Virgil at Re-Do Banshee recently completed a 421 Assassin build for our good customer, Rob. We posted some videos about the build on social media. Lane at Driveline Performance commented and shared some pictures of Dynojet charts from runs on their shop's Dynojet - along with explanations. I've shared the charts and info here.
I hope this makes it easy for interested folks to find and see the different HP and torque results on a 421 Assassin engine when carbs and pipes are changed. ~Janel
The following information is provided by Driveline Performance.
Driveline's Dynojet - Chart 1
This graph was taken with the 421 Assassin Banshee running pump gas (150psi compression), Shearer small bore pipes, V-force 2 reeds, and 40mm PWK carbs. It shows 91 H.P. When Driveline Performance changed out the 40mm for the 35mm carbs on the same motor, the H.P. dropped to 86-87 H.P.
Lane sent this graph to Mat at the time, so he could see how his pipe worked with Driveline's Assassin cylinders. This is a graph from Lane on a 421 Black/White Banshee that was also in their shop when Virgil visited Driveline Performance.
This 421 Assassin Banshee also has a set of Re-Do Banshee's D-arms on it. 👍
Driveline's Dynojet - Chart 2
Here is the graph for the 35mm carbs on the same black and white Banshee with 421 Assassin. When Driveline Performance was testing this motor, Keihin carbs were not available at that time because Sudco had gone out of business.
Driveline used some Mikuni TMX 35mm carbs for testing purposes.
They also turned the timing down slightly from +6 to +4 just to see the difference in the graph. Notice the same engine rev'd out a little farther from that change (this is typical).
The 3 runs shown on the chart were made one after another. The H.P. climbed a little every run as the motor heated up - from 84 up to 87 H.P. Driveline has an air fuel meter on the Dyno, which they typically use. They do like to see the H.P. climb slightly or stay relatively the same as the motor heats up. This shows that the jetting is close to where it needs to be.
Driveline's Dynojet - Chart 3
This chart is for another customer for Driveline Performance. Their Banshee has 421 Assassin cylinders, uses pump gas, has V-force 4 reeds, +4 timing, 28mm PWK carbs, and CPI pipes.
Lane and the guys at Driveline were honestly surprised at this graph - since the carbs were only 28mm. They didn't think it would get to 80 H.P. with that small of carbs. It was pretty snappy on the bottom end.
Lane liked the PWK 28 carbs so much on this customer's 421 Assassin - he went ahead and put PWK 28s on the Black and White Banshee. They've been on it ever since. It gets much better gas mileage also.