crankshaft assembly

katescottageiom · Oct 31, 2007

I have a '73 750 motor that I plan to install in a '69 frame as I endeavor to keep my promise to my soon to be 16 year old son, however, when I disassembled said motor about 1978, I neglected to mark the flywheel for proper reassembly. Is there any way to reestablish the correct side to bolt the cheeks to?

Keith1069 · Nov 1, 2007

KC
All you can do is try and check for any matching witness marks where the cheek faces contact the flywheel. You never know there might be something that matches up, depends if they've rusted over the years.
I'd go for under the dowel hole area. Good luck.

dave M · Nov 1, 2007

Just put them back together any way and then send the crank for dynamic balancing, you will be pleased with the results.

JimC · Nov 1, 2007

I definitely agree with Dave. That's the best $75 I spent on my Norton.

Ron L · Nov 1, 2007

Yeah, put it together with new studs and get it dynamic balanced. I'd do this even if I did know how it went together. In fact, it wouldn't be a bad idea to have it magnafluxed while it is at the crank shop. Better to know about any problems before you put it in the crankcases.

katescottageiom · Nov 2, 2007

Thanks guys, will do.

hursty · Nov 4, 2007

Hi,

I would also recommend the dynamic balancing.
I have had this done on three of my Commando's so far with the standard 52% balance factor for Isolastic frames & 77% balance factor for non Iso frames with great results.

teeb · Apr 28, 2008

Crankshaft assembly - which way round does the flywheel go?

Evening all.
I was putting together a list of engine parts I need to put my engine together and noticed I didn't mark the flywheel assembly direction many years ago.

Someone suggested looking for witness marks and I found that there are burnt on oil stains on the mating surfaces that would tell me which way 'round the flywheel goes.

Then I noticed where I used a center punch to mark a 'T' on one side of the outside flywheel surface

roll: ) and this agreed with my rochart 'oil' blot test.

I also found that the flywheel is machined differently on the timing and primary side. Check out these pics.

So the flywheel does have a timing side and primary side.
Anyone have a 850 crank handy to verify this?
How about a 750 crank to check if it is the same?

katescottageiom · May 5, 2008

Checked my '73 750's flywheel:
Timing side step depth-5.6 mm
Drive side 3.9 mm

I also seem to have painted the timing side with battleship grey paint and I am sure now that I did it to mark the timing side.
Very astute of you teeb. I am also going to send it out for a dynamic balance and rod polish. Luckily, I have trusted local craftsmen, do do the honors.
Jerry