Install Flywheel and Blower Housing

Installing the flywheel is a simply matter of sliding the flywheel onto the crankshaft and aligning the keyway with the flywheel key. Until I verify that I have spark, I usually don’t thoroughly tighten the flywheel nut. If I have to trouble-shoot an ignition problem, I’ll just need to remove the flywheel again. For a spark test, we only need the flywheel nut “slugged down” enough to hold the flywheel in place.
After installing the flywheel it’s time to check to see if we have spark. If everything was done correctly, and all parts are functional you should be able to flip the flywheel by hand and observe a spark. This is a setup I usually use to test to see if the ignition system is operating correctly.

You should not need to vigorously spin the flywheel. A quick flip by hand should generate a spark in ambient air.

For this test I've connected the spark plug wire to the top of the plug and I've rigged a wire from the engine block to the base of the spark plug.

click the picture to play the video
Now that we’ve established that we have ignition, we can snug-down the flywheel nut. Keeping the crankshaft from turning while you do this is a topic that has been discussed many times, and there are many ways to do this. My way is rotate the engine to bottom-dead-center, stuff a couple rags into the cylinder, and then bolt the head down with a few head bolts (no need to thoroughly tighten). You can now snug down the flywheel nut without the crankshaft turning, and you don’t take the chance of breaking flywheel fins by “chocking” the flywheel from movement. Lauson calls for this nut to be torqued to 35 foot pounds.

If you don't have a torque wrench, once again, “Gort the Gorilla” doesn’t need to make his appearance here; a tapered crankshaft with a well matched flywheel will mate properly without the need for your eyes to bug-out while tightening the flywheel nut. Take a moment to wipe the mating surfaces clean before assembly to assure a snug fit.
Once the flywheel is installed you will want to attach the starter pulley to the flywheel. It’s much easier to do this now, before the blower housing is assembled to the engine.
Now that we have confirmed spark and have the flywheel attached, it’s time to bolt down the cylinder head. Often an old gasket is serviceable, if not you will need to have a custom replacement made. New Lauson head gaskets are not available and NOS Lauson gaskets are very rare. I’ve used Gaskets-To-Go with success if you don’t mind waiting on shipping from Thailand, and they should have several of my head templates by now (no, I don’t personally know them or get a “kick-back” for this reference).

When you get to tightening down the head bolt nuts, once again our friend Gort would be an uninvited guest. Lauson calls for these nuts to be torqued to 12 to 14 foot pounds. Without the use of a torque wrench, you really only need to snug these down firmly, run the engine a few minutes, and then go around them one more time. Tighten side-to-side, diagonally across the head to spread out the pressure. Tighten all gradually by visiting each bolt numerous times and keep repeating your bolt tightening pattern until the head bolts will no longer turn under moderate pressure or your torque wrench reads appropriately.
Assembling the blower housing to the engine can have it’s own set of problems. Often, the threads on the magneto plate have been stripped by Gort, the overly enthusiastic repair person and this will need corrected before the blower housing can be firmly attached. I haven’t found an entirely satisfactory way to “fix” this yet, short of replacing the magneto plate. There doesn't appear to be enough "meat" on the mag plate to re-thread with over size screws, but then I haven't tried this either. I’ve attempted fiberglass repairs as well as JB Weld repairs with subsequent re-threading of the holes. Both seem to work fairly well as long as I remember that the magneto plate has been repaired and I can’t snug the blower housing attachment screws down as much as I normally do. Fortunately, this engine does not suffer this problem.

The flywheel is positioned very closely to the front of the bower housing on this engine and a short screw must be used at the bottom front in attaching the blower housing or the flywheel will drag on this screw. The stock parts used here were slotted head screws.

Sometimes you’ll find that the blower housing has been bent and deformed to the point where it will rub on the flywheel. It can usually be bent back into correct shape again by resting it over various surfaces of different flat and curved contours and hammering the bends and dents out. Holes can be repaired with body putty and/or fiberglass. With these type of repairs you want to strive to keep smooth flowing lines inside the blower housing as well as out. You want smooth lines outside for aesthetic appeal; you want smooth flowing lines inside to promote air movement for engine cooling.
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