mac-90 bottom drain hole

[taint]

i would like to know if someone knows were to drill and tap a hole for draining access gas and oil mix that collects in the bottom of the crank case on the mac-90. thanks joseph..

 

[Gyro28866]

I have had Macs' on my machines for over 20 years, and I don't know if I have ever seen a drain hole added by anybody.
If the engine will run, then air/fuel mixture is not the issue.
If you have just flooded the engine, while trying to start it. Then, Turn the Mag - OFF; and pull the prop through at least 5 complete revolutions in REVERSE; Then turn the mag - on and see if it will start as normal. If you are having an extreme amount of fuel being drawn into the engine, rebuild the carburetor.
If you have allowed the engine to sit for several months and the 100LL fuel has evaporated and left only the oily residue behind (which gets kind of gummy) and it is causing you to no be able to pull the prop through normally. Feels like it is sticky, pull each plug and squirt a liberal amount of oil into each cylinder, This will lubricate and seal the rings raising the compression ration and will help to start the engine.

 

[Ron Iaconis]

I have had drain holes drilled on the bottom of my 72 and 90 Mac engines,,,,,,,,and had thought that I needed to drain the crank case when ever I flooded my engine,,,,,,but as the previous post stated,,,
pull the plugs, squirt oil into the cylinders, and this will sufficiently raise the compression, and even then after the prop has been pulled through several times to get the oil to sufficiently coat the jugs, then maybe squirting some fuel int the jugs and your engine should fire up. If you have spark, timing is at about 20-21 degrees before TDC, and you got fuel,,,,she will fire up ......IF,,,,,IF........the jugs are oiled up and the compression is sufficient.

 

[taint]

Red who rebuilt the engines at R and D always put drains in these engines due to over time old gas and oil build up .

 

[Ron Iaconis]

You don't need the drain holes

 

[Brent Drake]

Ron is right. It doesn't need a drain hole. It should have a small copper tube that runs back up the side.

If you think it needs a drain hole. I'm thinking you have it flooded or using way to much oil.

 

[dabkb2]

the tube that runs up the side is only on the supermacs

 

[Gyro28866]

Thanks Dave:, I was going to ask What tube?, I have never seen one on of my Mac engines.
Twice, in the last twenty or so years, I have encountered a "sticky" engine, after it had sat for an extended period of time. I realized it was the 2 cycle oil residue left behind after the 100LL had evaporated. I simply pulled the plugs and squirted some regular motor oil at the top of each piston and pulled the engine through a couple of times to coat the cylinder walls and rings. You could feel the difference after the first complete revolution. Put the sparkplugs back in, and she fired right up - as normal. The oil lubricates the walls and rings, and helps seal the rings to create more compression. Higher compression will help tremendously to getting her to fire up.
.
If you have a FLOODED engine.
Turn the Mag Switch - OFF
Pull the Propeller through at least 10 pulls ( 5 complete revolutions) BACKWARDS
Turn the Mag Switch - ON
DO NOT give it any THROTTLE. The accelerator pump is only going to give it more fuel, and she is already been flooded.
You are trying to dry her out!
Prop it as normal, she should at least - Pop; because the air/fuel mix is getting close.
Then is should fire right up.