The Craftmans Shop > Model Engineering

2 cycle engine, spark ignition from bar stock


Brian Rupnow:
Gentlemen--I am looking for a set of plans for a single cylinder, spark ignition, air or water cooled engine, about 1" bore, built from bar stock, no castings. I started modeling the Wombat by Edgar Westbury, but found that there were enough mistakes in his drawings that I gave up on it. I have since found out that no-one has ever successfully built that engine. Apparently it was designed near the end of Mr. Westbury's life, when he was in ill health. If you have such plans as I require, and it is an engine that has been actually built and ran successfully, could you please email them to me at, or contact me about a purchase price.---Or, if you are aware of any books that carry such plans, please let me know what book it is and where I might purchase it. I promise a full "build thread" if I can run down a set of plans. I have spent 3 days contacting specialty bookstores and searching the internet, and I can not find what I want. I have built ten 4-cycle model engines, most recently a dual opposed single cam engine, very reminiscent of the old Volkswagen beetle engine. Now I want to try a 2 stroke, but not a glow-plug or diesel type.--I have attached a Youtube video link to the engine I have just finished.-Brian Rupnow

Thank you for posting Brian, I had a look at your engine - very nice runner.
Regarding your request for a two stroke from bar stock this one from jon-tom is all barstock. Have a look, the plans are free so nothing to lose. It may fit what you are looking for. Looks like only 1/5" bore may be a tad small, depends on what you fancy.
John B;

Alan Haisley:
Jan Ridders has plans for some two cycle spark ignition engines. You might find a basis to work from on his site.

Brian Rupnow:
Alan--I haven't completely ruled out Jan Ridders engines. Jan does some great work, but I know of a number of people who have built his two strokes and couldn't get them to run properly without modifying them. He does take a very novel approach, having a separate "expansion chamber" instead of using the crankcase as part of the induction system. Obviously they do run, I've watched the video's of them, but I was hoping for something more conventional, more like one of the aero diesels used in model aircraft, only with a lower compression ratio and a sparkplug rather than a glow plug.---Brian


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