I had been begrudging the cost of the motor for the Twister surface drive I bought for Bar Hopper. Initially I had planned on a Predator 670 V-twin from Harbor Freight. Its about a thousand dollars at this time, but its a 22hp motor. That’s 22 crankshaft horsepower. There is really no other way to fairly rate loose utility motors. Then I ran across a 500CC one lunger from a company called Duromax (not Duramax) that claims 20hp for only a little over HALF the price of the Predator. I seriously considered changing my powerplant. I had already purchased a 2 into 1 exhaust for the Predator, but it wasn’t as expensive as the difference in cost, and I could likely resell it.
My play money savings came up to the level where I could go either way, and I went with the Predator. Someday the Duromax may have an aftermarket, but there is a serious aftermarket for the Predator 670. Guys like Ike, John, and Charles at CarsandCameras GOT MY ATTENTION years ago by powering a full size chopper with one, and now they are running an alcohol fueled mini dragster at insane speeds and RPM based around the Predator 670 motor. And of course there is Robot Cantina that has put the Predator 670 in “road legal” automobiles. Videos at the bottom.
I have no such high powered goals. About all I plan to due is re-jet the stock carburetor to run right with the 2:1 exhaust, remove the governor, and respring the valves so I can get up to about 5000(+/-) rpm without floating a valve. Initially I will just assemble the surface drive, mount the stock motor, and see what it does. Assembly video to come. Maybe a river run clip at the end after breaking in the motor.
Cars & Cameras: Chopper 670
Cars & Cameras: 670 Alcohol Fueled Dragster
Robot Cantina: Renault with 670