Reply To: JW 14 compression numbers?

[Don]

OK, so you haven’t had the head off…So, the comments about the head gasket certainly apply….You want to pull the head to have a closer look at the cylinder walls anyway while inspecting head gasket condition… Again, attempt to loosen the exhaust cover screws to have a look at the piston skirts and rings, but don’t force the screws if they are stuck in place…Breaking those screws off is a battle you will lose. Once the head is off, position the engine in a horizontal position with pistons closing the ports. With the engine positioned this way, you can fill the cylinders with engine tuner (or the merc equivalent) and let it set for a day or two….This might help free up sticky rings. Be sure to clean this stuff out afterwards and oil everything up liberally afterwards.
OK, so both carbs behave the same way, good information. I agree, not likely that both carbs have the same issues, especially after an ultrasonic cleaning. Do you have the initial needle settings correct? Low speed (upper needle), 1.5 turns out from gently seated, high speed needle (Iower needle), 3/4 turns out from gently seated. Be sure the low speed needle packing nut is relatively “snug” to avoid pulling air in around the needle threads and to keep the needle from turning on its own. It might be worthwhile to put this engine on a boat and run it, the needles are easier to dial in this way.
I think I understand your description of how the engine is running… The engine will idle, kind of, but the throttle is positioned up at the start position…The engine won’t run with the throttle positioned down at the normal idle position. These engines idle with the carb butterfly completely closed. There is a certain point where the throttle cam starts to open the butterfly, “throttle cam pick up adjustment”. So, have a look at the throttle cam with the throttle lever positioned in the idle position. The metal cam follower shouldn’t be touching the throttle cam…If it is, and the butterfly is actually held slightly open, the engine won’t idle. Like I say, those stamped throttle cams are bent easily, especially if the butterfly gets stuck… The throttle cam can be adjusted by loosening the two screws that secure it to the mag plate, one of the holes is oblong allowing the idle end of the cam to be moved in and out slightly for this adjustment.
So, that leaves the final question: when should the cam start to open the butterfly? And, that is a little tricky on these engines. It depends on whether is an Evinrude or Johnson…Let us know which one you have so we can tell you where to set the throttle for this “pick up setting”. Again, be sure the butterflies close fully on their own (which they should after ultrasonic cleaning). There is a spring that goes from the metal throttle arm to the block also to make sure the butterfly closes completely on its own. The only other thing to check for on these carbs is throttle shaft wear that might be allowing excess air into the mix, sneaking in around the worn throttle shaft/body bushings….