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Banshee Bob's 397 4-Mil Build

Banshee Bob is a long-time Re-Do Banshee customer who has purchased several Banshee engines from us over the years, as well as many other parts. Bob decided to ship us this tired engine for a rebuild to freshen it up. He knew he wanted a +4-mil stroker engine. Once Virgil started the tear down, he found the cylinders had a really terrible port job. Those cylinders were replaced with a good used set of stock cylinders with a mild port job. Going up one bore size on the cylinders brought the engine up to 397 cc.

After building the engine in Re-Do's shop, Virgil did a leak down test and ran it through several heat cycles in our shop's test stand. It sounded great. You can listen to it in one of the videos in the playlist below. Bob installed the engine in his Banshee, finished the break-in procedure, and it ran great. He then sold the Banshee for a nice profit. The new buyer loved the way it ran and is very happy with it. We love that!

For more info on Banshee Bob's 397 build: 

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

 

Q- Have questions about selecting parts or getting help with your build? 
A- You can call 📞📱 or message us at 541-419-6054. 

We are flexible and will work with you. We can: 

  • Help you select the parts for your DIY build and ship them to you. - OR -
  • Build your engine and ship it to you to install. - OR -
  • Complete the whole build for you and install in your Banshee.

Bob's Engine Specs

  • BUILD NAME:  Banshee Bob's 397 4-mil Build.
  • EXPECTED RIDING CONDITIONS:  Recreational dune & trail riding
  • DISPLACEMENT:  397 cc 
  • ENGINE CASES (CASE HALVES):  Stock Cases
  • CYLINDERS:  Stock - Bored to 66 mm
  • PORTED:  Mild Porting
  • PISTONS: Wiseco 66 mm - 795 Long Rod
  • CYLINDER HEAD: Pro Design Cool Head
  • DOMES:  22 cc 13 degree
  • CRANKSHAFT: HotRods 58 mm long rod (4 mm over stock), trued and welded
  • COMPRESSION:  130psi (determines fuel recommendation)
  • TRANSMISSION:  Stock 
  • REEDS / CAGE:  Moto Tassinari VForce4 Reed Valve System
  • CARBS:  Stock Mikuni 
  • CARB JETTING:  (varies based upon engine build and elevation)
  • NEEDLES:  5N7U needles for Stock Mikuni.  
  • NEEDLE CLIP SETTING:  Center Groove on Slide Needle
  • AIR SCREW ADJUSTMENT:  3/4-1 turn out 
  • FUEL RECOMMENDATION: Premium Non-Ethanol (91-94 Octane) for 125-150 psi
  • WATER PUMP IMPELLER:  Stock
  • CLUTCH: Stock Clutch
  • CLUTCH BASKET: Stock
  • CLUTCH SPRINGS: 3 Stock & 3 Heavy Duty Springs
  • EXHAUST:  TBD
  • STATOR:  Stock with Used Aftermarket Timing Plate, Cast Aluminum
  • TIMING: Set to 4 degrees advanced 

 

 

 

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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