Add a decompression valve without modifying your engine

[LewieBike]

A lot of bigger chainsaws with higher compression and no rolling pedal start have them yes. Small saws don't have these.

Most of those saw engines above 50cc's, the compression release port is cast into the side of the cylinder about halfways or so up, so you have about half the compression ratio. They also auto close once the engine fires. pretty clever design. My Dolmar steel cutoff saw and my Jonsered 52 cc saw both have these decompression valves and I've seen them down to 44cc on the Makita home user saws.

It's another reason I keep looking at cheap Husky 273 cylinders and cranksets. It would be kinda brilliant if some China bike engine company could build a lower end that you could bolt up a Husky or Stihl top-end cylinder and piston kit into.

 

[curtisfox]

https://motorbicycling.com/threads/stihl-ms660-54mm-project.64042/ ...............Curt

 

[Kevin hate guess from des]

Ive woken up many times in the mechanical world with game changes you need to give it a go and do not listen to the guess from the desk or the know all who got lucky one day understand principles of a combustion engine and it will work use the rest for the details

 

[Travelingmechanic]

It's wild, you'd be hard pressed to find any truly new ideas.When my bro was 15 he thought he invented turning headlights, then read in an encyclopedia that Mercedes Benz did it in the 40's.
Very cool idea that never crossed my mind, make a 2-stroke have an easy pull start.

Volvo did it in the 90's