Alton Sprag Clutch Rotor Removal

I recently bought my third Commando (yes, my addiction is a bit out of control) and have some problems with the Alton starter that was fitted by a previous owner.
The motor on the Alton doesn’t turn and the inner chaincase is so close to the swingarm that you can’t remove the back swingarm cover.
So, I thought I would take the primary apart so I could investigate and fix the starter motor problem.
Sounds easy. Cover came off with some effort due to the three tubes or so of sealant that must have been used. Clutch came out easy. Crankshaft nut was very tight, but came off ok.
Here is my problem, the sprag clutch rotor will not come off. I know it is on a parallel part of the crankshaft with a woodruff key, so should just pull off.
I have tried pulling off using the AN puller with some high tensile 5/16 UNF bolts after several days of spraying in release oil and it will not budge.
I have tried a bit of heat, not too much as I would prefer not to damage the crankcase seal. I have tried freezing the crankshaft.
In desperation, I removed the small chain and have used a series of ever bigger pullers behind the chain wheel and have got absolutely no movement but have properly mullered the chain wheel.
Pullers are just not working.
I am beginning to wonder if the rotor has galled/welded onto the crankshaft for some reason. If I look down the slot, I believe I can see the woodruff key and I have tried a bit of gentle tapping with a drift. Still no joy.
I have reached the conclusion that I will have to cut the rotor off. I am thinking, put a jubilee clip on the crankshaft thread to protect and some strategically placed bits of steel sheet to protect the case and other parts and then using a cutting disc to make a cut across the rotor through the woodruff slot.
I know this sounds horrible, but if I don’t get the rotor off this bike is junk.
I would welcome any experienced advice from you learned gentleman!

I would use the AN puller and a lot of heat
This won't destroy the crankshaft oil seal but even if does it's not hard to replace
Maybe the key is half sheared in the keyway?

If they have managed to shear the woodruff key that can smear itself around the shaft and become and absolute sod to remove - at least that is what mine did.
I could not get a straight pull to move things and ended up with good tension on the puller tapping the sideways on the end of the tensioner at 12 o'clock, - 3 o'clock etc around and around and around, a bit more tension repeat. A bit ugly but it eventually worked.

Maybe try what ntst8 did with a 3 arm puller? And lots of heat. A few cycles, hot cold hot cold to try and release it.

At this point, what is a new seal on top of a new pulley?

Install the puller, putting however much tension it can handle. With the tension on, whack the center puller bolt (the one that is bearing against the crankshaft) with a hammer. Use a regular steel hammer or small sledge, NOT a soft hammer of any kind. A whack or three will usually shock the parts loose.

MexicoMike said:

Install the puller, putting however much tension it can handle. With the tension on, whack the center puller bolt (the one that is bearing against the crankshaft) with a hammer. Use a regular steel hammer or small sledge, NOT a soft hammer of any kind. A whack or three will usually shock the parts loose.

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Thanks for the input. Unfortunately, I have been doing this with no luck so far. In fact I am starting to get concerned about how hard I am hitting!

Perhaps a previous mechanic has used green Loctite bearing mount, intended to secure bearing races (both inner and outer), to secure the sprag rotor. They might have done this because of a worn shaft or hammered out keyway. IIRC the bottle says it will secure up to 0.008" clearance. If this has been used it will likely require heat in excess of 350 deg. F or so to release the Loctite.

SteveC said:

Thanks for the input. Unfortunately, I have been doing this with no luck so far. In fact I am starting to get concerned about how hard I am hitting!

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WOW, it's seriously seized!! As others have mentioned, the flame wrench is the next step! If heat and shock with the puller/hammer doesn't work, cutting the rotor off as you mentioned may be the only way.

gortnipper said:

Maybe try what ntst8 did with a 3 arm puller? And lots of heat. A few cycles, hot cold hot cold to try and release it.

At this point, what is a new seal on top of a new pulley?

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Agreed, I’ll try some heat and report back

When you think it's hot enough.... Give it another five minutes heating (maybe more!)

But if and when it does fly off, don't be in too much of a hurry to pick it up.....

(Been there, done that...)

I see rgm have the complete sprag/sprocket unit at £389 without vat
Ouch!

There's a theory that to release a pulley from a shaft for example that you should heat only in one spot
And it expands the hole in the pulley more

baz said:

There's a theory that to release a pulley from a shaft for example that you should heat only in one spot
And it expands the hole in the pulley more

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Heat an alloy crankcase in one spot next to a steel bearing and the hole reduces in size as the cold alloy surrounding the hot spot makes the hot spot expand into the hole. Got the T shirt to prove it , so I can't see that theory on the pulley working any better.

kommando said:

Heat an alloy crankcase in one spot next to a steel bearing and the hole reduces in size as the cold alloy surrounding the hot spot makes the hot spot expand into the hole. Got the T shirt to prove it , so I can't see that theory on the pulley working any better.

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Hmmm I've often wondered about the theory
Would this only be the case with alloy?

baz said:

I see rgm have the complete sprag/sprocket unit at £389 without vat
Ouch!

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Yes, Ouch indeed! Interesting that they have spares though……

SteveC said:

Yes, Ouch indeed! Interesting that they have spares though……

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Plus you still need to know what's up with the starter motor!

baz said:

Would this only be the case with alloy?

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No because even though the alloy does expand more than steel you still have a hot spot surrounded by colder metal. So same but less effect for the same temperature difference.

ntst8 said:

If they have managed to shear the woodruff key that can smear itself around the shaft and become and absolute sod to remove - at least that is what mine did.
I could not get a straight pull to move things and ended up with good tension on the puller tapping the sideways on the end of the tensioner at 12 o'clock, - 3 o'clock etc around and around and around, a bit more tension repeat. A bit ugly but it eventually worked.

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my first woodruff key failure somewhat welded the sprag clutch assembly to the crankshaft, but i managed to remove it with a two jaw gear/bearing puller. pretty much an all day effort and destroyed the sprag clutch assemblyin the process. second woodruff failure, not as bad - came apart without issues. no issues since incorporating the yves fix. BTW, first failure, a new sprag clutch assembly cost me $350 USD.

Update.
I bought a better 3 arm puller and gave the sprag a good heat.
unfortunately, even though I got it good and hot and gave it some serious force it just would not pull off.
In the end, I had to cut it off with a cutting disc. Jubilee clip around the crankshaft thread and a few strategically place bits of sheet metal in case the disc grabbed.
I managed to cut across, just above the crankshaft through the woodruff slot, without touching the crankshaft.
Once I was through I was able to hammer both ways to open up the centre slightly and finally it pulled off.
I found that the woodruff key had broken and gauged into the inside of the sprag, effectively making a lip that prevented it from pulling off. The broken bit of woodruff key tapped out of the crankshaft ok, and I think that the crankshaft will dress up ok.
All I have to do now is spend some more cash to replace the damaged parts!

Oh, I forgot to say. The starter motor was corroded inside and the brushes were seized. I have cleaned off the corrosion and now the brushes move freely. Starter motor now works!

Thanks to all for your Ideas and suggestions.

I wouldn't be putting it back. It would be out at the curb after that ordeal.