boyesen remembered
Amsnow
Unexpected Turns
Boyesen’s relationship with Mike started as a sponsorship. Mike’s Team Rosko tested several Boyesen prototype reeds and Rage Cages in its snocross race sleds with good results. So, last year Boyesen offered to do a complete engine modification on Mike’s open race sled. At first glance, Boyesen knew he could improve the Ski-Doo RS 600.
This master engine builder went to work in stages. First he improved the intake ports, making them smaller, directing the intake flow in a better pattern. He found the stock setup did not scavenge properly and the intake was so large the air/ fuel mixture had too much turbulence. The scavenging affects the burn, the carburetion and everything inside the engine.
With a few cylinder modifications Boyesen finished stage 1 and shipped the cylinders for testing. Mike installed them and found a big difference, he won the hole shot in every race the following weekend. He was so impressed; he called Boyesen Monday morning and wanted a complete set of cylinders for his entire team.
That didn’t happen, as unexpectedly and unfortunately, Boyesen developed leukemia and was hospitalized mid-project. He did recover for a while and returned to work, doing what he did best, developing and improving engine products. But the leukemia returned and Boyesen then suffered a massive aneurism in November and passed away.
Mike did finish last season with Boyesen’s cylinders, and was the No. 1 Ski-Doo Pro Open rider in Canada.
Still the master builder
Despite his ongoing illness, Boyesen did more work in developing stage 2 for the mod race engine this last summer. By using a pitot tube, Boyesen measured the flow throughout the engine. He did this with the heads off and could measure the intake flow, the flow through the transfer ports, crankcase pressures, power and exhaust flow.
What’s a pitot tube?
It’s a pressure measurement instrument used to measure fluid flow velocity. This instrument is widely used to determine the air speed of an aircraft and to measure air and gas velocities in industrial applications.
Boyesen continued to work on the cylinders; by opening the exhaust ports and filling in and improving the intake port angles. The new intake changes improved crankcase pressure and enabled the engine to breathe better.
He also raised the secondary transfer ports and raised the compression in the stage 2 engine. This project was tested on the dyno and Boyesen said it showed an increase of 9 horsepower on the bottom and 6 horses through the mid-range and all the way to the top.
“When this motor is in the mid range, it’s so strong that the dyno can’t keep up to the power. It’s impressive. All of this along with a smooth power curve,” Boyesen had said.
Some say the Boyesen mod is too little too late. Ski-Doo has made some changes to its 2011 MXZ X 600 RS and folks there are telling us that they have changed the intake ports and have a new head design. Sounds familiar, they are claiming a 4.5-horse increase on top end.
One thing is certain, when the green flag drops at the races this season, my money will still be on the work of the master engine builder, the 2-stroke wizard, Eyvind Boyesen!