Post by: Lobo on March 21, 2019, 02:32:53 AM
Slight oil weep on the ‘400, emanating within the fins / RHS. The engine was rebuilt about 500miles ago, and so figured I’d simply re-torque the head.
Which is what I’ve now done...
Have to say, and using ‘Clarkson parlance, “poo was coming out” as I slackened, and re-torqued each to the book figure (15 ft-lb). Fingers crossed the slight weep has been remedied.
The Rocker cover however, was a different matter, and I noted at least 3 thread inserts already in place. And whilst I couldn’t bring myself to use the book figure this time (6 ft-lb)... bloody #12 (the last bolt!) failed to tighten... even to my calibrated elbow.. and well below 5ft-lbs.
So... that thread has an insert now, and job fettled... til next time.
Q - any comments here wrt using book figures on 40 yo engines which may have indeed been apart more than once. And if so... given how soft these heads are... what are you typically torquing to? There seems to be a finite number of times these motors can be taken apart and put together!
Post by: Bryanj on March 21, 2019, 08:05:43 AM
Post by: Harold 400/4 on March 21, 2019, 08:51:24 AM
H
Post by: Lobo on March 21, 2019, 11:27:17 AM
Yep, you can easily access all 12 bolts to torque the cylinder head. Spark plugs 2 & 3 will need to be removed, as will a couple of oil spray bars. (They just lift out). You might want to stuff a lint free rag abouts the cam chain sprocket tunnel area, as anything dropping down there will surely spoil your day.
Note there’s a gradual tightening sequence up to full torque... basically working from the centre of the head (and indeed rocker cover) out.
Didn’t see it written anywhere.. but you probably want to consider loosening all the tappet adjusters to allow the rocker cover to naturally fit onto the head prior to buttoning it all back up.
You’re asking the wrong person here as to whether you need to ‘slacken’ each head bolt first - my logic was that ‘stiction’ would possibly screw the process, and that a gentle continuos tightening to required torque would give a more accurate setting.
Thanks for the comment Bryan... fits in with my gut feeling given the head’s made of something akin to butter...
Btw - took it out for a run this arvo... and so far all looking good. Phew..
Post by: K2-K6 on March 21, 2019, 11:54:32 AM
From an engineering point of view I don't feel that they wear out, as such. It's the case that the steel bolts can very easily exceed any torque aluminium castings can tolerate.
In tightening them, if the torque used succeeds in fracturing the threads ( in essence detaching the thread form from its root anchored to the surrounding metal) then they are scrap from that point onwards. It doesn't matter if it's the first, or many times its been used.
That joint is unusual in how it's viewed from a technical point. Using its two faces to provide the tolerancing for cam bearings, it only has to be tightened until the surfaces touch by which time the o-ring shouod have long been compressed into its sealing function. The remainder of tightening after this point is just to provide a "shakeproof" torque on the bolts. It really doesn't need much to do this.
There's anther factor that's not really considered, which is lubrication of the bolts and the affect it has on torque rating. I think Bryan made this observation about whether to lubricate the thread's some years ago (that was in relation to head studs, that I remember).
As I understand it, thread torque used is given for a dry thread UNLESS a lubricant is specified.
If you add a lubricant to this equation it requires you to use LESS measured torque to achieve the same clamping force, but the load on each thread goes upwards toward failure. Torque is just measuring friction and has to be qualified for the friction in place. Change the friction, and you change the measurement of torque as it's rotary and specifically doesn't measure the clamping force.
It follows that if you use oil and maximum torque specified, then you'll come closer to the materials capabilites to resist failure.
The general interpretation would be to reduce torque by 10 to 15% indicated by figures I can find.
Post by: Bryanj on March 21, 2019, 12:02:28 PM
Post by: Laverda Dave on March 21, 2019, 08:40:52 PM
Post by: Lobo on March 22, 2019, 12:26:00 PM
Question Nige.. will the threads maintain integrity if never torqued beyond the book figure... or will repetitive torquing eventually take its toll?
If the former, must we assume that over-torquing regularly occurs?
And as Harold asked.. is it good - or poor - practice to slacken any nut / bolt slightly before re-torquing it?
Cheers.
Simon
Post by: Bryanj on March 22, 2019, 02:30:54 PM
On the re-use of studs/nuts/bolts as long as you stay within the "elastic" limits of the metal involved you can use them till the thread wears out, this is why on most modern car/truck engines bolts have to be changed every time as they are not "torqued" but tightened through a set angle after initial seating which takes them very close to the "elastic limit point". Old Triumph motorcycles used to specify a "stretch" amount on big end bolts rather than a torque.
Are you now all suitably confused?--------- Good cos Swansea just sent me a letter telling me my licence is to be retuned to me in another letter so when it arrives i can go back to work!!!!!
Post by: Nurse Julie on March 22, 2019, 02:36:49 PM
Post by: Bryanj on March 22, 2019, 03:28:53 PM
Post by: Laverda Dave on March 22, 2019, 04:36:26 PM
A friend of mine had a modern MG (the one with the K series engine). Like all these engines the head gasket blew. The garage changed the gasket but not the stretch bolts, the gasket blew again a coupe of weeks later. To do the job properly cost £1,100!
Post by: K2-K6 on March 23, 2019, 02:37:27 PM
The technical points:- as you say Dave, the bolts are a real problem if corrosion gets into the threads. The zinc plating is the part that protects them originally, but as we all know when exposed to salty winter roads it will strip that off over time. The zinc is sacrificial so that when you see them going white in early stages of their life you are observing that process in operation. Once gone though, it starts on the components to give that siezed stage that can destroy the parts. Using something to avoid this is sensible as you do with coppaslip, just have to be aware of the effect on measured torque.
Bryan picked up on scale with things like this. it seems to trip up the unaware in not acknowledging the very small scale that is involved, many just don't believe that they are working with such small numbers, for both tolerancing and torque settings.
To elaborate on the cam cover bolts Simon, yes it should be true that if never over torqued they should be ok for most eventuality. They have more to them than is generally appreciated I believe. I mentioned earlier about the torque on the threads, what Honda have done on these though is to design in a wide head/flange on the bolt. The increase in the surface area is the principal element in how the torque is built up. If tightened correctly it'll reach the measured specification just from this surface and not overstress the thread area. As mentioned, the joint face is not compressed like a gasket, so once the two metal components come into contact that is job done, the bolts just need the torque setting to stop them backing out during use.
It's one of those assemblies in which some very subtle elements combine to give an integrated whole component.
Retightening head bolts, it's one of those things that I don't think can be answered definitely as to method, unless the original manufacture gives a prescribed routine.
Faced with trying to retourque them means it's already compromised the gasket to some extent, else it would not be required. Agree with Bryan in releasing first then tightening again to get a correct reading.
I'd do them one at a time so that the head casting is not released and in the original pattern of engine build if doing them all.
It's one of those things that you'd hope to get it to seal, but may have to accept it needs replacement if not effective.
That K-series engine Dave, as far as I remember they have bolts that go right through the whole assembly and hold crank main, pass through block, then the head to squeeze the whole assembly. It's quite a clever design, but like many things considered in that way, sometimes mis-understood.
They are definitely "stretched" bolts, in that they are pulled during tightening past elasticity into primary yeald to set them correctly and need replacing if taken apart.
Great irony of those engines is it's not this construction that causes the fault in the first place, but often gets blamed. The overheating usually originates with failure of water system sealing to the inlet manifold as I understand it. They run a fairly small coolant volume and will readily overheat because of this problem, by which time the head gasket is compromised.
Post by: Laverda Dave on March 23, 2019, 10:00:47 PM
Yes, the K series was known as 'ladder construction' I believe. I remember Suzuki made a big thing about it a few years ago with the GSXR engine even though most motorcycle engines are built using this method!
I've just bought a new Sealey 1/4 torque wrench as I think my SP one is out of calibration after 25 years!
Post by: Bryanj on March 23, 2019, 10:27:02 PM
Post by: Laverda Dave on March 23, 2019, 10:43:52 PM
We had a torque wrench calibration station at work and I used to walk past it thinking I would bring my wrenches in from home to test them before I retired, of course I kept forgetting and now I've retired!
Post by: Bryanj on March 23, 2019, 11:39:11 PM
OR if you are passing Gloucester call in and i will check it with my Snap On Torque Meter.
Remember most torque wrenches are only calibrated + or - 10%.
Post by: ka-ja on March 24, 2019, 09:19:12 AM
Post by: Laverda Dave on March 24, 2019, 06:11:38 PM
Thanks also Ka-ja.
I do always make a point of unwinding the wrenches after use to leave them on a zero setting as told in my school days leaving them 'set' weakens the spring and results in false readings. I don't know if true but I've always done it.
Post by: Lobo on March 24, 2019, 11:58:15 PM
Post by: Laverda Dave on March 25, 2019, 09:45:20 AM
Strangely the 6mm threads on the CB250RSA are also torque set at 8lb none have stripped!
Post by: K2-K6 on April 06, 2019, 12:37:30 PM
Question was "Why do the torque figures range over such a larger percentage difference given that some of the tolerancing is so very very fine and precise?" I couldn't answer this with credible logic.
Now, if we apply it to these bolts only, 7 to 9lb per foot, has the top figure something in the order of 9 being 33% increase on the 7lb setting!
If you add in "marketer's" psychology of giving a price range, the middle one being what you sell most of, the lower figure to make the middle purchasers feel they've got something a little bit better for their informed choice, and the highest cost, is just pure additional margin for those foolish enough to shell out for it :)
Comfortable we are in choosing the centre point, and it just seems so logic doesn't it. So, if you take the 8lb and work through possible errors/ potential for unquantified effects, you can get 8 + 10% torque wrench accuracy (depends which way it defaults) + 15% for grease/coppaslip change to torque measurements, you can end up with 10.1lb measured torque.
Or for those making a decision that you should use the highest torque figure, something like 11.4lb :o
It's easy to see why they are often stripped. Also why they gave us just screws on many of the covers on these engines so that generally people can't load too much torque onto them with just a screwdriver.
If you look at the joint on these cam covers, they are metal to metal with no gasket to compress (once touching with the o-ring compressed) so have no yeald built into the torque interface.
If you had to specify it, once the casting faces touch, then you'd only need something like 2 to 3lb of torque to prevent the bolt backing out in use. So a safety margin of double that, 6lb, would be a good set point to make sure they reliably exceeded a practical minimum during engine use.
Then if you set your torque wrench to 5lb, lubricated the threads ONLY, made sure the underside of the bolt head was clear of lubricant, along with the casting face. You should get a true torque of between 4.5lb (if torque wrench was 10%error in minus) to 6.3lb with all errors maximised to plus figures in above illustrations.
This would minimise potential of stripping them, and make sure they don't release in use.
Post by: ka-ja on April 06, 2019, 07:33:41 PM
Post by: Bryanj on April 06, 2019, 07:40:35 PM
Post by: Lobo on April 07, 2019, 12:00:50 AM
You mentioned lubricating the threads only - one turn of a 6mm thread would be approx 18mm, so (eg) a dozen turns would be getting on for 20cm worth of minimised thread friction? Would this not be very significant in terms of falsified torque readings?
Ka-ja / Bryan... you guys have the experience / skills of a lifetime fettling such things, us mere mortals can’t hope to accurately set torques using fingers!
Post by: K2-K6 on April 08, 2019, 08:56:47 AM
In addition to that, it's the reason why flat spanners and Allen keys etc have diminishing lengths as they go down in bolt size, to in effect limit the torque applied by the user and give some semblance of feel consistent with each size when tightening.
This is effectively subverted when using a socket set with one length handle for all bolt sizes, especially if you are using 1/2 inch drive with 10mm socket.
Even when using an appropriate rate torque wrench it seems like you aren't really tightening them enough.
I've no problem in judging without a torque wrench for non critical bolts, but have been involved with writing manuals in which a task has to be accomplished by users with very different skill levels. It's quite a challenge to convey the correct route to such a wide range of familiarity, and end up with the same final result.
There's an old description for this " those that can do and know they can are fine, those that know they can't do and seek assistance are fine, those that can't see that they can't do are where problems exist" :)
This thread seems to be more "behind the scenes" discussion of how the spec is affecting the final method on these engines.
To answer your last torque question Simon, it's useful to compare the cam cover bolts to the cylinder head studs to show the difference. The head stud has flanged nut operating on washers to reduce the torque measured from straight surface friction. This allows it, during tightening, to pull the stud into tension within its elasticity. The resistance in torque reading will mostly come from the thread pitch lengthening on the stud coming into conflict with the nut threads which are being compressed.
The cam cover bolts are never going to be at that level (even those size steel bolts will easily take something in excess of 10 tons of tensile load, they'd pull the alloy threads out of the casting long before that) so they delete the washer with the resulting torque you measure being just from friction between the underside of the bolt flange and the alloy casting. The threads really aren't being measured in this application.
It occurred to me that the numbers quoted in the manual are not really assembly accurate figures. They appear to be a range that "includes" torque wrench typical error figures. I.e. aim point plus or minus 10%.
That's not the same as giving the mid range figure and accepting the error of torque would do the job. It allows, promotes? A situation in which you can start at the extremes of error and then add some more with a torque wrench. :o
Post by: ka-ja on April 08, 2019, 09:22:27 AM
Post by: K2-K6 on April 08, 2019, 10:02:06 AM
https://www.wiggle.co.uk/x-tools-essential-torque-wrench-set/
1/4 drive and from 2nm about 1.5lb-ft
Post by: ka-ja on April 08, 2019, 11:49:35 AM
Post by: Nurse Julie on April 08, 2019, 11:56:29 AM
Looks the part in a handy case, My smallest is 3/8 drive britool about 40 yrs old.Trig uses the old Britool torque wrenches including the little 3/8 drive.
Post by: Lobo on April 09, 2019, 10:53:38 AM
Post by: Bryanj on April 09, 2019, 05:14:23 PM
If i have missed anything out i appologise and will re rant later!!!
Post by: SteveD CB500K0 on April 09, 2019, 05:20:13 PM
498cc is just over 30 cubic inches. Wouldn’t fit on the side panel would it.
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Post by: hairygit on April 09, 2019, 06:38:35 PM
But we all use cc do t we Bryan?Oh I don't know, 30/four would be okay!
498cc is just over 30 cubic inches. Wouldn’t fit on the side panel would it.
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Post by: K2-K6 on April 09, 2019, 06:55:56 PM
Just feel fitter in kg, and the conversion makes it easy to drink "foreign" beer without getting rumbled :)
Alot of things are better in decimal though:-
Diana Doors vs Bridget Bardot.
Lucas vs Cibié or even the super chic Sev-Marchal.
Austin Maxi vs Citroën DS
;D
Post by: Bryanj on April 09, 2019, 07:18:54 PM
Post by: taysidedragon on April 09, 2019, 07:40:13 PM
I think I'm ambi-dexcimal ;D
Just feel fitter in kg, and the conversion makes it easy to drink "foreign" beer without getting rumbled :)
Alot of things are better in decimal though:-
Diana Doors vs Bridget Bardot.
Lucas vs Cibié or even the super chic Sev-Marchal.
Austin Maxi vs Citroën DS
;D
Agreed. Maybe a VW Golf instead of a DS though. 😉
Post by: K2-K6 on April 09, 2019, 07:47:31 PM
Haven't seen a manual for Bridget Bardot :D
Post by: Moorey on April 09, 2019, 08:14:47 PM
Post by: taysidedragon on April 09, 2019, 08:27:25 PM
It always makes me smile whenever I get given a drawing to make something and its a mixture of metric and imperial. A case of whatever is convenient. These days tape measures should only have metric on them. What year did we go decimal.
It makes me laugh too. In Junior school about 100 years ago they taught us imperial and metric, then said we would be completely metric 'very soon!' 😂
Post by: Rozabikes Tim on April 09, 2019, 08:58:50 PM
Post by: TrickyMicky on April 09, 2019, 09:13:10 PM
Post by: K2-K6 on April 09, 2019, 09:24:11 PM
They are inches diameter, aspect ratio expressed as percentage of width, which is mostly in millimetres now! Not confusing at all :)
We drive around in miles still, but buy fuel in litres.
Aren't mainline railways all the same, apart from those cunning Spanish chaps?
And off down the pub for a pint of oldsquirrelbollocks, or is that now officially, I'll have a 568.261ml of old peculiar rats nadgers please barkeep.
Post by: bucksfizz on April 09, 2019, 09:26:33 PM
It always makes me smile whenever I get given a drawing to make something and its a mixture of metric and imperial. A case of whatever is convenient. These days tape measures should only have metric on them. What year did we go decimal.
It makes me laugh too. In Junior school about 100 years ago they taught us imperial and metric, then said we would be completely metric 'very soon!' 😂
We can never go completely metric - there are just too many products/protocols out there that are Imperial only.
All pedal cycles use 9/16" BSC (cycle thread or CEI) on the cranks and pedals, and it can never change, otherwise old pedals won't fit new bikes.
All taps use 1/2" or 3/4" BSP (pipe thread) - even in Europe.
A lot of pipes in the UK are 38 mm (a nominal value for 1½").
All socket drives are 1/4", 3/8", 1/2", 3/4" or 1".
Tyres are always in inches for the diameter - I was talking to a tyre fitter who claimed he didn't know Imperial until I pointed tyre diameters ;).
All aircraft fly in feet (Flight Level 350 = 35,000').
Minimum tyre tread depth is 1.6 mm, but that's just 1/16" translated to metric.
All fence panels are 6' wide.
Standard house doors are 2'6" wide, but I did see a DIY store selling 762 mm doors :).
Printer quality is measured in DPI (dots per inch).
There are probably dozens more examples, but I've probably bored you enough already.
Post by: Lobo on April 09, 2019, 10:03:35 PM
Much the world is indeed FL in feet, parts of (Russia, China etc) it in metres eg FL10800m. Aargh
Ditto masses... eg UK a/c weighed in Kgs... yanks use pounds on their load sheets.
Fuel... and accidents are recorded here... uplifted in Kgs most parts... yanks uplift in Lbs
Visibility... much of the world in km (or m in low vis).... yanks in statute miles
Wind velocity... mostly in knots, many places in metres / sec...
It’s a wonder there isn’t more prangs as aircraft fly between countries 😱
Post by: Nurse Julie on April 09, 2019, 10:31:28 PM
Post by: MrDavo on April 10, 2019, 08:21:07 AM
US gallons do my head in, trying to convert mpg figures and tank capacity to real imperial gallons, to give an idea of range is a nightmare.
Didn’t some multi million dollar Mars probe make its own crater because someone got a measurement’s units mixed up?
Post by: K2-K6 on April 10, 2019, 09:05:01 AM
It's one of those areas that can catch people out on these Honda engines. The discussion of bore clearance being one obvious topic. The engineering suppliers generally working on British biikes and cars never want to believe or accept how small a tolerance is quoted, usual response is "that can't be right" and followed by "what you need is".
Post by: Lobo on April 10, 2019, 09:13:25 AM
Post by: ka-ja on April 10, 2019, 09:28:02 AM
Post by: Nurse Julie on April 10, 2019, 10:02:03 AM
Bloody Hell MrDavo.... years of failed diet control, and you’ve cracked it. All grocery shopping now to be done on the 400F. 💀There's a lot to be said about doing the shopping on a bike. In the summer, 9 times out of 10, I will go to the supermarket on a bike with a ruck sack. The food shop bill goes down drastically when all i can buy is what i can fit in the rucksack 😀😀😁
Post by: taysidedragon on April 10, 2019, 10:30:57 AM
Both measurements are metric and they are exactly the same! Just a name change.
Absolutely pointless!
Oh, and America still use inches of mercury instead. 😣
Post by: MCTID on April 10, 2019, 10:41:23 AM
She also visited Rimini in Italy in her later years....and asked about catching the Bus into town. The Hotel Concierge told her which number Bus, and explained that she would know the right Bus because it would say 'Rimini' on the front, and they ran every 10 minutes. After an hour she went back and told the Concierge that she had not seen a bus in all that time........he looked a bit puzzled and apologised profusely........he then went outside with my Mum and after some discussion, he explained that she had been standing on the wrong side of the street and all the traffic on that side of the street was coming out of Rimini - not going to Rimini !
Maybe being my Mothers Son helps to explain why I'm a dopey git ! (no rude comments please....I'm rather sensitive these days).
Post by: ka-ja on April 10, 2019, 10:43:31 AM