CB750K7 Big End shell bearing identification

[ginger_jim]

Hi all, I cant see a number anywhere on the conrods to identify which bearing to buy.  Am I missing something?  Help!

[Bitsa (Ralph Wright - RIP)]

Hi ginger Jim.
Mind went totally blank for ages I could not remember what to look for.Crank case not a problem then it came to mind the big end shell numbers are printed on the two halves of the conrods.When you put them together you will see a number 1 to 3 if I remember right.Sorry for the sketchy view but you will see what I mean.
Hope this helps
Bitsa

[ginger_jim]

Oh dear, I thought you were going to say that!  It looks like there may have been a mark at some stage - looks like it was written in black marker pen but its impossible to make out for sure!

Looks like it might be a job for SEP http://www.sep-kegworth.co.uk/page1.htm

[Bitsa (Ralph Wright - RIP)]

Jim.
For sure it does look like a marker pen but for Christs sake I hope you dont have to look for the scribed number for the main bearings really hard big magnifying glass for this.I have done a few fours in my time 400 750 and to say conrod marks have been fine.I had a lot of trouble once trying to find out main bearings  and got in touch with an ex racing Honda man who told me with the sohc engines fit the biggest shells you can get and run it in gently and you will have no problems because of the age.I have to say I did not take that advice.We all learn something new every day so sorry leave it to you.
All the best
Bitsa

[Waggles]

Aha! I spot an opportunity for me to learn something before I need it! I thought the big end shells were colour coded ( color coded for US spec ) and that the colour was on the outside of the shell? If they are numbered any chance of a pic from somone to show what to look for?

Could the numbers on the rods b to identify which cap goes with which rod? ( and perhaps which cylinder the rod goes in? )

[Bryanj]

Shells are colour coded no matter what country they are for but after a time in the engine thay all look the same, there is a picture in the manual showing where the ID mark is on both crank and rod, plus a weight mark

[ginger_jim]

Hi, the number looks like it should be traversing the two halfs of the conrod but I cant see anything legible so I can only assume that they have worn off over time.  Its not the end of the world - as mentioned in the previous thread SEP in Derby will measure everything up for me and source new shells including the mains.  A bit more expense but at least ill be sure that everything is 100%.

Cheers

[ginger_jim]

Thanks oddjob, i did use a bit of WD40 to try and clean but didnt have much luck.  Following all the posts ill try again  - this is my first SOHC as I have traditionally worked on big Z's and oil head BMW's so its all a bit new.  Just to double check, the main bearing marks are lightly engraved/scratched onto a crank lobe right?  Looks like 5 b's - does that sound right?

[Bryanj]

Yes the crank is etched on a centre lobe for both the big ends and the mains so make sure you get the correct marks. From memory i thought the rods were etched the same way, if its a very early engine the marks were in japanese characters just to confuse you.

There should be on the US site all the Honda Service Bulletins and you want Number 14.

If i have done it right this link should take you to it

http://manuals.sohc4.net/CB750SB/750_14.pdf

[bytio]

I had the same issue on my F2 unable to read the crankshaft numbers so sent it all to SEP Kegworth, excellent job if you don't mind waiting a while, crank deep cleaned, all new big end and main bearing shells. All returned sealed bags and pre lubed.

[Waggles]

Thanks for that link Bryan, answers all my questions! and my comment re US spec was just a little jest on the spelling!

That looks like a good service bytio, was it expensive?

[bytio]

Was about £400 but hat included stove enamelling of all the engine cases to original satin black finish

[ginger_jim]

Bryan - that bulletin is really useful - thanks    I thought the markings for the big end were on the conrod but as ive got a later engine I now have an explanation or what I should look for.

[Bryanj]

You still need a mark from the rod as well as the mark from the crank to sort out the original size used

[ginger_jim]

yeah I worked that out.  SEP quoted me 200 quid plus vat and delivery to measure up and provide bearings for big ends and mains.  Thats about the same price I would have paid for shells from Dave Silver so im going to take the hassle out of the job and send the crank up to them.

Cheers Bryan