Onan 720 help

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   Picked up a 720 that seems to run strong.  Throttle response is good and only smokes for an instant at startup.  The issue seems to be the governor.  I have read the Onan master service manual on adjustment for tractor applications, and it doesn't seem to have helped. Operators manual recommends mowing in 2nd gear, however, engine bogs and speed slows when mowing taller grass/leaves.  An electric fuel pump was installed, and fuel supply is more than enough.  Any advice would be appreciated.

John

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ACJohn Members Profile Send Private Message Find Members Posts Add to Buddy List Silver Level Joined: 12 Sep 2009 Location: Horseheads, NY Points: 147	Post Options Post Reply Quote ACJohn Report Post Thanks(0) Quote Reply Topic: Onan 720 help Posted: 21 Nov 2010 at 11:44am
	Picked up a 720 that seems to run strong. Throttle response is good and only smokes for an instant at startup. The issue seems to be the governor. I have read the Onan master service manual on adjustment for tractor applications, and it doesn't seem to have helped. Operators manual recommends mowing in 2nd gear, however, engine bogs and speed slows when mowing taller grass/leaves. An electric fuel pump was installed, and fuel supply is more than enough. Any advice would be appreciated. John

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TREVMAN Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Joined: 04 Jan 2010 Location: Regina,Sask,Can Points: 1635	Post Options Post Reply Quote TREVMAN Report Post Thanks(0) Quote Reply Posted: 21 Nov 2010 at 12:09pm
	Time for a compression test, if you dont have 100 or better in each jug, not much power. Check your points, clean them they have a tendency to get oily, set the points, when I got my tractor it seemed to run o.k. but had no power, the points were not even close. Change plugs, who knows how old they are. See if this makes a difference. I'd check the coil and put new wires on as well. I also decarbed the heads and put on new gaskets, while I was in there I set the valves and got the carbon off of them. Dont mess with the governer until youve done these things first...These are the things I did when I got my 720, and the way it runs now and the way it ran when I got it, theres no comparsion...hope this helps, TREV.

Brian Jasper co. Ia Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Joined: 11 Sep 2009 Location: Prairie City Ia Points: 10508	Post Options Post Reply Quote Brian Jasper co. Ia Report Post Thanks(0) Quote Reply Posted: 21 Nov 2010 at 12:39pm
	I 2nd the check/replace the points and plugs. Below 100psi compression means it's getting tired. Make sure you properly set the timing too. There is an Onan engies group on Yahoo where there are some real experts on these engines. Like Trev says, it's wise to decarbon the heads. From what I've learned from the Onan group guys is they can have carbon buildup on the head and piston that can be enough for the piston to hit the head and break the connecting rod.
	"Any man who thinks he can be happy and prosperous by letting the government take care of him better take a closer look at the American Indian." Henry Ford

ACJohn Members Profile Send Private Message Find Members Posts Add to Buddy List Silver Level Joined: 12 Sep 2009 Location: Horseheads, NY Points: 147	Post Options Post Reply Quote ACJohn Report Post Thanks(0) Quote Reply Posted: 21 Nov 2010 at 2:13pm
	Thanks for the advice. I will replace plugs/wires (wires have straight boots and hit hood) and decarb heads. Will Seafoam do a good enough job or do I need to remove heads?

TREVMAN Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Joined: 04 Jan 2010 Location: Regina,Sask,Can Points: 1635	Post Options Post Reply Quote TREVMAN Report Post Thanks(0) Quote Reply Posted: 21 Nov 2010 at 3:34pm
	Remove the heads, its not an expensive or hard job. Seafoam isnt a bad idea, but the carb that was in my heads was not coming out with anything but mechanical intervention. Dont buy your gaskets from Cummins, find them on ebay they are usually cheaper. TREV.