I am looking for some advice in troubleshooting a hard start and poor idle condition on a 1960 40HP Evinrude Lark II. While testing the engine today in the hopes of fine tuning the carburetor the engine initially started easily then idle performance steadily degraded until it stalled. By playing with the low speed mixture I was finally able to get it to start and idle but it did so very roughly, so much so that I thought I might have ignition on only one cylinder.
I got the motor back home and pulled both plugs. Both looked wet with darker colored fluid but even. I got it running again and used a spark checker and both cylinders are firing consistently. All ignition components and associated linkage is new and adjusted per the manual. I was able to get a somewhat satisfactory idle but it still seems rough.
If I lean the low speed adjustment I can get a faster and smoother idle but the engine soon then becomes too lean, backfires and dies. There seems to be about 1/8 of a turn between too lean and too rich which seems like not enough. I did rebuild the carb so float, needle, seat, gaskets etc are new. The low speed needle is original and does have some visible wear around it’s tip but it’s not excessive. Any ideas on what could be going on here?
regards,
Mike
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