'72 engine bolt into my '81 Special II frame?

khanawalt

I think I have a bad main bearing, and found a 72 engine. I'd rather have an '80-'83 engine, but I can get a 72 pretty cheap. Will it bolt in? I know I'll have to either swap to points or figure out how to retrofit my electronic ignition to the old engine, but that's the least of my worries.

I just want to get my twin back on the road.

Thanks!

grizld1

It'll bolt right in. The ignition swap isn't a big deal. Just use the rotor, stator, etc. from your current engine. You'll wind up with a slightly hotter cam with the '72 mill, but mind the redline; it'll have the old 22mm wristpins that left the small-end of the rod a little less hefty than the ones in later designs.

khanawalt

It runs okay, but it seem pretty noisy, although it's not as noisy as the original engine was. But it does seem noisier than the original was 9,000 miles ago. Oh well, no guarantees on ebay. It runs, and they said it runs.

It does seem weaker down low, but it has at least equal power after I get it revved above 5K or so. I guess that's the price of a hotter cam, eh? I would be happier with the later cam for more low-end since I don't race the thing, but at least it's back on the road now.

Thanks for the help!

grizld1

There's not enough difference in the cams to make a big performance difference. Timing or carburetion might be responsible. If you're getting a bunch of engine noise, a loose cam chain could be the source.

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