AO42 Mule vs 2AO42 Power Plant Engine Differences

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13bravo
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Re: AO42 Mule vs 2AO42 Power Plant Engine Differences

Post by 13bravo » Mon Sep 28, 2015 8:20 am

Another manufacturer for rings that will do custom sets for decent prices is Hastings rings. I had to order a set of rings for an odd single piston compressor for a guy and they did it no problem, fairly fast and pretty reasonable.

Chuck W.
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Re: AO42 Mule vs 2AO42 Power Plant Engine Differences

Post by Chuck W. » Tue Dec 01, 2015 3:37 pm

Charles, did you ever figure out if there is an off-the-shelf ring set that will work in the AO-42 engine? Also, do you rebuild the cylinder heads or replace with new? If you rebuild, do you grind the valves and seats (what angle?) or replace? I'm thinking a motorcycle shop might be the place to have the heads rebuilt. Thoughts? Thanks!

muleman7
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Re: AO42 Mule vs 2AO42 Power Plant Engine Differences

Post by muleman7 » Tue Dec 08, 2015 5:02 pm

Chuck

John Emery has the AO42 Ring Set [6pc]. I have not tracked down the Perfect Circle Ring Sets that I used for the Mule piston. If I have time this week I will try to get the #s. I have a valve grinder and grind them at 45 degrees. If the seats look good I lap the valves and checked the contact area. Remember the engine uses a valve Rotator and this could aid in reducing uneven wear for the Valve and Seat. Any head that dropped the Exh Seat I discarded since there is not a lot of room to install a new seat and the expense could be prohibitive. Saturn Surplus will sell new Int and Exh valves but they are the 2AO42 {short stem] and the copper head spacer should not be used.

I discussed the differences in Horse Power ratings 10 Hp for the 2AO42 Power Plant and 14 HP for the AO42 Mule with an engineer. His explanation was the Power Plant had to be rated for 100% usable HP since it is figured at a constant load and RPM. Thus the manufactures could fit the correct engine to a generator, water pump or Etc and qualify it to operate under constant load. The Mule ran at varying loads and RPMs and its Max HP is listed. His conclusion was the mule could not deliver 14 HP constantly and survive.

The Carbs had to be different because the Mule required an Accelerator Pump to richen the fuel mixture upon acceleration. Remember they both are 42cu inch displacement and the 2AO42 runs a higher compression ratio.

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Re: AO42 Mule vs 2AO42 Power Plant Engine Differences

Post by Williamson » Thu May 18, 2017 5:00 pm

My Mule must have a gen set engine, I was trying to check timing on the magneto, and found it didn't want to indicate when they points open. On removing them mag. I found it to he a solid state magneto. I put it in the e gap position, and lined up the timing marks on the gear, which seems to coincide with the timing marks on the belt cover.
I replace the mag. In the same position as I removed it (marked it before removal). Engine won't start, and has every symptom of being grossly out of time.
Any idea's about what might be the issue. I used the left cylinder as viewed from the rear to set timing.
Thanks,
Dale

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Re: AO42 Mule vs 2AO42 Power Plant Engine Differences

Post by Williamson » Thu May 18, 2017 5:06 pm

My Mule must have a gen set engine, I was trying to check timing on the magneto, and found it didn't want to indicate when they points open. On removing the mag. I found it to be a solid state magneto. I put it in the e gap position, and lined up the timing marks on the gear, which seems to coincide with the timing marks on the belt cover.
I replaced the mag. In the same position as I removed it (marked it before removal). Engine won't start, and has every symptom of being grossly out of time.
Any idea's about what might be the issue. I used the left cylinder as viewed from the rear to set timing.
Thanks,
Dale


muleman7
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Re: AO42 Mule vs 2AO42 Power Plant Engine Differences

Post by muleman7 » Thu May 18, 2017 5:42 pm

Dale

If you have an inductance timing light [clips over a standard ignition wire] then:
1-remove the ignition lead from the blower side plug
2-insert a standard spark plug lead [I use ignition wire that has metal [solid core] instead of the carbon core. it makes connecting to the spring end of the Military cable end easy.
3-insert the standard lead with a small amount of the metal core exposed and a distributer boot to hold it in place into the spark plug.
4-strip about 1 inch of the outer jacket from the metal core and wrap it over the spring on the end of the military cable.
5-clip your pick-up onto the standard lead to check timing.

both plugs should fire on each revolution 1 on compression and the other on exhaust then vice versa.
I would set the V on the Mag gear tooth in line with the V on the Cam gear root and the roll pin should be at 9 o'clock.

Timing with the engine running should be 18 degrees advanced.

I have a unit and will check the gear to see what you mean by the e gap position.

On the regular magneto there is a line stamped into one of the tangs on the impulse coupler that drives the gear and that must line up with the tooth and not a root of the mag gear.

I have not used my solid state magneto in the last few years. But I hear that they are not reliable but it had not failed me when I pulled it.

Grossly out of time could be the mag gear is 180 degrees off. Remove and change.

I will post tomorrow when I check mine.
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