First proper start-up for my home built split-single, 170cc engine. (twin)

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Jul 14, 2020
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I've finally got it all together to e able to start the split-single 2 stroke engine which, along with 2 of my sons, Philip and Ian, designed, then first fabricated, partly in wood and from a 3D printer parts, and now have assembled, from machined alloy castings etc, and parts along with other mechanical/electrical bits from a Victa Twin 170cc mower engine. (mainly pistons, a single's crankshaft, magneto and flywheel)
As the dual, alloy con rod now forms its own big end bearing, (no needles) I've had to use a fuel/oil mix of 10:1. This has proved to mean, it will only start and run at present in the cold-start throttle position. Anything else leans it out too much with its old G4 carbie fitted.. It hums well at about 1500 to 2000 rpm I guess. As we have not yet machined the head or cylinders' cooling fins into it yet, -running time is in minutes only possible, to prevent it seizing up. As that machining is a major task, I wanted to be sure it would start and run properly first, at least, before we tackle that task.
A properly jetted M/C carbie should cure the lean, wider throttle opening problem also. I've been able to re-mount the engine via an adaptor plate, then to the base of an old Victa 18" cut mower for convenience. This by chance, will also permit it to be used in a test comparison, eventually, as a mower engine itself when fully assembled, with proper air cooling, for power, endurance and economy. Then maybe on an outboard motor leg.

The limited rev range for now is also convenient, so on dismantling it for machining, I'll be able to check how the big end and cylinders are wearing, esp. as the already run-in used rings are running in, now, the honed, alloy-only cylinders. Later, cast iron or nikasil cylinders may be fitted. The porting shape and machining within the head between the cylinders, seems to be adequate for now.

It looks like there is still a lot to be done for its perfection. I'll attach some photos soon.

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