Dan originally contacted Re-Do Banshee about a transmission fluid leak on his Yamaha Banshee engine. The leak appeared to be coming from around the drain plug area, possibly caused by spider cracks in the stock cases.
At first, the goal was simple: reseal and repair the engine.
But once Dan began disassembly, the project escalated. The input shaft bushing would not come off, and the primary gear was stuck on the crankshaft. Rather than continue fighting aging stock cases — especially ones that may have continued leaking — Dan decided to send the partially disassembled engine to our shop.
After discussing options, he chose to upgrade instead of repair.
We ordered new Driveline Performance engine cases along with Assassin cylinders and moved forward with a full 421 cc build.
While waiting for the new parts to arrive, Virgil carefully disassembled and inspected the original engine. The stuck bushing and primary gear were safely removed without damage (you’ll see that in the video below).
Once the new cases and cylinders arrived, the engine came together smoothly. The usable internals were transferred into the new cases, the 421 top end was assembled, and the engine passed leak down testing. After final assembly and a successful test stand run, the engine was shipped back to Dan.
What started as a leaking drain plug repair turned into a fully refreshed 421 cc Assassin Yamaha Banshee engine built on brand-new cases — completed in about two weeks from first contact.
For more info on Dan’s 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.
Dan's Engine Specs
- BUILD NAME: Dan's 421 Assassin Build
- EXPECTED RIDING CONDITIONS: About 700 ft elevation. Mostly dirt trail riding.
- DISPLACEMENT: 421 cc
- CYLINDERS: Assassin Nikasil
- PORTED: As cast - no additional porting
- PISTONS: Wiseco Blaster Pistons 68 mm 12198M06800
- CYLINDER HEAD: Redline Racing Head with RE-DO logo
- DOMES: 23 cc
- CRANKSHAFT: 58 mm (4 mm over stock)
- COMPRESSION: 155 psi
- REEDS / CAGE: Mototassinari VForce4
- CARBS: Smart Carbs - we heat cycled this engine with Keihin PWK 35 mm carbs in our shop. Dan installed the engine into his Banshee with the Smart Carbs he had.
- CARB JETTING: Smart Carbs do not use jetting
- NEEDLES: Smart Carbs do not use jetting. They use metering rods.
- AIR SCREW ADJUSTMENT:
- FUEL RECOMMENDATION: Premium Non-Ethanol (pump gas)
- WATER PUMP IMPELLER: Stock
- CLUTCH: Stock clutch with 3 stock springs and 3 heavy duty springs
- EXHAUST: Shearer small bore pipes
- TIMING: Set to 6 degrees advanced