thoughts connecting rod free play?

Thinking about rebuilding a motor is much more difficult than actually doing it. I don't like it - so if I need to do it, I make my mind go blank. Read Phil Irving's book 'Tuning for speed'. You need to think about how good your motor will be when it is better. I would hate to rebuild a road bike motor, if it was not going to be faster after the rebuild. It is not really brain surgery. We could really do something with that.
 
I have just stripped my 36,000 mile 850 down to replace the damaged drive side case and have been really surprised (shocked) by the lack of wear. Almost zero wear in the bore and the big end shells look almost perfect. I will still replace the shells as a matter of course because...why not? If it was good before, it can only be better with new bearings
 
I have just stripped my 36,000 mile 850 down to replace the damaged drive side case and have been really surprised (shocked) by the lack of wear. Almost zero wear in the bore and the big end shells look almost perfect. I will still replace the shells as a matter of course because...why not? If it was good before, it can only be better with new bearings
It's generally a bad idea to change 1/2 of the case due to alignment issues. You might be OK, but if your cam bushings are of 1-2 degrees, the cam won't turn, if the crank is off it will probably seem OK but not be, and so on. I would find a matching set and use those.
 
If you going to replace the crank case you should be replacing with a matched pair, not just one side that is damaged.
 
The bearing housings in crankcases are probably line bored. It is difficult to bore a smaller hole. So if the unmatched cases need to be corrected, bigger outside diameter main bearings would be needed of a similar type to standard. I suggest the un-matched crankcases might be a path towards a mess.
 
The bearing housings in crankcases are probably line bored. It is difficult to bore a smaller hole. So if the unmatched cases need to be corrected, bigger outside diameter main bearings would be needed of a similar type to standard. I suggest the un-matched crankcases might be a path towards a mess.
I have read that commando crankcases were never line bored at the factory
But it's hard to know the truth unless an ex factory employee pops up and confirms
Also didn't Steve Maney supply heavy duty drive side cases until he started producing full crankcases?
 
I have read that commando crankcases were never line bored at the factory
But it's hard to know the truth unless an ex factory employee pops up and confirms
Also didn't Steve Maney supply heavy duty drive side cases until he started producing full crankcases?
I wouldn't shocked but then they are numbered on the bottom which would seem to indicate otherwise.

I can't imagine how they would get the holes in the right places and the cylinder surface flat if not bolted together and machined.

The dowels hold the cases close, but certainly not perfect - you always must bump the cases to get the cylinder mating surface flat. There is the one machined surface on the timing side case, but none that I can think of on the drive side.

Just changing the timing side cam bushing can be a PITA on "matched" cases as the cam won't turn or won't turned correctly if very slightly miss-aligned so hard to figure how that would be done without the cases together.

Of course, me not imagining it does not mean that a machinist could not find a way :)
 
I wouldn't shocked but then they are numbered on the bottom which would seem to indicate otherwise.

I can't imagine how they would get the holes in the right places and the cylinder surface flat if not bolted together and machined.

The dowels hold the cases close, but certainly not perfect - you always must bump the cases to get the cylinder mating surface flat. There is the one machined surface on the timing side case, but none that I can think of on the drive side.

Just changing the timing side cam bushing can be a PITA on "matched" cases as the cam won't turn or won't turned correctly if very slightly miss-aligned so hard to figure how that would be done without the cases together.

Of course, me not imagining it does not mean that a machinist could not find a way :)
Yep I agree
And what would be the point of stamping the cases as pairs otherwise
But that's what I have read
 
Yep I agree
And what would be the point of stamping the cases as pairs otherwise
But that's what I have read
Actually, since Norton made little to no parts, the cases were probably already done when they arrived from the manufacturer so it may well be true that Norton didn't machine them!
 
OP:
Lock a conrod with the big end at +/- 90 deg. ( using wrist pin, bar.. clamp..your imagination..)
Then (try) turning the crankshaft.
This way you can make an educated guess about the free play.
Do each rod separately.
If the crank does not move at all, you're good to go.
 
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I have just stripped my 36,000 mile 850 down to replace the damaged drive side case and have been really surprised (shocked) by the lack of wear. Almost zero wear in the bore and the big end shells look almost perfect. I will still replace the shells as a matter of course because...why not? If it was good before, it can only be better with new bearings
For what it's worth, older Harleys have belly numbers that should match on each side, since they are bolted together and line bored from the factory. One of the main things to look for when shopping for one. I would imagine any engine with bolt together halves would be the same.
 
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