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AC 312H front electric PTO

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Has anyone found a replacement for the front electric PTO for

the AC 3/400 or AC built Homelites?

I followed the link in the Tech-resources section


but its still a little greek to me...

what are the current solutions... I spoke with someone a few

months ago that gave me the impression that I could just

go buy a new one... and that he had purchased one recently

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I have never been inside one of these...

is the magnet part the "wear" part...

such that it would be a good idea to replace it

before it goes or.... any suggestions on good

preventative maintenance?

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Chris,Here's a shot at Homelite/AC "electric clutch 101". A schematic of the clutch:

PTO PartsSchematic.JPG

A pic of the clutch mounted with the replacement coil assembly ("magnet") part #5:


The only pic I have of a "disassembled" clutch:

Old clutch.jpg

To me, there are 3 main parts of the electric clutch:1) The coil assembly which is stationary and is mounted to the engine block. The old style (as pictured in the parts schematic) used a "formed" mounting plate that placed the coil at the proper distance from the block. The replacement coil assembly is mounted on a flat plate and uses spacers to position the coil at the proper distance. It is the part laying flat on the ground in the third pic.The second two parts rotate: 2) A heavy circular piece that is keyed to the engine shaft and slides over the coil assembly (with a close fit). It has a "nose" that inserts into the other rotating part. This part is shown on the parts schematic "sitting" on the coil assembly. In the third pic, it's the part on the right side of the combined rotating assembly that's "standing up". 3) What I call the "pulley assembly":


It consists of a formed pulley, a bearing cup, bearing, 3 "fingers", and the "pull-in" plate. The bearing is common and easily replaceable once you get the "pulley assembly" off of the other rotating part. My first clutch failure was the coil assembly. The mounting bolt (part #1) had fallen out, and over time the rotating assembly rubbed on the wiring and shorted them out. Bought a new coil from Simplicity, made a spacer (part #4) and I was back in business.Second clutch failure was in the "pulley assembly", a "finger" broke, due to one or more of the rivets holding the fingers to the formed pulley failing:


After some dis-assembly:


I fixed that failure by making a "finger" out of a hacksaw blade and putting it back together as best I could. I did notice that the formed pulley bolting area was in bad shape, the holes were elongated and cracks were starting to form. The third and final failure was too much cracking/hole elongation in the formed pulley. The unit wouldn't stay concentric - there was rubbing and the clutch wouldn't stay "pulled in".



After the second failure, knowing the days were numbered for the clutches rotating assembly, I started digging for info on the clutch. Someone at Simplicity in Port Washington led me to Warner and Dick Hall. With his help I got a "new" style electric clutch that would replace the one that was sure to fail. Here's it shown mounted on my "16GTH-L":


Then I found this club, the wealth of info available here, and used parts availability, especially on eBay. I picked up a spare clutch, so when the third failure occurred (took several years), I installed the used rotating assembly on my Homelite. Only downside to finding this club, was I was infected with tractoritis causing the acquisition of the 17GTH-L with blown engine, hence the installation of the "new" style clutch on it. As to "preventative maintenance", IMO, there's not to much that can be done. Foremost is to be sure the main bolt is installed keeping things tight. You can replace the bearing if it's noisy, or "just because". Others have re-potted the winding in the coil assembly, especially the open face to minimize the chance of shorting (over time, the potting compound dries out and falls off). Best is to buy a used spare and have it available. If you take the clutch off, it's best to leave the coil assembly attached to the block, avoiding alignment on reassembly. The coil assembly and the rotating assembly must be concentrically aligned. The trick to doing this is the use of a plastic shim that you wrap around the field coil, then put the rotating assembly over the shimmed field coil and tighten the field coil mounting bolts. If you don't use the shim, it's almost impossible to align the parts to prevent rubbing. The plastic shim was provided with the replacement coil I purchased from Simplicity. You can see some of my notes on the parts schematic. BTW, one of the advantages to a the new style clutch is there's no alignment. The clutch comes in a single "connected" stack that you mount on the engine shaft. Only a small finger from the block is needed to prevent the stack from rotating. Two bearings are used. Here's a .jpg of the 5215 new style clutch:


For anyone interested, I have a .tif of the clutch for better clarity (too big to upload).











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OK, now ive had a chance... I "think" I may some clue here....

I have another question or 2... the "new style" replacement replaces the rotating parts AND the coil? I think I am understanding that the new style is a good replacement but requires spacers and would not require alignment?? now i think im seeing you went from 4 bolts to the 3 bolts on the new clutch using a round plate you made?



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Chris,The "new style" electric clutch replaces both the stationary and rotating parts of the old style clutch. It comes as a self contained unit. It does not require spacers and does not require the "concentric alignment" of the old style 2 piece clutches. It does need a "stop" or "finger" mounted to the engine block to prevent the entire clutch assembly from rotating. The "finger" inserts into one of the 3 oval slots in the triangular plate. It can be seen here in the 1 o'clock position:


I did not make any "round plate" for the new style clutch installation. The black round plate in the pic is part of the engine, I believe it's the plate that holds the front crankshaft bearing. The "spacers" are required for the old style clutch setup when you replace the old style field coil ("domed" mounting plate not shown in any pics) with the replacement field coil. The replacement style field coil is shown in the first and second pics above. The spacers can be seen in the first pic between the field coil plate and engine block. 4 spacers are required to set the field coil in the correct axial position relative to the rotating assembly. (The rotating assembly axial position is set by the position of the "step" (diameter change) on the crankshaft stub.) 4xbill,I put a post in the tech tips section with a link to this post. Best I can do to get it "recorded" in the tech tips section.


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Help me to know if I am understanding this correctly...The original clutch had 4 mounting holes which 4 bolts held it to the engine block. The new clutch has 3 mounting holes (maybe these are not mounting holes).It was just luck that there were threaded holes in the block to accomadate the new 3 mounting hole clutch ... OR...there is no bolting to the block... just the one point "finger" attachment that prevents the "coil" portion from rotating?also, you mention the axial position is determined by the change in diameter of the crank.... the 3/400 are Kohlers...I didnt think the crank was tapered on that end...or am i still misunderstanding somethingyour earlier diagram seems to show the same thing...the clutch on the blunt untapered end...

crank jpg.jpg


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I used one of the four mounting holes (for the old style clutch) to bolt the metal "finger" I used to stop the new style clutch from rotating. My basis for selecting the hole was how the wire from the clutch was positioned; you can use any of the three holes. The block holes do not line up with the three holes in the new style clutch. The "finger" is "L" shaped and was custom made.The new clutch assembly is axially positioned on the same crankshaft "step" that positioned the old style rotating assembly. The crankshaft of the Briggs is not tapered but has 2 different diameters. Without the "step" the clutch (or a standard drive pulley) would just slide down the crankshaft and hit the engine block. The "step" is visible just after the keyway ends in this Briggs crankshaft parts pic:


The rotating assembly is firmly bolted in compression on the crankshaft - one end of the assembly against the crankshaft "step" and the other end held by the end washer/bolt combination. The position of the crankshaft "step" and the design of the clutch together set the position of the clutch drive pulley in relation to the tractor frame. If the "wrong" clutch is used, even though it would bolt up, the relationship of the drive pulley to the idler pulleys would not be as designed. This could cause belt rubbing or premature failure. The further away from design position, the greater the risk of failure.


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Does anyone know the length of both the briggs and kohler pto shaft

from tip of crank to "step"? Id hate to remove the clutch just to measure as my clutch is working ... just noisy...

and are they the same diameter?

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For a 16HP single cylinder Briggs, the distance is about 2 11/16". The shaft diameter is 1".

I haven't seen many Kohler engines, and done from the A/C 300 and 400 series vintage. The Kohler engine in a A/C 712 has a 1 1/8" diameter shaft; don't have the distance info.

Stan D,

I bought my new style electric clutch from J Thomas. They were recommended to me by Dick Hall at Warner. I agree with your opinion.

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I have taken one of these clutches apart, its very easy.

I was plowing snow and I heard a funny noise from the front of my 416. I said to myself "I'll finish up and then I'll check it out." Two minutes later all censored1.gif broke loose and I picked up two very large pieces off my driveway. Nothing to it! I'll find a few more on the lawn this spring.

So much for attachments driven off the engine for awhile...

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