Honda 400EX / 400X 88mm Big Bore Kit – Stage 2 Cam + Studs

Honda 400EX / 400X 88mm Big Bore Kit – Stage 2 Cam + Studs

Regular price$599.99
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🔥 88mm Big Bore Top End Kit – Honda TRX400EX / TRX400X / XR400R
Complete Performance Upgrade – Bolt-On Power With No Machining Needed

Looking for real power without having to open your crankcase or machine your cylinder head? This bolt-on 88mm big bore top end kit includes everything needed to increase displacement, improve valve lift, and keep your motor reliable for the long haul.

Fits all years of Honda 400EX, 400X, and XR400R
No case or head machining required
✅ Includes top-quality brands: Wiseco, Hotcams, Cometic, Talon, SKF, NGK


📦 What’s Included:

  • 🧱 88mm Heavy Duty Cylinder

  • ⚙️ 88mm Forged Piston (Wiseco or Wossner based on availability)

  • 🔩 Nitrite-Coated Rings, Chrome Wristpin & Circlips

  • 🏁 Hotcams Stage 2 Camshaft – Boost mid-to-top end power

  • 🛠️ SKF Cam Bearings

  • 🧰 Cometic Big Bore Gasket Kit

  • 🧱 MLS Big Bore Head Gasket – Multi-layer steel construction

  • 🔒 Talon Titanium Head Stud Kit – Lifetime Warranty*

  • 🔧 Heavy-Duty Cam Chain Conversion

  • 🔥 NGK Spark Plug

  • 🎁 Stickers + 1-Year Warranty


⚙️ Key Features & Benefits:

  • 🔧 Direct Bolt-On Installation – No machining or case boring needed

  • 💥 Displacement Increase = Real HP Gains

  • 🧩 Built for Reliability – All parts brand new and performance-proven

  • 🛡️ Titanium Studs = Superior Sealing & Torque Retention

  • Compatible with Pump or Race Gas


📌 Fitment Compatibility:

Year Model
1999–2008 Honda TRX400EX (Sportrax 400)
2009–2014 Honda TRX400X
1996–2004 Honda XR400R

⚠️ Warranty Notice:

  • ✔️ 1-Year Warranty on the complete kit (new and used parts)

  • 🚫 This is not a DIY project — professional installation is required for all warranty claims

  • 🛠️ Warranty covers parts only after they are returned and inspected for manufacturer defects


📦 Shipping Time:
Ships within 3–5 business days. Tracking provided after fulfillment.

💬 Customer Support:
Available Monday–Friday, 7 AM to 4 PM PST
Live store chat available 24/7

We ship next day most of the time. Modquad parts are shipped Monday-Thursday. Engine Kits are 3-5 business days.

We don't do backorder! If your items has already sold you will be notified immediately and you money refunded on the spot.

Sold items are removed daily.

If you see it on this website, it is 100% in stock unless it just sold before you clicked buy.

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Customer Reviews

Based on 6 reviews
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K
Kris Coleman
426 kit rocks !!!

426 kit really rocks !!! So glad that I went this way, went to 14/36 sprockets and the R that I had wouldn't be able to handle it !!

K
Kris

The studs suck before I got to 33 lbs ft they rounded

D
Daniel Williams

Great product highly recommend it

J
Jonathan Betzel
426 big bore kit

Broke a valve on my 400ex 3 weeks before a riding trip. Ordered the kit and they shipped it fast and got it done in time. Thank you!

K
Kris Coleman
Nice

It's a very nice kit I haven't finished the install yet as I had to buy a clutch cover gasket and it's not top priority but hopefully this weekend Ill ride it..

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