650 ss queries

Scenex

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Apr 21, 2020
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Hi

I’m in the process of rebuilding a 650ss motor and have a problem with the left handed oil pump drive thread.

it looks as though it has suffered when the crank was driven out of the case.

Does anyone know what thread form it is please?

if it can’t be retrieved do you think it would be possible to have it metal sprayed and the standard thread re-cut?

Also, is it best to stick to the standard main bearings, one roller and one ball?

And which dealers are best for Norton parts. Not played with a Norton before, any other things I should look out for?

thanks

Dave
 
Chances are, if it was caused by hammering it out, that the damage is confined to the very end of the thread and you might be able to save it with careful use of a thread file or a needle file.
 
You can't use two rollers as mains, or crank will "float" sideways. Unless you fit taper roller bearings. Yes it has been done on another famous marque.
 
AFAIK Every single NHT from model seven through E-start here in the new england area (by club members 120+) is built with a pair of FAG or NTN NJ306E - C3 clearance bearings. Float? The crank is always lightly pulled to the right to provide drive thrust for the oil pump. How ever doing the ball/roller method is not bad, and is entirely acceptable. My friends MKIII lasted 160,000 miles before replaceing the FAG's.
Any 650, atlas or commando crank cheek through 1974 will likely be easier and cheaper than fixing what some amature/butcher screwed up. A little heat on the case and the cranks falls out with no additional effort. Work is best performed with the brain(research) instead of a hammer.
 
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I missed that the item damaged was a spiral GEAR end of either 3 or 6 start pump drive gear. I envisioned the LH crankshaft THREAD being damaged.
The oil pump drive gear touches on a very narrow sector If the gears shiny wear line is not affected, and IF it will install and cycle through without any binding, I would just run it.
 
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Just checked an 850 crank I have [ I'm pretty sure the dimensions are all the same] it is 3/4 x20tpi which i'm told is the course form of cycle thread.
 
This is how a bit of history is often unknown or ignored. While early norton's up to slimline were predominantly British threads, as they went from featherbed to commando production, the new commando parts were made with UN threads. Therefore predominantly all cycle parts, being new were UNF or UNC.
The NHT 20M3 and gearbox were almost entirely unchanged as BS threads. 20M3S had "some" thread changes. 200000+ had more changes on the new cases and studs. By the MKIII there were few, but some, residual BS hardware. The "basic" crank and oil pump, among a few others, details did not change so the early thread forms never changed. Of course the crank is very likely "LH" 20 series CEI threads.
Before I retired I had access to an optical comparator to check the thread angles...but no more:(
This constant changing threads is certainly a challenge to many self help norton owners. Not knowing the threads and what tools to use is often damaging to the hardware and value of the machine.
 
dynodave said:
Of course the crank is very likely "LH" 20 series CEI threads.
Click to expand...
However, according to Madnorton recently, various 20 and 26 TPI threads can be Whitworth and not necessarily CEI/BSC.

Where do you guys find your bolts?

I have found Custom Fasters in Wales (UK) to be excellent for all types of fasteners. I would thoroughly recommend them: http://www.custom-fasteners.co.uk
www.accessnorton.com www.accessnorton.com
 
Separate from the on hand discussion:
Tracy tool has my general respect. it may have been almost 30 years ago I was looking for CEI taps and they declared that they did not believe anyone in the world made real CEI taps and dies anymore. Currently they are the only ones I have found where I can get the taps and dies to sort out the pre commando front triple tree stems and nuts. Certainly no luck in the USA (or china) so far....13/16x26
I was able to get command tap and dies from china 13/16x28


https://www.tracytools.com/taps-and-dies/20-TPI-CYCLE-PITCH

For the crank and drive gear-How about LH?
3/4-20LH: https://www.tracytools.com/taps-and-dies/left-hand-thread-taps-dies-cycle

Unless they (AN) has genuine prints, my "guess" is as good as their "guess". Have they been able to read the angle on their optical comparitor or the print?

3/4 10 or 12 is BSW typical but of course 55 degree anything custom is always possible.
 
Tracy tools just supplied me with 1/4 cycles taps & dies for feathered swinging arm chain " adjusters" from stock in 3 days. I've had fork stem dies & bottom yoke stud taps & a gearbox mainshaft did.
Ace company
 
Chris said:
Tracy tools just supplied me with 1/4 cycles taps & dies for feathered swinging arm chain " adjusters" from stock in 3 days. I've had fork stem dies & bottom yoke stud taps & a gearbox mainshaft did.
Ace company
Click to expand...
sorry
Off Topic for this thread, but have you ever figured why slimline swing arm chain adjusters "bottom out " and prevent full span of adjustment ? None of my chain adjuster in this case have full range of motion?
A custom axle puller from the rear seems like the only cure to allow full range of adjustment.
 
Never had a set of threads in good condition! 6 bikes, over the years, all shot, all at least two thirds of adjustment not available.
Rubbish idea. Pullbacks on the back of the arm tried & tested.
 
Thanks everyone for your replies, sorry I haven’t replied earlier.
My bike is 1963 and had been raced. It’s also come with an earlier engine (1962? - anywhere I can check engine numbers?)
I presume I could use the earlier crank if necessary.
I don’t think the left hand thread is recoverable which is why I wondered if it could be metal sprayed and re-machined.
Any recommendations on best parts suppliers of quality parts?
I hope everyone is well and managing during this dreadful time.
 
Hi
No to metal spray, good in compression but not good in tensile stress, post some pictures of the damaged thread as it may be able to dress up and thread chase in a lathe, not a big job for a skilled machinist.
I also have a 1963 that had been raced, most of the issues were with the frame.
Burgs
 
My chain adjusters snapped off so I drilled and tapped the arm threads out to take the later Atlas? adjusters .Don't think it helped with range of movement,perhaps that was limited by the factory machinery?.
 
So was my origin interpretation that it WAS the LH crank threads? not the gear?

Per Burgs:"post some pictures of the damaged thread as it may be able to dress up and thread chase in a lathe, not a big job for a skilled machinist."

I fully agree
If a fair percentage of the threads are still present a lathe clean up is (IMO) easily achievable.
Even I could do it....
 
OT swing arm adjusters
norton bob said:
My chain adjusters snapped off so I drilled and tapped the arm threads out to take the later Atlas? adjusters .Don't think it helped with range of movement,perhaps that was limited by the factory machinery?.
Click to expand...
Was unaware there was more than one type of slimline swing arm adjuster. Internal cast steel end piece has internal blocking topography with no method obvious to eliminate the conflicting piece.
 
Adjusters with the bigger thread were around (don't know from what) ,drilling out and tapping was a tedious process due to restricted access , All done without any machinery ,shade tree style!. My current workbench is the top of the wifes washing machine. And she objects !!. Wonder why?.
 
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