maytag 72D ignition timing

[KeithW]

I just got my Maytag 72D twin cylinder running. Does anyone know what the ignition timing should be set at. I've got it about 15 degrees BTDC and it seems to run pretty well. Belted it up to an old Datsun alternator. Big pulley on the motor so the alternator spins about 4000 rpm. Varied the field current to load down the motor. It'll charge a car battery at about 1.5 amps with the Maytag running between 900 and 1000 RPM. Anyway, it's noisy, smells and is a horrably inefficent way to charge a battery, so, what's not to like about it!
keith

[Andrew Mackey]

The tiiming is set automatically, if the ignition plate is installed properly. There are 2 tabs of aluminum, cast into the ignition plate, that straddle a cast iron lug on the engine base, that sets the timing. If the tabs are broken off, approximately 25 to 30 degrees advance is close. I have a model 72-D that I have belted to a GM 45 AMP 12 VDC alternater, with remote regulater. I start the engine, push a button to initialize charging, and the engine - alternater set up will put out 15 amps. If the battery is really down, the engine speed will fall off, but the alternater will maintain the 15 AMP draw. Eventually, as the battery charges, the AMP rate will fall off to nearly zero. It takes about 2 Hrs (a tank of gas) to fully charge a battery. The pully ratio is 1 : 1, that is, they are both the same. Engine RPM - 1150, as set at the factory The Alternater is from a Corvair automobile. The Alternater and Regulater were purchased from an auto salvage yard for $25.
Andrew

[KeithW]

Thanks,
I found the lug on the cover and the remains of the tab on the backing plate. I'll reset the timing and try another load test. It seemed like it should have beem making more power and the timing being late could explain it.
Alternators like to spin fast and are more efficient at higher RPM. You get more output for the amount of field current at higher RPM.

keith

[KeithW]

Hello all,
I reset the timing. The lug and tabs line up at 25 degrees BTDC. It is making much more power.
Thanks,
Keith

[KeithW]

Hello all,

Well, with the timing set properly it makes more power but I can't seem to pull more than about 3 amps out of the alternator. That's about 45-45 Watts. The 72D is supposed to be 5/8 HP which is about 450 Watts. Even allowing for various inefficiencies that seems pretty low. Seems to run fine, just not making much power. One thing I didn't do when I went through it was to replace the rings. Anybody ever run a compression test on one of these? What should I expect?

keith

[KeithW]

Hello all,

Did a compression test. 55 PSI dry, 100 PSI wet. New rings are on the way. Does anyone know what the piston to wall clearance should be?

Thanks,
keith