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Cylinder stud too short!!

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Fogdevil:
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

K2-K6:
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.

Orcade-Ian:
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

Fogdevil:
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 >:(

Nurse Julie:
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.

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