Once I was getting enough revs-the engine started easily. Since then I have mounted it on my big pink and have no luck starting it
Are you using the same system and getting the same rpm?
Try some fresh fuel, fresh plug. Remove the plug and clear the cylinder by spinning prop, put the plug back in loosely and try to start with reduced compression. If it goes let it warm up, shut down and tighten the plug and see if it will start. Worked for me. but a royal pain... Elec ign made life much easier.