1970 4 hp evinrude lightwin-full throttle issues

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someone1357

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Joined
Jul 24, 2010
Messages
24
hello, I recently got this motor off a guy on craigslist for 160$, I checked under the flywheel, replaced an old cracked coil that was in there with a new coil (the guy who owned the motor before me already replaced one, and left the other old (cracked) one intact), I set the points to .020", and set the spark plug gap to .030", cleaned the carburetor, and when I start it up and idle it, it idles amazingly. It can idle at a very slow speed without dying. But, when I bring it up to full throttle, the speed fluctuates (e.g it runs at full speed for 5 seconds, then it dies down a bit (takes my 8 foot inflatable off of a plane) for 5 seconds, and it goes back up to full speed (puts it back on a plane) etc...) If I adjust the needle valve on the high speed jet by turning the knob on the motor counter-clockwise for a richer mixture, the problem gets less noticeable, but if I want to eliminate the problem completely I have to adjust the needle valve even further counter-clockwise. So then the problem is completely eliminated, but it does not run at the highest rpm possible. Is this considered a problem, or am I supposed to just run it with a richer mixture so it doesn't run at the highest rpm I heard it running at while fluctuating? any suggestions on how to fix this?
 
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Rick.

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Jul 30, 2006
Messages
3,740
Re: 1970 4 hp evinrude lightwin-full throttle issues

I would recommend doing a spark check right on the water when it starts giving you trouble. If the spark is good always I would re clean your high speed circuit in the carb. Best of luck. Rick.
 
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someone1357

Cadet
Joined
Jul 24, 2010
Messages
24
Re: 1970 4 hp evinrude lightwin-full throttle issues

okay, I checked the spark, and it seems to be good, I thought I might also point out that the spark plugs currently in the motor are old champion J6J's, and those arent in production anymore... the previous owner may have just had them sitting around still new and put them in during the 3 week period he owned the motor... or they are just really old, i'm changing them anyways with new champion J4C's. I have rebuilt the carburetor, and there was some varnish or something to clean out of the high speed jet, so I cleaned it out (was probably the source of the problem), also one of the coils looked kind of odd, I didn't really trust it so I replaced it as well. I suppose i'll say how it runs next time I run it in a barrel and/or get on the water...
 
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