Rocker Box Stud Lengths

[Mosin]

Due to stripped thread issues I recently ordered four new studs to re-mount my rocker box onto the cylinder head in an attempt to stem the persistent oil leaking from around it. My head is an alloy one and I took care to make sure I ordered the correct part from Draganfly who listed all four studs as being the same part number. However, today when I actually got around to fitting the new studs, I discovered that the two towards the rear of the bike (which also happen to be the two which are stripped) are a good half inch or so longer than the two towards the front of the bike and subsequently the new studs from Draganfly don't reach far enough through the head for me to be able to get the nuts on! Can anyone offer any explanation for this?

Also, since it is looking like I am going to have to have a pair of the longer studs made up, can anyone enlighten me as to what pitch the finer thread at the bottom of them is? - I know that the thread which goes into the rocker box itself is BSW - it's the other end that I am after!

Cheers,

Simon

 

[JohnH]

I have no suggestions about the bolt lengths - but I have no doubt that you will get the answer on this forum.

Regarding the thread ibto the alloy head, if it's finer than Whitworth then it's going to be BSF (British Standard Fine). You should be able to get details of pitch etc from any enginneering handbook - although I hastily add that I'm no expert.

The guys on this forum really know their stuff - you'll get loads of replies.

John

[RichardL]

Simon,

I'm not taking my rockerbox apart right now to measure mine, but if you go to http://www.burtonbikebits.net/TRIStock.pdf and look at page 157 (the pdf page number, because there are no page numbers on the actual document) you will see part number 67-1117. Is this what you bought from Draganfly? You can see in the Burton catalog that the 67-1117 is shown for alloy head and is 1-7/8" long. (I've seen another seller listing them at 1-13/6" but, no biggy, literally.) Part number 67-1245 is shown further down the same page as being 1-3/8" long and for an iron head. This would seem to explain the 1/2" difference. As I recall (though I could be recalling wrong, as I don't have my parts book in front of me) all four studs are the same length and long enough to capture the head-steady brackets. Both are shown by Burton as CEI/WHIT, meaning, 18 TPI Whitworth (BSW) into the cylinder and 26 TPI Cycle Engineers' Institute (CEI) for the nuts. You should not need to have these studs made up custom, as they are readily available. If you can buy them from Burton, that might encourage them to keep posting the very useful hardware dimensions.
 
Richard L.

[muskrat]

G'day Simon,
                     ditto to what Richard said. The rear studs are longer but do not protrude through the head as the front ones. Long nuts (similar to the rocker cover nuts only bigger) go up the holes to meet the studs. Just thought I'd mention this as a PO might have used even longer studs and normal nuts.
Cheers

[RichardL]

OK. Muskrat has convinced me to check my parts book when I get home. One thing I surely said wrong applies to the head-steady brackets. Those are bolted down.

Sorry for any confusion, but I'll try to make up for it.

Richard L.

[RichardL]

Confirmed. 67-1117 x 4.

[Rocket Racer]

I'm no purist so have replaced the front and back rocker box studs on my alloy head a10 with UNC capscrews and done the same for the tappet cover studs

[bsa-bill]

I had issue with the same studs from Draganfly, the studs were correct for length but the thread lengths were wrong, this takes a bit explaining - one end of the studs is cycle the other Whitworth, the Whitworth end should be shorter than the cycle end, mine were the reverse, meaning the extended nuts could not reach to the cycle thread.
If I still had a stud I would post a picture. which would explain it better.
Simon don't forget you need special (thicker) washers to go with the extended nuts

Sorry if this doesn't make sense, I emailed Draganfly to tell what was wrong but they didn't seem interested, the part number they supply supersedes the original part number but is wrong

[muskrat]

Doh, just pulled the rocker box off the '51 (alloy head). They are the same length.
 And to teach me a lesson the front L/H stud snapped, bugga.
Cheers

[RichardL]

Rocket Racer,

I'm confused. For my forward studs, getting the nuts on requires using a needle-nose pliers while holding my pushrod comb under the nut to keep it from continuously dropping through the head fins below. On the the rear studs, where the long nuts are, barrel fins would block the way of cap screws. There is no way, that I see, on my bike at least, that cap screws could replace the front and rear rockerbox hold-down studs.

Found a picture on eBay. Though, I'll tell ya', if this part came to me I would probabaly roll the CEI end against my grinder to knock off the square end of the thread. http://cgi.ebay.co.uk/BSA-A7-A10-RGS-S-R-LONG-ROCKER-BOX-STUD-67-1117-NEW-/250640859293?pt=UK_Motorcycle_Parts&hash=item3a5b5c009d

Richard L.

EDIT: Hey! I just noticed this is from Leigh Classics. Andy there is a great guy and I definately think you can trust him to stand behind all parts and give a fair deal. Also, a visit to his shop can be a good time if you can get to Leigh-On-Sea.

[bsa-bill]

nice pic Richard you can see the difference in the length of the threads, this is what I was referring to, the ones I got were the opposite way.

When fitting the extended nuts do not have anything else tight as you need to jiggle the nuts and/or the rocker box the get to get them started.
the front nuts want to be started before you fully drop the rocker box down onto the head (wedge the front up a tad with something to big to get lost in the box )
and that little BSA spanner is handy, you know the one that fits two sizes at each end

[JohnH]

This is an interesting thread and has taught me to keep my trap shut until I've done a bit of research! For those interested, there's a handy (but quite brief) guide to motorcycle fasteners in the August 2010 issue of The Classic Motorcycle. I was certainly wrong in saying that the finer thread is going to be BSF and Richard was spot on in saying that its likely to be CEI (or BSC). There's a significant difference in thread angle so you certainly wouldn't want to mix the two up!

Apologies for the misinformation. I was spot on in making the point that you would get the answer on this forum though!!

Cheers,
John

[Rocket Racer]

Richard,
Have just assembled my rocker box today on the road rocket.
The back studs I've bored out the holes slightly so the cap screws are tucked inside the head and not visible.
At the front, I drop the cap screws in from the centre then poke an allen key up through the holes. It was remarkably easy. I'd seen it done on another A10 so knew it was fairly straightforward.
I still have four normal bolts going down through the centre section of the rocker box and another inside the rocker box at the back centre. but no studs front or rear on the rocker box and none on the covers either.
I'll try and take a photo 2moro... not sure if my phone will show clearly though.
Tim

Rocket Racer,

I'm confused. For my forward studs, getting the nuts on requires using a needle-nose pliers while holding my pushrod comb under the nut to keep it from continuously dropping through the head fins below. On the the rear studs, where the long nuts are, barrel fins would block the way of cap screws. There is no way, that I see, on my bike at least, that cap screws could replace the front and rear rockerbox hold-down studs.

Found a picture on eBay. Though, I'll tell ya', if this part came to me I would probabaly roll the CEI end against my grinder to knock off the square end of the thread. http://cgi.ebay.co.uk/BSA-A7-A10-RGS-S-R-LONG-ROCKER-BOX-STUD-67-1117-NEW-/250640859293?pt=UK_Motorcycle_Parts&hash=item3a5b5c009d

Richard L.

EDIT: Hey! I just noticed this is from Leigh Classics. Andy there is a great guy and I definately think you can trust him to stand behind all parts and give a fair deal. Also, a visit to his shop can be a good time if you can get to Leigh-On-Sea.

[RichardL]

John,

When it comes to mistakes, I am King. You might need a lifetime to de-throne me. Just on this topic I have made, at least, three mistakes. First (as I've already confessed) I said the studs would hold down the head-steady brackets - WRONG!, those are bolts. Second (and this I just noticed from my first post), I brain glitched and said the 18 TPI Whitworth goes in the cylinder instead of the rockerbox. Third, I said I thought it would not be possible to use cap screws in place of studs, and Rocket Racer has done just that. GAWD! I hope there aren't more mistakes in this very paragraph, I might never catch up.

John,

Still confused on the front cap screws. Do you mean that you drop them into the holes in the head fins before you put the rockerbox on or that they can actually be sneaked in after the fact?

Richard L.

[muskrat]

I would be weary of using screws in stead of studs. Every time they get screwed in, out and tightened the alloy thread will wear. Might be ok for the first  1/2 doz times, but it will happen.
Cheers.