Honda CB750 Sandcast
The Restoration Shop => Frame and Chassis Related Elements => Topic started by: markb on January 22, 2011, 12:28:19 pm
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I understand that the early bolts are 146mm long and the later ones are 148mm. I would assume that the thread length is probably the same and the unthreaded portion is what is 2mm different. In that case a later bolt could be used to make a replica early bolt by shortening it by 2mm and chasing 2mm more thread. Anyone ever do this? Are the heads the same on early and later bolts (hex size, "8's")? Anyone have one of each that they could compare?
Thanks,
Mark
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Pictures attached (hopefully!) of original bolt from #302 and a NOS "020" one. Head size is the same, and is plain - no "8" on either. length is shorter as you already know. Chamfers more pronounced on early one. as you say, appears to be possible to modify late into early type.
Cheers - Chris R.
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That is excactly what I was hoping to see. I think I can do that. I see what you mean about the chamfers. Looks to be close to 30 degrees instead of 45. Don't know what that would be in metric (just kidding). ;) Chris, would it be possible for you to give me accurate dimensions of the early bolt. I should start scrounging for later bolts. I need two pairs but once I'm set up to do them I should do as many as I can.
Mark
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No probs - I'll get you the dimensions this week.
I did not re-use the correct shorter bolts on #302 as it is fitted with HM300 pipes (+ longer bolts) right now. The plan was to ride it occasionally, but two years on from finishing the resto I still have not! I do have a et of Yamiya "lotus roots" for it, but not sure if they are accurate in the detail of the pillion fottrest mount. Anyone else know?
Cheers - Chris R.
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Hi Mark & Chris,
I have a set of the later bolts, lock & flat washers with nuts, if you need/want them, Mark. Either nos or used.
Chris, i used the early shorter bolts which came with 232, they were still present, holding HM341's in place with nuts and lock washers only. (Still amazes me how much of 232's original small parts were still with 232, considering it had gone through 2 engine changes after leaving the assembly line.....) Using these early shorter bolts with lock and flat washer and nut tightened on Yamiya LR's, i have about 3mm of the bolt protruding. When i took receipt of my Yamiya LR's in 2006, I remember measuring the mounts, i cannot remember the width of each mount nor the combined width of both mounts.......... Nor, did i write down the width of the mount.....
What i can say, as a FACT, is what i photographed and recorded in the "Technical/Restoration Support" section of the website - http://www.cb750sandcastonly.com/support23.htm (http://www.cb750sandcastonly.com/support23.htm)
The photos and measurements i took from a set of 3 original production LR's and 1 original production "no.no" exhaust i owned 3-4 yrs.ago. The measurement of the muffler mount hole on the LR muffler = 55mm. "no.no" = 58mm. Hence, obviously the reason the early LR style exhaust use a shorter bolt, and "no.no" exh.use the longer bolt.
I am going to assume because (on 232) i have approx. 3mm of the early bolt protruding beyond the face of the nut, the Yamiya LR's muffler mounts are the earlier 55mm thickness....... I DO have a set of unmounted HM300's, dedicated to 2157, if Mark measures his LR mount thickness, i can measure the thickness on these HM300's.
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I did try to fit the HM300's to #302 with the early bolt, but would of needed to leave out one of the washers as Steve says, hence fitted the longer bolts so it at least looks right wrt the bolts.
Bolt measurements (originals from #302)
Head = 17mm A/F, 7mm thick
Plain shank = 14mm diameter x 117.5mm long to START of "mid" chamfer
Mid chamfer = 22° from axis of bolt x 3.5mm length
Thread = M12 x 14mm long
End chamfer = 22° from axis of bolt x 2.5mm long
Gives a TOTAL bolt length of 144.5mm (checked and confirmed by measuring overall length to make sure the above all "add up").
Lengths of chamfer and thread are measured as near as possible as deciding where the intersect between thread and chamfer starts ios not exact due to helical nature of thread.
If you need any more Mark, just ask.
Cheers Chris R
PS, turns out looking through my stock of silencer mounting bolts that I have THREE distinctly different lengths. The longest one is likely from a K7, which I will probably shorten as Matrk suggests to suit one of my earlier bikes.
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Chris,
Thank you very much! ;D Just to make sure, you are including the thickness of the head in the length? I usually go by the convention of measuring the length under the head (except for flat heads) but no worries. I'll post back with my results. I'm assuming the originals also had the earlier, duller finish zinc? Of course after machining they should get replated.
Thanks again,
Mark
Actually, looking back at your pictures, they both look quite shiny.
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Yes, the overall length of 144.5mm does include the thickness of the head (I agree that usual convention, here in the UK too, is for the quoted length of the bolt to be taken from the underside of the head). Using normal convention then , the bolt length is really 137.5mm.
They are shiny because they were re-zinc'd along with all the other fasteners, the original finish having grayed over the preceeding 40 years.
Cheers - Chris R.
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Mark, like i said, if you need bolts/wshrs/nuts, lemme know. i can measure them to make sure they are what you can modify for use.
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Steve,
Do you have some later bolts that you would sell? I'm not sure if they're available anymore but a search on ebay come up empty. Although Yamiya has them for $28 a piece. Ouch. Their picture is not too good but it looks like the later style.
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Mark
I believe 90146-300-020 is a good number from Honda for the low low price of 21.49 ea. ;) There's an ebay listing for a whole kit including the later pillion bolts.
http://cgi.ebay.com/ebaymotors/NEW-EXHAUST-HARDWARE-BOLT-KIT-HONDA-CB750-1969-76-P41-/270695372253 (http://cgi.ebay.com/ebaymotors/NEW-EXHAUST-HARDWARE-BOLT-KIT-HONDA-CB750-1969-76-P41-/270695372253)
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I guess $66 for the kit isn't too bad if the bolts are $43 of that, but still. I know the part number in the listing is for the later bolt but doesn't it look in the picture like it has the lower-angle chamfer like the early bolt?
(http://cb750sandcastonly.com/coppermine/albums/userpics/10002/Exhaust_Kit.jpg)
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I'm confused. Here's some pics of some bolts. The top one is off of 5383 (although no way of knowing if it's original. The bottom one came out of an unopened bag with part #901146-300-020. Both should be the later bolts. Notice the top one has the chamfers like the early bolts but it is the longer of the two, 142mm (under the head). The -020 bolt is 140.5mm. Also the 5383 bolt has a center drill in the end of it. So here's my questions:
Is it possible the 5383 bolt is a fake?
Is the later bolt 3mm longer than the early bolt?
(http://cb750sandcastonly.com/coppermine/albums/userpics/10002/DSC06148.JPG)
(http://cb750sandcastonly.com/coppermine/albums/userpics/10002/DSC06147.JPG)
(http://cb750sandcastonly.com/coppermine/albums/userpics/10002/DSC06150.JPG)
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Never seen a bolt with that centre drill in the end! I do sometimes wonder whether items like this (especially if NOS spares which may have been manufactured later) will have some detail variations as you observe.
Yes, the later bolt is slightly longer that the early type (pre 1001222) - about 3mm sounds right.
Cheers - Chris
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Mark, I believe the bolt with the center drilled end was machined from a longer bolt. The "torn/rough" finish on the long bevel and the "torn/rough" finish in the threads indicates that it was either machined on a less than ridgid lathe setup or machined at too slow of speed. It is highly unlikely (IMO) that original Honda parts would exhibit those specific conditions.
Keith
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Good observations. After a much closer inspection I see now that the entire length of the longer bolt is machined. That's why the center in the end. I can also see sprial machining marks on the head. I think it was machined out of hex stock. The guy must have had an early bolt that he was copying to match the angles. Overall not too bad a job. I guess I'll swap them for the ones on the diecast so that 5383 has the correct bolts. Thanks guys.
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Hi! I have one bike #1462 that came with short bolts. This bike also had no number original exhaust so I presume these short bolts are original. What I mean is: at least up to #1462 was short bolts used. Total lenght of the bolts is 145 mm. Regards, Bo.
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Below info from website "Prod.Models."
I'm pretty certain below info came from in later parts books. (not the length, BUT the pn's)
Bolt, pillion step
1 - 1221
90146-300-010
Bolt length 146mm
Bolt, pillion step
1222 - 7414
90146-300-020
Bolt length 148mm
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OK, I'm confused again (sometimes not hard to do). I think we all agree that the overall length of the later bolt (including the 7mm thick head) is 148mm. Maybe I'm being nit picky but I thought we decided that the early bolt was 3mm shorter or 145mm (144.5 by some measurements) including the head. I personally would go with the 145mm nominal dimension (instead of 144.5mm) because I've never seen a Honda bolt called out to a length in .5mm increments and the later bolts that I measured varied from 147.5 to 148 (typical manufacturing variation). As long as I'm picking nits here, the correct way to specify the length of a hex head bolt is the measurement under the head. So the correct length of these bolts should be 138mm (early) and 141mm (late) to avoid confusion. ::) ;)
Mark
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I've always understood, to determine "length of bolt," the measurement is of actual shaft length; taking measurment from under the head. (not including bolt head thickness.) This is how i have always measured bolt lengths. Generally, the shank is considered the "working distance" of a bolt and length of bolt is determined by shank length.
On another note, just last week, Chris and i were discussing concern for losing the thought processing how we induce, deduce, come up with conclusions for what we believe most accurate about sandcast details; simple case in point, pillion bolt length.
I can't remember where the 146/148mm measurements came from i listed in this thread from "Prod.Models."
I know in the past, when i was restoring 232, i measured early and late bolts, i wrote it down "somehwere" and now the only place i can find the measurement is in the website.
I know Chris and i had conversations about these lengths. I know Chris has measured these bolts. The parts books acknowledge different pn's ending at 1221 and beginning at 1222. When the data listed in "Prod.Models was loaded, i loaded engine info, Chris loaded chassis info. So, as far as length, without puling a bolt from 232 and puling a bolt from 4363, i think that's about all i can offer. I am guessing i took the 146/148 meaurements from the Prod.Models when i was putting "88 Distinctions" together.
If i took those 146/148 measurements, they were taken starting under the bolt head, NOT including bolt head.
I guess the bottom line here is that topics such as length of pillion bolt has been discussed and we've lost the info which created confusion or having to "reinvent the wheel."
What concerns me is losing this info, Chris says it best in his email ato me a few days ago, "Between us all, I am sure we have pondered in great detail so many of these anomalies – I still worry that our reasoning’s may gradually be lost over time. I suspect it ALL needs to be recorded somehow, and web sites are not necessarily the best way to do that given that if enthusiasm to maintain such resources wanes, or without others prepared to continue the work, they can simply be switched off and lost at some point."
I've not seen seen a center drill mark in a pilion bolt, other than Mark's and i've seen a fair number of pillion bolts.
Bo, it's probably just as difficult to explain your first hand observation of why 1462 has short bolts as it is my very distinct memory 4779 having a smooth round oil cover. Maybe some of these differences were not as "hard and fast" as parts books say.
I just measured the bolts i am using for 2157, which i believe to be late bolts. The shank length, measured under bolt head is 142mm. The total length, including (7mm) thickness of bolt head is 149mm. I took these measurements three times.
I can't remember how thick an early bolt head is. I can't remember how long an early shank is. Nor can i remember the difference in length between early and late bolts...... 2mm ? 3mm ? I went through all this a few years ago, and now it's seemingly lost to the ages. (should have started that old fashioned notebook i thought of starting several years ago.)
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Looking at all the previous posts on this thread, i believe i've written mostly drivel confusing things more.
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If i took those 146/148 measurements, they were taken starting under the bolt head, NOT including bolt head.
I just measured the bolts i am using for 2157, which i believe to be late bolts. The shank length, measured under bolt head is 142mm. The total length, including (7mm) thickness of bolt head is 149mm. I took these measurements three times.
No disrespect intended here but aren't you saying two different things here? Not quibbling about the 1mm difference (I'd call 148 or 149 close enough to the same) but first you say 148mm not including head and then you say 149mm including the head. I think the head is 7mm thick for both.
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No disrespect taken :) Like i said, "i believe i've written mostly drivel confusing things more."
To try to clarify how i took the measurement: I measured head thickness the same; 7mm. 142 = shank length +7mm head thickness = 149mm total bolt length.
"Eyeballing" the length of entire bolt with mm scale beside (parallel to) bolt, appears just a hair over 148mm.
Laying another scale on top of (transverse to) the threaded end of bolt, with this scale (going across bolt's threaded end) to the scale measuring length of bolt, I measure 149mm.
Hope this makes sense.
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I scored on two pairs of the short pillion bolts, 90146-300-010. You can see in the pictures that they measure almost exactly the same as Chris’s measurement of 144.5 (including the head). The chamfer on the end isn’t quite as pronounced as the one in Chris’s picture but it is right on in every other detail including the finish. It looks like the more dull zinc and they look like they’ve been sitting around for a while. It definitely is not the long bolt.
(http://cb750sandcastonly.com/coppermine/albums/userpics/10002/DSC07716.JPG)
(http://cb750sandcastonly.com/coppermine/albums/userpics/10002/DSC07717.JPG)
Here’s a link to where I bought them if you are interested.
http://www.hondarestoration.com/nosResults.asp?models=CB750K%2CCB750K-750+Four-1969 (http://www.hondarestoration.com/nosResults.asp?models=CB750K%2CCB750K-750+Four-1969)
There are three groups of parts. Scroll all the way to the bottom of the third group. It says he has 17 available but that’s what it said before I bought my four so who knows how many he really has. I was tempted to buy more and try to sell them but decided to pass along the lead instead. I bought them with Paypal and got an email confirmation right away and they arrived in less than a week even though it says they’re coming from a different supplier and may take a couple of weeks. I don’t know much else about the seller so take it for what it’s worth. At $14.35 each I didn’t think it was a bad price. He also has the -020 bolt for $21.49 and has some other unavailable parts too. I picked up a couple of the Bolt A front engine mounting bolts while I was at it. I don’t know where he is getting his parts but this may be a good site to check from time to time.
By the way I prefer to call out the length of the bolt under the head. Mine were closer to 145mm (including the head) so I call the -010 one 138mm long and the -020 one 141mm long.
If you’re interested, good luck.
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Great heads up Mark and thanks. Seems someone read your post and beat us all to the stash and got the remaining 13 bolts. I suspect we'll see them on eBay soon enough.
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:o ??? :-[ Well that didn't work out the way I thought it would. I figured there would be plenty for everyone that needed them. I guess next time I'll just buy them all.