750 exhaust studs, nuts and washers

S

smlav

Senior member
Location
Shropshire UK
On removing the exhaust system three of the nuts were seized such that the studs came out intact rather than nut coming off the stud. Better than the stud breaking! The nuts have what looks like a copper coating, but it appears to have broken down allowing seizure. The nuts had no washers, they have a splay on the end which goes against the clamp.

So I’m going to fit new studs and nuts. These are m7 studs.

what is best practice ? Should I
Fit a spring washer, and if so is stainless okay
Do I put copper slip on the stud going in head?
Do I put copper slip on stud when fitting nut?

I was going to use the BMW brass self locking nuts which are said to be for exhaust studs.

Thanks for any advice
Sean
 
The nuts should be brass and have steel spring washers, that's what was fitted by the Factory.
Seems like a DPO has fitted steels, possibly passivated/
Locknut the cylinder head end of the studs in a vice. With a torch and pentrating fluid it should be possible to free the nuts.
It should be possible to get brass nuts but, at a push, the BMW ones should do.
Take care when tightening, it's quite easy to crack the alloy clamps. DAHIKT?
 
Pretty sure triples use 7mm exhaust studs. They take brass nuts and spring washers as std. SFs with big valve heads (SF1/2/3) went to 8mm studs, again with brass nuts and spring washers as std. Studs should never come out with the nut. My recommendation would be to remove the seized nuts, fit the studs tightly back into the head (careful not to strip the soft alloy) and use brass nuts and spring washers. I've never used any kind of locking or anti-seize agent on mine and have never had an issue, or had any loosen. I doubt any product would cope with the heat anyway.

On the small valve head I used as the base for the SfQ quite a few of the stud threads had stripped in the head. I upped them all to 8mm using recoils.
 
Thanks, I have a small valve head from GTL and two large valve SF1 heads. All have the same size studs, 7mm.

The GTL and one SF1 have OE brass nuts and stainless washers, the nuts are 13mm across the flats (right side on photo). The other SF1 has what I believe are the BMW type nuts which look like they are copper coated, splayed end, and are 12mm across flats, and three of them are seized.

So I guess solid brass nuts and stainless washers is best.
 

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smlav said:
Thanks, I have a small valve head from GTL and two large valve SF1 heads. All have the same size studs, 7mm.
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Must be a very rare SF1 ... mine was an early build (13768) and it has 8mm studs inlet and exhaust. Never seen a large valve head with 7mm studs. Are you sure it hasn't been fitted with an earlier head?
 
piranha-bro2 said:
Must be a very rare SF1 ... mine was an early build (13768) and it has 8mm studs inlet and exhaust. Never seen a large valve head with 7mm studs. Are you sure it hasn't been fitted with an earlier head?
Click to expand...
Am I measuring the stud corr3ctly? See photo.

I have a GTL engine, owned since new, 18089, small valve head.
I have SF1 engine, bought from breakers in 1981/2, 15319, large valve head
I have recently acquired SF1 14005, large valve head, quite a few owners

They all have identical sized inlet and exhaust studs. The GTL and first SF1 motor have all brass nuts.
 

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smlav said:
Am I measuring the stud corr3ctly? See photo.

I have a GTL engine, owned since new, 18089, small valve head.
I have SF1 engine, bought from breakers in 1981/2, 15319, large valve head
I have recently acquired SF1 14005, large valve head, quite a few owners

They all have identical sized inlet and exhaust studs. The GTL and first SF1 motor have all brass nuts.
Click to expand...
More or less.
You should measure the threaded part.
Paul
 
smlav said:
Am I measuring the stud corr3ctly? See photo.

I have a GTL engine, owned since new, 18089, small valve head.
I have SF1 engine, bought from breakers in 1981/2, 15319, large valve head
I have recently acquired SF1 14005, large valve head, quite a few owners

They all have identical sized inlet and exhaust studs. The GTL and first SF1 motor have all brass nuts.
Click to expand...
Truly bizarre - as mentioned, my SF1 is 13768, so older than both your SF1s. 8mm studs. Maybe they fitted an SFC head to mine :ROFLMAO: :ROFLMAO: :ROFLMAO:
 
I use stock studs but with custom made long domed end brass nuts, made from 7mm hex bar, never corrode and because wired never come loose.
CLEM
 

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smlav said:
Is there a recommended torque value for the nuts going on exhaust studs?
Click to expand...
Probably - but in 50 years of ownership I've never used a torque wrench on them - I do them tight but not too tight :cool: . But then again, I've known people who have a vast propensity for overtightening every nut and bolt on their bikes and subsequently stripping threads everywhere. Your oddball 7mm studs (on an SF1) won't handle much.
 
I’ve done them up tight, but not too tight. I wonder if anyone has ever put longer studs in and then put a brass half nut on after the main nut to act as a lock.
 
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