Engine/Mount Shake at Idle


Roy Carpenter

I've made an observation recently about my Robin/Suburu 35cc GEBE setup. When I got the kit, I noticed that the engine idle seemed a little fast. I adjusted the idle screw, and was barely able to get the engine to idle at what I thought would be right for a small 4 stroker. After starting my engine just prior to a cruise, I noticed that at the frequency/rpm that the engine was idling at caused substancial "shake" within the engine mount, and mount straps. By "substancial" I mean that that whole assembly was moving back and fourth about an eighth of an inch or maybe even more, at an extremely rapid rate, due to the frequency of piston/crank/flywheel movement within the engine. After watching it idle for a half minute or so, scratching my head..lol...I realized that if I would continue to let this happen, something would eventually break within the mounting system. I then adjusted the idle setscrew to where it was from the factory, (idling just slightly fast), and BINGO! There is little if any noticable vibration/movement within the assembly during idle now. With time, all that movement adds up to breakage. I know I find myself in situations in the city that I have to idle for 3 or 4 minutes sometimes.

Just food for thought:)