Honda-SOHC
SOHC.co.uk Forums => CB500/550 => Topic started by: deltarider on March 14, 2022, 07:26:51 AM
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A mini quiz of just two questions. What do we see here?
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Go on then…punch line?
Looks like a 500 shock mounting….
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A top rear shock mounting with a lock in it somehow
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A top rear shock mounting with a lock in it somehow
Correct. It's the stud RH side. BTW, what looks like a lock, does not play a role. It's merely the camera in combination with the flash which exaggerates it. But now to the second question. What do we see here?
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Same mounting when the threaded bit has been broken off then drilled and taped to take a bolt instead
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Same mounting when the threaded bit has been broken off then drilled and taped to take a bolt instead
And drilled off-centre :D
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Obviously did not file flat and centre punch before drilling, personaly would screw in a piece of studding and use original chromed acorn nut, if different thread make a double ended stud
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You guys are experts. Here's a little background. June 1980 I had past my licence test without having had even one lesson. Back then this was legal. Not now anymore, thank goodness. No wonder I've learned a few things the hard way in my riding career. The first event was not a real accident but a narrow escape. Exiting a motorway and at 90 km/h leaning in one of these gentle curves, I learned that it is not a good idea to pull the front brake...
Only a month later I had an accident on a minor semi-dirt mountain road in Greece. Another curve and leaning, no braking this time but grit. I survived and in a hospital they have spent an hour plucking the grit from my chin. Could have been much worse though, as I, as well as my lady on her CB350F, were dressed in thin cotton summer pants and - the horror - Greek sandals. Can you believe it? Anyway I went down. The leather bag must have absorbed most of the impact; the bike was saved but for a bent or snapped stud, the threaded part. For repair a schoolboy had directed us to a blacksmith, with in his yard an old tractor, at least some sign of technical civilisation. I had forgotten about this, until yesterday, when I replaced the luggage carrier for the new BUMPER, REAR (Hondaspeak), which makes the bike look so much better.
I can't remember what the man exactly has done, but he must have known what he was doing. He has probably cut the bent threaded part of the stud and has taped a new thread. Simple and effective. He refused payment but insisted on us sharing a glass of Retsina with him.
Off centre, hm, I dunno, I'll make another pic from the right angle. Would it matter much if it was off-centre?
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Nope, all the nut does is stop the shocker falling off, its the big tround plain bit that locates it
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Thanks Bryan. Now that we are on the subject. How crucial are the original 10X32 bolts (PN: 93000-10032-0A) at the bottom of the shocks. They are for a part - don't know the word - 'shouldered'? Is that 'shoulder' very important? If so, I must order them, 'cause the hardware store doesn't have them. As you probably know the clovis of each shock has thread in only one hole and I've noticed I must have damaged the one of the RH shock long time ago, as I have fit a somewhat longer bolt there, to have a nut on the outside of the clovis to fasten things.
How about the rubber bushes (PN: 40548-268-000)? I can imagine you renew them if you are to powdercoat the frame (I won't), what should one look for, to detect wear?
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OK, those bolts are an odd thread so you may have to order one for the undamaged one. They dont have nuts as there is limited space on the inside but if all clears no problem.
I have had swing arms powder coated with those bushes left in and they survived, others havent BUT they are a swine to change as they are a tight fit in the hole, wear, if any, is obvious play
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The rubber bushes that the shocks locate onto can perish, check the rubber for signs of cracking etc. If spotted, change. TBH after so many years I'd advise changing them anyway, the rubber can go hard over time.
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- 'shouldered'? Is that 'shoulder' very important? If so, I must order them, 'cause the hardware store doesn't have them.
Do you mean that it is not full thread. Don't know the exactly "how" important.
A bit of info here.
https://www.fmwfasteners.com/blogs/blog/full-thread-vs-partial-thread-screws
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Thought the bottom fix bolts are shouldered to prevent the shock "legs" from pinching together?
Usually something like this tightens on the fixed end of the thread to prevent it backing out, but leaves the legs and pivot effectively floating so that it doesn't bind in the bush core.
It's a double shear joint to distribute load evenly across the design.
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Never realised they have a special thread.
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Not special just not the"normal" pitch for that diameter, still a standard metric though
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Thanks for clearing that up, Bryan. If the thread of the clovis has been accidentally knackered by me, the LH side will have the same solution, I did RH side: a somewhat longer bolt and a nut on the other side. I believe there's room. Could be it implies temporarily removing the wheel, which is not that much work.
@ Ash Does not seem very off-centre. Camera lens has a will of its own, resulting in a personal view, I guess. ;)
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Functionally I don't suppose off centre is that bad anyway ... I am just trying to jig up some 250k crankcases to drill out a broken off an M6 screw ...trying to use a sleeve in the other half case with a tight fitting, long series drill to guide the drilling centrally.
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Never realised they have a special thread.
Just M10 x 1.25 which seems to apply to most 10mm threads on the bike.
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I'm sorry to revive this thread, but there are still a few things not clear to me. It's about the fastening of the rear shocks at the bottom. Let's look at these, what we call, breast bolts (10x32).
I can understand the clevis has a thread on one side, to save space.
What I don't understand is:
A) What is the breast part of the bolt for?
B) And if it is useful, why is the breast part not longer? The inside of the bushing is plain. Why would you need a thread there?
C) Another thing. In the pic we see the clevis and the bolt but no washers. Is a washer or spring washer not needed here?
I do not have a real problem, but I'm just curious what's the ratio behind it.
If you mount the rear shocks, is there a working order to observe? I mean to not damage the threads. In the past I must have done something wrong. On the RH side I have a longer and fully threaded bolt, with an extra 10mm nut against the outside of the clevis.
On the LH side, the bolt has the original length, but does not really fasten.
I must have done something wrong, but I can't remember it. Too long ago.
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To describe the joints, the rubber composite design (it doesn't need to control geometry here as the swingarm does that) is relatively cheap way of making a joint that can't rattle over time as the rubber flexibility keeps it quiet but allows limited movement.
The centre bore is usually clamped between the shock (at the bottom) with that part not moving at all in relation to the shock. As the suspension moves, the rubber twists (inner and outer metal parts of the bush move separately) with the rubber accounting for all the movement needed through suspension travel. The inner doesn't move on the securing bolt (it would be better engineering practice to have no threads there as you indicate) but with the bush clamped against the shock forks it shouldn't matter much.
It's a double shear joint, the push and pull forces are taken by both ends of the bolt (it would be very very hard to break the bolt in this design) also it makes no rotation torque on the bolt and so will not come loose even without securing washers etc. In reality you could almost put it there with your fingers and it should be safe.
The top mount is just the opposite in how the centre bush is now on the frame, with the outer on the shock. Same deal force plane though. The top pivot is long and passing through two frame wall sections usually to give support for the one sided design else it would bend that mount if just sticking out from a single piece of metal. This one will more or less work without the security nut/bolt as all of the suspension load is taken by the main spindle not the bolt.
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Always facinating to hear an engineering perspective on something we just take for granted Nigel. Never thought about the top mounting spindle going through 2 walls of the frame but when reading about it, makes complete sense.
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[...] it would be better engineering practice to have no threads there as you indicate but with the bush clamped against the shock forks it shouldn't matter much [...]
It seems I am not particularly lucky with these breast bolts. BTW, is that the correct word in English? Please, allow me a sidestep. Below a pic of another breast bolt, the one that is supposed to hold the kick arm in place. Already in 1980, when I acquired my bike, it was wobbly and now this is what the shaft looks like. Needless to say the kick arm slips. If any of you has a tip to improvise something... Suggestions in the international forum were not useful. It's a known CB500 problem; many suffer from it. I hope to find a solution without having to replace the shaft.
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We call those shouldered bolts, a bolt are those which are partially threaded, like a shouldered bolt, setbolts are fully threaded.
Never had a 500 kickstart slip, I'd just replace the kick start shaft myself, if the knurls are worn you'll never get it to tighten properly again.
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As above, with shaft worn it's difficult to get a good solution.
Something that's possible to help (this is quite common in moto-X bikes with kickstart used alot) using a black (engineering) allen/socket bolt, plus a washer under the head and grease on the bolt threads. It can let you tighten the kickstart the most possible to clamp it with the teeth available.
They are the strongest bolt and not plated, so will rust and need to be covered in grease after installation. If that bolt can't clamp it, then it's absolutely a new shaft as this will take more torque than any other generally available bolt.
[attachimg=1]
This type of bolt.
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Thanks for the advice. Some years ago I have managed to restore grip by using a special file. Alas, now the problem has reoccurred.
[...] Never had a 500 kickstart slip,[...]
Could be there were various models. Mine is PN: 28300-374-000
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Just highlights the necessity to to have these pinch bolts properly tightened in the first place to prevent any movement on splines. Not sure if there’s torque settings for these.
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As above, with shaft worn it's difficult to get a good solution.
Something that's possible to help (this is quite common in moto-X bikes with kickstart used alot) using a black (engineering) allen/socket bolt, plus a washer under the head and grease on the bolt threads. It can let you tighten the kickstart the most possible to clamp it with the teeth available.
They are the strongest bolt and not plated, so will rust and need to be covered in grease after installation. If that bolt can't clamp it, then it's absolutely a new shaft as this will take more torque than any other generally available bolt.
Otherwise known as a high tensile bolt ( or cap head socket set screw!) 😉
(Attachment Link)
This type of bolt.
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Yes, I wasn't quite sure how to describe it as deltarider translates to dutch I think, and how that would come out.
Picture to cover it off though.
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I have never quite understood the effects of grease in combination with torque.
A sidestep, if you allow me. In my archives I have a socalled riders report, published in Motor, which magazine in the 70s was a weekly (!). Owners had been invited to answer a long list of questions about the experiences they had with the CB500. In those days the CB500 was a miracle of reliability. There were few complants. Typical complaints however were about the plugcaps and - ofcourse - the sweating/leaking of oil at the head. Honda The Netherlands had issued this recommendation: grease the washers with molykote and then torque the nuts down to the original value.
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ANY lubricant on surface or thread allows the nut to turn easier on the thread and this alters the torque setting when the nut stops turning thereby altering the clamping force applied to the items in question.
You shouls always use the manufacturers setting in which should be specified dry, oiled or grease and if so which type.
Honda do specify molycoate on some of the GL1000 bolt settings
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As Bryan says above.
Fundamental problem is that (for convenience) the assembly uses a torque method to measure rotating resistance (friction is changed with lubricant type) to carry out setting of tensile (stretching the cylinder stud) loading.
There's conversion between the two, controlled by friction, which can be changed with the lubricant used.
Make the nut more slippery and for the SAME torque number, it will pull more tensile load on the stud, clamping the cylinder joint tighter.
Ultimate (and how the original engineering design sets the torque) is to put a dial guage on the end of the stud, measure elongation, and compare that to tensile load specification for material used. Example maybe, you get 0.5mm elongation for 10lb/ft torque.
Think of the stud as a elastic "bungy" cord.
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I wonder how that would affect stainless steel cylinder head studs Nigel. I mean it's not really practical to measure the stretch and as they are stainless you need grease to prevent galling so how would you know the correct torque after using say Nickel grease.
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In reality the stretch and calculations would be done for a representative fixing to give a torque number that's suitable and not by individual stud in situ. So measuring and practicalities involved to give usable working figure, same as any stated torque setting.
There's a more fundamental issue, in that generally available stainless steel has nowhere near the tensile load capability of these std studs. In other words it lacks the ability to clamp the structure to the same force needed to keep the head and barrels on during use.
If the tensile load could be matched, then it would likely be a very similar figure.
The stud is working (the bolts on the engine are steel that's "quenched and tempered" ) with a minimum tensile capability to give the clamping force the designers intended. The effect on changing to ss that didn't match this would be like not doing the bolts up sufficiently, the same rotary torque would likely stretch the ss into yeald and not clamp the structure.
These studs may look ordinary, but there's alot of interesting features in them, probably a topic on it's own.
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I've got an engineer making me some stainless steel studs for the 500/550. I find they rust through the barrels. So I sent him one and asked him to match it, the first bolt failed the stretch test, at 16ftlbs it stretched too much due to the waisted look of the old bolts, he's now reducing the waist to see if he can get one that works whilst sort of keeping the original look. I'll also be fitting stainless steel shouldered head nuts, hence the question re the torque.
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It's quite an involved subject, changing material in relatively high stress application.
The shape, waisting, of the stud is not cosmetic but coincidental to it's function. To fit in the space of the design it's an advantage to be smallest possible, that brings the stress it's asked to take closer to the material design limitations hence the higher tensile heat treatment and correct metallurgical composition to accommodate this.
The stud is then designed with a waist such that the root diameter is consistent from one end to the other with the threads sitting outside this. What this does is to allow the highest tension to be applied for the space available by evenly distributed stretching across each successive mm and consistent from one end to the other. If you increase the waist diameter that equilibrium starts to shift as you can't increase the root diameter of the threaded portion of the stud.
Now as you load it, the centre won't stretch (because the cross section is larger) to the same degree as the thinnest part, this accumulated difference is greatest as the diameter is forced to change going into the threaded section. This effectively overloads (all the stretch has to happen here) the material at that point and the tensile load capability can even go down as you've produced a failure point (shear coupling? ) with all of the forces directly focused at those two transition. Focusing it there can simply be more than that section will ever see ordinarily as the rest of the increased stud no longer shares the stretching.
What needs to happen is to increase the tensile specification of the stainless (loops back to material properties again) rather than change the cross section.
This is why bolts generally fail at the thread juncture if over torqued, the shape of them.
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A good wright up K2-K6.
I don't think any stainless with do this job, even if you torque up to 18 ftlb and re-torque the compression will just stretch stainless. You have 4 hammers (pistons ) at 170 psi trying to push the head off. I think Stainless is just asking for trouble ;)
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It's odd that the 400 cylinder stud doesn't appear to be waisted Nigel. I wonder why that is?
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It's odd that the 400 cylinder stud doesn't appear to be waisted Nigel. I wonder why that is?
I'm pretty sure mine were.
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If the 400 doesn't use that waisted type it would likely be because the loading required is further within the capacity of the material for the 400. That smaller percussive effect of the cylinders takes a fair amount of load off the overall design compared to the larger engine.
I feel the stainless studs would creep too, think of it in structural terms as more like toffee :) sustained load on it gradually deforms over time. The quenched and tempered steel very specifically produces a mild spring like property that is maintained even under loading.
Additional to all of the above (common I think to most of the bolts used on these bikes) the threads are rolled not cut with die or screwcut on a lathe. The effect of this is to effectively forge the threads into the steel structure such that the peaks and troughs are formed leaving no sharp cut into the material surface. This is much stronger and difficult to match by other methods, particularly critical at the thread lead out into the straight stud section.
They really did throw alot of pure engineering theory at these bikes, more from aircraft sphere than other fields (Sochiro was originally in that discipline I believe) which can be seen in the concept of these components.
Also why many "heavy duty" studs are just funny, they include all the faults Honda avoided in original design. Most, all? go with thicker is better claim, avoiding answering the material spec completely.
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All engine threads are rolled on SOHC's.
Julie has just reminded me that i did a CB350 four that the owner had rebuilt with stainless head studs . There were so many warped mating surfaces that were beyond repair, the customer found it cheaper to buy another engine and i rebuilt that ;)
A Die cut thread does not match a rolled thread. Found this out on building a sand cast 750 many moons ago. We here having trouble finding some of the original correct number 8 crank case bolt. The customer had found some longer number 8 bolts to be cut down and a new thread die cut. I have put the crank cases together but, when i went to tighten up the bolts they just spun on the threads and then i remembered that all the threads were rolled. Crank cases spilt, inserted V-coils and that was the only way for the die cut threads to take grip in the threads and take the torque settings :o
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These are the engine studs on my 400f. Main shaft of the stud is smaller diameter than the threaded sections.[attachimg=1]
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Forgive me... what is a rolled thread?
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It is a thread formed by rolling plain bar inside rollers with thread form on them, no metal is removed and threaded bit ends up bigger than plain bit, most common on wheel spokes
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Cheers Nigel. Well that looks to be a busted idea, shame but that's sometimes the way things go. I'll have to either buy new ones or plate the old ones after a good polish up to get rid of the pitting etc.
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Thanks Bryan.
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Cheers Nigel. Well that looks to be a busted idea, shame but that's sometimes the way things go. I'll have to either buy new ones or plate the old ones after a good polish up to get rid of the pitting etc.
Yes Ken, it's these and the conrod bolts that appear to be running the closest to their design limitations out of all of them, and so difficult to make alternative.
Polishing would certainly take them in the right direction though, removing production marks that are sticking out (without removing base material bulk) will improve them in regard to ultimate stress capabilities and a good move with the polishing skills you have used on other parts. If you've a spare to experiment on that would give you good insight as to how they come out.
Plating though, no. It's another process that can cause problems with load performance so I'd stay away from that as a finish.
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Are they not zinc plated initially Nigel? I'd have said yes or they'd rust for fun. By plating I meant zinc not chrome. I wouldn't of course use acid dip to clean them.
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They've not looked it to me, certainly that could be wrong on my part though.
They do look as if they've been rolled to form the waisted section though, which will always improve the corrosion resistance on steel from compressing the outer layers and giving less voids for corrosion to establish.
Manufacturing when quenched is usually in oil too (possibly whale oil then) because it controls the cooling rate, establishing the desired grain structure. When the hot steel is plunged into oil it immediately heats the oil next to it's surface with this effect partially stalling the cool down phase, with this rate critical in how the grains in the steel propogate to make the steel come to it's target tensile specification. Too fast and it heads more brittle, too slow and it stays more malleable. So the goldilocks quench is just right ;D
The oil stage also adds some resistance to corrosion too.
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They can be plated BZP but, there are two parts on a SOHC that can't be pickled, Head studs and carb butterfly. The studs have to be in good condition to plate. Here is a picture on this page of plated studs >>>
http://www.sohc.co.uk/index.php/topic,20419.150.html
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Still in the process of learning... I've dimensioned a bolt similar to the one in the pic, only 35mm, so I can add a nut on the end. Question: is it crucial to have the shoulder part of the bolt on the outside of the bike or does it not matter much?
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No need for a nut, there is one welded to the shock mount ;)
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Not on the Koni's. They have only thread in the hole (one). The thread of one is suspect (either the clevis or the bolt, I still have to find out). Before I start anything, I realise I have two options for reassembly.
a) Have the threaded hole of the clevis on the outside and so the shoulder part of the bolt on the inside of the bike or b) vice versa which is how Honda assembled it.
This matters for eventual removal in the future.
a) implies removal of only the rearwheel, where as
b) means you'll have to remove the exhausts (original) to be able to get the bolts out.
Option b is clearly not my favourite. That's why I'd like to know if it matters much, whether the shoulder part of the bolt, which ofcourse needs to go through the unthreaded hole of the clevis, is on the outside like Honda had it, or just as well can be on the inside of the bike.
I realise this may seem a futile detail, but I hope to learn more on non standard fasteners.
This post (45 minutes!) has stressed my handling of English, but I hope I've made it clear. ;)
Addition: I still find it odd, Honda did not chose the shoulder part of the bolt to be longer. The inside of the bushing is plain. Not only you don't need a thread there, but in theory the bolt's thread could gnaw on the metal in the bush.