1972 Johnson 25Hp Refurbish

[kdeitrick46]

I have a Johnson 25RL72R. It’s been sitting in my barn for 25 years. Ran good when put in barn. I want to bring it back to life and install on my Lone Star King Commander. My plan is to first check compression and then spark and then, depending on those results, determine if this effort is economically feasible for me….given the cost of engine parts.

Problem is that the engine will not turn easily….even with the plugs out and engine in neutral. It will easily turn part of a revolution and then meets resistance and with great effort I can turn it through the rest of the revolution. Almost feels like it is in compression or pulling a vacuum.

Any thoughts as to what might cause this and remedy? My initial thought is that the reeds are not opening.

Any and all thoughts are appreciated.

 

[MrGiggles]

Rust in the cylinders most likely. Best have a peek with a borescope or pull the head.

 

[kdeitrick46]

Rust in the cylinders most likely. Best have a peek with a borescope or pull the head.

Rust in the cylinders most likely. Best have a peek with a borescope or pull the head.

 

[kdeitrick46]

Pulled the carb. Reed valves look clean and move freely. So, I don’t believe they are the problem. Mr Giggles suggested that It might be rust in the cylinders. I don’t have a bore scope and didn’t want to pull the head immediately.

Thought that if rust was the issue that it was most likely near the top of the piston travel. Put a straw through the spark plug hole to determine which piston was at the top of its travel when resistance was encountered at the flywheel. It was the bottom cylinder.

So I fogged that cylinder with a lubricant and spun the flywheel. Wa-La…much less resistance and after 4-5 turns everything was good. Thanks to Mr Giggles for putting me on the right track.

I still may pull the head, but not till I check compression and see what it will take to get spark.

 

[LaqueRatt]

I just picked up a running 25 HP. It is a BRUTE to pull start. In the process of switching over to electric start. What you describe I suspect is normal. My advice is set the timing, points, clean the carb and see if she'll start. Along with that I'd change out the fuel lines and put a filter on it. At least that's my plan. Mine doesn't have points though. Pretty sure yours does and they will definitely need attention, if not replacement.

 

[kdeitrick46]

I just picked up a running 25 HP. It is a BRUTE to pull start. In the process of switching over to electric start. What you describe I suspect is normal. My advice is set the timing, points, clean the carb and see if she'll start. Along with that I'd change out the fuel lines and put a filter on it. At least that's my plan. Mine doesn't have points though. Pretty sure yours does and they will definitely need attention, if not replacement.

 

[kdeitrick46]

Thanks Laqueratt. That’s just about my plan. After I got the flywheel to spin, I checked for spark and had none. I just pulled the flywheel and found everything in pretty clean and good condition, with the exception of corroded points. I dressed the points and will next check for spark. I want to methodically go through this to identify any major issues( read: cost) as I go. I don’t want to be driven to invest more dollars by the amount already invested.
I do know that the electric choke is going to require significant attention. I think I can fix it…we’ll see. Another cost will be an impeller, if I get that far.

As the project develops I’ll continue to post regarding obstructions, solutions, and progress. And ask for help.

Thanks all.

 

[kdeitrick46]

Dressed the points and got spark on both cylinders. Now on to the carb and the choke solenoid whose mounting strap is broken. I’m going to try to repair the strap before I breakdown and source one. Just wondering where best source of carb kits/parts might be.
Also this motor is set up with remote start and choke that I’d like to retain. Cable is badly deteriorating especially at the switch end. I think I can shorten 6-9 inches and solder new terminals. Any thoughts on this?

 

[kdeitrick46]

Regarding the electric choke solenoid. Found corrosion on the mounting cradle that prevented proper grounding. Cleaned both the solenoid and the cradle with steel wool and that solved the problem. Solenoid now works.
Still need to fix or source clamp.
View attachment IMG_2594.MOV

 

[RaisedByWolves]

Pulled the carb. Reed valves look clean and move freely. So, I don’t believe they are the problem. Mr Giggles suggested that It might be rust in the cylinders. I don’t have a bore scope and didn’t want to pull the head immediately.

Thought that if rust was the issue that it was most likely near the top of the piston travel. Put a straw through the spark plug hole to determine which piston was at the top of its travel when resistance was encountered at the flywheel. It was the bottom cylinder.

So I fogged that cylinder with a lubricant and spun the flywheel. Wa-La…much less resistance and after 4-5 turns everything was good. Thanks to Mr Giggles for putting me on the right track.

I still may pull the head, but not till I check compression and see what it will take to get spark.

You’re most likely going to be low on compression on that bottom cylinder at first.

Running it and “heat cycling” 4-5 times it may free up the rings if they are stuck and you will want to do this before taking it out on the water.

 

[kdeitrick46]

Well, I ordered a head gasket today. Surprised at the cost, but I just did not want to risk damaging a cylinder without ascertaining what caused the difficult turning of the flywheel. Plan to remove the head tomorrow and clear any debris before any scoring might occur. Also ordered a fuel pump and impeller. Carburetor is clean and everything seems to be in order. That will go on tomorrow along with new hoses. I’ll also test the starter and do some maintenance on the Bendix. Once I get the starter on I’ll do a compression test. Probably a week or so away from a start up try.

 

[kdeitrick46]

Pulled the head. Glad I did. Bottom cylinder full of debris. See pics below. A little rust at 2 o’clock. Dressed with 400/600 wet/dry. Cleaned up piston tops and head. Waiting for head gasket to reassemble and test compression. Anything else I should be doing in this area while I’m waiting for parts?

 

[LaqueRatt]

Well I hate to say, it, but your motor was likely just fine. They just are hard to pull. As simple as that. When you get done it may not be any easier to pull. You shoulda tried to start it before you tore it down IMO. I'd have tossed it before getting this far into it.

 

[LaqueRatt]

Just realized your 25 isn't much like the two I got which are newer and a lot bigger in displacement. So maybe I'm all wet on how hard yours should be to pull. Mine, I think are detuned 35s, or maybe 40s! Lots bigger and prob harder to pull. Still though if the motor spins and has compression and spark, is there any reason not to try to start it? Heck sometimes I just hookup a fuel tank and start pulling on these old motors I drag home. Amazing how often they'll start even when sitting around for years.

 

[kdeitrick46]

Just realized your 25 isn't much like the two I got which are newer and a lot bigger in displacement. So maybe I'm all wet on how hard yours should be to pull. Mine, I think are detuned 35s, or maybe 40s! Lots bigger and prob harder to pull. Still though if the motor spins and has compression and spark, is there any reason not to try to start it? Heck sometimes I just hookup a fuel tank and start pulling on these old motors I drag home. Amazing how often they'll start even when sitting around for years.

 

[kdeitrick46]

I’ve done the same on motors that I’ve drug home. I’ve owned this motor for 30 years. So I knew that prior to putting into storage that it ran fine and had no catastrophic failures. The fly wheel was very hard to turn with a breaker bar at a point in a revolution…easy to turn through the remainder. Ascertained that when the bottom piston was at the top of its travel that the resistance appeared. Surmised that there was likely something in that chamber that was impeding travel. Loosen that up by fogging the cylinder. That solved the rotational problem. At this point I didn’t know what the “something” was and didn't want to trash the engine by startling it with some foreign material in the cylinder. So I pulled the head to investigate. Glad I did.
No metal in the debris…just a lot of carbon. Any ideas what would cause this on one cylinder and not the other?

 

[thill]

I'm late to the party, but I was going to tell you to tilt the motor up and pull the plugs and shoot in a good amount of 2-stroke oil with a little gas into each one, about a 1:1 mixture. Thick enough to give serious lubrication, but thin enough to penetrate deeply.

Turn the flywheel by hand and the mixture should do it's thing. Then, pull the cord slowly, and things should start to loosen up a bit. Keep adding shots of the oil mix. Then, pull the cord hard and fast, and it should start feeling completely loose.

Put the plugs back in and pull a few more times, and things should be well lubricated and feel good.

THEN, put some 50:1 to it, and see if she will run. If she runs, GREAT. If not, determine if it's fuel or spark. Once you have done that for awhile, and you have rinsed the heavy oil out of the cylinders, THEN check compression, so you get an accurate reading to know where your cylinders are.

I learned years ago to do this before taking anything apart. Usually, a motor that ran when set many years ago will start up after this, but almost always will need the carbs done, brittle wires replaced and a few other things, depending on how long it sat and the conditions.

Hope it works out for you!

 

[RaisedByWolves]

That’s an insane amount of carbon.

Do a lot of trolling?

 

[kdeitrick46]

That’s an insane amount of carbon.

Do a lot of trolling?

Yes. And it was solidly packed in the head and top of the bottom cylinder. It was actually impeding the turning of the flywheel. It puzzles me that this was only on bottom cylinder. Any ideas what could cause this? Maybe faulty ignition or a cold plug?

 

[kdeitrick46]

That’s an insane amount of carbon.

Do a lot of trolling?

That’s a “no” on the trolling.