johnson 4hp compressor request

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floyd36_

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Jun 20, 2004
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Hi, someone know how much compressor on the 2 cylinder, because i have 60psi on each, engine start find but when is hot engine stop, end how much for gap on set point.<br /><br />Thanks!<br /><br />Johnson 4HP #4W72S
 
JB

JB

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Re: johnson 4hp compressor request

As long as the two read within 10% of each other you are okay, floyd. Some folks would call 60psi low, but you have a rope start engine and probably didn't spin her through 5 times on each cylinder.<br /><br />Set the points at .020".
 
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floyd36_

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Re: johnson 4hp compressor request

Ok thank JB, so maybe my probleme is the point! i will clean carb. and change plug and adjust point and try another time.
 
Scaaty

Scaaty

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May 31, 2004
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Re: johnson 4hp compressor request

I have an 84 4hp that I just pulled on for checking PSI, and I get 120 PSI each.... squirt a little oil in there with the motor tilted up, run her through a few times, open the throttle , and give a few good manly spins and see what ya get. I have older 5HP that get anywhere between 60 and 80. Agree with JB on the 60 being a little low
 
JB

JB

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Re: johnson 4hp compressor request

Just reread your post, Floyd.<br /><br />Compression is not your problem. Both cylinders never fail the same amount at the same time. From what you tell us it is probably either overheating (needs new water pump impeller) or it is running out of gas from restricted fuel feed or tank vent.<br /><br />Good luck. :)
 
X

Xcusme

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Re: johnson 4hp compressor request

I'm with JB, my money's on the water pump...
 
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Paul Moir

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Re: johnson 4hp compressor request

Yup. The 4hp will run fine on 60psi, maybe a little hard to start. I've done a lot of work on mine and have it up to 95psi, but I'm sure it's hardly made a difference at all in it's performance. It started out at 70psi (on 4 pulls) by my gauge.<br /><br />As for the overheating, there is an tricky issue with the 4hp that can sometimes be a problem. Go ahead and rebuild the water pump since it's due, but if it's still getting hot (water sizzles when you place it on the head where the spark plugs screw in) have a look at this:<br /> http://shareaproject.com/pages/imageDetail,p,182,i,2538,00.html
 
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