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Skipp72 
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Joined: 12 Oct 2019
Location: PA
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 Topic: 720 engine removed
Posted: 28 May 2020 at 5:58pm |
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OK, so here is what I would like to know. What things should I be doing/checking while the engine is out.
Back story... I had a pretty bad oil leak that I could not trace without pulling the engine. After pulling the engine and removing the casing, I was able to find the issue. One of the bolts for the oil pan had worked itself loose (read - halfway out). I have had previous issues with one motor mount bolt coming loose, and one of the hood bolts as well.
So, I would like to know if there are any issues I should be addressing while the engine is out. Would hate to get it all back together, just to find another issue that would require me to remove it again.
Thanks
Skipp
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HudCo
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Joined: 29 Jan 2013
Location: Plymouth Utah
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Posted: 28 May 2020 at 11:36pm |
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starter and charging system and the the wireing the conections on that starter have to be very clean and tight
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Skipp72
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Posted: 29 May 2020 at 7:47am |
  I thought I kept my tractor pretty clean, until I removed the engine. Lol. It is amazing how much crap is hidden in there where you can't normally get to.
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Skipp72
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Posted: 29 May 2020 at 7:51am |
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Will definitely need to do a thorough cleaning before it goes back together.
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Skipp72
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Posted: 29 May 2020 at 7:56am |
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Hudco, Will definitely be looking at the electrical. My starter does not always want to engage the flywheel. Is there a way to rebuild the starter?
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Steve in NJ
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Joined: 12 Sep 2009
Location: Andover, NJ
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Posted: 29 May 2020 at 9:29am |
Speaking of the Starter motor, there's a bracket that bolts to the block that the Starter motor bolts to. When I first bought my 620 from the P.O., I was under the impression when I bought it, that the engine developed a knock and locked up. The P.O. shut the engine off immediately, and parked the Tractor in the corner of his garage. There it sat for 8 years till your's truly came along and purchased it locked up. After purchasing the Tractor and getting it home, I yanked the engine like you did figuring this thing is gonna havta' come apart. Well, after further investigation, looking down through the flywheel, I saw a bolt sticking out. It was sticking out of the bracket that I mentioned earlier that the Starter bolts to. As I rotated the flywheel, I saw the flywheel hit that bolt. Nah, can't be the knock could it?? It was! I spun the bolt back in with my fingers and the engine turned over without locking up with a lot of compression happenin' as I turned it over. Well, I usually don't step in chit' to often, but that's what it was. So getting back to the Starter motor after this long winded post, I would remove those bolts and locktite them puppies in so that doesn't happen to you. Sorry for the long post.
If you need parts (especially electrical) or a wiring system, I build them for the 616-720 Tractors. If you visit our website you can see what we offer in the 616-720 category... HTH
Steve@B&B bb-customcircuits.com
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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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Skipp72
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Posted: 29 May 2020 at 10:57am |
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It appears that my starter issues were due to dirt buildup. I removed the starter from the engine and cleaned it all up, and it appears to be working properly now.
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Steve in NJ
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Posted: 30 May 2020 at 10:20am |
Inspect the Starter cables real good to. They get pretty toasty from the heat those Onans put out. You'll be a bit surprised how much grass and debris gets stuck down around the bottom of those engines where the Starter is located. Add some blow-by, and you have everything sticking to that area.... 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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Skipp72
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Posted: 30 May 2020 at 12:50pm |
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Exactly what I ran into. The grass and such was packed in tight around the starter. With the oil leaking from the pan it was a gunky mess. It was also packed in under the casing at the back of the engine.
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AC720Man
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Posted: 31 May 2020 at 7:01am |
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If you replace the oil pan gasket replace the LOCK washers on those bolts!!!! I had a leak and reused the bolts with what appeared to be perfectly good lock washers. As anyone who has had to pull one of these engines out it is no fun. Engine ran fine for about 5 minutes and then I noticed it started to vibrate. Oil was leaking out of the pan again. Pulled the engine again, cleaned it up, put lock tight on the bolts, torqued the bolts. Reinstalled engine, started the engine the next day to run the rotary mower and the vibration came back!!!! Pulled engine again, put new lock washers on and have not had any issues since. That was 3 years ago. I always replace lock washers now, a hard lesson taught me to quit being a tight wad and replace them. I have read they are to be replaced whenever loosened or removed. I may reuse on something that has no vibration to it but I definitely replace them on a engine.
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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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AC720Man
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Posted: 31 May 2020 at 7:11am |
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I would also remove the flywheel and clean up the stator or at least get a extension for your air compressor tip and blow out debris from there as well. These little engines can become a fire hazard if debris is allowed to build up. As Steve said, clean up your wiring connections at the starter, clean with Emory cloth to guarantee a good connection.
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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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Skipp72
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Posted: 31 May 2020 at 8:55am |
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I found two of the bolts for the pan were loose, one the head is half broke off. I figured I had better pull and replace all four.
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Skipp72
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Posted: 31 May 2020 at 9:02am |
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As for the flywheel, is there a trick to removing one that refuses to move. I have put a good bit of force on it but it won't budge. I am familiar with the dirt issues in the flywheels on these engines. I have a wheelhorse with an onan that I have cleaned up a couple of times before. I am a little afraid to use any more force as this flywheel looks a little fragile (at least in comparison to the one on the wheelhorse).
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Skipp72
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Posted: 31 May 2020 at 12:42pm |
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Got the flywheel off finally. It was very stubborn.
It definitely needed to come off though. It was not pretty in there.
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Skipp72
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Posted: 31 May 2020 at 12:46pm |
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On a different subject...
Has anyone ever tried to put electronic ignition on one of these engines?
From what I can see, it should be possible. I see a couple of issues, but think they could be resolved.
Any thoughts?
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tadams(OH)
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Joined: 17 Sep 2009
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Posted: 01 Jun 2020 at 3:04pm |
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You can but it's expensive.
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