Should nuts be inside?

Previously wrote:

( Please excuse the title)

Do any of you knowlegeable laddies know how the tachometer gearboxeswere originallyfixed to the timing covers on either a 650SS or Atlas.

Both of my covers have clearance holes with bolts and nyloc nuts on the inside to hold the tacho gearbox in place, I suspect that originally the covers were tapped can anyone confirm this and if so what threasd size should they be.

Regards Ben

Hello Ben well in a word no there are not any threads in the outer timing case On my 650 Manxman my rev-counter gearbox its bolted with nuts on the inside your lady Norton Manxman 650 owner restorer hope this help you your anna j

Hello,

I also have a 650SS and was about to ask the same question as Ben. I bought a 2:1 drive from Norvil to fit to my bike (62 model) and discovered that when I removed the blanking plate, theholes in the timing cover were tapped. The holes must have been enlarged from their original size as they now acceptone of the timing cover bolts, which I think are a 1/4" whitworth (I read on another post that they should be 2ba screws) Another give away is that themounting holes on the tacho drive itself are too smallto accept a 1/4 boltand will need to be drilled out in order to mount it.

Myother problem is the tongue in the tacho drive doesn't seem to be long enough to engage with the slotin the shaft on the inside of the timing cover, unlessI remove the thin mounting plate that came with the drive. However the mounting plate seems to be necessary, as it has araised circular surface that corresponds exactly with a circular recess on the time cover.

Any advice would be greatly appreciated and apologies to Ben for hijacking his original post.

Kind regards Adam

Previously wrote:

Hello,

I also have a 650SS and was about to ask the same question as Ben. I bought a 2:1 drive from Norvil to fit to my bike (62 model) and discovered that when I removed the blanking plate, theholes in the timing cover were tapped. The holes must have been enlarged from their original size as they now acceptone of the timing cover bolts, which I think are a 1/4" whitworth (I read on another post that they should be 2ba screws) Another give away is that themounting holes on the tacho drive itself are too smallto accept a 1/4 boltand will need to be drilled out in order to mount it.

Myother problem is the tongue in the tacho drive doesn't seem to be long enough to engage with the slotin the shaft on the inside of the timing cover, unlessI remove the thin mounting plate that came with the drive. However the mounting plate seems to be necessary, as it has araised circular surface that corresponds exactly with a circular recess on the time cover.

Any advice would be greatly appreciated and apologies to Ben for hijacking his original post.

Kind regards Adam

Hi Adam,

I cant speak about the tongue issue, but as to the 1/4" whitworth holes, if it were mine I would have the holes welded up (heliarc welding for aluminum) & re-drill them. If you want original, drill the holes & put nuts inside, if you want better & smarter, predrill for a 2BA tap & thread the holes. You will be able to see a slight difference in color of the repair, so re-locating the hole wont be a big deal, plus you have the drive unit as a template. If you want to be extra precise, put two 1/4" bolts in the existing holes, make a jig to hold the cover on a vert. milling machine & locate the 2 bolts on the x/y axis & record the dimensions. After welding, re locate the hole centers , drill & tap right on the milling machine.

Skip Brolund

Hi Ben.

The 59 parts-list lists nuts(pt No18507)as well as screws (pt No18506)to attach the rev-counter driveto the timing cover.

Regards.

Ian.

Thanks for the advice Skip, very much obliged

Cheers

Adam

Previously wrote:

Thanks for the advice Skip, very much obliged

Cheers

Adam

Happy to help Adam,

I was thinking, a helicoil steel thread insert my be an even better way to go, if the existing holesaren'ttoo big? Let me know if you need them, I can send you links to several UK vendors that carry the English thread sizes.

Skip