Author Topic: Crankshaft Retaining Nut  (Read 408 times)

Online tomkilde

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Crankshaft Retaining Nut
« on: 28.11. 2020 02:17 »
Hello, new member here from New Jersey in the USA.  I recently bought a 1958 A10 that sat in the previous owner's shed more than 30 years.  Starting to tear it down for a complete overhaul, but I'm puzzled by the cotter pin securing the crankshaft retaining nut.   Is there some trick to pulling this pin out of the deep recess in the nut?   I have the Haynes manual, but it's not much help.  It just tells you to "withdraw the split pin" without telling you how.
1958 BSA A10 Super Rocket

Online Billybream

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Re: Crankshaft Retaining Nut
« Reply #1 on: 28.11. 2020 05:52 »
Just one of the challenges with owning an A10, you will need to tap and pull the pin out, most probably damage it in the process. Upon reassemble the nut has to be very tight, something like 165ft lbs. SRM offer a replacement nut with hexagon fixing thus making tightening far easier.
1960 Super Rocket, owned since 1966, back on the road 2012 after being laid up for 29yrs.

Online KiwiGF

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Re: Crankshaft Retaining Nut
« Reply #2 on: 28.11. 2020 05:56 »
Hello, new member here from New Jersey in the USA.  I recently bought a 1958 A10 that sat in the previous owner's shed more than 30 years.  Starting to tear it down for a complete overhaul, but I'm puzzled by the cotter pin securing the crankshaft retaining nut.   Is there some trick to pulling this pin out of the deep recess in the nut?   I have the Haynes manual, but it's not much help.  It just tells you to "withdraw the split pin" without telling you how.

The split pin is generally thought to be a “last resort safety” item, if the castellated nut is touching it, it probably means it has come loose and just the split pin has prevented it falling off, the split pin will probably need to be bent to remove it. I just use wire instead of a split pin myself, it's easier. You could possibly do the nut up if it has unscrewed, and that make removing the split pin easier.

There should probably be a lock washer between the nut and splined sleeve, also not easy to get at through the coils of the spring. Generally I just use a rattle gun to undo the big nut, and a socket with strips of metal welded to it, to engage in the nut slots.
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1956 A10 Golden Flash (1st finished project)
1949 B31 rigid “400cc” (2nd finished project)
1968 B44 Victor Special (3rd project,in progress)
2001 GL1800 Goldwing, well, the wife likes it
2007 KTM 950 Adventure, cos it’s 100% nuts

Online Swarfcut

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Re: Crankshaft Retaining Nut
« Reply #3 on: 28.11. 2020 08:16 »
  Tom..  To add to previous comments, the nut will screw back onto the crank just enough to allow the pin to be jiggled out or cut away. On re-assembly the nut has to be re-tightened to some 65-75 Ft Lbs, a quite fearsome figure and a proper peg spanner is essential either a bought item or a homespun solution like KiWi.  The usual backyard method was a hammer and drift, which accounts for the damage evident on your nut. Incorrectly tightened or no tab washer means the nut comes undone, the split pin has done its job and stopped the nut loosening completely. Aftermarket nuts are available with an improved design as mentioned by BillyB.

 Plenty of pictures on the net of primary covers damaged by the nut, unrestrained by a missing pin,  machining away the inner cover. 
   The crank will need to be locked, either with a clutch locking plate, or reassemble the clutch, put in gear and hold still with the brake. With the barrel off, the crank could be blocked against the crankcase, but this is an unnecessary risk bearing in mind the strength of old alloy castings.

 As a new member, head over to the intro section and give us a little of your backstory.

 Welcome to the Forum.

 Swarfy.

Online Greybeard

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Re: Crankshaft Retaining Nut
« Reply #4 on: 28.11. 2020 10:41 »
I use a pair of side-cutters to grip the head of the split-pin, (cotter pin) and tap the side of the cutters to extract the pin. As already posted, that pin does nothing unless the nut has worked loose.

There was/is no lock washer on my Plunger. Should there be one?

Online Swarfcut

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Re: Crankshaft Retaining Nut
« Reply #5 on: 28.11. 2020 12:25 »
  GB. The plunger type nut has an extended nose to bottom on the drive sleeve, and as such no locking tab washer could be accommodated. So relax, all is as it should be. I've also used side cutters, like you, to tease it out, and sometimes cutting away the exposed part in stubborn cases to allow the nut to move down the threads and unscrew off.
   The swing arm nut design is flat faced towards the crank, early S/A A7 and A10 engines have no locking/ tab washer or indents in the nut. With the introduction of the Shooting Star and Road Rocket comes a nut with indents to accept the knocked in tabs and the circular tab washer internally splined to match the crank. In addition the drive sleeves changed and there is scope for the use of incorrect parts. The tabs are accessed through the coils of the big spring. All in all not the finest arrangement. An extra proper castellated locking nut used with the existing split pin would have added pennies to the cost.

 Swarfy.

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Re: Crankshaft Retaining Nut
« Reply #6 on: 28.11. 2020 18:33 »
G'day Tom  *welcome*
I make a washer to go between the nut and split pin so if the nut comes loose (never has) it can't go far. A loose nut will cause extra crank end float and destroy any shims used to adjust end float as well as the thrust face of the t/s bush. The nut MUST be done up to 65-75 ft/lb.
Cheers
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Muskys Plunger A7

Online Roger (Doomtrainbarx)

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Re: Crankshaft Retaining Nut
« Reply #7 on: 28.11. 2020 22:21 »
I fitted both the crank nut and the mainsheet nut - power gunned them up.
1962 Super Rocket
2003 Kawasaki Z1000
1987 Kawasaki ZL1000 Eliminator
1989 Harley FXRS (Turbo)
1978 Triumph T140 Bonneville

Online tomkilde

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Re: Crankshaft Retaining Nut
« Reply #8 on: 29.11. 2020 03:25 »
Thanks for all the advice.  I found the crank nut was quite loose, and I was easily able to screw it in enough to access the pin.  The inside of the primary cover has indeed been "machined"by the nut, as described by Swarfcut.  Tracked down SRM's aftermarket crank nut on the internet and added it to my shopping list.  The (six spring) clutch basket came off easily as well, and miraculously I was able to find all the balls that fell out of the bearings.  However, the inner bearing race was firmly stuck on the sleeve, trapping the back plate.  After about an hour of gentle pulling and tapping, the race, back plate and sleeve suddenly popped off as one piece.
1958 BSA A10 Super Rocket

Online KiwiGF

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Re: Crankshaft Retaining Nut
« Reply #9 on: 29.11. 2020 04:12 »
Thanks for all the advice.  I found the crank nut was quite loose, and I was easily able to screw it in enough to access the pin.  The inside of the primary cover has indeed been "machined"by the nut, as described by Swarfcut.  Tracked down SRM's aftermarket crank nut on the internet and added it to my shopping list.  The (six spring) clutch basket came off easily as well, and miraculously I was able to find all the balls that fell out of the bearings.  However, the inner bearing race was firmly stuck on the sleeve, trapping the back plate.  After about an hour of gentle pulling and tapping, the race, back plate and sleeve suddenly popped off as one piece.

The splined “sleeve” is generally referred as a “clutch centre” and is a taper fit (with woodruff key) into the gearbox shaft. If you look at the clutch centre’s end you will see a short threaded section which is used by a special “puller” tool to remove the centre, they don’t usually come off the gearbox shaft easily  *eek*

The clutch bearing is usually supplied in 3 pieces, but aftermarket variants are around, the inner ring of the bearing should be a sliding fit on the clutch centre (it is clamped up tight by the main clutch nut so does not need to be a tight fit).
New Zealand

1956 A10 Golden Flash (1st finished project)
1949 B31 rigid “400cc” (2nd finished project)
1968 B44 Victor Special (3rd project,in progress)
2001 GL1800 Goldwing, well, the wife likes it
2007 KTM 950 Adventure, cos it’s 100% nuts

Online chaterlea25

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Re: Crankshaft Retaining Nut
« Reply #10 on: 29.11. 2020 12:29 »
Hi Tom,
If the bike was run with the nut not fully tight you had better check the crank end float  *ex* also rmove the sump filter and look for broken up shims
The split pin is a "last resort" to hold the nut,  serving no other purpose
I recommend degreasing the threads and use thread locking fluid then tighten to 65-70 ft lbs,
Having the cush drive nut fully tight can and will save you a full engine strip *eek*
I have done it this way on dozens of bikes
and never had one come loose

John
1961 Super Rocket
1963 RGS (ongoing)