Author Topic: Cylinder stud too short!!  (Read 1728 times)

Offline Fogdevil

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Cylinder stud too short!!
« on: February 18, 2018, 11:01:30 PM »
Hello everybody
After having a fantastic day in the garage I come to the final job of the day-fastening down the cylinder head-only to find that the cylinder stud with the 'open' flanged nut(on the offside) will not grip.I can only assume that the stud has been put in too far.The other open nut/stud is fine.
If I omit the copper washer then it will fasten no problem.
If I use the copper washer with the original nut then it will fasten!(But have now stripped the original nut-and it was pretty grotty anyway).Indicates to me that the shortness of length of the stud is minimal.
I have hand tightened the nuts but just put copperslip under the problem nut for now.
Soooo.Do I:
Torque down the nuts as they are-leaving out the copper washer on the problem stud and assume that Honda overenginering will compensate?
Try to get a thinner copper washer?(Washer thickness 2.3mm)
Try different flanged nuts to see if one will 'grip' the stud.The new nut is original Honda part from DS.

I don't know enough about engineering to know if this is an irritating problem or an oil leak waiting to happen.

I am rather hoping my first suggestion is acceptable as I really,really,really DON'T want to undo all my good work so far. :(

What is the purpose of the copper washers?

Ta

Online K2-K6

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Re: Cylinder stud too short!!
« Reply #1 on: February 19, 2018, 07:22:00 AM »
Copper washers are usually used to seal an oil path properly (you could consider them a veeeeery stiff rubber in engineering terms) so it's needed for that. In effect the copper deforms to fit the other metals and creates a good high pressure resistant seal.

All things being equal,  you need to have the nut fully covering the threads to be able to reach the torque required to work as intended. If you could get a copper washer that's thin enough to achieve both aims, then it's possible to use it.

It looks like it's the answer you don't want,  the correct length stud is really needed. If not, you run the risk of it releasing in use or oil leaking possibly. It's a real pain to go back over the assembly you've already completed but it's probably the last point at which it's relatively easy to correct it without much cost.

I'd pull it apart and replace the stud at this point rather than going further.

Offline Orcade-Ian

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Re: Cylinder stud too short!!
« Reply #2 on: February 19, 2018, 08:31:54 AM »
If the difference between apparent success and the inability to get it to tighten is only the thickness of the washer, then that doesn’t even equate to two threads, so as K2-K6 says, you need a longer stud - check the other corresponding one as well.  Yes, it’s a pain to have to retrace your steps but look on the bright side - if you do it now you can re-use the head gasket but if you carry on and it leaks, you have to remove the carbs and exhaust and will definitely need another head gasket.
Btw, the studs should bottom out on the shoulder anyway so can’t be in too deep.

Ian

Offline Fogdevil

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Re: Cylinder stud too short!!
« Reply #3 on: February 19, 2018, 10:17:16 AM »
Oh darn and blast it!!
I wrecked some of the studs on removal so got a complete set of second hand engine studs from a 400/4 breaker and even stipulated the longer studs for an F2.
I remember measuring the lengths and they were all correct but didn't measure the relative lengths of the studs after installation.
I think I'll have to take the problem back to the engineering firm that installed them.(I wanted proper torque on the studs and haven't got that sort of ability to do it without graunching some metal)

Thanks for the info lads.

I'll let you know how I get on.

Mutter,mutter,mutter >:(

Offline Nurse Julie

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Re: Cylinder stud too short!!
« Reply #4 on: February 19, 2018, 10:30:21 AM »
That's a shame but, as others have said a 'bodge' will only come back and bite you on the arse. What I cant quite understand though is if all the studs measured the correct length before you had them put in why does one now seem too short?. They can only go in so far and no further so the chances of the one in question being in too far seems a bit obscure.
Edit...make sure they have not put the stud in too far and cracked the case.
« Last Edit: February 19, 2018, 10:36:42 AM by Nurse Julie »
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Offline Fogdevil

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Re: Cylinder stud too short!!
« Reply #5 on: February 19, 2018, 11:02:30 AM »
You're right Julie.

I think it needs an engineers touch.

Having seen the state of your pistons and cylinder head ,yet the bike still functioned ,made me wonder if a little problem like mine would have been coped with by Honda engineering.

Better safe now than costing lots of money later


Offline Nurse Julie

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Re: Cylinder stud too short!!
« Reply #6 on: February 19, 2018, 11:17:04 AM »
I think Honda engineering can put up with an awful lot but only if the correct parts are fitted in the correct places. What I have learnt recently is that Honda didn't fit certain parts for fun, they were put there for a reason. Some of the items fitted, in this cast the copper or copper covered steel washers are what contributes to making these engines so resilient but the parts need to be in the correct place, to the correct spec for optimum resilience and performance.  I have learnt something this morning, I never knew the head studs were different on the F1 to the F2, I thought they were the same sizes on both models.
« Last Edit: February 19, 2018, 11:18:47 AM by Nurse Julie »
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Offline Fogdevil

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Re: Cylinder stud too short!!
« Reply #7 on: February 19, 2018, 12:12:29 PM »
I know I have read somewhere that the early F1's had a minor oil leak problem on some bikes.
Honda increased the length of some studs(couldn't tell you which ones) by 1mm to cure the problem.
However, if this info is inaccurate I am sure someone on here will inform me.
I would hate to start an 'urban myth'.

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Re: Cylinder stud too short!!
« Reply #8 on: February 19, 2018, 12:44:45 PM »
Picking up on Julie's post about how they could be correct length but short when installed.

If they are different on each end (ie one end to set the depth into the case, one for the nut)  then it's possible the "wrong ones" could be upside down, and so will allow them to go in too far.

Honda,  along with any decent engineers,  are very particular about studs and their loading. General practice would be that a stud should never hit the bottom of the hole it's in. They'd normally be arranged so that the top part of the thread restricts them going too far.
The true torque loading only comes onto the whole assembly once you tighten the last nut, making them kind of "free floating" in engineering concept terms.

If anyone has a set out of the cases it maybe helpful to look at them to see if the differ each end.

Offline Nurse Julie

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Re: Cylinder stud too short!!
« Reply #9 on: February 19, 2018, 01:22:04 PM »
Picking up on Julie's post about how they could be correct length but short when installed.

If they are different on each end (ie one end to set the depth into the case, one for the nut)  then it's possible the "wrong ones" could be upside down, and so will allow them to go in too far.

Honda,  along with any decent engineers,  are very particular about studs and their loading. General practice would be that a stud should never hit the bottom of the hole it's in. They'd normally be arranged so that the top part of the thread restricts them going too far.
The true torque loading only comes onto the whole assembly once you tighten the last nut, making them kind of "free floating" in engineering concept terms.

If anyone has a set out of the cases it maybe helpful to look at them to see if the differ each end.

I was just talking to Trig about this and he suggested the stud may have been put in upside down, thus not leaving enough thread at the top for the nut to engage.
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Offline Fogdevil

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Re: Cylinder stud too short!!
« Reply #10 on: February 19, 2018, 01:59:08 PM »
I have just gone onto the DS website to have a look at a picture of a stud.
You are all quite right. There is definitely a bulbous part to the shaft, just above the thread, at one end.
Looks like it has been put in upside down!!
Oh well.A trip back to the engineers is on the cards.
I refer to my earlier comments:"Mutter,mutter,mutter"

Thanks for your help.I will let you know the outcome.


Offline Nurse Julie

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Re: Cylinder stud too short!!
« Reply #11 on: February 19, 2018, 02:37:11 PM »
I know I'm keeping on  ::) ::) but having read your original post again, I'm a bit confused. Which stud is it exactly that your having problems with, maybe a photo would help. I'm thinking are you fitting a copper washer where there should be a Dowty washer?
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Offline Orcade-Ian

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Re: Cylinder stud too short!!
« Reply #12 on: February 19, 2018, 03:37:13 PM »
I just checked the other 400/4 - a 76 F1 and this engine has not been molested before I got it.

Steel rule measurements only

These are the results from the Orkney Jury:

[ Guests cannot view attachments ]

If they are upside down, they can be wound in much further on some of them


Ian

Oops, forgot to say those measurements are with the studs fitted and the distance is from crank case top face to top of stud
« Last Edit: February 19, 2018, 03:41:34 PM by orcadian »

Offline Nurse Julie

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Re: Cylinder stud too short!!
« Reply #13 on: February 19, 2018, 03:43:42 PM »
Soooo, could one not just put double nuts on the top and wind the stud out by 2 threads?. It would save Foggy stripping the top end down again.
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Offline Fogdevil

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Re: Cylinder stud too short!!
« Reply #14 on: February 19, 2018, 03:51:22 PM »
It is in the front row of studs,offside, second one in.(E227 90032-377-000 in parts manual) [ Guests cannot view attachments ]
On Orcadian's picture it is the left hand(as we look at it) 100.
Just to complicate matters my parts manual describes it as 8x122, which I assume means 122mm long?

 

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