1967 Johnson 3hp Rebuilding and stuck

[meyerboy]

This post is not for the casual tinker-type (which I am), there is a problem here that is beyond my ability.

The motor: Guy goes out and buys this fold-a-way in 1967 brand new, and as the proud owner, he puts gas in and fires her right up. He made only one mistake, after all, he has a mower that runs on just gas.

The powerhead seized in about 4 minutes of run time, and thats all the motor has on it. I love a challenge, so I rebuilt from the ground up, and used OMC rings and beaded the cylinder walls real nice, no cutting was needed.

Every other part is showroom condition, as this guy put the motor back in the case, and stuck it away where it sat for 43 years. It still had the srtaight gas in the tank when I got it.

OK, the problem: when I pull the rope, it feels really tight. She will fire, but not run. Sorta like I am trying to start it in a barrel full of sand. What did I do wrong?

Compression : 70 over 71
Impeller, brand new
Great Spark

 

[kfa4303]

Re: 1967 Johnson 3hp Rebuilding and stuck

Make sure that all exhaust ports are nice and clear. You may also want to try sparying a bit of PB blaster, or similar substance into the cylinders to pre lube the walls and rings. Also, check to make sure that you have no air leaks in or around the carb. I had an air leak in the carb and it showed similar symptoms. After tightening up all the fasteners on the carb and hi/lo needles, she runs like a top. Keep us posted. Pics are nice I'd like to see a fold away model. Good luck.

 

[Chinewalker]

Re: 1967 Johnson 3hp Rebuilding and stuck

When it seized up, is it possible the bearing surfaces on the crankshaft got tweaked? How about the bronze bearing surfaces on the rod ends? Did you inspect them when you had it apart? Also possible the rods got bent when it seized - not uncommon with the aluminum rods. Any slight bend or out of round on the rod caps can cause the drag you're noticing.

 

[meyerboy]

Re: 1967 Johnson 3hp Rebuilding and stuck

When it seized up, is it possible the bearing surfaces on the crankshaft got tweaked? How about the bronze bearing surfaces on the rod ends? Did you inspect them when you had it apart? Also possible the rods got bent when it seized - not uncommon with the aluminum rods. Any slight bend or out of round on the rod caps can cause the drag you're noticing.

That is exactly what it feels like. The bronze bearings all looked and felt brand new, remember the motor has 4 minutes of run time, but there could be damage to the rods that is harder to see, but still there.

I am going to post a pic or two, she is a beauty that really needs to be saved, if I can.

 

[Tim Frank]

Re: 1967 Johnson 3hp Rebuilding and stuck

How does it feel pulling over w/o plugs?

 

[meyerboy]

Re: 1967 Johnson 3hp Rebuilding and stuck

I have been spinning (with a drill) the powerhead without the plugs (but plenty of fogging oil) in the hope of "loosening" it up. That is also how I got the compression numbers.

Yesterday I went back in to the crank and thought I would loosen the rod caps, maybe I tightened to much?? But when I loosened just one flat on the bolts, I felt a tiny bit of play in the cap. I did'nt think that was right, so I re-assembled at the old torque. When I put her back together, I used enough re-assbly lube to make sure the problem is not a dry surface anywhere. She will fire, and smoke a lot on every pull, but the resistance is too much to let her run for any time period. I am using 24-1 to make sure everything is oiled.

 

[meyerboy]

Re: 1967 Johnson 3hp Rebuilding and stuck

here is a look. you can see why I am so determined. Click to enlarge.



This is the exaust tube, not cleaned, this is the way it has been since 1967.

 

[58rude]

Re: 1967 Johnson 3hp Rebuilding and stuck

Its not direct drive with the lower unit froze up is it?

 

[meyerboy]

Re: 1967 Johnson 3hp Rebuilding and stuck

Its not direct drive with the lower unit froze up is it?

No, not the lower unit. I took it apart, and checked the gear case and the impeller, and all it free spinning. I even tried to fire the motor with the bottom unit folded out of the way, and no change. Still too tight to run.

Maybe I need to cut the cylinder walls 10 thousandths ??? that would be fun, seeing how I have never done it before.

 

[58rude]

Re: 1967 Johnson 3hp Rebuilding and stuck

Did you check piston sidewall clearance and piston ring end gap? Check the pistons too see if they were egg shaped?

 

[meyerboy]

Re: 1967 Johnson 3hp Rebuilding and stuck

Did you check piston sidewall clearance and piston ring end gap? Check the pistons too see if they were egg shaped?

Do you take the head off to do that??? I was hoping to leave the head on, as I will have to order another gasket. I did mill the head to make sure it was true.

Here's a question, can you re-install the pistons from the case side??? I can just pull them out, but getting them back in may be impossible.

 

[F_R]

Re: 1967 Johnson 3hp Rebuilding and stuck

OK, did you put the rod caps on the original rods? You can't swap them. Also, did you put the rod caps on the same way they came off? You can't put them on 180 degrees off.

Are you saying that it has 43 year old gas in it? I'll bet that's a stinking mess. If you rebuilt it and didn't change the gas, did he run it on straight gas after you rebuilt it? Did you test it after rebuilding? Seems like we aren't getting the whole story here.

 

[1946Zephyr]

Re: 1967 Johnson 3hp Rebuilding and stuck

Well, if there was straight gas run in it, you'll most likely need to have the crank and rod assembly miced out and the surfaces thouroughly checked for any damage. Rod clearances to crank should be .0007 - .0017.

The pistons are likely scored from lack of lubricant also. Bead blasting the cylinders is not a good idea. They should be honed instead.

Love your comment on the gas, F_R. Gas that old couldn't burn, even if you used a blow torch.

 

[1946Zephyr]

Re: 1967 Johnson 3hp Rebuilding and stuck

That is exactly what it feels like. The bronze bearings all looked and felt brand new, remember the motor has 4 minutes of run time, but there could be damage to the rods that is harder to see, but still there.

I am going to post a pic or two, she is a beauty that really needs to be saved, if I can.

A beauty like that, would be worth the expense of a new crank and rod set, if it were me.

 

[meyerboy]

Re: 1967 Johnson 3hp Rebuilding and stuck

OK, did you put the rod caps on the original rods? You can't swap them. Also, did you put the rod caps on the same way they came off? You can't put them on 180 degrees off.

Are you saying that it has 43 year old gas in it? I'll bet that's a stinking mess. If you rebuilt it and didn't change the gas, did he run it on straight gas after you rebuilt it? Did you test it after rebuilding? Seems like we aren't getting the whole story here.

No, No and No..... the motor ran once, 43 years ago, I bought the motor from his grandson, (grandpa died, hence the motor for sale) and am in the process of rebuilding now.

The old gas was a mess, but not as bad as fuel that old that has oil in it!!

I am using fresh 24-1 fuel now to try to bring her back to life. I have cleaned the tank, BUT, I am using a funnel-feed that allows me to use a rope to start as opposed to the coil starter on top of the motor.

 

[meyerboy]

Re: 1967 Johnson 3hp Rebuilding and stuck

Well, if there was straight gas run in it, you'll most likely need to have the crank and rod assembly miced out and the surfaces thouroughly checked for any damage. Rod clearances to crank should be .0007 - .0017.

The pistons are likely scored from lack of lubricant also. Bead blasting the cylinders is not a good idea. They should be honed instead.

Love your comment on the gas, F_R. Gas that old couldn't burn, even if you used a blow torch.

I used a hone bit to clean the cylinders and they were like a mirror, that clean.

What I have learned so far from this board is that getting the rod caps back excacly as they came off is critical. I did not pay attention to that. I think it's back to the crank and I take pictures and post.

 

[F_R]

Re: 1967 Johnson 3hp Rebuilding and stuck

There should be index marks on each rod and cap. Align those ends and you will have that part correct. As for getting them on the right rod, you have a 50% chance of getting it right.