Johnson 1980 70 Hp will not start

[phled]

This motor has not been started in 15 years. Started a restoration project. So far I have had the carburetors rebuilt, in stalled new fuel pump, new fuel lines, fuel tank including primer bulb and line, new spark plugs, new battery. The motor will turn over just fine but does not want to start. It will start for a few seconds after pushing the key to prime the carburetors but that's it. I mixed the oil to fuel heavy at the suggestion of someone else. Would it make any difference to try the recommended 50:1? Also what should be my next step? I'm stuck.

 

[jbjennings]

Re: Johnson 1980 70 Hp will not start

1) the float needles are stuck, not allowing fuel to fill the bowl.
2) your floats are adjusted incorrectly, not allowing bowl to fill.
3) The low speed circuits of the carbs are still clogged.
4) the low speed circuits are incorrectly adjusted.
5) you aren't getting good spark on all cylinders---have you checked for spark with a spark tester to see if it will jump a 1/4" air gap at LEAST?

 

[jbjennings]

Re: Johnson 1980 70 Hp will not start

BTW, welcome to the forum! As long as you're not over 24:1 on oil, I doubt it would make any difference on the fuel.
Question: Who rebuilt the carbs?
JBJ

 

[phled]

Re: Johnson 1980 70 Hp will not start

Thanks for the welcome. A local service shop did the work on the carbs. Not much to choose from where I'm at. I checked the low speed needle valve and found the screw bottomed out on all 3 carbs. According to the Johnson service manual I acquired that seemed far from correct. Sounds like I may have to pull the carbs back off and go through them myself. I'll have to get a spark tester but this info helps me get started again. Thanks

 

[jtexas]

Re: Johnson 1980 70 Hp will not start

That motor has old-school choke plates, and won't hardly start cold without choking. Lift the hi-idle lever full up, push the key in and hold it in while turning it over to "start". It should start in just a few seconds. Back off the throttle, giving it just enough to stay running. If it starts to die during warm-up, punching the choke just for a second usually keeps it running.

All 3 jets on your carbs are fixed, including the slow-speed jets; that's a screw plug covering the idle jet and should be screwed in tight.