2-cycle ratios

[Shannow]

Originally Posted By: JimCT
Shannow, so are you advocating for a 32:1 mix to cover all three?? Or would you go 40:1? (Or something else entirely?)


32:1...I run between 24 and 32 in all my stuff, even the stuff "designed" for 50:1...

BTW, here's the book

http://iheartstella.com/resources/manuals/tuning/Graham-Bell-Two-Stroke-Performance-Tuning.pdf

Starting page 167...

 

[boraticus]

I downloaded that file several years ago. It is truly a gem of knowledge even after 24 years of publication.

Not too sure that I'd be wanting to run richer than 32:1 in modern engines though.

As he states, a wet (oily) exhaust is not desirable. I think I'd let that be my guide. Find the ratio that starts to moisten the exhaust then back off the oil in decrements until it stops.

 

[AVB]

Running a rich air/fuel ratio will also cause a wet exhaust.

 

[boraticus]

Originally Posted By: AVB
Running a rich air/fuel ratio will also cause a wet exhaust.


As will running at too low rpms. When I take my Yamaha RDs out for a ride and just poke along at slow speed, I'll notice the end of exhaust silencer being wet. If I run them hard it dries right up. Two strokes like to rev.

A mistake people often make with two cycle OPE is not running it fast enough.

 

[Donald]

Originally Posted By: boraticus
Originally Posted By: AVB
Running a rich air/fuel ratio will also cause a wet exhaust.


As will running at too low rpms. When I take my Yamaha RDs out for a ride and just poke along at slow speed, I'll notice the end of exhaust silencer being wet. If I run them hard it dries right up. Two strokes like to rev.

A mistake people often make with two cycle OPE is not running it fast enough.


I keep hoping that running my Husqvarna backpack blower at its full RPM will turn it into a James Bond jetpack, but it has not happened yet. Maybe I need to loose a few pounds?

 

[Cujet]

I run 32 to 1 in everything. It's really the best ratio for overall use.

I agree with the advice about oil ratio and carb jetting. However, the switch between 50 to 1 and 32 to 1 is so minor, it's not likely to affect the jetting on your equipment. The change is 0.8 ounces per gallon, or roughly 1/2 of one percent jetting. Temperature changes and barometric changes are more significant than this.

 

[SwedishRider]

The 2-stroke engine I use the most by far is a string trimmer that calls for 40:1. Given that it sees a lot of use and the others very minor, occasional use, 40:1 might be the best choice for me. It's right in the middle of the range, and many of you are saying the difference across these ratios is actually pretty minor anyway.