1961 CB72 Project

[jensey]

Hi Graham,

That requires some patience

Not really, the motor is pumping while I'm doing other things. I always start with the engine when restoring a bike. Not in the picture, but always used is an filter set-up to filter the fluids before pumping back into the bath.

After breakfast I switch on the pump, and before going to bed, I switch the pump off, that doesn't sound like a lot of work to me....

Decomposed oil ? Not really, like I mentioned, the ZDDP layers are there, and sometimes layers of other additives, but also a lot of non magnetic and magnetic metal is in there. Clutch particles are an other thing.

Me too, switch to synthetics / filter after this process. After cleaning, the synthetics will just finish your work...

Good luck with pressing this crank back together !

Jensen

[Tim Miller]

Jensen,

It would be some wishful thinking to believe soaking a assembled crank in anything that would really clean it properly. This stuff is rock hard and very difficult to brake down even in my industrial ultrasonic cleaner. It takes some serious scraping and wire type pipe cleaners to get this crap out. You might just be loosening this stuff up to later migrate through the rollers / fragile cages later.

That's what makes Graham's style of rebuild so impressive. He knows his crank is clean and his roller and cages are good. There's no substitute for visual inspection.

Tim

[G-Man]

Tim

Jensen said that this crank was only 1500 miles old so that would help. I would have two reservations. A) relying on the solvents and US to actually break the stuff down, and B) that the process would actually get the stuff out of those tortuous and "dead end" oil ways.

It would be interesting to actually get an US transducer and bolt it directly to various parts of the crank while it is in the bath. You might need a lot of power for that one.

Looking at the stuff in my crank and in oil filters I have dismantled, it does look like these engines are a good attempt at re-creating millennia of geological sedimentation over just a few years....... 😊

I can feel my next Cappelini filter purchase edging nearer but might have to make my own.......

Thanks for the comments, gentlemen. It's all food for thought and helps us all learn.

I must admit that my own cleaning process now involves solvent, to remove the sticky stuff, bead blasting to remove the hard deposits and ultrasonics to give a final clean plus a final rinse in water with a little hand soap to inhibit rust....

G

Jensen,

It would be some wishful thinking to believe soaking a assembled crank in anything that would really clean it properly. This stuff is rock hard and very difficult to brake down even in my industrial ultrasonic cleaner. It takes some serious scraping and wire type pipe cleaners to get this crap out. You might just be loosening this stuff up to later migrate through the rollers / fragile cages later.

That's what makes Graham's style of rebuild so impressive. He knows his crank is clean and his roller and cages are good. There's no substitute for visual inspection.

Tim

[jensey]

Jensen,

It would be some wishful thinking to believe soaking a assembled crank in anything that would really clean it properly. This stuff is rock hard and very difficult to brake down even in my industrial ultrasonic cleaner. It takes some serious scraping and wire type pipe cleaners to get this crap out. You might just be loosening this stuff up to later migrate through the rollers / fragile cages later.

That's what makes Graham's style of rebuild so impressive. He knows his crank is clean and his roller and cages are good. There's no substitute for visual inspection.

Tim

Hi Tim,

I agree with you, if I didn't have access to a industrial US. It consumes 3000W, and has special transducers for frequency's (on the low side) which are effective on breaking up the dirt, I would do the same as Graham. A CB450 K0 crank is also different then a CB72 crank, the oil passages are attainable from the inner bearings, so mechanical cleanable.

The amount of dirt, collected in the bottle is the dirt from the passages only, the dirt from the centrifugal area is also cleaned with scrappers and is not included in the bottle I show.

Jensen

[jensey]

In the end the bearings went in the hot bath with the other parts for a final clean up. These are the jets which direct oil to the big end and they are critical to the long and healthy life of the hard-worked big end.

Hi Graham,

I found cranks with the big-end oil ways clogged almost 100%, but no damage on the big end itself. It seems that oil mist and splashing keep the big ends more or less in good shape (with avoiding high rpm's and heavy loads). The small-end however, is a better indicator of oil feed problems to the big end. The small-end is lubricated with oil mist produced from the big end, and if there is not much oil mist in that area, the small end goes first, also with a low to moderate rpm and low to moderate loads.

Many owners of these bikes don't ride their bikes as they were designed for, being anxious to damage the bike. Small-end failure is very common to these bikes, and when they hear the small-end start making noise, they stop riding on the bike or sell it.

This is my opinion, as I see many small ends worn out (almost always the left side), and following the trail, it seems to originate at the reduced oil feed to the big-end (and in some cases a worn oil pump).

Jensen

[G-Man]

Hi Jensen

Yes - I notice that the oil feed holes in the big end pin are situated to keep them clear of any dirt that is collected, but it is always a worry that that stuff gets re-dissolved in the hot oil.

Interesting observation about the small end. Honda obviously changed the design of the lubrication holes / slots but those small ends appear to be a problem. Bernard Saunders told me that they had a lot of small end problems with Hepolite pistons in race bikes. Putting original Honda wrist pins in the Hepolite pistons in improved the problem. Metallurgy plays its part.

After talking to Jerry I may increase the thickness of my small end bushes or scrap the rods. It would be nice to build a proper test installation to learn about all these things. Perhaps when I retire....

Great to have to back here on the forum.

G

In the end the bearings went in the hot bath with the other parts for a final clean up. These are the jets which direct oil to the big end and they are critical to the long and healthy life of the hard-worked big end.

Hi Graham,

I found cranks with the big-end oil ways clogged almost 100%, but no damage on the big end itself. It seems that oil mist and splashing keep the big ends more or less in good shape (with avoiding high rpm's and heavy loads). The small-end however, is a better indicator of oil feed problems to the big end. The small-end is lubricated with oil mist produced from the big end, and if there is not much oil mist in that area, the small end goes first, also with a low to moderate rpm and low to moderate loads.



Jensen

[jensey]

Great to have to back here on the forum.

Never bin away really, but not very much to tell, so big pauses between responses.
As can be seen on the Hondatwins forum, I had my hands full with the 450's, one K0 for testing the 10W60, one red CB450 K2 (next year rider) complete engine rebuild including Cappelinni oil pump and filter set-up, and one blue K1, restoring to stock (no modifications here).

I also building a CB500T engine with oversized pistons, Cappelinni oil pump / filter, needle bearings on cams, electronic ignition etc.

After the 450's it's a 1964 dream on the stand for a complete restoration (was my daily driver years ago).

In the mean time I'm making room, just by dissembling 6 early dream engine's (C71/C76) which are lying on the floor, on the hunt for 2 good cranks.

Here some pictures of the 450's :