Farm Equipment - More AC 620 Problems

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More AC 620 Problems

Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=35197
Printed Date: 16 Sep 2025 at 6:03am
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Topic: More AC 620 Problems

Posted By: Kid at Heart
Subject: More AC 620 Problems
Date Posted: 08 Aug 2011 at 8:09am

I've been wrestling with an AC 620 that I got for mowing a bigger yard. Actually, the neighbor said if I got a good rider, that he could use too, he'd do the mowing for both of us. Hmmm, I think he's getting the better part of the deal. It's four hours of push mowing for either one. If the AC can do both yards in an hour, he's waaaay ahead of the game.

Anyway, I still have two problems with the tractor. The engine only wants to run on one cylinder. As near as I can figure, with the two-poled coil, the ignition fires both cylinders simultaneously, every time the cylinders come up TDC. What I need to know is whether the Onan CCKB engine runs the points off the cam or off the crankshaft. I'm thinking one of the cam lobes could be worn just a bit and not opening the points properly like the other. The "off" cylinder will occaisionally hit and makes a big improvement in engine performance....DUH. Believe it or not, the thing will still mow, just at a very slow speed on one cylinder.

Next, I have a bad pulley, again, on the mower deck. This one is on the middle spindle shaft, and runs the blade pulleys. The main deck pulley (belt from engine) bolts to this thing. Anyway, the pulley is all wallowed out. With the engine running and the mower engaged, the middle pulleys flop around real bad. The neighbor used to be a machinist and said the spindle shaft looks good, no wearing and sharp keyway cuts. He says the pulley is bad.

Any ideas where to get another pulley? Seems a lot of you guys have mower deck collections going. Spare parts?

Regards,

David

Replies:

Posted By: Jeff Z. NY
Date Posted: 08 Aug 2011 at 8:55am

Give a Simplicity dealer a call about a pulley.
The Simplicity Power Max 4041 should be the same tractor.

I also think the points run off the cam.
A stuck valve is also common on those older Onan engines.

Posted By: farmtoybuilder
Date Posted: 08 Aug 2011 at 7:56pm

I would say you have other problems on engine! As Jeff said valves! Check compression and if low, pull head off and check-look at valves! Most of those old onans are worn out in these tractors. Pulley shouldn't be hard to fine.

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5 different TT-10's,5 TT-18's Terra Tigers,B-10,2 B-207's,B-110,2 B-112's,HB-112,B-210,B-212,HB212,2 Scamp's & Homilite T-10. Still hunting NICE HB-112 & anything Terra Tiger & Trailers for them.

Posted By: Kid at Heart
Date Posted: 08 Aug 2011 at 8:16pm

I guess I'll call Sandy Lake Implement again and see if I can get the small pulley from them. I already got the big pulley.

FWIW, I stuck my thumb over the plug hole and cranked the engine and it blew my thumb of quickly. It felt like good compression.

Thanks for your thoughts guys.