Crankshaft Taper

[dwhitford]

I pulled off my ol' Looper flywhell hub yesterday for use on a new project. It came off easily, even though it had been on the crankshaft for 48 years. The reason is because it went onto the crankshaft totally dry . . . even though the flywheel hub itself had a patina of rust on it from many years of less-than-pristine storage.

I know that most Stock & Mod racers nowadays need not pull flywheels often for servicing points (or whatever .. . . maybe Y 102 owners ?), but here I'll offer a hard-won tip: Always lap in your flywheel to the crankshaft taper every time you have the flywheel off. The heavier your flywheel is, the more important is this procedure, to prevent galling of the crankshaft-to-flywheel interface. This can be ovedone' obviously, when the lapping finally results in too low a flywheel mounting (Not ever bloody likely!).

Here I'll add that it's never the crankshaft key that prevents a flywheel from spinning on the crank. It's instead the close (lapped-in) fit of the crank-to-flywheel tapered interface. The crankshaft key is merely for timing the ignition.

I use a two-can product of lapping paste that I bought as "Clover" brand 40-50 years ago for lapping automotive valves. One can was for "Coarse: and the other for "Fine". Obviously I used them in the correct sequence. If you can't find Clover brand, I'm sure NAPA can supply an equivalent product. Lapping the crank-to-flywheel interface takes only 15 minutes and is golden time well spent.

Be sure to re-assemble the crank-flywheel interface totally dry, hosed off with brake cleaner or lacquer thinner beforehand. The last thing you'd ever want is that interface to spin on lubrication! -- d

[KURPS]

I have a totally different point of view from running Konigs, never lap in a flywheel to the crank taper. Scott Smith said Konig did not recommend it. Konig's flywheel does not have a key. Instead, scratch lines into the taper to help "grip" the flywheel and to prevent slipping. Worked for me.

[KURPS]

dwhitford, that was 40 years ago! I do remember helping a racer on the highway to Winona, but didn't remember what was the problem.
I had a used Konig that I lapped the flywheel to the crankshaft taper, and it would slip timing until I added the scratches to the crankshaft. It never slipped after that.

[ZUL8TR]

Interesting on the scratches and the timing process. Some idea of how deep these scratches were and did you use a straight edge rule or free hand with what kind of tool? Did Dieter do the scratches at the factory and recommend re-do the scratches if the flywheel was pulled?

[KURPS]

ZUL8TR, I never seen scratches on a new Konig crankshaft. I did the scratches the full length of the flywheel, and about 1/8" apart. I used an hand scribing tool with a carbide tip, all done freehand.