removing/replacing norton magneto bottom nut?

Wow! Interesting to see this old thread resurrected. I ended up getting a long steel nut and was able to turn down the shank a bit to clear the crankcase split and has served me well. It is a bit of a pain to start the nut on the thread, but it works.

However, my Dommi has been down for a year after I holed a piston. :oops: I've been held up stripping the engine with a stuck woodruff key in the crank now. Oh well...
 
there are no time rules that I am aware of and sometimes a thread gets resurrected due to new information coming to light or a new member.

I myself recently resurrected the thread on 'Daytona' first gear fitting as I had put a pair of gears in over a year ago when I started my latest restoration and only last weekend had the first opportunity to evaluate and report on the performance.
 
Well, the BSA long, waisted bolt/nut arrived today - it didn't fit. It fouled, just by 2mm, the flange between the crankcase halves.
I decided I wasn't going to grind the flange thinner so further "waisting" the bolt/nut it was. I don't have a lathe so bench grinder and sander provided an effective, if not pretty, result.
The photo below shows where I got to. It is still safely enough metal to take twice the torque required to tighten this nut. Hopefully no issues arise undoing it!!
It works well. You have to start the top two nuts then tilt the maggie upwards to put the lower washer on then "start" the extended nut.
At the diameter I have ground to it (6mm) is still just rubbing the crankcase flange as I tighten it
All in all a good solution
Cheers
Rob


removing/replacing norton magneto bottom nut?
 
Hi Rob,
I have just ordered a long waisted bolt/nut for the magneto in my Atlas project so your solution is of interest if I have the same clearance problem.
I have a question about the bolt and washer(s) for the bottom mount. My parts manual tells me that the bottom mount is a bolt, two washers (one steel and one fiber) and a nut whereas the top mounts are studs, washers and nuts.
Can you tell me whether you have a fiber washer on the bottom? I cant find one anywhere.

Thanks,
Ed
 
Ed
Not sure what year your bike is.
My 1964 650SS has studs in all 3 positions for the maggie. I believe Norton changed the lower one to a bolt (as well as thinning the boss it passes through) some time later. If the boss was not thinned the lower nut would interfere with the magneto chain.
The lower bolt arrangement would require some kind of oil sealing which may be the fibre washers you talk about. My engine does not have, or need, these washers as thread sealant for the studs (3) is sufficient.
It may be worth considering Dowty waters for your application.
Hope this helps
Cheers
Rob
 
@APRSV

The bolt, washer, nut solution for the lower nut is for later (65? or 66 and later) Atlas models. Early models must be retrofitted with a spot face inside the timing case to make a sealing surface for the fiber washer, and room for the nut to clear the timing chain.

If yours is an early model, the bolt, nut, washer will not work without some machine work inside the timing case.

Slick
 
I found my vernier calipers and measured the extra waisted portion of the BSA bolt/nut is 5.6mm (8mm originally) and gives 0.012" clearance off the central crankcase flange when snugged up. You can tell clearance is there because it hums like a tuning fork when "plucked".
I think some clearance is wise to ensure the bolt/nut is not overloading in bending.
I may drill down the centre of the "head" to reduce weight here which will raise the harmonic frequency - don't want the thing to "hum" while running. May fatigue the lower stud, given that it's not tensioned to proof.
I'll get it satin chromed with a bunch of other parts when I'm ready.
Cheers
Rob
 
So Ed, what do you have?
lower stud or bolt (nut inside the timing chest)?
Just interested in where you're going
Cheers
Rob
 
Hi Rob,
I dug out the cases and find that I have the later type for bottom bolt. Looks like I won't need the extension since, I believe the bottom bolt is reduced to take a 1/4" nut and the extension is 5/16".

Ed
 
That's good Ed.
Just have to be careful to get good oil sealing here!
Cheers
Rob
 
I have also seen a Hy Loc fastener used. These have a head like a rivet but the center of the shank has a hex machined into it. Allows you to hold it with the hex key and tighten the nut. Something like this. Thttps://www.lisi-aerospace.com/en/product/bolts-and-screws/
I have photos of the actual item used on a G15 Hybrid. I have not yet taken the time to find one.
 
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