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Curtis’s 385 4-Mil Engine Build - Completed June 2026

Curtis’s 385 4-Mil Engine Build - Completed June 2026

Curtis has trusted us with his Banshee before, bringing it in for maintenance and tuning to keep it running its best. After another solid season of riding, he ran into a shifting problem that left the transmission stuck in 3rd gear. Virgil suspected the shift shaft needed repaired or replaced.

Since the engine was already coming into Re-Do Banshee's shop for repairs, Curtis decided it was the perfect opportunity to add some horsepower. He stepped up to a 385cc +4-mil engine build that would gave his Banshee a noticeable boost in performance while keeping it reliable and pump-gas friendly.

For this build, the cylinders were sent to Redline Racing for a dune port by Cameron. Combined with a new long rod crankshaft, new Wiseco pistons, new domes, and Curtis's existing Cool Head setup, the result is a strong, responsive engine package built for years of trail and dune riding. The dune port really helped bring this combination to life, delivering a healthy increase in power without sacrificing reliability.

Watch the Build

Want to watch how this project came together?

  • 👀 Watch the video below. 
  • ⬇️Scroll down for the link to watch the build's whole playlist on Youtube. 
  • ⬇️Continue below to see the project specs below the video.

 

Q- QUESTIONS About Your Project?
A- You can call 📞📱 or message us at 541-419-6054. 

Project Specs

  • BUILD NAME:  Curtis’s 385 4-Mil Build
  • EXPECTED RIDING CONDITIONS:  Recreational dune & trail riding
  • DISPLACEMENT:  385 cc
  • ENGINE CASES (CASE HALVES):  Stock Cases
  • CYLINDERS:  Stock - Bored to 65 mm
  • PORTED:  Dune Port from Redline Racing
  • PISTONS: Wiseco 65 mm - 795 Long Rod
  • CYLINDER HEAD: Pro Design
  • DOMES:  22 cc Modquad
  • CRANKSHAFT: HotRods 58 mm long rod (4 mm over stock), trued and welded
  • COMPRESSION:  150 psi (determines fuel recommendation)
  • TRANSMISSION:  Billet Pro-Mod Transmission
  • REEDS / CAGE:  Moto Tassinari VForce4 Reed Valve System
  • CARBS:  Stock Mikuni 
  • CARB JETTING:  330 mains, 27.5 pilots (when it left the shop)
  • NEEDLES:  5N7U needles for Stock Mikuni. 
  • AIR SCREW ADJUSTMENT:  3/4 turn out
  • FUEL RECOMMENDATION: Premium Non-Ethanol (91-94 Octane) for 125-150 psi
  • WATER PUMP IMPELLER:  Stock
  • CLUTCH: Stock Clutch
  • CLUTCH SPRINGS:  3 Stock & 3 Heavy Duty Springs
  • CLUTCH LEVER:  Aftermarket
  • EXHAUST: Toomey T5 Pipes
  • STATOR:  Stock with Used Aftermarket Timing Plate, Cast Aluminum
  • TIMING: Set to 4 degrees advanced

 

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Do You Have a Project?

If you have a Banshee to restore, want to upgrade your suspension, or are planning an engine build, we're happy to help.

We specialize in Yamaha Banshees. If you have a different project in mind, contact us and we will let you know if we can take it on and what you can expect. 

CALL 📞📱 or message us at 541-419-6054. 

We offer a range of services. We can:

  1. Help you select parts for your DIY build.
  2. Help you Pack and Ship your Engine to us, build your engine, then ship it back to you to install.
  3. Complete the engine build for you and install in your Banshee.
  4. Inspect, repair and service the whole Banshee for you.
  5. Build or restore your Banshee.
  6. We may also be able to locate a local Banshee for you - then install your newly built engine in it.

Project References:

  • We calculate engine displacement based on the bore in the engine's cylinders and the stroke length of the crankshaft. Click here for more explanation in our Banshee Engine Displacement blog article. 
  • Click here for information about Banshee engine break-in procedures. This includes our recommendations for Fuel to Oil Ratios and Selecting the Correct Fuel.

About the Authors:

This project article was written by Janel with plenty of help from Virgil. Virgil is the Banshee mechanic, and I am the website mechanic. I do own and ride a Banshee, which helps. 

The Re-Do crew hopes sharing our project info and specs may help some with their own projects, or that you find it interesting. I want our technical info to be accurate and helpful.

Please do let us know if you like our project articles, or if you think I need to correct something. You can send an email to info@redo-parts.com - and your comments will be passed along to me. 

Thanks ~Janel 😉👌

Email to: info@redo-parts.com