Crankcase - bearing housing measurements

[Phil-UK]

Hi

Looking at a set of CB72 crankcases which may have too much clearance where the crankshaft main bearings fit, so I referred to the Shop Manual.
In the section for "Upper * Under Crank Case" measurements are given for the various bearing housings quoting "Standard" and "Repairing Limit" but for the L/H and R/H bearings they don't make sense:

... part of bearing L/H Standard = 76.97-76.987 Repairing Limit = 76.93 more ( this is less than STD )

... part of bearing R/H Standard = 64.97-65.987 Repairing Limit = 64.93 more ( the upper limit for STD looks wrong and again the Repairing Limit is smaller than STD )

Anyone looked into this before and have definitive measurements ?

thanks in advance

Phil

[teazer]

Good question Phil. The spec's do appear to be incorrect for sure.

I never stopped to measure the cases before. If there is visible wear and/or fretting in the cases try to assemble them with a crank but without the locating pins and see if the bearings spin in the saddles with it just buttoned up.

If they are tight and don't rotate I wouldn't worry, but Loctite Bearing fit (red) might help.

If they seem loose, measure the bearing OD and saddle bore and see if you have negative clearance to zero clearance.

In the case (all puns intended) that the crankcases need to be machined, it's not a huge job but it's far from trivial or cheap. In fact if you have to machine the cases and line bore ALL the shaft bearing seats, might as well weld it up to take a six speed while you are in there :-)

[LOUD MOUSE]

I recall that the DREAM crank had a larger L/S bearing in the very early years.
I don't recall who it was I sent one to a couple of years back. ..................lm

Hi

Looking at a set of CB72 crankcases which may have too much clearance where the crankshaft main bearings fit, so I referred to the Shop Manual.
In the section for "Upper * Under Crank Case" measurements are given for the various bearing housings quoting "Standard" and "Repairing Limit" but for the L/H and R/H bearings they don't make sense:

... part of bearing L/H Standard = 76.97-76.987 Repairing Limit = 76.93 more ( this is less than STD )

... part of bearing R/H Standard = 64.97-65.987 Repairing Limit = 64.93 more ( the upper limit for STD looks wrong and again the Repairing Limit is smaller than STD )

Anyone looked into this before and have definitive measurements ?

thanks in advance

Phil

[Phil-UK]

Thanks Guys

I like the idea about trying them without the locating pegs.

I have cheap bore gauges but they aren't reliable so to actually measure them would probably need a dial bore gauge i.e. a trip to a local engineering shop.

cheers

Phil

[malcolmgb]

Where in the UK are you Phil?

[conbs]

LM,

I am not sure if the L/S bearing was any different in terms of ID/OD. I didn't think it was. But, the rollers for the big end of the rods are larger for sure on the very early Dreams. So, the holes in the counterweight and pins for the rods are smaller than on later cranks. I.E. those parts from the early/late cranks will not interchange.

IIRC it was only for 1960 and part of production in 1961 so very few bikes.

[LOUD MOUSE]

I am sure.
A feller had me measure all my L/S bearing for size and I had one that was the OS diameter he needed. .......lm

LM,

I am not sure if the L/S bearing was any different in terms of ID/OD. I didn't think it was. But, the rollers for the big end of the rods are larger for sure on the very early Dreams. So, the holes in the counterweight and pins for the rods are smaller than on later cranks. I.E. those parts from the early/late cranks will not interchange.

IIRC it was only for 1960 and part of production in 1961 so very few bikes.