Moturo 440cc Big Bore Cylinder Kit 89mm fits Honda TRX 400EX

Moturo 440cc Big Bore Cylinder Kit 89mm for Honda TRX 400EX

The Moturo 440cc Big Bore cylinder kit for your Honda TRX 400EX ATV (MY 99-08) — more displacement from the 397cc base. 89mm bore, 70mm stroke, ready for installation.

This cylinder kit expands the stock displacement of your TRX 400EX from 397cc to 440cc. 89mm bore, 70mm stroke, 10:1 compression ratio — specifications as per the Big Bore variant data sheet. OEM quality at a more affordable price.

The scope of delivery includes the cylinder, piston, piston pin, piston rings, piston clips, and gaskets, ready for assembly with your existing cylinder head.

Installation takes about two to three hours using a hex key set, torque wrench, piston ring compressor, and a new cylinder head gasket.

Cylinder kit for the Honda TRX 400EX ATV, manufactured by Moturo.

Performance · Material · Specs

• 89mm bore, 70mm stroke
• 10:1 compression ratio according to data sheet
• Bore-up from 397cc base to 440cc displacement
• OEM quality, ready for assembly

Important notes – please read

Component for race and off-road use. No ABE/StVZO approval. Not for public road use.

Fits the Honda TRX 400EX (model years 1999 to 2008, 397cc base). Not compatible with the TRX 450R, TRX 450ER, or Sportrax 300EX. Verify bolt pattern and cylinder head geometry with your existing engine before ordering.

Tools & Time required

• Hex key set in common sizes
• Torque wrench
• Piston ring compressor
• Fresh cylinder head gasket (purchase separately)
• About two hours for an experienced mechanic

Scope of delivery

1 × cylinder, 1 × piston, 1 × piston pin, piston rings, piston clips, gaskets. Not included: tools, cylinder head gasket, coolant, engine oil.

FAQ

Does this kit also fit the Honda TRX 450R or TRX 450ER?
No, the cylinder geometry and mounting points are different. This kit is designed exclusively for the TRX 400EX (model years 1999 to 2008, 397cc).

Do I need TÜV registration?
This kit is designed for race and off-road use and does not have StVZO approval. Not for public road use.

What is the compression ratio of the kit and what fuel is required?
10:1 compression ratio according to the data sheet. We recommend Super Plus with 98 octane.