[Arich0908]

I have a 2 stroke motor . I want to stroke it .
If I were to add a longer connecting rod to it with a spacer on the cylinder would that do anything? If so what would it do. It would not make the displacement any larger correct?

What would I be looking at in building a stoker crank for my motor . I have never attempted anything like this before. Would my objective being designing a new crank and where the rod connected to the crank should I be designing it to sit X amount of millimeters lower.
Any thoughts or ideas would be great ,
Thanks

[RICHARD ZASTROW]

A longer rod and a spacer equal to the increase in rod length, placed at the bottom of the cylinder, will move everything higher.

The cylinder displacement won't change. However, the crankcase volume will increase and the crankcase compression ratio will decrease. Probably will also have a slight effect on port timing as well.

A longer stroke will put the piston higher by the amount of increased crank swing. It will increase the displacement which, I assume, is the objective.

Personally, I wouldn't mess with either the rod or crank. Two strokers are fussy little buggers. If you are looking to improve performance, I'd look to port timing, port area, port shapes etc.

Dick Z

[Coxsteve]

Slightly different as I used to destroke small 2T race engines to fit specific classes,The method used was a high precision offset bushing into the flywheels and the same can be used in some cases to go the other way just spin the offset the other way.

Stroking can be quite effective in 2T engines,just remember rod stroke ratios regarding rod length,Changing the length of a conrod can be beneficial or Disasterous denending on the characteristics of the original design.

Get it right and happy days get it wrong and they break or suffer excessive bore wear,Things such as Piston Pin offset can be used advantageously as well.

Four strokes(4T) can benefit from a long rod conversion as it increases dwell time at TDC and effectively softens cam timing,With a 2T changing Rod length and or stroke will influence piston speed over the port openings sometimes positively othertimes not.

Look at some similar spec engines to what you envisage for some other ideas as to whether it will achieve what you want.

There are some good 2T design software programes out there these days,Remember with the www the world is far smaller when it comes to design software,As an example google Ian Williams Tuning in South Australia he has a demo of some software you can look at which will broaden your knowledge.
Cheers Steve http://www.iwt.com.au/MOTA.HTM