Discussion in 'Norton Commando Motorcycles (Classic)' started by swooshdave, Aug 17, 2018.
Good catch on the journal bearings!
Yeah, I’ll measure. Anyone want to take bets on the size?
1.75 so standard, correct?
I marked everything! Glad I got the Dykem pen in my stocking!
Very light scoring on the bearing. I can feel it with a fingernail.
And of course, the money shot.
So definitely bearings, con rod nuts, and I'll just get the crankshaft bolt and nut kit. Can I just leave the con rod bolts where they are?
Crankshaft is at 1.75. Is undersize at 1.74? I'll have my mechanic mic them and give me the actuals as the HF tool might be off. My money is still on that they are standard.
Revised shopping list.
Swoosh, the ‘correct’ answer is that ‘thou shalt not’ re-use con rod bolts etc.
But back in the real world (now I’m gonna get shouted at too), if it’s a low use / low budget build, I would re use the con rods bolts. Even more so, I’d re use the crank bolts (some folk reckon the originals are better than the new ones anyway).
It certainly looks like a good bottom end you’ve got there and it’s a good job you split that crank to clean it!
I would urge you to polish the big end journals with very fine emery.
There is a school of thought that says re use con rod bolts as they have been tested and new ones have not
I'm sure there are many opinions on this
Reuse of bolts is fine, new nuts though. Worth checking under the head of the bolt for a sharp edge left from the machining and polishing/filing it out, this can lift a piece of aluminium from the rod and trap it under the bolt head making torque figures wrong and risking a nut loosening off.
For a US order the VAT should drop out at checkout.
But do I even need to take the bolts out of the rods at this point? Just pop in new bearings and apply new nuts.
VAT will come off but I’m still waiting from AN for a shipping estimate.
I knew the bottom end was solid which is why I was so hesitant to pull it apart. If you ever just felt the parts were perfectly fit and taking it apart could just make it worse?
I’ll look at the crank bolts. They were all well staked and at least one is toast.
Why hit the journals with emery cloth? Do they need a rough surface for the new bearings to bed into like a hone on a cylinder?
The journal polish is to make the current surface less rough than it is not rougher as you do with a bore, you will use a fine emery cloth. It was the last operation on the journal when I worked in a factory producing crankshafts after final grinding.
The journals weren’t recently ground, just broken in so the surface is immaculate. I would be very hesitant to touch them.
They will have been polished by the shell bearings, so leave well alone if immaculate.
Agreed. I’d normally expect to see some evidence of slight wear and that’s what I’d polish off in order to protect the new shells as any slight wear on the journal will accelerate wear of the new shells. But, if they’re really immaculate, then leave ‘em alone.
I’ll have my machinist look at them to give me a expert opinion when I pick up the cleaned cases. He builds race bikes all day long.
He couldn’t understand how the other set of cases had dirt in them. I had to explain with vintage parts you never know how long or where they’ve been in the last 50 years. He just shook his head.
Check for ovality on each crank journal. Section C20 of the Maintenance manual 0.0015 in. max. Check at TDC and 3-9 o'clock with a 1-2 in. micrometer. Also mark your flywheel timing side in some way, so you don't reverse the flywheel when you get to the reassembly. I use a center punch dot at the top where the T/S crank half sits (non machined surface) and a dot on top of the crank cheek timing side. Then clean everything spotless.
Yes, marked and roundness will be checked. Wouldn’t you feel any ovality in the con rods as you spun the around?
Not sure? but it is the underside that show the wear the most on the journal (6 o'clock) if there is wear. You look like you have a good crank there.