JW 14 compression numbers?

[20mercman]

I had a couple of JW’s dropped off at the house recently. One JW-14 and a JW-17 The 17 was stuck, and will absolutely need rings. They were rusted, but thankfully the bores look pretty good. The JW-14 does not idle well. I rebuilt both carburetors, and neither one will idle down properly. The 14 has new coils, (at least they are recent coils), and the points are clean and set. The spark seems fine, but it will not ldle down, just kills, no matter the adjustment of the low speed needle. It only has 60 -65 psi compression. I checked my gauge on a Merc, 110 next to it, it has 115+,. so I know it is not the gauge. So I am looking at needing to find two sets of rings? Hen’s teeth? Any other ideas?

Steve

[Tom]

This may not be your problem, but… I had a JW that ran great, started easily, pumped well, but died when idled down. Simple fix was to keep the carb from closing too far. It may have been a carb from a different year, or some other part was switched out, but with a piece of wire in the linkage to keep it from completely closing the carb, it idled down really well and came back to speed without hesitation or stumble.

T

[fleetwin]

Yeah, you might want to try the carb from the other engine to see if the 14 runs the same. 60PSI is certainly marginal for one of these engines, but it is even on both cylinders. I have one lightwin with fairly low, but uneven compression numbers, but even this poor ol wore out engine idles “pretty good”. It will idle down but kinda loses steam after a minute or so, then fades away and dies…
So, I’m thinking there is something else wrong with yours if it won’t idle at all…..
Does it look like someone has had the powerhead apart.
Has the intake manifold been off? If so, perhaps they have the wrong intake gasket in place behind the reeds.
All of this reminds me how important it is to check and trust the basics. Have spent a few days trying to help out a buddy at his shop. One customer has two beautiful older engines….A 1976 6hp that looks “almost new”, and a 1980 15hp that looks so new I was afraid of scratching it up. The 6hp wouldn’t pump, so Gary had me replace the water pump, but it turned out the thermostat bypass was plugged up…Got it going, but the starter was kind of funky, and it didn’t idle like a 6hp should…Monkeyed around with it for a bit, then decided I would bring in a known good carb from home….As my luck goes, the starter spring popped out when I attempted to slide it over removing the carb…Got the starter to work well enough to start it, but it still ran the same….So, decided to put the original carb back on. Decided to replace the starter rope, the old one was cut short. Still couldn’t get the starter to work properly. Finally had to replace the spring cuz someone had bunged it up before me, that person had been inside the carb also. So, finally got the rewind working properly, and thought at least the guy can use the engine even though it didn’t idle properly….Finally, I decided to put a compression gage on it, 60/90PSI….I could have saved alot of time if I did the basic compression test first…But, I was fooled by how “new” the engine looked. Don’t know what Gary’s customer will decide to do now, but at least the engine is usable. No water in the cylinders or signs of overheat, so am guessing there are stuck rings or internal problems.
In your case, compression is even, and the gage is always suspect when checking compression on these tiny combustion chambers. Just reread your post, does the 14 idle at all, or does it just cut out when you attempt to idle it down. It seems like you have had the head off and didn’t see any obvious issues, correct? Perhaps you should attempt to remove the exhaust cover, if the screws will come loose, don’t mess with it if the screws are stuck. Maybe the rings are stuck, a good soaking with engine tuner might help. I am not afraid to rough up/deglaze the cylinder walls on these things with some fine emery/crocus cloth…Crude yes, but this will remove the glaze and might help the rings to seal…Just blow out the dust with compressed air and clean it up with the carb cleaner spray.

[lindy46]

Did you clean the idle circuit underneath the little dome on top? Also check link and synch.

[fleetwin]

Yes, make sure the throttle shaft doesn’t bind and the butterfly closes completely on its own, without “help” by looking at the butterfly with the carb off while operating the throttle shaft. On the other hand, perhaps the throttle shaft is worn allowing air to sneak in around it…Trying another carb will answer help decide if this is a carb issue….Those little stamped throttle cams get bent very easily, so perhaps someone “bent it back” and this is holding the butterfly open at idle….
PS: There is supposed to be a little spring on the cam follower to help make sure the carb closes fully at idle…

• This reply was modified 3 years, 9 months ago by fleetwin. Reason: correction
• This reply was modified 3 years, 9 months ago by fleetwin. Reason: addition

[outbdnut2]

JWs are known for a headgasket leak between the two cylinders and this makes for the low compression readings that are the same on both cylinders. Usually it’s more like 35 pounds and it won’t start, but you may have early stages of a headgasket leak. When this happens, the head is usually warped a bit and needs to be rubbed on emery paper on a hard flat surface to flatten the head. If the headgasket is bad, you will see the problem in the gasket when you remove the head.

I’m assuming your compression gauge has it’s checkvalve at the spark plug hole and not on the gauge at the end of a rubber hose. If it’s on the gauge end of a hose, you add the volume of the hose to the compression factor, and on these little cylinders, I’d expect a reading of 60 pounds or less. There have been message strings here in the past about this problem, and I’ve experienced it with a gauge I no longer use on really small cylinders.
Dave

[fleetwin]

outbdnut2 wrote:

JWs are known for a headgasket leak between the two cylinders and this makes for the low compression readings that are the same on both cylinders. Usually it’s more like 35 pounds and it won’t start, but you may have early stages of a headgasket leak. When this happens, the head is usually warped a bit and needs to be rubbed on emery paper on a hard flat surface to flatten the head. If the headgasket is bad, you will see the problem in the gasket when you remove the head.

I’m assuming your compression gauge has it’s checkvalve at the spark plug hole and not on the gauge at the end of a rubber hose. If it’s on the gauge end of a hose, you add the volume of the hose to the compression factor, and on these little cylinders, I’d expect a reading of 60 pounds or less. There have been message strings here in the past about this problem, and I’ve experienced it with a gauge I no longer use on really small cylinders.
Dave

You are correct of course…I based my responses on my assumption that he had the head off already…. Maybe not…

[20mercman]

Thanks for all of the replies fellas! No I have not had the head off yet. I did try both carburetors on the motor. Both went through my ultrasonic cleaner. (I don’t know if you folks have used these, but they really clean out hard to reach passages.) In any event, it will idle for a bit, 20 or 30 seconds, but dies out and does not want to stay running when you advance the throttle. I can adjust the high speed, and get it to be able to throttle down, and then back up, but when you then adjust the low speed, it does not stay in tune. As for the compression gauge , it does have the check-valve on the gauge end. I had not thought of that….. Back to basics, I recheck things over again. I do find it hard to believe that both carburetors would have the same issues. Carb sync, I am a Mercury guy, so not as much experience on these little guys, but I will check these tips out. One more thing is that the idle is when the throttle handle is in “RUN”, not even down to “SLOW” Perhaps that may be a clue. Our JW-10 and Lightwin runs like a clock, so I know how nice these can run.

Thanks again!

Steve

[fleetwin]

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….

[20mercman]

Well, a bit of an update. Again, thanks so much for the high quality posts! I greatly appreciate it. I did go back to the basics again today. I went back through the magneto, the points are spotless, ohm well, I reset and synced them 180 degrees. It has good spark. I also went and resent the carburetor through the ultrasonic cleaner….it is spotless. I have the low speed further out than the 1.5 turns, the high speed is about where you say. The high speed is very fussy, it likes it at a very small range. It will now idle, but not as it should. When it is down low, it still will not run much below the “START” range. The throttle pick-up is open at this point. As you said, I thought that these should idle with the throttle closed. The throttle cam looks like it is opening the throttle properly. One thing is that when I have it running at or near idle, It looses power on the top cylinder more than the bottom. It will smack you but good, so I know it is not loosing spark. I am going to pull the head, and also the reed block to make sure I don’t have poor seating reeds. By the way fleetwin, these are both Johnson’s, 58 & 61 I do have a Lightwin, but I shouldn’t have mentioned it and added confusion to the topic.

Steve

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