Johnson Seahorse (JW-10) not sucking...

[aborgman]

Motor has:

1) Good spark
2) Correct timing
3) reeds in good shape
4) rebuilt carb
5) Good compression numbers (80-82psi)

...and it still won't start for anything, and the few times I've gotten it started (using starting fluid) it hasn't run very well or for very long.

So I took it out in the snow, put the tank back on, and spun it over about 30 times... and the plugs are dry. So it appears she ain't sucking. The question now is why not?

--
aborgman

 

[F_R]

Re: Johnson Seahorse (JW-10) not sucking...

Pistons skirts scored? Exhaust plugged up with dirt daubers nests? Main bearings worn out? It can have all this stuff and still have comperssion.

Actually, I sort of don't believe it isn't sucking as you say. But who knows what wierd thing might be going on. But it would be wierd.

Put your thumb over the carb air intake (not the silencer) and pull it over a couple of times. Do you have a wet thumb and/or gas pulled up now? If so, it is "sucking".

 

[aborgman]

Re: Johnson Seahorse (JW-10) not sucking...

Pistons skirts scored? Exhaust plugged up with dirt daubers nests? Main bearings worn out? It can have all this stuff and still have comperssion.

Well, I know the exhaust is clear, but those others could certainly be an issue.

Actually, I sort of don't believe it isn't sucking as you say. But who knows what wierd thing might be going on. But it would be wierd.

Put your thumb over the carb air intake (not the silencer) and pull it over a couple of times. Do you have a wet thumb and/or gas pulled up now? If so, it is "sucking".

It's got enough suction to get gas to pull up into the carb, but not enough to make it into the combustion chamber - the carb air intake (and don't worry about the silencer - I don't even have one) is dripping with gas, yet the plugs after 20-30 pulls are dry as a bone.

--
aborgman

 

[lark2004]

Re: Johnson Seahorse (JW-10) not sucking...

when you rebuilt the carb, did you remove the little silver disk on top and clean out the idle jets? even a small amount of crud in there could cause the engine to not run.

 

[F_R]

Re: Johnson Seahorse (JW-10) not sucking...

Lets' reason this thing out. On a two stroke engine, on the piston up-stroke there is a partial vacuum in the crankcase. That causes it to draw air and fuel through the carb and reeds. Then on the piston down-stroke that air in the crankcase is compressed. When the piston gets almost to the bottom of the stroke, the intake ports open and the compressed air/fuel charge in the crankcase is blown into the cylinders. Then it repeats.

OK, you say it is sucking gas from the carb. Even to the point of dripping. So that means you have crankcase vacuum. If you have vacuum, there is no reason that it wouldn't have at least some crankcase compression to blow it on through. It should work.

As I said, almost lightly, a worn out powerhead or plugged exhaust could interfere with the process.

I really think you are putting too much importance on getting wet plugs. Actually, wet plugs means a flooded engine, not what you are looking for if you want it to run.

You should start at the beginning again. First recheck the spark. It should jump a 1/4" open air gap. If it does not, then you don't have spark. Jumping the spark plug gap held against the head or lighting up your eyeballs if you hold the wire is are not valid tests. If you don't have 1/4" spark you are wasting your time messing with the carburetor.

Grab hold of the flywheel and try to move it fore and aft. It should not move any more than just barely, barely perceptable. If it does, the motor is worn out.

Take the flat exhaust plate off the side of the cylinders and look thru the exhaust ports at the piston skirts. If they are all scored up, you have problems there.

The problem is right before you eyes. You just need to make a systematic and logical search for it.

 

[JB]

Re: Johnson Seahorse (JW-10) not sucking...

If starting fluid will get it to start forget all except the carb.

By the way, never use starting fluid. No lubrication and ether are deadly to 2 stroke engines. Use fuel mix.

Rebuilding/cleaning a carb is like decontaminating a cyanide container. If you don't do everything thoroughly you might as well have not even tried.

 

[itstippy]

Re: Johnson Seahorse (JW-10) not sucking...

If it were a just a spark issue and you pulled the rope 30 times I would expect the plugs to be wet and the motor in a "flooded" condition. That is not to say that there isn't a spark issue, but dry-as-a bone plugs indicates a definate fuel issue (breathing problem) doesn't it? I have a good running JW10 out in the shop. I'll pull the spark plug wires and crank her over a few times and then check the plugs to see if they're wet. Now I'm curious as to whether I've made a false assumption. Do recheck the spark, though. Easy enough to do.

Starting fluid will get a poorly breathing engine to run because the fuel is already atomized. Even motors with pathetic compression will run on ether fumes. As noted, starting fluid is terrible stuff,especially for 2 strokes.

Old JW's develop two common problems according to the local guru who has helped me with parts and advice and such. One is breathing problems similar to what you describe. They wear out and just can't seem to inhale enough fuel/air mix to run properly. In my experiece this happens at about 70 PSI compression by my tester. Other internal issues (besides compression loss) could cause the same problem. The other common problem is stripped driveshaft splines.

If I have time I will try the "crankcase suction" test described in your earlier string. In my memory, though, there is a very noticable vaccuum in a healthy motor. Not straining to see a bit of tissue paper move.

 

[ezeke]

Re: Johnson Seahorse (JW-10) not sucking...

My experience has been that a fully closed choke will get fuel to any engine that can be started on starting fluid. When cold, leave the choke closed until you get fire.

That being said, no matter how much vacuum you have, if the orifices are clogged or the float is stuck, all you will pull through the carburetors is air.​

 

[Scaaty]

Re: Johnson Seahorse (JW-10) not sucking...

Oh for crying out loud..(I own 3)...DID YA CLEAN OUT THE DAMN TANK? ALL LINES CLEAR AND FLOWING? ...its GRAVITY FEED, and just a thought..did ya turn on the petcock?

Need to edit here a touch now that I can (seems you are getting gas out the carb)...but just need to make sure on the above..and even a lame tank vent will kill in quick

 

[itstippy]

Re: Johnson Seahorse (JW-10) not sucking...

Calm down folks. Aborgman has made the common mistake of starting a new thread instead of sticking with his original. He's been methodically working on this old gal for a couple weeks trying to get it ready for fishing season. I should have posted the link to his original thread in my reply - without it my comments sound a bit looney at best.

http://forums.iboats.com/showthread.php?t=190436

Hopefully I can perform the "suction test" on my JW10 tonight after work to see what the results are on a known runner. I'll post results.

 

[itstippy]

Re: Johnson Seahorse (JW-10) not sucking...

Here are my test results:
Known good runner. Starts easy. Idles excellent. Compression: 82; 85

Pulling the rope start with the air silencer off and checking for vaccuum at the carb intake (sparkplugs in) showed nothing. The choke butterfly is in the way so you can't really feel too well, and it's an impossible task to feel delicately with one hand or observe the behavior of a whisp of paper while yanking a rope start. An exercise in futility.
After 30 pulls the plugs were very slightly damp. FAR from being flooded. Not "bone-dry", but certainly not dripping wet. I had to really look to see the moisture.

I went to the drill, an 850 RPM 1/2" chuck variable with a 5/8" socket on the flywheel nut.
Vaccuum at the carb intake was noticable but not dramatic. I could feel it better because I wasn't trying to yank a rope. Also I was maintaining a sustained 850 RPM. It was far from impressive though. Real light.
The plugs weren't any wetter after 20 seconds on the drill at 850 RPM than they were after the 30 rope pulls. Not flooded. Not dripping. Barely beyond bone dry.
There is fuel mix puddled in the mouth of the carb's air intake.

PS: I should have tried to flood the spark plugs with the choke closed. Forgot to do that. These tests were all done with the choke open.

 

[itstippy]

Re: Johnson Seahorse (JW-10) not sucking...

PPS: I couldn't stand not knowing for sure so I just gave her another 10 seconds on the drill with the choke closed. The plugs are still just slightly damp. Maybe a little damper than before but not flooded by any means. Also, the drill is not hitting 850 RPM while cranking the motor. More like half that, by the sound it makes with no load vs cranking the motor.

 

[aborgman]

Re: Johnson Seahorse (JW-10) not sucking...

Oh for crying out loud..(I own 3)...DID YA CLEAN OUT THE DAMN TANK? ALL LINES CLEAR AND FLOWING? ...its GRAVITY FEED, and just a thought..did ya turn on the petcock?

Yep - tanks is clean as a whistle, and my petcock works so poorly that as much gas goes through it when turned off as turned on...

--
aborgman

 

[aborgman]

Re: Johnson Seahorse (JW-10) not sucking...

Here are my test results:
Known good runner. Starts easy. Idles excellent. Compression: 82; 85

Pulling the rope start with the air silencer off and checking for vaccuum at the carb intake (sparkplugs in) showed nothing. The choke butterfly is in the way so you can't really feel too well, and it's an impossible task to feel delicately with one hand or observe the behavior of a whisp of paper while yanking a rope start. An exercise in futility.
After 30 pulls the plugs were very slightly damp. FAR from being flooded. Not "bone-dry", but certainly not dripping wet. I had to really look to see the moisture.

I went to the drill, an 850 RPM 1/2" chuck variable with a 5/8" socket on the flywheel nut.
Vaccuum at the carb intake was noticable but not dramatic. I could feel it better because I wasn't trying to yank a rope. Also I was maintaining a sustained 850 RPM. It was far from impressive though. Real light.
The plugs weren't any wetter after 20 seconds on the drill at 850 RPM than they were after the 30 rope pulls. Not flooded. Not dripping. Barely beyond bone dry.
There is fuel mix puddled in the mouth of the carb's air intake.

PS: I should have tried to flood the spark plugs with the choke closed. Forgot to do that. These tests were all done with the choke open.

I've resorted to the electric drill myself - eventually...

Latest update:

Rechecked timing - good.
Rechecked spark - good, will jump a 1/4" gap.

I took it out for another try - pulled and pulled and couldn't get it to start. Then I improvised an electric starter (cordless drill + socket on flywheel nut) and used that to attempt starting.

It will start if it is choked and spun with the drill - it takes a bit of spinning, but it reliably fires... and immediately dies if you don't open the choke. About half the time it dies almost immediately even if you do open the choke.

When it does run it will run for somewhere in the 30 seconds to 3-4 minute range and then just die. If you attempt to move the throttle off the start position (~3/4 throttle) to a faster position, you can move it a little without it quitting but not much. If you attempt to adjust the throttle downward at all it immediately quits.

While it is running it is turning considerably below the rated RPMs - it should be 4000RPM at WOT, and when it's running at 3/4 throttle I don't think it's even turning 1000RPM.

Adjusting the high/low speed needles seems to have almost no effect, other than if you adjust the high speed needle too lean you can manage to cause it to quit.

So in summary:

1) Good spark and timing.
2) Can't get started pulling by hand, but if you can spin it over quick enough it will start.
3) When it does run, it runs REALLY poorly and even looking at it funny makes it quit.

--
aborgman

 

[aborgman]

Re: Johnson Seahorse (JW-10) not sucking...

when you rebuilt the carb, did you remove the little silver disk on top and clean out the idle jets? even a small amount of crud in there could cause the engine to not run.

No, I didn't - because the rebuild kits for the carb I have didn't come with one. Here is the carb I have:

http://www.outboard-boat-motor-repa...Outboard Boat Motor/images/3012 parts pg4.jpg

You're talking about part #48 on that diagram, correct?

I did blow carb cleaner through the opening for the low speed needle valve and made sure I was getting good flow out through the inlets into the carb throat behind the throttle butterfly.

--
aborgman

 

[Chinewalker]

Re: Johnson Seahorse (JW-10) not sucking...

Okay, let's back up a bit. You state that the RPM is not picking up as it should, but the motor is running, and more-or-less, stays running for a period of time. Have you checked the head gasket? Good chance you will destroy the old one when you check, so have a new one onhand.

Is the float level set per spec in the manual? Float should be bang-on level with the carb body when inverted. The clearance spec should be in the manual (I think it was supposed to be 1/32", but check it in the book). You've got good flow to the carb, but the motor sounds like it may be running out of fuel. A low float level setting could cause that.

You state that timing is "correct". Are the points set at .020" with the fiber rider aligned with the crankshaft keyway? Front plug wire is running to the top plug? Flywheel key hasn't sheared?

The methodical approach - eliminating what it absolutely cannot be, should get you there eventually.

- Scott

 

[aborgman]

Re: Johnson Seahorse (JW-10) not sucking...

Okay, let's back up a bit. You state that the RPM is not picking up as it should, but the motor is running, and more-or-less, stays running for a period of time. Have you checked the head gasket? Good chance you will destroy the old one when you check, so have a new one onhand.

Yeah - I pulled the heads to check out the water jacket, and the head gasket looked good. If it were leaking I think I'd have noticed it in the compression numbers.

Is the float level set per spec in the manual? Float should be bang-on level with the carb body when inverted. The clearance spec should be in the manual (I think it was supposed to be 1/32", but check it in the book). You've got good flow to the carb, but the motor sounds like it may be running out of fuel. A low float level setting could cause that.

The float is level, and the carb itself seems to be getting fuel - in my running position it is slightly tipped toward the carb and it will literally drip gas out the air intake.

You state that timing is "correct". Are the points set at .020" with the fiber rider aligned with the crankshaft keyway?

I don't use gap to set the timing - I put a multimeter on the points and make sure they are opening at the correct marks on the flywheel - basically the method shown here:

http://www.outboard-boat-motor-repa...on 3 HP 1952-1967 Ignition System Tune-up.htm

under the heading "Install, Set, and Test the New Points"

Front plug wire is running to the top plug?

Yep...

Flywheel key hasn't sheared?

No.

The methodical approach - eliminating what it absolutely cannot be, should get you there eventually.

That is what I'm trying to do, but so far none of the "logical" things has turned out to be the problem...

--
aborgman

 

[lexkyboater]

Re: Johnson Seahorse (JW-10) not sucking...

I may not add much here, but with your drill cranking it over, have you verified that the plugs fire consistently and strong on every stroke on both cylinders? Have you pulled the flywheel and made sure everything is still okay, and nothing has worked loose? Compression sounds okay, so let's ignore that. Can you keep it running if you get a spray bottle with gas/oil mix and spray that into the carb throat? If so, you've likely got some small port somewhere that's still clogged. All it takes to keep these things running is compression, gas and fire, as we all know, and sounds like the gas is the more likely culprit.

 

[aborgman]

Re: Johnson Seahorse (JW-10) not sucking...

I may not add much here, but with your drill cranking it over, have you verified that the plugs fire consistently and strong on every stroke on both cylinders?

They appear to, but at the speed it is spinning it's pretty hard to be certain. It is throwing a nice consistent seeming spark that will jump a 1/4" gap though.

Have you pulled the flywheel and made sure everything is still okay, and nothing has worked loose?

Yes. I've had the flywheel off about 5-6 times now and checked everything and it looks good - timing hasn't moved a bit.

Compression sounds okay, so let's ignore that. Can you keep it running if you get a spray bottle with gas/oil mix and spray that into the carb throat? If so, you've likely got some small port somewhere that's still clogged.

I'll give that a try when I have a chance to pull it out again - that would definitely confirm it as a carb issue. I'm beginning to be a little more suspicious of the low speed needle valve area and what is under that expansion plug on the top of the carb - if I had a replacement I'd pull it apart and take a look.

All it takes to keep these things running is compression, gas and fire, as we all know, and sounds like the gas is the more likely culprit.

I agree... although I'm still not sure that the gas isn't a problem because of a lack of "suck".

--
aborgman

 

[itstippy]

Re: Johnson Seahorse (JW-10) not sucking...

I've always pulled that little disc and cleaned under it when doing a carb. The kits have always come with replacement discs - sometimes three different sizes. I don't know why your kit didn't. The books, the experts on this board, everyone emphesizes pulling that disc and cleaning under it. Since the kits often come with several different sizes I imagine that a dealer or repair shop has many of them rattling around in a parts bin left over from previous jobs. You ought to be able to find one the right size easily and cheaply enough.

You've put so much effort into this motor already that you won't be done until you pull the carb again and clean under that disc and put in a new one. To get the old disc out you carefully drill a hole in the center. Don't go too deep! I use a benchtop drill press but if you have steady hands and good eyes you won't have a problem doing it freehand. Once you have a hole in it you pry it out with a pick or awl. Clean thoroughly and blow dry. To put the new one in you use a socket extender without the socket on it and a light hammer. The square head of the socket extender is rounded just exactly right to dimple the new disc in. I use a really light film of gasket sealer around the edge of the new disc just to make sure I get a good seal. A really light film, though - you don't want a gob of gasket sealer getting into those little orifices.

The fact that the motor won't run at low speeds could well mean that the low speed jet (idle jet) is not working properly and the motor is only getting fuel from the high speed jet.