1972 Johnson 50 does not want to start after the winter. Has fuel, spark and compres

[andrewbabich]

1972 Johnson 50 does not want to start after the winter.

I drained all gas and filled it up with fresh gas. (i did use last weeks 93 octane 32:1 premixed amsoil mix I made last week for my dirtbike that I had at the house, I wonder if too high of octane and too much oil could be my problem)

Has fuel, spark and compression and will crank all day long.

The plugs come out wet after I crank it. (so then I let it air dry for 10 min to an hour and retry, still no luck)

The plugs have spark when I check them.

Each cylinder has 135 compression

I spray the intake with starter fluid, and also try spraying it into each plug hole. I also try starting it without starting fluid. No luck.

It sometimes fires for one explosion the first time I crank it.

The last time it fired for a split second cranking will immediately stop. Like it got a signal that it was starting or something so it kills the starter.

Immediately I can turn the key again and crank it for another 5 seconds or however long I want but it won't catch.

I have the choke start/run lever all the way up to start postion and also try it at 3/4 up. I'm also holding up on the electric choke toggle switch below the key while I crank it.

This motor is always a pain in the butt to start but this year after winterizing its just not co-operating and I have no idea what to do.

I'll try new plugs, but the current ones have spark.

 

[hotshot123]

Re: 1972 Johnson 50 does not want to start after the winter. Has fuel, spark and com

if i had fuel, spark, and compression, i would take a look to see if the flywheel key had sheared and got it out of time. Timing is the last critical item and it is not on your list. If you have fuel that is being compressed, you throw a spark to it at the right "time" and it should run.

 

[eavega]

Re: 1972 Johnson 50 does not want to start after the winter. Has fuel, spark and com

I drained all gas and filled it up with fresh gas. (i did use last weeks 93 octane 32:1 premixed amsoil mix I made last week for my dirtbike that I had at the house, I wonder if too high of octane and too much oil could be my problem)

First off, I believe that motor uses 50:1, not 32:1. Second, is that oil TWC III? There is a difference in oil for use in air-cooled and water-cooled engines.

The plugs have spark when I check them.

How are you checking spark? Are you using an air-gap spark tester or are you simply holding the plug against the block? You may get a spark that way, but the spark plug will behave differently while under compression. I believe that spark has to jump an 7/16 air gap in order to spark under the 120+ PSI of pressure inside the combustion chamber.

I spray the intake with starter fluid, and also try spraying it into each plug hole.

You realize that starter fluid has no lubrication for your cylinders, and can damage the engine, right?


In any case, PP is right, if you have adequate compression (you do) and adequate spark (you need to verify this with a real spark tester), and adequate fuel (plugs are wet, so we will assume that is the case for now) then the next likely culprit is your timing. Look in the "Top Secret Files" for Joe Reeves timing method, and verify that your motor is not out of timing. If it is, you may want to pop the flywheel and check for a sheared key.

Rgds

 

[andrewbabich]

Re: 1972 Johnson 50 does not want to start after the winter. Has fuel, spark and com

You're right is does call for 50:1 and 87 octane too. I'm not sure what exact amesoil mix it is. Its what I use for my liquid cooled snowmobile and dirtbike.

And you're also right I didn't use a spark tester and went right off the block.

I half @$$ed it and have some work to do before I have to start looking into the timing issue.

Thanks guys.

 

[boobie]

Re: 1972 Johnson 50 does not want to start after the winter. Has fuel, spark and com

If you didn't use a spark tester to check your spark, you're peeing in the wind. Checking spark with just the plugs will tell you nothing.