1990 15 hp Johnson won’t start, sort of sounds like it’s sucking air/leaking air

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racerone

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You must know the usual stuff by now.----STRONG spark.----Crankcase compression.-----Correct amount of fuel.----Cylinder compression.
 
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OptsyEagle

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Did you say that you swapped out the spark plugs for different ones? I mean I can't think of anything else. Your cylinder compression numbers are fine and yes, your spark looks awesome. I think the key is good as well. I would think that if any of the key aligned with the groove in the flywheel that your timing would be there right up until it sheered so it could not stay aligned anymore. With that said, I have never seen a sheered key, so my comment on that part is not worth too much.

I doubt a loss in crankcase compression would have prevented a pop when you put gas directly into the cylinders, so either your spark plugs are bad or that key is bad. I cannot think of anything else.
 
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jitterbug127

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I bought spark plugs this evening and swapped them out, still nothing. I mix my fuel at 50:1 and I know it’s good. I’ve got STRONG spark. My compression is 96/100. I don’t know how to measure crankcase compression… I’ll look that up. I’ll go ahead an order a new key. I think this one is alright, but for $14 bucks I can’t go wrong! I’m legitimately at a loss on this one.
 
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OptsyEagle

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I would also think that if you aligned that flywheel with the key you have, be it a good key or bad, your timing would be set. If you torqued that flywheel down with it set that way and pulled the starter rope, the motor would probably pop for at least few papumps, so as to mis-align the key again, if it was indeed sheered.

Even if I was wrong you should easily be able to verify after a few failed pulls, if the flywheel groove is still aligned with the key you have. If it is, the timing is fine, with respect to the flywheel key. You could check that.

The other item of spark timing is the timing advance that is set by properly aligning the mark on the throttle cam with the middle of the roller when the cam JUST touches the roller. The link and sync. You should definitely verify that is still set right.
 
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racerone

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Fact are needed and heeded to.----You put fuel directly into the cylinder.----The motor did not fire up and bark at you.-----That means it is NOT a fuel issue.---So why would you spend an effort and put another carburetor on it ?----It is a spark / timing issue.----The wire from powerpack to top coil is orange with a blue stripe ??
 
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David wright

David wright

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racerone said:
Fact are needed and heeded to.----You fuel put directly into the cylinder.----The motor did not fire up and bark at you.-----That means it is NOT a fuel issue.---So why would you spend an effort and put another carburetor on it ?----It is a spark / timing issue.----The wire from powerpack to top coil is orange with a blue stripe ??
Click to expand...
He said it was running fine and hasn't changed wiring as far as we know so would that be an issue ?
 
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racerone

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The man has to do some listening and trouble shooting.----No more effort from me to try and help on this simple issue..
 
David wright

David wright

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I still think the woodruff key is not meeting the flywheel properly on this image I can see a gap between the flywheel to the key
 

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racerone

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???----You will always see that " gap "----Was there from the day it left the factory !!
 
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