"8"bolts

[o1marc]

We're having a discussion elsewhere on the "8" bolts found on different places on a CB750. It doesn't appear to be a hardness grade. But no one can determine what it means or where they actually go. And without those answers, whether they are a noticeable fail if they are not on a restoration. There's talk that a "sharp eyed AMCA judge" might deduct points for it. In all the talk we have about what's right or wrong on a sand cast the question of these "8" bolts has never come up. Any answers from our experts here?

[Steve Swan]

Marc, I'm not sure i entirely understand what you are asking.  I'd be really surprised if any "8" bolt would Rockwell to Grade 8 spec.  I can't think of need for Grade 8 bolts to be used for general chassis fittings.  Nor can i imagine Honda incurring expense of Grade 8 bolts which would drive up production cost.  Honda very definitely wanted to contain production costs for an attractive and competitive retail price of $1495.  There has been quite a number of threads and posts on this forum about "8" bolt types as seen within abd between various vin ranges.  "8" bolts were used on all sandcasts.  I am not aware any sandcast to not have "8" bolts fitted.  Further, i am not aware the later "hog nose" type 8 bolts as seen on later vin CB750's and K1's were ever fitted to sandcasts.  If i understand your comments, AMCA judging would deduct points for "8" bolts not being fitted..?  I would certainly hope so !  I'd have to be convinced an AMCA judge would know the differences between early, mid and late type "8" bolt fonts as well as what fonts one would expect to see on a specific vin or vin range.  I can't imagine a conversation of what's "right or wrong" on a sandcast without some mention of the topic of "8" bolt types coming up.  Not knowing qualifications of any particular judge, there are only a small handful of people i consider qualified to judge a sandcast for correctness.  Frankly, I'm not sure i am all that qualified to judge correctness and i am not being modest.  There is so much we have learned and so much yet to learn.  There are a couple guys on this forum with incredible memory who have done more observation than most.  And at least one member who has done some quite exhaustive documentation of his findings.

The different "8" bolt font types seen on various vins is not a simple or brief discussion.  These discussions and photographs can be found in a search of this forum.   Hence, I'm not going to try to discuss the complexity and diversity of the whats and wheres of these "8" bolt distinctions.

 

[Steve Swan]

As to what "8" means, no one has given an answer one can take to the bank.  As far as meaning goes, we've discussed hardness,  manufacturers marking.   Furthermore, other Japanese brands have "4", "6" and "9" on the bolt heads.  I know I've seen "4" on bolt heads on 60's Suzuki's and if i recall correctly, "6" is seen on Kawasaki units.  KP would certainly know.

[kp]

Very thorough response Mr Swan and yes; you would be one who is very qualified to be a judge. Kawasaki Z1 72 and 73 manufacture have 7 but some early examples have 4 on many bolt heads.
The only #8 bolts that seem to be common to all sandcast VINs are the engine case bolts including the internal bolts such as rocker gear etc

[UK Pete]

page 4 of the parts manual


link to service bulletin
http://forums.sohc4.net/index.php?action=dlattach;topic=136711.0;attach=256851

[Steve Swan]

So, i learn something new every day.   

Looking at my original CB750/CB750K1 parts book, print date February 1971, page "b," there is a detailed explanation of numbering on the bolt.  States, "A number,  the strength of the bolt,  will be embossed on the top of the head.  This mark will appear on modified J.I.S. bolts of all sizes." 

I would need more info to be convinced "8" = Grade 8.  Because other Japanese bolts have other numbers on them, i. e. 4, 6, 7, 9.

[markb]

The number may be an indication of the strength but the "8" cannot be the equivalent to US grade 8 bolts as they are much harder and stronger than the "8" bolts on CB750's.

[Steve Swan]

The number may be an indication of the strength but the "8" cannot be the equivalent to US grade 8 bolts as they are much harder and stronger than the "8" bolts on CB750's.

agreed.