Thinking about maybe trying a rotary build out of my Adventures 700c

GoldenMotor.com

Which would be a better fit in an Adventures 700c frame?

  • Sachs KM40 160cc rotary

    Votes: 1 100.0%
  • Piston engine, 2-stroke or 4-stroke, of the same displacement as the rotary

    Votes: 0 0.0%

  • Total voters
    1

jmason92

Member
Apr 8, 2016
33
0
6
31
Lawton, OK
So, I started thinking about maybe sourcing a Sachs KM48 160cc 2-stroke rotary and doing a build around it using my Adventures 700c, since it's already there, and a rotary seems like it would fit in the frame better than a 5hp Briggs flathead would, and would look a bit better than a 2-stroke kit piston engine as well, plus it suits the look of the frame better. As for the transmission, a CVTech CVT would be used, and the pedal and stock crank and gearbox would be replaced by a jackshaft and a rear sprocket aimed at high speeds. Stocking up on apex and rotor seals would also be required, as well as rebuilding the motor whenever the apex seals fail, which the 13b and 20b guys also have to deal with in the 4-wheel world, and everything that would make it safe and legal on the highway would be taken care of as well.

So, which would be a better fit in the Adventures frame, a 160cc rotary, or a piston of the same displacement?
 
Last edited:

Agreen

Member
Feb 10, 2013
792
11
18
Southeastern GA
I have more experience with rotary engines than most people do with any engine. I know rotaries. You don't just "stock up" on apex seals. When an apex seal lets go, the engine is done. At least the rotor housing is. It's like if you break a piston ring, you aren't just going to replace the rings.

And while the apex seals may be the popular whipping boy for rotary issues, the real problem is the people that don't understand them. The reason apex seals give (or side seals) is the same reason piston rings give. Improper tuning and lubrication.

And because people don't understand them, there is little aftermarket support. So if you want something weird, cool, and different, by all means give the sachs engine a shot. If you want to be able to get replacement parts quick and cheap, you need a briggs 5hp flat head.