Honda CB750 Sandcast
The Restoration Shop => Engine Mechanical => Topic started by: Steve Swan on March 20, 2011, 11:24:44 pm
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I'm posting this email i received from Bill Taylor, looking forward to the membership to share your fine experience.
"Still getting my pocket cleaned out on parts that I’m buying for the bike. Most of them from ebay. Anyway, a couple of quick questions. First when it comes to fitting new crank and rod bearing. I can’t for the life of me see any distinguishable marking on the crank weight next to the primary drive. Without this I’m thinking I would have to plasti gauge the clearances. Now that makes a new hurdle. If the clearances are too big or small I have no idea which way to go as far as what bearings to get. In American engines say a Chevy V8 we go + .010, + .020 and so forth. As far as I know the Honda bearing go by colors which doesn’t tell me if green is thicker than yellow for instance. I would appreciate your input on how to best fit the proper size bearing on both the crank and the rods. Remember my engine was completely, ever nut and bolt, disassembled when I got it years and years ago."
"One more thing. The clear coating that Honda used on the external covers. What can we use to duplicate that as close as possible. Clear Lacquer??"
Bill Taylor - Bill@e-zoffice.com
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Bill,
Here's a link to a copy of the Honda Service bulletin #14 from the SOHC4 site. This should answer a lot of your questions.
http://data.sohc4.net/SB750/750_14.pdf (http://data.sohc4.net/SB750/750_14.pdf)
I doubt you will find any color markings on used bearings. If you can't find any markings on your crank, you will probably have to mic them (within a couple .0001"). There is only about .0002" difference in the thickness of the bearings. I would recommend plastigaging the bearings no matter what you choose.
Good luck,
Mark
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I couldn't find the markings on my crank so I mic'd it. All of the main journals fell within 35.99 - 35.995 mm.
So that makes my journals what looks like the Japanese equals sign in the manual chart. ( = ) (There are 2 ranges your main journals can fall into if they are within spec.)
My case is marked B A A B A
From there you just go to the chart and pick the two variables per journal.
So starting at the timing side the table it give me this selection of main bearings:
Green - Yellow - Yellow - Green - Yellow
Easy once you get your head around it. Also, I learned that all bearings, regardless of color are marked "STD". That really threw me off as I'm used to undersized bearings be marked as such.
Once you get your brg's selected and installed, plastigage them to make sure you are in spec. I had to change out a couple after I double checked them. Not sure if it was my mic, user error or just the way it is. I was fussy though at where I wanted them in the range.
They go black, brown, green, yellow, black being the thickest, yellow the thinnest.