left hand crankshaft bearing

[Dick Eastman]

I have two cranks that I'm considering using; however, the bearings on the clutch side are different diameters - one is a Nachi 630657HS[75 mm od], the other is an NSK B30-38 [77 mm od]. My case bore is 77mm. The crank with the 75mm bearing came with my parts bike, but obviously is not the crank that came with the rest of the engine. The s/n of the case is 10428xx.
When did Honda change this diameter?
Several questions:Is the Dream crankshaft the same as the SuperHawk?
Has anyone here ever pressed a crank apart? I don't see in the parts book a listing for the two inside bearings, or rod bearings, either.
Any comments here?
Thanks,
Dick

[Tim Miller]

Hello Dick,

It was in early 1961 when left bearing changed from 75 to 77mm.
As for the dream: they have larger counter weights for 360 degree balance. But generally use same rods, center section, rollers & cages. Only very early parts books have crank lay out.
I have rebuilt a dozen or more and highly advise anyone that wants good peace of mind. There's a lot of crud blocking oil flow in there. Most of the time cages are bad or pitting from water damage.
From what I've seen you do this is right up your alley.

All the best,
Tim

quote="Dick Eastman"]I have two cranks that I'm considering using; however, the bearings on the clutch side are different diameters - one is a Nachi 630657HS[75 mm od], the other is an NSK B30-38 [77 mm od]. My case bore is 77mm. The crank with the 75mm bearing came with my parts bike, but obviously is not the crank that came with the rest of the engine. The s/n of the case is 10428xx.
When did Honda change this diameter?
Several questions:Is the Dream crankshaft the same as the SuperHawk?
Has anyone here ever pressed a crank apart? I don't see in the parts book a listing for the two inside bearings, or rod bearings, either.
Any comments here?
Thanks,
Dick[/quote]

[Dick Eastman]

Thanks, Tim.
I do recall hearing from the fellow I bought my parts bike from that he had swapped some of the parts for a build he had done - it's a shame, though, because the parts bike had only 2370 miles on it.
The other crank I have is from my runner, and it has 19K on it, and the bearings are usable, but for this build, I want everything in top condition - it appears I may have to press the cranks apart for a thorough inspection/recondition - it may take more than the two cranks on hand to do this to get the necessary parts to meet spec.
Tim, do you have an exploded view of the cranks in their component state from an earlier book, as mentioned - I would be interested in seeing this.
If this is the route I eventually take, I will post photos of the process, and what I find. The cranks in these small engines are exceptionally robust, but I still don't understand why Honda increased the diameter only two mm.
Thanks,
Dick

[Tim Miller]

Dick,
Left bearing is enter changeable (same ID). Yes, it can take disassembling 10 or more cranks to have enough good parts for 2. It's also a good time to bush little end for rods. Send a PM with email and I'll send parts book. Also check out G mans restoration blog.

Tim

Thanks, Tim.
I do recall hearing from the fellow I bought my parts bike from that he had swapped some of the parts for a build he had done - it's a shame, though, because the parts bike had only 2370 miles on it.
The other crank I have is from my runner, and it has 19K on it, and the bearings are usable, but for this build, I want everything in top condition - it appears I may have to press the cranks apart for a thorough inspection/recondition - it may take more than the two cranks on hand to do this to get the necessary parts to meet spec.
Tim, do you have an exploded view of the cranks in their component state from an earlier book, as mentioned - I would be interested in seeing this.
If this is the route I eventually take, I will post photos of the process, and what I find. The cranks in these small engines are exceptionally robust, but I still don't understand why Honda increased the diameter only two mm.
Thanks,
Dick

[G-Man]

Dick

The CMS site has plenty of exploded diagrams of crankshafts.

http://www.cmsnl.com/honda-c72-1960-196 ... ml#results

As Tim says - I did quite a lot of stuff on crank dismantling and how the oiling works in my 1961 CB72 restoration thread.

http://www.honda305.com/forums/1961-cb7 ... 1-238.html

Its amazing to see how much nasty stuff gets into those oilways - particularly the centrifugal feed to the big ends.





G


Left bearing is enter changeable (same ID). Yes, it can take disassembling 10 or more cranks to have enough good parts for 2. It's also a good time to bush little end for rods. Send a PM with email and I'll send parts book. Also check out G mans restoration blog.

Tim

Thanks, Tim.
I do recall hearing from the fellow I bought my parts bike from that he had swapped some of the parts for a build he had done - it's a shame, though, because the parts bike had only 2370 miles on it.
The other crank I have is from my runner, and it has 19K on it, and the bearings are usable, but for this build, I want everything in top condition - it appears I may have to press the cranks apart for a thorough inspection/recondition - it may take more than the two cranks on hand to do this to get the necessary parts to meet spec.
Tim, do you have an exploded view of the cranks in their component state from an earlier book, as mentioned - I would be interested in seeing this.
If this is the route I eventually take, I will post photos of the process, and what I find. The cranks in these small engines are exceptionally robust, but I still don't understand why Honda increased the diameter only two mm.
Thanks,
Dick

[/quote]

[Dick Eastman]

Thanks Graham - a picture worth a thousand words.
Been reading your blog, and have really enjoyed it!
I've been measuring the three cranks I have, and the bearing journal on the stator side [all three] measure 1.1808" [30mm = 1.1811"]. The id of the roller bearings: one is 1.4968", the other, showing wear, is 1.4976" [38mm = 1.49606"]. These were measured with a .0001" increment dial bore gage; The pins mic .1571" [4mm = .15748"]. The journal od + two pin diameters = 1.495", the smallest bearing id is 1.4968" - this is a .0018" clearance. If all dims were nominal metric dimensions [30mm + 4mm + 4mm =38] there would be no running clearances. What should be the proper running clearance for this side?
Also one of the cranks had Nachi 630657HS [75mm od] and the other 630656HS, same as third one NSK B30-38, both77mm od. I just picked up a Dream engine, with a very clean interior, hoping to cannibalize crank bearings, maybe rods - it has a Nachi 630656HS also. I still have on hand some C954 hard bronze [used for valve guides], and will use this to bush small ends, if needed. I do think, if I bush these, that I should make a provision to get the oil from the rod slots, out to the edges of the bushings.

[G-Man]

Dick

The bearings are metric, of course. The big issue on the stator side is the state of the crank journal on which the rollers run. I managed to pick up some NOS roller bearings for that side and the 4 x 10 rollers are pretty easy to get from a good bearing supplier.

http://www.rgpballs.com/pdf/precision_c ... ollers.pdf

The only thing to watch out for with the Dream crank is that (on early engines) the con-rods are heavier around the small end.

As for the bushings, the slotted ones (small end) are the early type. Later ones had drillings. The underside of the piston and small ends are lubricated from the big end by an oil slot that faces the small end and directs a jet of oil upwards. Later Honda engines include some oil holes at the bottom of the small-end to capture a bit more of this splash.



That's the only way that oil gets to the small end as any surplus on the crank web is skimmed off by those little 'L' shaped plates in the crankcase and oil coming from the valve gear goes down the cam chain tunnel, missing the cylinder bores.

I've been toying with the idea of making up a 'repair kit ' for these engines using Suzuki GS750 rods and a standard roller cage. The big end is a little wide and the small end is 16mm, so easily bushed for a 15mm pin.




G

Thanks Graham - a picture worth a thousand words.
Been reading your blog, and have really enjoyed it!
I've been measuring the three cranks I have, and the bearing journal on the stator side [all three] measure 1.1808" [30mm = 1.1811"]. The id of the roller bearings: one is 1.4968", the other, showing wear, is 1.4976" [38mm = 1.49606"]. These were measured with a .0001" increment dial bore gage; The pins mic .1571" [4mm = .15748"]. The journal od + two pin diameters = 1.495", the smallest bearing id is 1.4968" - this is a .0018" clearance. If all dims were nominal metric dimensions [30mm + 4mm + 4mm =38] there would be no running clearances. What should be the proper running clearance for this side?
Also one of the cranks had Nachi 630657HS [75mm od] and the other 630656HS, same as third one NSK B30-38, both77mm od. I just picked up a Dream engine, with a very clean interior, hoping to cannibalize crank bearings, maybe rods - it has a Nachi 630656HS also. I still have on hand some C954 hard bronze [used for valve guides], and will use this to bush small ends, if needed. I do think, if I bush these, that I should make a provision to get the oil from the rod slots, out to the edges of the bushings.