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720/Onan Loss of power


eagle5473

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I have an A/C 720 with 19.5 Onan in it...I just got finished putting it back together after a tear down to replace gaskets and find an oil leak. Engine has Good Compression, and seems to run fairly smooth, the govoner seams to work at idle and not under load.....my problem is that with the front PTO running the 60 inch deck the tractor losses power going up slight grades. If I attempt to add more throttle the engine will not come up to speed untill it is going back down hill..... Anyone have any ideas on what the problem may be? There is good compression 130-140 #s
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Try lenghthening the gov to carb rod, if that helps give it a little more. If it makes it worse shorten the rod. Check condition of points & condensor & timing first. Stan
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Timing is critical to these engines. Make sure it's up where it needs to be. Also a note on the govn. rod. If your sure it wasn't moved when you dissasembled it, then check elsewhere first. However, the proper adjustment for the linkage is with the engine off, pull the end off the carb, push the throttle to the wide open position. Then pull the govn. towards the direction off the wide open throttle possition and the linkage should slide back on while the butterfly stays in the wide open possition. In other words, wide open on the carb. should also be wide open from the govn. Make sure you have a real good fuel flow on the return line ensureing that the engine isn't starveing for gas when heavily loaded. Also, if the engine was down for even a few days the diaphram in the fuel pump may have gotten dry and a spec gone in and blocked the flow at the needle valve inlet. This will restrict the fuel flow causeing it to lean out and starve for fuel. Did you mess with the valves any?? Even a small adjustment could cause you to loose some comp. and power. Most of all these conditions will only show up while it's under a heavy load.
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thanks for the info... I adjusted the govn rod to 3/16 out of the end as the book sugests and it also looks like the spring may be worn out a little after 30 years I will try to get a new spring, and check the timing the points and condensor looked new when I opend up the box, and I only cleaned the top of the valves no adjustments to them.....the tractor had loss of power under load before I tore down the engine so I dont think anything got into the fule pump, but I just might try your electric pump option in the futere thanks
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Do you know if the throttle is opening more as the engine sees more load? You can remove the hood and check to see if it is reacting as it should.
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the govoner does not seam to open further under load.....I plan on checking the timming and finding a tac to make sure the carb is adjusted correctly....the sprig for the govoner seems worn as well I will try to find a new one
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I have exactly the same problem with my 4041. Let me know if you find a solution. As of this point in time I have not solved the problem.
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