Crank Question -WTF?

I have been assembling parts, cleaning parts, painting bits, and buying stuff in preperation of finally getting the 850 back toward being a motorcycle instead of a pile of pieces.

I did not notice this until I reassembled the crank. These photos are not opitical illusions, they are shot from dead overhead the flywheel. Notice that the flange for the journal on the left (drive side) is almost completely visible. It is completely seated and torqued. The cutaway in the flywheel is that much deeper on that side. Is this normal? Common? Unheard of? What's the deal with that?!!!





It is going into the cases today regardless. It just struck me as odd. At first I couldn't understand why I couldn't get that side to seat properly until I got some light in there to see that it was seated!

Russ

Well they are not all that way but I don't think it will make any difference.
I just looked at two on the shelf and they are not perfectly centered but they are not off as far as yours is.

Nice to know I am special. After stewing about it I decided there really wasn't any harm in running it like this, but it really did raise my eyebrows when I first realized that everything was home and it was that far off. I have to wonder if there was a casting defect that needed to be ground out, or maybe Albert ground one side before lunch and did the other after his lunchtime pint!

Russ

Very possible. Or maybe he fell asleep on the handle after a hard night before. :?

I could be way off base on this, but wouldn't the off set put more force on the right bearing and maybe cause more or odd flex of the crank at higher RPM?

I checked my spare, it's eaven. It looks as thou yours has one side of the flywheel indent area deeper than the other. This should have minimal if any effect on things.

If spins free mounted in cases and rods end up centered in bores then it'll fly. Might be worth measuring run out when installed and easier to do. A few 1000ths is ok under redline. Glad it ain't mine this time, so thanks for that.

I seem to recall the flywheels were handed or at least that is how the manuals said to handle them. Marking the flywheel so the timing side would return to the timing side and so forth. If I were rebalancing I would not sweat it but a simple rebuild and it can make a difference.

I never saw an offset like the one you are showing. If it were anything but street riding I would replace the flywheel with steel equivalent.

If there's no gaps, everything is buttoned up tight and as mentioned before, it spins freely in the cases it will work.

Dances with Shrapnel said:

I seem to recall the flywheels were handed or at least that is how the manuals said to handle them. Marking the flywheel so the timing side would return to the timing side and so forth.

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I believe this is correct, the flywheel should always mate to the proper cheek and the purpose is to maintain the original configuration as was balanced from the factory. I'd mount the rods snugly but not torqued so the nuts are re-usable and then check to see if the fat part of the flywheel looks centred between the rods as Hobot suggested. It is possible the flywheel should be flipped. Are the flanges on the cheeks the same thickness?

I made sure it went back together in the same order it came apart. The manual says something about marks but I can't say I found any. I just scratched a small "T" on the timing side so I could keep track of it.

Russ

Looks like the counterweight is in the middle its just the journal end thats poorly machined -I wouldnt worry about it, However My first 750 had a slightly lighter crank as standard (1971/2 750 interpol poss converted combat motor came from police with new crankcases) and it snapped at drive end so please check drive end radius. I got bike direct from police and it was training school bike with 15k miles from new so crank snapped at 20k miles, I suspect new crankcases were due to main bearing failure spinning mains in case.
Anyway back to the point - crank was lighter than standard and the journal end of the flywheel was machined thinner on both sides possibly to recover balance factor.