Johnson 6 hp won't start

creeksidelc

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Jul 10, 2006
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Hi, I recently purchased a 1975 Johnson 6 hp. I used to have a 77 model so I'm pretty familiar with this motor. It will not start or even try to start. Compression is 70 in both cylinders. I cleaned carb and put a rebuilt kit in it. I replaced coils and points and set them correctly. I've got good spark on top and bottom. I can't get the motor to even try and start. I've even tried starting fluid just to try and rule out a fuel issue. Even with starting fluid motor does nothing. Any ideas what it could be?
 

oldboat1

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Apr 3, 2002
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What counts as "good spark?" If it won't pop with starter fluid, something is amiss.
 

creeksidelc

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Jul 10, 2006
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The sparks are blue and loud and I can see them in the daylight. I sent the wired back to the coils they were before. I guess it's possible that they are backwards? If they are right though and I switch them could I damage anything?
 

oldboat1

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Might retest the compression, screw-in type tester. Should run with 70 or 80 lbs. Test with plugs out, pull it over four or five times until the needle stops moving.
 

creeksidelc

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If the condensers are bad I would have no spark or weak spark, correct? Any chance it's condensers?
 

oldboat1

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If measuring spark with an open air tester, and getting 1/4 inch (assumption), maybe you have incorrect plugs or plug gaps. The oem plug would be a Champion J4, I believe, gapped at .030.

Did you measure spark with an open air tester, and what plugs are you using?
 

lindy46

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Nov 27, 2008
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Spray some gas/oil mix into the cylinders and see what happens.
 

ondarvr

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Apr 6, 2005
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He already tried starting fluid.

​Check to see if the timing is right, or if there's a sheared flywheel key.
 

tomhath

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Dec 5, 2007
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From what you said it sounds like either timing is off or it's really flooded.

My guess is the timing is way off. Pull the spark plugs and the flywheel, then turn the crank until the piston is at Top Dead Center. The points on that cylinder should be just starting to open.
 

creeksidelc

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Jul 10, 2006
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So spark was jumping 1/4 in to the block. Today I bought an inline spark measured and it is now not making 1/4 inch gap. One will jump about 1/8 and the other a little less. I did air it out and then squirted starting fluid straight into the cylinders with still no results. I have ordered condensers and will replace plugs again and wires.
 

creeksidelc

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Jul 10, 2006
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I am using the plugs that the motor calls for. I believe champion j8c or something like that.
 

racerone

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Dec 28, 2013
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36,030
J4C is the correct plug.----I and many others suspected weak spark.-----If it will only jump 1/8" then you do NOT have good spark.-----Review work on the magneto.----Coil spacing and point gap need attention too.
 

creeksidelc

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Jul 10, 2006
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So I cut the ends of the plug wires off and checked all magneto work. Now I have an excellent spark. It will jump more than 1/4 inch with an inline tester and is popping loud and blue. Motor still does not start. I checked timing again reqlized that I could have been making a rookie mistake. I had been moving the flywheel to the notches and setting accordingly with continuity tester. But what I didn't realize is that the whole assembly that holds the magnetos spins and that can affect where the gap is. So do I set timing with it at idle or do I set it with the throttle reved up?
Thank you
 

racerone

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Dec 28, 2013
Messages
36,030
Well----It does not matter where you set the points.----Full throttle or idle can be used.----Set points to 0.020" at widest or use timing marks on flywheel and magplate and a meter.
 
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