Another Twin

[balsaman]

While it might seem as if I am doing nothing, I have been working on a twin by hacking two week eaters. Once this one is done, I will get back to my other twin.

[WOODKNACK]

how are you connecting the cranks together?

[balsaman]

I cut one off at the throw, then drilled and tapped it for the 10mm threads the other crank has on it's end. Locktight and a tapered pin hold it together.

Eric

[WOODKNACK]

looks good. keep up the good work!

[RotarySMP]

Could you post a picture of the final crank please?

[balsaman]

Yes and no. I needed to assemble the crank with parts of the crank case in there between the two throws. Now that it's permanently assembled, the crank can't be removed. I will take some pictures the next time it's apart for a closer look.

Eric

[aspenelm]

Interesting. I have a stack of mcculloch chainsaw motors that I want to do something with.

are you going to have one or two carbs? are there sync issues? I assume the crankcase housings are completely separate. Also what is the relationship between the first and second piston, is one at the top of the throw while the other is at the bottom of the throw?

[balsaman]

The crank cases are seperate. One carb, the pistons are 180 degrees apart. I need to work out the ignition. I may make one flywheel with two magnets, one magneto and an electronic ignition module.

Eric

[RICHARD ZASTROW]

You could fire both at 0 & 180 (- spark advance) My 3-cyl. fire all 3 3 times per rev. Only the one in compression actualy ignites.

[balsaman]

That's the plan...

Eric

[vulcom1]

After looking at your conversion I thought you may want to see what I have been working on. 2 Ryobi's for 60cc's horizontally opposed. I am now working on the ignition so I can start it to see if stays together. On the ignition (cdi) I am learning new things like programming a pic and think I may have aquired enough knowledge to get it done. I have had help on the ignition and now just working out some of the bugs when you change components.
With your ignition being 180 deg. differance in firing I would be tempted to install 2 magnets (180 deg.apart)for your pickup and waste a spark as mentioned. I am not sure if mine will have the output to fire 2 coils at the same time which I will have to try or install two systems in parallel. I have my board down to 1.5 x 2.125 so far.
John

[Arthur Clampitt]

Originally Posted by RICHARD ZASTROW You could fire both at 0 & 180 (- spark advance) My 3-cyl. fire all 3 3 times per rev. Only the one in compression actualy ignites.

I know this is done on 4 strokes with little problem , With 2 strokes the area around bottom dead centre has a combination of exhaust gasses exiting the cylinder and inlet mixture entering via the transfer ports ( Assuming that is the way these little engines work ) A spark firing might not be the best idea ?