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CB350F Restoration by royhall (NOW FINISHED)
royhall:
Okay. Back to the shells. Have done some very careful measurements. Have torqued up the crankcases and measured the two outside journals with telescopic gauge and micrometer. I agree with Honda they are B&C. Cant check the inners with a telescopic gauge as I cannot get the gauge out after the measurement. An air gauge would be perfect for this job. So will assume the other three journals are correct.
Measured the crank journals, mains and big ends, and they are all exactly 1.2590" not even a tenth thou in them. Checked for taper and ovality and all bang on. Top marks to Honda for managing to build a crank to those tolerances. Impressive. Torqued up the conrods and measured them, they are as Honda states all No.2s
Checking the tolerances in the manual with my measurements I get the following, Mains 1-3 are green 4-5 are brown. Big ends are all green.
Using the crank etchings, Mains 1-brown, 2-green, 3-4-brown, 5-black. Big ends are all yellow.
Colour coding on existing shells is still clearly visible (paint on side), Mains 1-4-brown, 5-black. Big ends all brown.
What an utter load of nonsense that lot is. Very little correlates together. Either Honda have put the wrong shells in this engine or (more likely) it's been rebuilt before and the mechanic used the wrong bearings (or whatever they had on the shelf). Well I trust my own judgment and measurements so am going with the top line which is what the ACTUAL measurements are. In any case if you go from the largest bore size to the smallest crank size there is only 1 thou and 8 tenths difference anyway. Just goes to show it's never wise to just trust somebody else, always check and double check. Mistakes get made.
Decision made now so I am going to get the shells ordered tomorrow. I've been so careful with this I am confident I am right. 8)
Checked through the rest of the engine parts and all appears to be in extremely good nick. All the bearings feel like new, no wear on the selector forks etc. Am very impressed with the engine in general, there are some very well made parts in there. Top marks Honda.
Now the engineers bits finished, time to put the mechanics hat back on (this is where things may get tough). ;D ;D
Tiny Tim:
Very interesting read Roy, I look forward to see the finished motor. Might be picking your brain in the future when I have my engine apart. That is a way off yet.
Tim
royhall:
Thanks Oddjob. I was just looking at the paint for further confirmation really, had no intention of using it for replacements. As you rightly say some of it has deteriorated, but some is still surprisingly clear.
I would rush to point out that I am no mechanic and have no experience with Honda four rebuilds at all. One week ago I had no idea about the colour codes on Honda's shells, but Oddjobs superb explanation sorted that out.
The real problem started when I could not really be sure about 2 of the numbers etched onto the crank webs. The first two could have been either 1 or 2, so being the engineer I wasn't settled with that. Then for No.5 the black shells don't exist any more. Then the actual Honda workshop manual does not even mention crank numbers, it advises to measure yourself. I realise that most people don't have the tools to measure a crank to a 1/10th thou, but with my previous job as a Toolmaker, I do (your local engineering shop would measure it for you cheaply). And when measured it revealed that the crank etchings on two of the webs were in fact wrong. If any member that lives near me a Blackpool would like to pop in (kettles on) and re-check it they are most welcome. I am 100% sure the original measurements contain mistakes.
On No.5 it was fitted with a tighter shell (black), and the amount of wear showing on that shell is more than on the others. The thing is though, the difference between the largest diameter case bore to the smallest crank journal is only 1.8 thou, not a lot. You wouldn't want to, but you could probably fit any shell to any journal and with careful running in it would be alright. That's possibly why you can only get Green and Brown now, the middle tolerance bearings.
For Honda to make a crank to such good tolerances is nothing short of superb, but they have Human Beings in the mix and that means mistakes. It is just impossible that Honda turned out every engine to perfection with zero errors. People make mistakes, that's why they put rubbers on the end of pencils. ;D By the way talking of mistakes, the Haynes manual has a mistake in the shell sizing table, misprinted tolerances.
I'm happy with my measurements, and all you can do is go with what the actual sizes are. If it seizes up first time out I shall fall on my sword. ;)
Big thanks to Oddjob for a top explanation of how the coding system works, cheer mate!!
PS. Just looked, and this has taken pages of the thread. Sorry, Just hope it helps someone else.
AshimotoK0:
Interesting project Roy and great detail ... I remember my first 400/4 rebuild way back in '81. I got a crank & rods from a breakers in Hull that had done less than 1K miles but I had to get main bearing shells to mach my crankcases so I genned myself up and went into the 5-Star main dealers in Hull for them to check if I had chosen the correct shell colours. None of them had a clue so I just ordered them and fitted them and they worked out fine.
and yes Honda do make mistakes like here:-
As far as I can make out they never corrected it until the 1977 Shop manual.
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royhall:
Now I'm doing it as well. The mistake in the shells table is in the Honda parts book and not the Haynes manual. Bloody humans, keep making mistakes.
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