Maytag 72 (Twin) Main Bearings

[John Newman, Jr.]

With the recent postings regarding Maytags, I dug my 72 out and decided to get it running again. Mine has a Wico mag and originally had an aluminum tank with no mounting holes (must have been a 'Hanging' motor). I now have a cast iron tank with ears on it that I picked up at a show a few years ago. It had a clogged pick-up tube and / or check valve. Got those cleared and tried to fire it up. I could get it to sputter a few times with the pedal but not much more, so I cheated a little and used an electric drill to spin it. Got it to fire and with a little air tube cap adjustment I got it to keep going on its own. However, I noticed that I was getting a spray pattern on the floor in line with the starter end of the block. By holding my hand over the end of the block I could feel pulses of pressure from blow-by. I shut it off and checked for play in the shaft. It has enough that I am sure this is the reason it doesn't run smooth or seem to have much power (even for a Maytag) It also makes an occasional clanking sound. Possibly the flywheel end moving enough to be hitting something. I know that it now has to come completely apart and these bearings replaced. Are they available as reproductions from anybody, or am I going to have to make them? Anybody done a bearing job on one of these that can offer any tips?
Thanks,

[KeithW]

I pressed the old one out and turned a new one on the lathe out of bearing bronze, not Oilite. As I recall there is an O-ring in there also, standard size available at the hardware store.

keithw

[Bill Geyer]

Hey John,

I'll bet some of the sponsers have a bushing, if not Bobs Small Engine will.
319-377-3339. Never have had a 72 apart, only ignition, and carb work. Bought the bushing from Bob for my 92, it was on the starter side and easy

Good Luck,
Bill

[KeithW]

A pre-fab one would be easier. I just have this weakness for making bushings for some reason.

keithw

[BWegher]

There is a seal, called an oil retainer in the service manual, Maytag part number 14452. Also check the tank vent hole, just below the set screws on the air horn base. The vent is small and often plugged.

[BWegher]

Also, as for the clanking, the governor screw and the dummy screw may be hitting the inside of the crankcase. There is very little clearance. Open the access plug on the top of the crankcase and rotate the crank slowly by hand to see if there is clearance. They can work loose, so just screw them both down until they are flush with the surrounding crank bosses.

The worn bearings would make this an opportunity to do a full overhaul.

[Andrew Mackey]

there is no physical seal for the crank on the 72 series. The part referred to merely keeps oil that has seeped past the bearings, from dribbling down the side of the engine. It acts as a dam, and lets the excess oil seep back into the bearing. There are actually 4 main bearings on the twin. Two behind the flywheel, in the removable crank cover, and 2 by the starter - one inboard, and one outboard of the crankshaft timing port.
If the bearings are worn to the point of spitting fuel, I would check the rod big ends, and the wrist pin ends as well. The rods are made of gunmetal bronze, and can wear excessivly if the crank is wobbly. Check the mag armature as well - if the crank gets too loose, it will cause interferance fit between the mag core and the magnet on the flywheel If this gets bad enough, it can cause the mag core to be busted off the backing plate When doing main bearings, replace ALL of them. If you do not, the new ones will be wiped out in a hurry. Larry Simpson, of Simpson's Motors used to carry the mains in stock. I do not know if he still has them, but he can give you their dimensions.
Andrew

[John Newman, Jr.]

Well, I got my Maytag torn down and it is worse that I first thought. Both of the rod big ends are very sloppy on the crank. What can I do about them, since there are no inserts that I can replace?
I was about to start making a stepped pin to press the main bearings / bushings out, but it was getting late and I was getting hot & tired, so I put it on my mental list for tomorrow.
...More news as it develops....

[MarylandSteam]

Measure the crank/piston pins and the rod bores and post the measurements, did it knock at all when it ran?

Generally filing or machining some material off of the mating surface between the cap/rod is the way to go but only do a little at a time, and hand fit, if the fit is too tight there won't be clearance for oil and it will heat up and seize when running...

same for the main bearings, they will need to be broken in, run for a while then cool down, run again, then cool, etc for the first couple hours of running and if the case gets hot where the bearings are or the engine sounds like its under load shut it off and let it cool before kicking again, also use extra oil for a while (plain sae 30 non detergent).

Here is some info if you decide to make them http://www.maytagshed.com/fscbush.html he also sells them for $15 each http://www.maytagshed.com/forsale.html

[BWegher]

On several Maytags and Briggs, I've filed a rod cap about 50 thousanths. Assemple the cap, mount in a machine vise, then use an adustable chucking reamer. This will allow you to restore the original spec on the rod, assuming no changes to the crank pin.
I believe the Maytag service manual also states that the rod cap bearing has extra material to permit reaming and hand fitting to the crank pin.

[John Newman, Jr.]

Finally got around to pressing the main bearings / bushings out. They are both one piece. The starter end one is worn the worst. I.D. is not round and checks from .885" - .888". Flywheel end is round, but checks .883". Crankshaft checks good, with the flywheel end being ever so slightly out of round - checks .8725" one way & .873" the other" (Am I nit-picking?) The other 3 journals are all nice and round and all check .873".
Have to see if there is anything in the budget to buy new bearings, otherwise I might have to make some, but I won't be able to cut the figure '8' oil grooves in the flywheel end bearing like the old one has...

[KeithW]

I used my air powered die grinder (dremel style tool) with a small tip to gring the groove. Not a pretty as the original but functional.

keithw