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Centre stand through bolts into engine plates

Submitted by tony_wood on Tue, 01/06/2021
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Heavy Twins

Hi. I’ve just fitted the engine into my 1960 Dommie 99 project. The centre stand bolts are hollow and the holes through them align with holes in the engine plates. It looks like there should be a bolt passing through the stand bolt and engine plate to clamp the two parts together. However, the hole through the stand bolts is 5/16 inch diameter and the hole in the engine plates is 1/4 inch. So is there a special waisted bolt (5/16 plain shank and 1/4 inch threaded part) that fits this application? I can’t find it in any of the main parts suppliers lists.

Thanks

Regards

Tony

Submitted by richard_hudson1 on Tue, 01/06/2021

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Hi Tony, this subject was discussed about a year ago, it seems that a lot of bikes are missing the bolts. My 1957 99 certainly has them fitted but I’m sure they are 5/16” right through. The bike is on the lift at the moment so if I remember I will check tomorrow and possibly get a photo for you.

Regards

Dick Hudson

Hi Tony,

sorry for the delay but I have taken a photo of both ends of the bolt, if I can find out how to attach them. Bolt head and nut both have 13.7ish mms across the flats and the nut bore (thread root dia) is about 6.8mm this suggests that it is a 5/16” BSC nut and I don’t think that the bolt was shouldered.

Hope this helps.

Regards

Dick

Submitted by simon_carver on Wed, 02/06/2021

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Hi Tony

I think the shouldered bolts you need are part number 11466 -Centre stand bolt : Pair : Stainless steel - Shank 0.435in diameter and can be found in the NOC shop

cheers

Simon

Submitted by tony_wood on Thu, 03/06/2021

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Simon, thanks for the part numbers of those bolts. However, I think they are actually stand fixing bolts that fix the stand to the frame, not the bolts that pass through the hollow stand fixing bolts into the engine plates used on a 60’s Dominator. 
Regards

Tony

Submitted by tony_wood on Thu, 03/06/2021

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Hi Richard. Thanks for the photos. I put a 6.5mm drill into the hole in the engine plate and it passed through with a bit of clearance. So I took the bull by the horns and drilled the holes out with a 7.5mm drill - no metal shavings but lots of very hard powder coating shavings. Then it was just a matter of using a 5/16 drill bit to open the hole up further so that a 5/16 bolt would pass through the engine plate. Once again, lots of powder coating shavings but with just a tiny bit of steel. So I think you were correct all along - definitely 5/16 bolts.

I guess the guy who did the powder coating on my engine plates just got a bit ‘over-enthusiastic’ when applying the powder around those holes!

All I need to do now is order some 2.5 inch long bolts - I didn’t realise how long they needed to be - they’re long!

Thanks again for all your help.

Regards

Tony

Submitted by ian_hay on Fri, 04/06/2021

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Over the years I have owned seven F/bed Dommie's from a 1951"88" to a 1962 one owner 650ss , none of these motor cycles had bolts through the centre stand bolts. It never occurred to me that bolts should have been fitted and the spare parts book bought in 1955 showed neither bolts or the spacers which would also have been needed.                                                            This question arose about a year ago and since then my friend ( who is a long term Norton owner) and I have formed the opinion that the through holes were possibly an aid to assembly on the production line.                                  The engine/gearbox unit is an awkward lump to fit in the frame and usually requires two persons.                     Assuming the engine unit to be in the frame, a 5/16" rod would be passed through the centre stand holes ,  the engine unit would pivot on the rod allowing a single person to complete the fitment of front and rear engine plate bolts.                                                     I think the through bolts if they existed at all would have been a time consuming aggravation on the line and very quickly left in the parts bin.               I think it is likely that where fitted it has probably been done by a previous owner and I see no real benefit from doing so.

I have also had several Dommies and singles over the years and none had these bolts (none had matching frame and engine numbers, headstock or gusset plate covers either), I don't  know if they were ever fitted or not, their absence from the parts lists tend to say to me that they were not. However a couple also had some bowing of the bottom frame rails from dropping down onto the centre stand thousands of times and it does occur to me that had these bolts been fitted they would have resisted this a little. It also occurs to me that once bent a little they would have been murder to get out and next to impossible to put back in.

 

Just to put my mind at rest, I have been looking through the Roy Bacon book "Norton Twin Restoration " which I expect most of us have, and in it there are six or seven excellent contemporary  press photographs of brand new original bikes with these bolts clearly in place.

So clearly they were fitted, but why they do not appear in the parts lists is still a mystery.

I bought my 1957 99 in early 1962. It had never been stripped down and still has matching numbers. I stripped it down for some light tuning and HC pistons plus a complete respray in late 1962. The bolts were present when I stripped it and still are.

Regards

Dick

Submitted by john_oldridge on Sun, 06/06/2021

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I wrote an article in RH a number of years ago after noticing on the Austrian rally  about 50% of featherbead Nortons (Slimline and Wideline) had not had the bolt  fitted. If these bolts are not used, then the only fixing for the engine/gearbox is at the front and rear, and a certain amount of "flexing" is possible especially on the larger capacity engines.

Even my M50 has the bolts fitted, Norton certainly intended bolts to be fitted through the stand pivot, and put holes in the engine plates for this purpose, ................not for any other reason.

Regards John O

 

 



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