Primary chain case screws

[Nomad54]

I have an alternator model a10 ex police bike that I am rebuilding. During the strip down I seem to have lost the 3 off 5/16 screws to hold the primary chain case on. I purchased a complete new set but these screws are to short. The new screws are 2" long but I need longer screws as the alternator casing is deeper than a dynamo casing. Does anyone know the length I require and where I could purchase them. These alternator models are a pain as lots of things are different with not a lot of info out there.
Tom

[Greybeard]

This may help. The rearmost screw on the primary chain case of the Plunger model is extra long* as it provides a mounting for the oil relief pipe to exit above the chain. If you check Draganfly you should be able to identify the part number. Good luck🤞

* Well, it was on my bike😁

Update: Screen grab from the Draganfly website.
Further update: size is 1/4 BSW x 2.75"
Price is £1.82 + VAT!!!!


Whoops! I see you need 5/16 thread 🤔

[Nomad54]

Thanks for the info but nothing like the alternator casing
Tom

[Triton Thrasher]

I need longer screws as the alternator casing is deeper than a dynamo casing. Does anyone know the length I require

You will know the length required, when you measure the depth of the holes

[Radlan2]

Hi Nomad. I have an ex police bike too but unfortunately the crank and primary cases were changed before it came to me (Anyone got an alternator type inner?)
There is a 5/16" UNC X 2 1/2" hex bolt Pt No 14-6121 on a T160 Triumph which could be converted to fillister head (if 2 1/2" is long enough) if you know someone with a lathe. I know the thread angle is a bit different but the pitch is the same and it would be ok. Also there were Webco competition screws made from hex bar available back in the day, which are easy for someone with access to a lathe. Be aware the tapped holes probably go right through the crankcase, if the screws are too long they can touch the crank itself.
          HTH Chris

[limeyrob]

Why not order from a fastener place?  They be either 5/16 BSF or Whit.  You can order 2 1/2 and 3" and cut down to fit.  I think its very unlikely that they are UNC.
They are cheese head bolts:
https://www.ebay.co.uk/itm/176534048791?chn=ps&_ul=GB&mkevt=1&mkcid=28&google_free_listing_action=view_item

[jhg1958]

My 1961 A10 uses 5/16" BSW (Whitworth) screws.  However I was looking for stainless cap screws so I used UNC screws instead.

To my knowledge UNC and BSW are interchangeable except 1/2".  Otherwise BSW and UNC have the same thread count but only slightly different thread angle 60/55.

There plenty of references on the interweb thingy.

John