Evinrude Lark ii sputters at mid to high RPM's

[SquirrelTurds]

I am trying to determine if my engine is misfiring at high rpm's because of a bad fuel mix, or timing. Here is a video: https://www.youtube.com/watch?v=80L3-aDPgwk&feature=youtu.be Compression on the top cylinder is 118 bottom 114. Water pump works perfectly FYI. I accidentally used lucas 2 stroke oil which is not environmentally kosher for boating, but I don't see how that could change anything! However here is what it looked like after a 10 minute run (I will switch out to the proper oil before I put it in the water)

 

[SquirrelTurds]

Re: Evinrude Lark ii sputters at mid to high RPM's

I forgot to add this is all under neutral. No drive on the engine.

 

[Chris1956]

Re: Evinrude Lark ii sputters at mid to high RPM's

Do you have enough water in that bucket to prime the waterpump? Check her for overheating. A lark II is early 60's right? You should be running 24::1 on motors older than 1964.

See if your timing plate is loose, causing the points to jump around. My old 35HP had a 40HP carb on it (Frankenrude-style), and used to miss every 10 seconds at idle. Ran perfect under load though.

 

[SquirrelTurds]

Re: Evinrude Lark ii sputters at mid to high RPM's

Pump would always show water after about 2 min of running. And yes the bucket covered the screen. I'm running 50:1 though. I guess that's my problem!

 

[racerone]

Re: Evinrude Lark ii sputters at mid to high RPM's

Covering the intake screen is not good enuff.-------Water must be 6" above the water pump !!!!!!!-------Open the slow speed mixture 1/2 turn as it sure sounds like it is running lean.----Perhaps the throttle plate is opening to soon.-----Stop motor.---Take and post a picture of the linkage at the towershaft where the adjusting collar is on that rod.---------At slow idle it usually does not touch there.---Again make sure you have water 6" above the water pump.

 

[F_R]

Re: Evinrude Lark ii sputters at mid to high RPM's

In the first place, what are you doing trying to run it at high speed with no load anyway? If nothing else, that should cause the vacuum cut-out switch to cycle, which would be seen as an ignition miss. However, your motor sounds like it is lean-sneezing, caused by lack of fuel in relation to the amount of air. I strongly suspect the throttle synchronization is out of whack. (Carburetor butterfly opening too soon.) But could be high speed jet set too lean.

That crud in the barrel is normal. Get used to it. It will be better on the lake, where it was intended to be run.

 

[SquirrelTurds]

Re: Evinrude Lark ii sputters at mid to high RPM's

Thanks for all the help! I guess I'll just have to run her on the lake! With the correct 25:1 ratio!