake disc and sprocket.

Engine cases protected by a tough urethane skidplate.

Rear mudguard with rigid footrests.

Maintenance-free battery.

Keyed ignition switch offers added security.

Multi-function handlebar switch assembly is simple to operate.

Easy-to-use parking brake.

Tool kit includes low-pressure air gauge and owner's manual.

Assembled in Timmonsville, South Carolina.

Transferable six-month limited warranty.

Ownership includes one-year complimentary Membership in the Honda Rider's Club of America(tm). Benefits include discounts, travel benefits, roadside assistance and much more. For HRCA(r) details, call 1-800-847-HRCA.

Available Accessories

Flag kit.

Specifications

Model: TRX400EX

Engine Type: 397cc RFVC air-cooled dry-sump single-cylinder four-stroke

Bore and Stroke: 85mm x 70mm

Carburetion: 35.5mm piston-valve with accelerator pump

Ignition: Solid-state CD with electronic advance

Starter: Electric

Clutch: Manual

Transmission: Five-speed

Driveline: O-ring-sealed chain

Suspension Front: Independent double-wishbone with Showa shocks, five-position spring preload adjustability; 8.2 inches travel

Suspension Rear: Pro-Link fully adjustable single Showa shock; 9.1 inches travel

Brakes Front: Dual hydraulic 174mm discs

Brakes Rear: Single 220mm disc

Tires Front: 22 x 7-10 knobby radial

Tires Rear: 20 x 10-9 knobby radial

Length: 72.2 inches

Width: 45.3 inches

Height: 43.7 inches

Seat Height: 31.9 inches

Ground Clearance: 4.3 inches

Wheelbase: 48.4 inches

Turning Radius: 10.5 feet

Dry Weight: 375 pounds

Fuel Capacity: 2.6 gallons, including 0.4-gallon reserve

Colors: Red, Yellow
 

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23,581 Posts

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Premium Member
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7,533 Posts
Info on the 2002
Sportrax 400EX

The highly acclaimed Sportrax(tm) 400EX dominates the competition with outstanding performance and handling.

Features & Benefits

New for 2002

• Honda Racing-inspired graphics.

Unique Features

• The 397cc RFVC(tm) engine draws its breath from the same engine that powers the bulletproof XR400R.
• The ultra-lightweight TRX400EX weighs only 375 pounds.
• Long-travel suspension exceeds that of even Honda's legendary TRX250R.
• Rugged steel frame with removable subframe for easy maintenance.
• Beautiful one-piece cast aluminum swingarm offers exceptional rigidity.
• Radial tires for exceptional handling.
• Triple disc brakes provide superb stopping power.
• Aggressive body style complements the all-sport appearance.

Engine/Drivetrain

• High-performance 397cc dry-sump air-cooled four-stroke single-cylinder engine.
• Radial Four-Valve Combustion Chamber (RFVC) for maximum combustion efficiency and horsepower.
• Camshaft timing developed especially to meet ATV requirements for torque and useable horsepower.
• Gear-driven counterbalancer minimizes engine vibration for smooth operation.
• Dual intake and exhaust ports for maximum engine efficiency in sport operating conditions.
• Maintenance-free automatic cam chain tensioner.
• Closed crankcase vent system safeguards against engine oil contamination.
• 35.5mm carburetor provides light throttle effort, superb air/fuel mixing and excellent driveability. An accelerator pump assures excellent throttle response for maximum power.
• Stainless steel dual exhaust headpipes resist corrosion.
• USDA-qualified muffler/spark arrester offers quiet operation and maximum power.
• Solid-state CD ignition with electronic advance and 9100-rpm engine rev limiter.
• Heavy-duty clutch has 2mm-thick plates designed to stand up to sport ATV demands.
• High-efficiency oil cooler supplements the large-capacity oil tank for maximum engine cooling.
• Five-speed transmission with gears designed and ratios selected specifically for sport ATV use.

Chassis/Suspension

• Round-tube steel frame with removable subframe is lightweight, durable and very strong.
• One-piece cast aluminum swingarm for maximum strength, rigidity and durability.
• Independent double-wishbone front suspension offers 8.2 inches of travel from twin Showa(r) shock absorbers with five-position adjustable spring preload for superb ride quality over harsh terrain.
• Pro-Link(r) rear suspension with a fully adjustable large-diameter aluminum-body piggyback Showa shock absorber provides 9.1 inches of travel.
• Triple disc brakes for excellent stopping power and a weight-saving aluminum rear caliper stay.
• All Pro-Link components are made of aluminum to further reduce vehicle weight.
• Lightweight aluminum wheels reduce unsprung weight for even better handling.
• Radial tires with knobby pattern provide superb traction and cornering ability.
• Durable and lightweight heavy-duty O-ring-sealed drive chain.
• Easy-to-use eccentric chain adjuster.

Additional Features

• Engine design produces low emissions and meets California Air Resources Board (CARB) off-road emissions standards.
• Convenient push-button electric starting.
• Long, narrow seat provides excellent comfort and superb sport riding ergonomics.
• Aggressive styling of front cowl, fuel tank and fenders complements pure-sport ATV design.
• Plastic fuel tank is durable and won't rust.
• Dual 30-watt headlights integrated into front cowl provide distinctive sport style and excellent function.
• Snorkel-type airbox to avoid water and dirt contamination.
• Washable, two-stage large-capacity foam air filter.
• Oil tank features a dipstick for easy maintenance.
• Comfortable dogleg levers; clutch lever has cable adjuster and dust cover.
• Tough steel front skidplate.
• Heavy-duty steel skidplate protects rear brake disc and sprocket.
• Engine cases protected by a tough urethane skidplate.
• Rear mudguard with rigid footrests.
• Maintenance-free battery.
• Keyed ignition switch offers added security.
• Multi-function handlebar switch assembly is simple to operate.
• Easy-to-use parking brake.
• Tool kit includes low-pressure air gauge and owner's manual.
• Assembled in Timmonsville, South Carolina.
• Transferable six-month limited warranty.

Additional Features

• Flag kit.
• Work stand.

Specifications

Model: TRX400EX
Engine Type: 397cc RFVC air-cooled dry-sump single-cylinder four-stroke
Bore and Stroke: 85mm x 70mm
Carburetion: 35.5mm piston-valve with accelerator pump
Ignition: Solid-state CD with electronic advance
Starter: Electric
Clutch: Manual
Transmission: Five-speed
Driveline: O-ring-sealed chain
Suspension

Front: Independent double-wishbone with Showa shocks, five-position spring preload adjustability; 8.2 inches travel
Rear: Pro-Link fully adjustable single Showa shock;9.1 inches travel

Brakes

Front: Dual hydraulic 174mm discs
Rear: Single 220mm disc

Tires

Front: 22 x 7-10 knobby radial
Rear: 20 x 10-9 knobby radial

Length: 72.2 inches
Width: 45.3 inches
Height: 43.7 inches
Seat Height: 31.9 inches
Ground Clearance: 4.3 inches
Wheelbase: 48.4 inches
Turning Radius: 10.5 feet
Dry Weight: 375 pounds
Fuel Capacity: 2.6 gallons, including 0.4-gallon reserve
Colors: Red, Yellow
 

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Discussion Starter · #11 ·
Thanks guys.I guess any year 400ex carb would work then.But do you think it will add any better throttle response and air.
 

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Thanks guys.I guess any year 400ex carb would work then.But do you think it will add any better throttle response and air.
If it's bigger, it would have to flow more air.

I can't believe my repair manual says 38 mm. What good is a repair manual if it's not correct.
 

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Discussion Starter · #13 ·
I don't know.Moose said his added a deeper tone to the exhaust when he put his 400ex carb on.
 

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I don't know what to tell you. I don't have much experience when it comes to something like that. I always left mine stock or, at least, close to stock.
 

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I can tell you that mine is 38mm and the power is there. It seems to be alot more responsive, along with the deep throaty tone now.
 

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Discussion Starter · #16 ·
So it's one of the 04+ models.
 

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Discussion Starter · #18 ·
I'm gonna try to get me one soon.How much did you have to give for yours?
 

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Discussion Starter · #20 ·
Wow thats a good price.Do they use the same style pilot and main jetts as the 250x carbs?
 
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