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rrhead(SD) 
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Joined: 11 Sep 2009
Location: Canton, SD
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 Topic: 720 running rough UPDATE
Posted: 04 May 2019 at 9:20pm |
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I am having trouble with my 720. When I first start it up it runs fine. Either mowing or just pulling a wagon, after about 30 minutes it starts running rough, sputtering and backfiring. Seems like it is getting to much gas. Let it cool down for awhile and it will start right up and run for another half hour and do the same thing. Any suggestions to resolve this problem would be appreciated. Thanks, rrhead(SD)
Edited by rrhead(SD) - 15 May 2019 at 9:30am
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2 WDs,WD45,D-14,D-17,D-19D,180,7020,6080FWA,6080 2wd, 6080 2wd(cab),8050FWA,8550,4W-305,Massey 8250. Gleaner L3, R62 &R65 Agco-Allis 1616H & 1920H, AC 720, Terra-Tiger
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mnoonan-NEWI
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Joined: 11 Sep 2009
Location: Marinette, WI
Points: 738
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Posted: 04 May 2019 at 10:55pm |
 rrhead(SD) wrote:
I am having trouble with my 720. When I first start it up it runs fine. Either mowing or just pulling a wagon, after about 30 minutes it starts running rough, sputtering and backfiring. Seems like it is getting to much gas. Let it cool down for awhile and it will start right up and run for another half hour and do the same thing. Any suggestions to resolve this problem would be appreciated. Thanks, rrhead(SD) |
Condenser or coil?
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AC CA, Ferguson TO-20, Ford NAA, M-M BG, AC #3 Mower, SC Plow, PH Digger, AC 720's with Ark 700 loader & Brantly Backhoe, "Mini B" w/flathead Ford V8
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Steve in NJ
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Joined: 12 Sep 2009
Location: Andover, NJ
Points: 11791
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Posted: 05 May 2019 at 10:18am |
I'm wit' Mike. Sounds like ignition breakdown. If it was a overfueling problem there would be black smoke. You didn't mention any black smoke. Check your wiring in and around the engine compartment. Overheated wiring can cause voltage drop resulting in rough running. Steve@B&B
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39'RC, 43'WC, 48'B, 49'G, 50'WF, 65 Big 10, 67'B-110, 75'716H, 2-620's, & a Motorhead wife
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DonBC
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Joined: 12 Sep 2009
Location: Courtenay, BC,
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Posted: 05 May 2019 at 11:48am |
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My guess is a bad coil. They work fine when cold but begin to misfire as they get very hot from being defective.
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Jack of all trades, master of none
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injpumpEd
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Joined: 13 Sep 2009
Location: Walnut IL
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Posted: 05 May 2019 at 3:24pm |
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Mine started some of that crap yesterday! If I remember right, every time it gets running crappy, it needs the points replaced. Is there anyone making an electronic conversion that's easy to install? Having the push-rod setup seems to make the conversion a challenge. Every time I put a new set in it seems like it's got so much power, it's unstoppable. lol! I think the timing just slowly keeps retarding(like me) over time till it hardly even runs.
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210 "too hot to farm" puller, part of the "insane pumpkin posse". Owner of Guenther Heritage Diesel, specializing in fuel injection systems on heritage era tractors. stock rebuilds to all out pullers!
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rrhead(SD)
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Joined: 11 Sep 2009
Location: Canton, SD
Points: 432
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Posted: 05 May 2019 at 8:52pm |
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Thanks everyone for the suggestions. I will start with the points and condenser and go from there. Always very good information from this site. I finally got my 1920 running today. Would not run either, then I found a wire was loose on switch and not connecting solenoid on carburetor. Got it to run and mowed the rest of the day. Thanks again. rrhead(SD)
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2 WDs,WD45,D-14,D-17,D-19D,180,7020,6080FWA,6080 2wd, 6080 2wd(cab),8050FWA,8550,4W-305,Massey 8250. Gleaner L3, R62 &R65 Agco-Allis 1616H & 1920H, AC 720, Terra-Tiger
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rrhead(SD)
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Location: Canton, SD
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Posted: 15 May 2019 at 9:34am |
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Couple days ago I put new points and condenser in my 720. Talk about a difference in running! It has more power, runs like new, and I mowed with it for about 2 hours with no problems. Thanks to all the good information. rrhead(SD)
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2 WDs,WD45,D-14,D-17,D-19D,180,7020,6080FWA,6080 2wd, 6080 2wd(cab),8050FWA,8550,4W-305,Massey 8250. Gleaner L3, R62 &R65 Agco-Allis 1616H & 1920H, AC 720, Terra-Tiger
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Dave (NE)
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Location: Eagle Nebraska
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Posted: 17 May 2019 at 10:12am |
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Rod, sent you a PM, but am also going to post this to get input, as I am also having problems with my 720. Some of the google search I've done seems to indicate earlier models of the Onan engine may take a different set of points than later models. My engine is model #CCKB-MS/2733J. What would be the appropriate points and condenser for this engine? Where can they be purchased? Also, replacing the coil is mentioned above. Where is a good place to get a new coil and is any special one required? Thanks for the assistance. Dave
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Do not argue with an idiot. He will drag you down to his level and beat you with experience. Mark Twain.
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den/southern illinoi
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Location: Sparta, Illinoi
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Posted: 17 May 2019 at 11:04am |
Dave, I found you can't go too far wrong with Brenda at Sandy Lakes Implement who are in the advertising section. Den
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Own 4 wheel 20, 2-5015, 5020 and associated equipment and 2 electric forklifts.
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Dave (NE)
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Posted: 19 May 2019 at 10:28am |
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Thanks, Den. Does anyone know about the need for different points/condenser depending on the engine model?
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Do not argue with an idiot. He will drag you down to his level and beat you with experience. Mark Twain.
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Dave (NE)
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Posted: 20 May 2019 at 9:59am |
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I asked Rod, but will ask others too, have any of you had issues getting the bolts that hold the heat shield out, as they are into the manifold? Thanks, Dave
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Do not argue with an idiot. He will drag you down to his level and beat you with experience. Mark Twain.
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den/southern illinoi
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Posted: 20 May 2019 at 1:43pm |
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Yes. I have a couple (maybe more) that broke off instead of coming out. Ended up drilling out the broke off bolt and putting a bolt thru everything. A little more difficult but gets the same result. Den
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Own 4 wheel 20, 2-5015, 5020 and associated equipment and 2 electric forklifts.
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Dave (NE)
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Location: Eagle Nebraska
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Posted: 23 May 2019 at 10:51am |
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Well, finally got the points in. An Onan guy did say there are two different types of points for this Onan engine. He had a set that matched what was in there (don't know the part number, as it wasn't evident on the points), so good to go with that. Didn't break the bolt when getting the heat shield off/out of the way. All in all, this isn't a real easy task. But, in the end, it does seem to be running well. I will give it a better try out over the next few days. Thanks all for the help. Dave
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Do not argue with an idiot. He will drag you down to his level and beat you with experience. Mark Twain.
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rrhead(SD)
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Location: Canton, SD
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Posted: 23 May 2019 at 11:15am |
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Glad it worked out well for you. Used mine again the other day mowing for a couple of hours and it never missed a beat. I think you will see a big difference in it's performance. rrhead(SD)
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2 WDs,WD45,D-14,D-17,D-19D,180,7020,6080FWA,6080 2wd, 6080 2wd(cab),8050FWA,8550,4W-305,Massey 8250. Gleaner L3, R62 &R65 Agco-Allis 1616H & 1920H, AC 720, Terra-Tiger
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coggonobrien
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Location: Eastern Iowa
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Posted: 28 May 2019 at 9:28am |
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Don't forget about the point actuating rod. real cheap
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Dave (NE)
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Posted: 28 May 2019 at 10:22am |
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What is the point actuating rod? Something separate from the points?
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Do not argue with an idiot. He will drag you down to his level and beat you with experience. Mark Twain.
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AC720Man
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Posted: 28 May 2019 at 9:31pm |
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I believe its the plunger he is referring to that runs off the crank to open and close the points. It comes up through the bottom of the points box. I replaced mine along with the guide. They wear over time and should be replaced very 500 hours or if noticeable slop is found in the guide. Still available through Cummins whom bought Onan.
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1968 B-208, 1976 720 (2 of them)Danco brush hog, single bottom plow,52" snow thrower, belly mower,rear tine tiller, rear blade, front blade, 57"sickle bar,1983 917 hydro, 1968 7hp sno-bee, 1968 190XTD
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coggonobrien
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Posted: 29 May 2019 at 10:13am |
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injpumpEd
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Posted: 30 May 2019 at 8:51am |
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I bought 160-0262 after I found that part number in my parts manual. It is the pushrod and guide bushing. I've had my 720 for about 22 years, and have replaced points several times, but never this rod or guide. Still gotta get it tuned up, weeds are growing like, well, weeds! lmao!
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210 "too hot to farm" puller, part of the "insane pumpkin posse". Owner of Guenther Heritage Diesel, specializing in fuel injection systems on heritage era tractors. stock rebuilds to all out pullers!
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coggonobrien
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Posted: 31 May 2019 at 8:48am |
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Ed, I'm guessing if a person takes the time to set the timing right the rod probably takes for ever to wear. But to be honest I'm not one of them so I've done it every other year. at $6/rod i'm ok with that.
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injpumpEd
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Posted: 31 May 2019 at 9:35am |
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as far as timing, I've just slid the box over all the way to advance it the most. Seems to run like a raped ape when points are fresh lol! Loses power over time so slowly it's hard to notice, until it will barely run.
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210 "too hot to farm" puller, part of the "insane pumpkin posse". Owner of Guenther Heritage Diesel, specializing in fuel injection systems on heritage era tractors. stock rebuilds to all out pullers!
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coggonobrien
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Posted: 31 May 2019 at 10:57am |
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which direction advances the timing? I think I'm somewhere in the middle.
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injpumpEd
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Posted: 02 Jun 2019 at 7:18pm |
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moving it to the left (as sitting in seat) I think advances it, since the crank turns counter-clockwise from front. I went to put my parts in today, and pushrod is too short, and new points would not work either lol! I did get to use the new condenser, since that is what I figured my problem was. It runs a lot better now, but ever since I put that new carb on (it has a smaller bore, so...), it sure doesn't have the power. As much as I use it now day, I should just do the 24 hp honda repower.
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210 "too hot to farm" puller, part of the "insane pumpkin posse". Owner of Guenther Heritage Diesel, specializing in fuel injection systems on heritage era tractors. stock rebuilds to all out pullers!
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