STRIPPED THREAD ON T140V CYLINDER BASE STUD

[sTe140Ve]

I was just getting towards the end of top end rebuild on my 1976 T140V and have found that one of the outer cylinder base studs (the ones without multipoint nuts) will not tighten up properly. I need to put a helicoil into the crankcase but I don't know the thread size. It may be UNF thread but I'm not sure. Does anyone know?

[250greeves]

I had to repair one of my base stud threads when I rebuilt my '78 model. I'm pretty sure it's UNC at the crankcase end of the stud and UNF at the nut end - if you see what I mean.

When you pull the stud if you find that the thread is more coarse than the nut end it's UNC; if it's the same it's UNF.

Hope this helps,

T

[sTe140Ve]

Thanks. Can you remember what size UNC thread it was?

[L.A.B.]

Thanks. Can you remember what size UNC thread it was?

That stud is stepped, so is, I think,  5/16" UNF x 3/8"UNC.

Just measure the stud diameter and count the TPI (threads per inch).

UNC thread chart:  http://www.britishfasteners.com/threads/unc.html

UNC threads: http://www.britishfasteners.com/threads/unf.html

[250greeves]

Thanks. Can you remember what size UNC thread it was?

I'm sure the studs are 3/8"UNF x 3/8"UNC - I don't think they're stepped, the Triumph Manual doesn't appear to show this.

So the base thread is 3/8"UNC.

T

[L.A.B.]

I'm sure the studs are 3/8"UNF x 3/8"UNC - I don't think they're stepped, the Triumph Manual doesn't appear to show this.

 
According to the parts books, the outer studs, are, as far as I'm aware, part 71-3013?

And here is that stud as shown in the  Tri-Cor catalogue:
http://www.tri-corengland.com/cgi-bin/sh000001.pl?REFPAGE=http%3a%2f%2fwww%2etri%2dcorengland%2ecom%2fcgi%2dbin%2fss000001%2epl&WD=71%203013&PN=71%2d2500_to_71%2d3295_6%2ehtml%23a71_2d3013#a71_2d3013

Clearly it's a stepped stud.

The nut end of the outer stud is 5/16" diameter, as I checked a spare outer base nut for size, it is 5/16" UNF thread with a 7/16" A/F hexagon.  
http://www.tri-corengland.com/cgi-bin/sh000001.pl?REFPAGE=http%3a%2f%2fwww%2etri%2dcorengland%2ecom%2fcgi%2dbin%2fsh000001%2epl%3fREFPAGE%3dhttp%253a%252f%252fwww%252etri%252dcorengland%252ecom%252fcgi%252dbin%252fss000001%252epl%26WD%3d71%25203013%26PN%3d71%252d2500_to_71%252d3295_6%252ehtml%2523a71_2d3013&WD=21%202177&PN=21%2d2010_to_21%2d2182%2ehtml%23a21_2d2177#a21_2d2177

[250greeves]

I'm sure the studs are 3/8"UNF x 3/8"UNC - I don't think they're stepped, the Triumph Manual doesn't appear to show this.

Yes, I remember that now. They're shouldered as well.

That's a good link.

Thanks,

T
 
According to the parts books, the outer studs, are, as far as I'm aware, part 71-3013?

And here is that stud as shown in the  Tri-Cor catalogue:
http://www.tri-corengland.com/cgi-bin/sh000001.pl?REFPAGE=http%3a%2f%2fwww%2etri%2dcorengland%2ecom%2fcgi%2dbin%2fss000001%2epl&WD=71%203013&PN=71%2d2500_to_71%2d3295_6%2ehtml%23a71_2d3013#a71_2d3013

Clearly it's a stepped stud.

The nut end of the outer stud is 5/16" diameter, as I checked a spare outer base nut for size, it is 5/16" UNF thread with a 7/16" A/F hexagon.  
http://www.tri-corengland.com/cgi-bin/sh000001.pl?REFPAGE=http%3a%2f%2fwww%2etri%2dcorengland%2ecom%2fcgi%2dbin%2fsh000001%2epl%3fREFPAGE%3dhttp%253a%252f%252fwww%252etri%252dcorengland%252ecom%252fcgi%252dbin%252fss000001%252epl%26WD%3d71%25203013%26PN%3d71%252d2500_to_71%252d3295_6%252ehtml%2523a71_2d3013&WD=21%202177&PN=21%2d2010_to_21%2d2182%2ehtml%23a21_2d2177#a21_2d2177

[sTe140Ve]

Huge thanks to L.A.B. & 250greeves for not only providing the info I asked for but a couple of links that will be of use in the future, for sure.