Cylinder base stud repair?

recently, one of my cylinder base studs loosened up out of the crankcase, which I'm sure is stripped. Can anyone tell me the type of thread that is? Though I have not taken it apart yet, I'm sure its going to need a helicoil.

this is the way its described at stainlessbits.com:

06-2639 STUD ??? 3/8"x16-24x2"

not sure about that "???"

Thanks!

Don

I read a double ended stud 3/8"od and 2" length with 16 tpi (UNC) at one end and 24 tpi (UNF) at the other end.
'???'= dunno (maybe email stainlessbits.com and ask them).
Stainless steel is pretty.

needing said:

I read a double ended stud 3/8"od and 2" length with 16 tpi (UNC) at one end and 24 tpi (UNF) at the other end.
'???'= dunno (maybe email stainlessbits.com and ask them).
Stainless steel is pretty.

Click to expand...

Thanks! have a good weekend.... cheers, Don

DonOR said:

this is the way its described at stainlessbits.com:

06-2639 STUD ??? 3/8"x16-24x2"

not sure about that "???"

Click to expand...

http://www.nortonmotors.de/ANIL/Norton% ... s-list.php

CYLINDER BASE STUD 3/8"UNF/UNC

Click to expand...

needing said:

(maybe email stainlessbits.com and ask them)
Stainless steel is pretty.

Click to expand...

Although the 'stainlessbits' list is still up, the company ceased trading some years ago now, so there's a chance that enquiries will not be answered.

I noticed that many threads on my 74 850 are helicoiled an seem to have been done at the factory. These include the 4 long cap head screws used to hold the barrel but the stepped studs where in good condition and fixed very solidly in the cases so i left them in place an don't know if they to are helicoiled but it may be wise to get it apart before purchasing a kit. My barrels were a very close fit on the studs (as they are meant to be for location) so great care should be taken to repair the stud an maintain it's position or you may have to "adjust" the corresponding barrel hole.
Jim an his bronze inserts an CNC miller would be the best fix but that would involve much more work an shipping to.

toppy said:

....... so great care should be taken to repair the stud an maintain it's position or you may have to "adjust" the corresponding barrel hole......Jim an his bronze inserts an CNC miller would be the best fix..........

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+1...... I was thinking the same thing

I'm fairly certain that at some point the base nuts were cycle thread which was changed to UNF later on.

Might be worth checking the dates of that.

Just for interest sake.
At 3/8" od
UNFine = 24 tpi
BSCycle = 26 tpi

pommie john said:

I'm fairly certain that at some point the base nuts were cycle thread which was changed to UNF later on.

Might be worth checking the dates of that.

Click to expand...

From serial 200001.

So donOR, with a 1972 Combat Roadster it appears you have selected the correct stud for the helicoil repair to the cases if required i.e. 3/8" UNC. Good luck with the repair - perhaps a good time to do all those threads.

L.A.B. said:

pommie john said:

I'm fairly certain that at some point the base nuts were cycle thread which was changed to UNF later on.

Might be worth checking the dates of that.

Click to expand...

From serial 200001.

Click to expand...

Interesting, mine is a '72 with matching numbers 152292, and its UNC/UNF.....

many thanks for the responses. Cheers, Don

DonOR said:

L.A.B. said:

pommie john said:

I'm fairly certain that at some point the base nuts were cycle thread which was changed to UNF later on.

Might be worth checking the dates of that.

Click to expand...

From serial 200001.

Click to expand...

Interesting, mine is a '72 with matching numbers 152292, and its UNC/UNF.....

many thanks for the responses. Cheers, Don

Click to expand...

That is interesting, as the generally accepted changeover to Unified for the crankcase fasteners up to now has been the start of the '200000' series cases:

http://www.norvilmotorcycle.co.uk/catalogue.htm

069156 SET - STUD - CYLINDER BASE 750 200000 ON -SET OF 9-PLATED-W5
069157 SET - STUDS - CYLINDER BASE 750 PRE 200000-SET 9-PLATED-W5

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However, as 152292 would actually be a reasonably late '71 model, so it's possible the changeover occurred prior to 200001 ? :?

That is interesting, as the generally accepted changeover to Unified for the crankcase fasteners up to now has been the start of the '200000' series cases:
However, as 152292 would actually be a reasonably late '71 model, so it's possible the changeover occurred prior to 200001 ? :?

Click to expand...

Highly unlikely a 71 /152xxx came with UN hardware from the factory. My (unmolested) engine 152589 has BSW/CEI studs...as well as all other pre combat breather cases I own.

Much more likely a butcher put later hardware into early cases.

I note the reference to stainless fixings ....and if you are considering using them.....
A great many years ago I fitted a set of stainless crankcase studs but a few years later when I tried to remove them they did not want to come out. A lot of heat and even more grunt and they eventually came out ALONG WITH A LOT OF GREY DUST. Thus I learnt at a young age about mixing dissimilar metals and that aluminium alloy and stainless steel are dissimilar........ Luckily the holes were reclaimed.
Many years later I spent many years playing with naval anti missile defence radar systems and the use of stainless fixings was standard. However all fixings were cadmium plated and passivated and when assembling a stainless fixing into aluminium alloy the fixing was first dipped into a pot of yellow 'gunge' called Duralac. The reason is best given below from a Duralac web page.

Duralac is a chromate containing jointing compound designed to inhibit electrolytic decomposition between dissimilar metals – often called galvanic corrosion. It is a single pack, air setting product. Used correctly, Duralac prevents anodic decomposition.

Personally I worry about the use of stainless steel bits especially critical components wheel spindles simply because to my knowledge there is only one particular grade of stainless that matches the tensile and shear strength of the original components employed and in the case of Norton wheel spindles I understand had a tensile strength of 55 tons per sq inch with an Izod value of around 35-40 ft lbf. Now it may well be that the original materials used for wheel spindles were well over the top but not many years ago a friend had his stainless rear wheel spindle fail half way across the USA while on a coast to coast ride on his Commando.I have often wondered what grade of stainless steel was used to manufacture that wheel spindle / dummy axle........Did not Les Graham die during a pre WW2 German G P due to rear wheel spindle failure on his works Norton??? Well that was the tale my late Father told me as we visited his memorial on The Mountain in the late 1950s.

Just a thought.........

Much more likely a butcher put later hardware into early cases.

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Or perhaps the original cases were damaged and replaced with new factory replacements of later manufacture, re-using the original serial number. Not hard to imagine with Combat model.

To take JM Leadbeater's post a bit further:

The 400 series stainless alloy fasteners should NEVER be applied to aluminum alloys.

The 300 series stainless alloy fasteners should be applied to Aluminum alloys in the MARINE environment, ONLY with caution and proper galvanic protection.

The 304 and 316 series stainless alloy fasteners (the common variety found in most hardware stores) may be applied to aluminum alloy if kept DRY, BUT IT IS BEST TO USE an anti-seize compound, or better yet Duralac or equivalent.

Hope this helps.

Slick

BTW .... helicoils are a 300 series stainless, thus if they are to be used as a thread repair in aluminum alloy, the anti-seize or anti-galvanic compound should be used when inserting the helicoil. With a stainless helicoil insert, a stainless fastener can be used with no concern, except where the fastener contacts the alloy surface .... use a sacrificial alloy washer, or a nylon washer if it will hold the torque.

Slick

BTW .... helicoils are a 300 series stainless, thus if they are to be used as a thread repair in aluminum alloy, the anti-seize or anti-galvanic compound should be used when inserting the helicoil. With a stainless helicoil insert, a stainless fastener can be used with no concern, except where the fastener contacts the alloy surface .... use a sacrificial alloy washer, or a nylon washer if it will hold the torque.[/quote]

Would red locktite on a helicoil insert have the required anti-galvanic protection? Most installation instructions for helicoils say to use red locktite.
Pete

Deets55 wrote:

. Would red locktite on a helicoil insert have the required anti-galvanic protection? Most installation instructions for helicoils say to use red locktite.

Good question. Red Locktie is recommended because no one wants the Helicoil to back out when removing the fastener. LockTite is a plastic material, and as such, is an electrical insulator and should provide galvanic protection (if it gets between the dissimilar metals). In any event, If the joint is kept dry the compatibility tables say no coating is absolutely necessary, so any coating whatsoever which shields the dissimilar metals is a plus.

I went to the Henkel (LockTite Parent Co) website and did a search for the answer. All I could turn up on the site is LockTite provides "corrosion protection". I contacted Tech Support for a more definitive answer, and will append this post if/when I get an answer.

Slick

BTW .... Helicoils are awfully hard to back out unless one has the special extraction tool. It may well be no bonding agent is necessary, and the use of the proper anti-galvanic coating is the better choice. My memory says NASA recommends use of an anti-galvanic coating similar to Duralac when inserting Helicoils into aluminum. The NASA stuff is not something either of us are going to find at the local hardware/auto parts store, thus when I inserted some 6-32 helicoils into my rear hub for the outer cover, I simply used NAPA anti-seize compound.

Hi texasSlick.
Having a helicoil and the alloy interact as nature intended would surely fix it more securely in place so the locktited steel stud cannot dislodge it i.e. the stainless steel helicoil becomes 'as one' with the crankcase.
Ta.

Helicoils are bandaids and a last resort. Motor builders will forsake alloy threads and drill and tap for threaded inserts as a perminate and secure solution where ever applicable. It's may be a bit more work, but you'll never pull another stud.