Our customer brought this Yamaha 450 into our shop. Re-Do Banshee specializes and focuses on Banshees. So... why did we agree to take on this project? Because it is a hybrid ATV with a Yamaha YFZ 450 rolling chassis and a stock Yamaha YFZ 350 BANSHEE engine.
The chain came off the rear sprocket and damaged the stock Banshee engine case set. The cases were leaking. We took the internals out of this OEM set of cases and re-cased them in a new and upgraded set of Driveline Performance engine cases. This was a set of their non-trenched cases.
Even though we re-cased this engine, the internals on the original engine were in good shape. The engine did not have much runtime on it. This made it worthwhile to move most of the internals over to a new set of engine cases.
The original set of Banshee engine cases were stock with an aftermarket non- trued and welded crankshaft. While we had everything apart, we had the crankshaft trued and welded. The trued and welded crank made a good, solid foundation for the new engine setup.
The pistons were oversized Wiseco pistons. Because of this, we know the cylinders had been bored over stock specs at least two times. The pistons and the OEM cylinders were in good shape and we transferred them over to the new set of cases.
The cylinder port work was very, very mild on these OEM cylinders. A cool head loaded with 22cc domes topped off the cylinders. After we reassembled the engine components in the new set of cases, we tested the compression. It had 130 psi compression on each cylinder.
The carburetors on this engine are stock 26 mm Mikunis that are appropriately jetted for this engine's compression and power needs. We went through both carburetors, cleaned them, checked them, and they function perfectly. It had K&N air filter pods on the air intake.
One intriguing thing about making a hybrid ATV is that sometimes you have to try to figure out where things should go. On this ATV, we added torsion bars to the bottom of the engine to put the engine and chain in better alignment. We made new billet aluminum engine mounts to mount the front of the engine. We also moved the rear sprocket from the inside to the outside of the rear hub to help the chain track better. We added a new DRW case saver, trimmed it to fit, and trimmed it to help the chain track better. We hope all these changes work together to prevent the chain from coming off and damaging the engine in the future.
The expansion chamber pipes were raw steel. We cerakoted them in a beautiful glacier silver color. We know the expansion chambers were handmade hand-coned pipes custom made for this hybrid, because Banshee expansion chambers will not fit in a Yamaha 450 chassis. The expansion chambers were quite large. Because space was limited, it was a challenge for the builder to figure out the best pipe to build for this bike.
We really have to take our hat off to the people that custom make the expansion chambers for exhaust pipes. There is a lot of math, formulas, and science involved in creating expansion chambers that put the power band where you want it.
The result with using these particular pipes is the engine wants to rev really fast and really high. I have seen other 450 hybrids with a different set of pipes on them that probably put the power band in a different place. However, with these pipes on this Banshee engine, it likes to rev out very high.
There were a lot of interesting and challenging details to work out on this 450/Banshee Hybrid. This is a healthy stock engine for this bike and it should run very good for a long time. We think it turned out fabulous, and we hope Dean is able to enjoy riding this unique bike for years to come.
What do you like best about this build? Let us know in the comments. ⬇️