Engine Timing A042 vrs A042-KM

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Guest 1
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Engine Timing A042 vrs A042-KM

Post by Guest 1 » Fri Feb 23, 2018 8:12 pm

With a recent purchase of a M274A2 with a KM engine SN#KM000054 (early) that has the on engine, hour meter, fuel priming pump, and crankcase breather inlet. Why does this engine have a note in the TM 5-2805-213-14, Figure 3-17, “Turn magneto gear counterclockwise and position magneto gear timing mark two teeth from camshaft gear timing mark”? Did the KM engine originally come with a different magneto?

Research in the -24P dated 13 Feb 1984 it does not reference any (Use On Code) like most other military vehicle TMs. My experience with other vehicles, if there are differences between models, next to the description (parts pages) there is a code, then listed at the beginning of the TM it will tell you which model that part will go on.

The magneto that came on this A2 is a Fairbanks Morse PE1-2B14A1 and has a rebuild tag “DMA Albany”, so I know the Mag was removed at one time, nor do I know if this is the org. Mag after rebuild. With that being said, with no apparent major internal engine differences between the A042 & A042-KM couldn’t you just time the Mag like the late Bill Watson Mag timing instructions or per the TM skipping the note for KM?
Thanks in advance!
W. Roberts
MVPA 1401

muleman7
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Re: Engine Timing A042 vrs A042-KM

Post by muleman7 » Sat Feb 24, 2018 4:28 am

Guest 1

The important setting is the timing while running and all engines were timed at 18 degrees advanced.

The impulse coupler uses a stop pawl / pin and rotates 15 degrees until it clicks [impulses] causing a 15 degree retard at cranking speed.

I initially set the mag so it clicks at 3 degrees BTDC. Then the mag will fire around 18 degrees BTDC while running.

I use a timing light to check and set the mag with the engine running. There is no mechanical advance system for the mag so the timing will be 18 degrees BTDC at any running speed.

I like the mag positioned in the middle of its travel it looks bad at the bottom or top. That is only my choice and has nothing to do with the running of the engine when timed at 18 degrees advanced.

To get the mag positioned at its mid travel point I may have to time it V to V or one tooth off.

I would be interested in seeing mag pictures of your mag drive gear positioning to determine how the gear is set on the impulse coupler then I will compare it to the NOS mags I have in stock.

The other thing to check if you pull the mag is count the teeth between the V on the cam gear and the / mark which is the timing mark that aligns with the crank gear.

Something is different in the KM engine e.g.:

Mag
Mag impulse coupler
Mag gear
Cam gear

To cause the initial setting of the mag gear 2 teeth off from the cam gear on the KM over the V engines.
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Guest 1
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Re: Engine Timing A042 vrs A042-KM

Post by Guest 1 » Sat Feb 24, 2018 7:57 am

Muleman,

I will try and get picture of mag gear posted. Note on attachment below the difference might be the A1 on FairBanks Morse Mag.
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Mule Magneto.jpeg
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W. Roberts
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muleman7
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Re: Engine Timing A042 vrs A042-KM

Post by muleman7 » Sat Feb 24, 2018 8:10 pm

I pulled a number of mags and found FMPE1-2BUs and PE1-2B14A1s

FMPE1-2BUs

Image

Image

Image

PE1-2B14A1

Image

Image

The Condensers above are QX2433 the ones used on the genset FM mags. The QX2433 can replace the original VX2433 but will not be waterproof. The WX2433 usually found in available mag kits do not fit with out enlarging the hole and the hole spread on the mounting flange does not align well with the mule cap.

Image

Image

PE1-2P14A1-1_1 the pic above and below is of different impulse couplers the bottom pic is adjustable and found on 2AO42 genset mags but this one is on a mag with the cap for a mule engine and has a waterproof case not the vented case used on the genset engine.

Image
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