A10 won't start.

[KiwiGF]

This didn't work.... the puller legs are bending.

Arc Weld a 1/2” nut to a short piece of tube, weld the tube to the gear, put a washer on the crank end to protect it and use a bolt to pull the gear off?

May or may not be able to use the gear afterwards.....

Obviously important to not put sufficient force on the crank that it could be damaged.

[Swarfcut]

 Ewen.   OK, that's the Mk 1 version, time for the Mk2.

    I suggested a slide hammer arrangement to avoid a heavy load onto the crank nose. If you still go for a puller, take care to avoid damage to that thread, this part of the crank is soft and will bell and bend if you're unlucky.
  Crank has a left hand thread which is easily damaged. Best to replace the locknut onto the crank to support and protect the crank nose. Plus a protective something for the draw bolt to bear on rather than pressing directly onto the crank. The closer to the pinion the arms are, the less bending moment there is trying to straighten the arms rather than pull the pinion.

  Angle iron jaws carefully shaped for a good close fit, welded to the arms are a better bet, and the nearer the pull is to the pinion, a better chance of pulling it off square. So, shorter length arms. All to try and preserve the pinion.

 Here in the UK the pinions are still available as used items at a more reasonable cost so sacrificing the pinion remains an option.

 So with the prospect of a replacement pinion, Kiwi's suggestion is certainly simpler and with a good chance of success.

 Swarfy.

   

[Ewen]

Thanks Kiwi. I did think of that but I am reluctant to weld onto the pinion unless I have to. First I will try a better puller arrangement with the legs of the puller right against the pinion to reduce likelihood of bending. 35mm box section is just the right size (see photo) I haven't finished it yet... I will drill through and insert 2 bolts to keep it clamped firmly on the pinion. I will use Swarfy's idea and try  a slide hammer  (might have to make one) to spare the crankshaft.

[Ewen]

Here's the bike.

[Ewen]

[groily]

What an unenviable problem Ewen.
When I had a not dissimilar nightmare on another bike with a camshaft keyway shearing and welding shaft and pinion solid  following a bottom end explosion, I had to grind the parts off because there was no way to get behind  the gear and I'd busted the standard chunky 'two-studs and T bar' tool used typically to draw the pinion. But a camshaft is 'just' a camshaft, not a hens' teeth crankshaft in other wise good shape. I just hope the key hasn't ripped an arc of metal off the crank as things locked up.

If you have access to, or a mate with, a lathe, maybe you could try a split-clamp profile tool, made out of 'decent' using high tensile bolts to clamp onto the rebate on the gear, perhaps with a close-fitting cup that also encased and bore onto the teeth (to provide max pressure over the largest area)? Then, using heat and a serious T bar arrangement, you might be able to get it off?
Chaterlea will show a cracking good weapon, that's for sure. Meantime, here are a couple of clampy jobs I've got for getting things off shafts. The hassle is they do have to be tailor-made, but the benefit of 360° contact and a very good squeeze is in a different league from using a two-legged puller directly, or even a knife puller, which could break. It would probably be a bit nadgery to get clearance all round (but looks do-able), and angles to get the clamping screws in from the left-hand side, but short of carting the whole thing off to an engineering company for their attention, I think it's what I'd try next. In the hope it wouldn't be a triumph of optimism over reality!

[KiwiGF]

I see the advantages of a slide hammer (the advantages had not actually occurred to me) but I would not go TOO mad with what is “sideways” hammering on the crank, firstly I am not sure just how strong the case and bush is, it’s prob fine but consequences very bad if not, and if there is any end float the effects of hammering/shock going through the crank web, journals shells and rods etc just seems a bit wrong? Not what they were designed to withstand?

Having said that I would try it first before sacrificing the gear.

[Jules]

Agree with Kiwi regarding the slide hammer, the resisting force to the sliding hammer will be the crankshaft in the case until such time as the pinion moves....although I think it will need that type of action to shift the pinion, I'm not convinced that a tensioned puller will ever have enough power to pull it over the jammed key....
I had an issue like this with an old B&S flywheel with a sheared/jammed key and ended up "hanging" the motor assy off the flywheel and then whacking the (protected) end of the crankshaft - all the weight and shock load was on the flywheel not the crankshaft, unfortunately you cant do that with the motor in the frame Ewen 

[RDfella]

Pains me to see people struggling on a job like this. The pinion slipped whilst driving the camshaft / dynamo (after the key had sheared). That's not a lot of torque, so whilst the pinion may well have a bur or other restriction frustrating pulling off, it's not actually very tight as regards rotation. As John and I have suggested, rotate the pinion (easily done) until it finds a less tight spot and then pull it off. In fact I'd be surprised if it wouldn't come off just by rotating it back and forth whilst pulling (eg mole grips). Once it has started to move, pri-bar or similar will fit behind for better leverage.

Add: I note in the puller pic, the puller is acting directly on the end of the crank. NEVER do that as it'll create more damage.
Also, that puller has no chance - the arms (between the G clamp) need to be as short as possible - preferably no more than 1/4" long and shaped as much as possible to fit the curve.

2nd add: Last resort. Some have suggested cutting the pinion. That's not possible given it's hard up against the crank and trying that virtually guarantees destroying the crank. Try this instead (always works). You'll need a hammer, sharp cold chisel of appropriate size and acetylene gas (nozzle No 7 would be about right). It can't be done with a blowlamp. 
1. support the crank under the pinion area as you're going to wallop the pinion from on top and don't want to bend the crank.
2. heat a small area of the pinion to cherry red (getting localised heat quickly, before it affects the crank requires acetylene).
3. hit that area hard with hammer / chisel. That will expand the pinion permanently and it'll slide off. Done that many times to get the inner part of ballraces off shafts etc. Of course it destroys the pinion, but is simple and non-destructive to surrounding parts.

[RichardL]

Regarding RD's puller comment, I've successfully  used the exact same method with, i believe, the exact same puller and heat. Regardless, I agree with RD that it is the wrong puller for the job.

Richard L

[chaterlea25]

Hi All
Groily's split collar would be the best tool to get a solid grip on the pinion but I would still try and rotate the pinion and see if it has a looser position
Attached pics of my homemade puller legs, the yoke is from Sykes Pickvant I place a 1/4 in thick piece of copper between the crank and puller, there is just enough room to fit them at one crank position

A short aside story, a few weeks ago one of my friends vintage Ariel shed its magneto chain and it wrapped around the cam sprocket !! the weakest link was the camshaft sprocket which sheared the ring of teeth from the centre boss luckily the cases and oil pump escaped significant damage
The pinion boss must have turned on the taper jamming it even tighter on the camshaft
It resisted the proper puller and a slide hammer fixed to the puller body and had to be ground away until it split
once the metal was thin enough to let go 

John

[Ewen]

Thanks very much guys. Some very interesting and informative points. I will get back to those because I have more questions. There were comments about my first puller pic.... the pigs might fly one which even I knew was wildly optimistic. But no one has commented about  my 35mm box section pic which I thought I might as well try. It is only mild steel which is obviously a problem but at least the fingers which hook into the grooves are as short as they can be. I will attach a drawing so that you can see what I was thinking. Heat is pretty essential isn't it? I would appreciate opinions.

[sean]

I found a battery terminal puller worked to pull my pinion I put some pressure on the puller and tapped the end of it with a hammer it popped off ....I have a lot of different pullers but they were all too big .

[Ewen]

Here is the tool I am making. Just have to weld a piece of 10mm x 10mm on to each side for the puller legs (a decent one) to hook on and take a bit more metal off so that it will slide into the pinion grooves.
Do you think I should heat the pinion first.

[groily]

But no one has commented about  my 35mm box section pic which I thought I might as well try.

Might do it Ewen, you never know! If only you could get the pinion to move on the crank a bit, as has been suggested, it would make it a lot easier. However, noting the crankcase has already shown a tendency to shed bits of casting, extra care in jamming the pinion with anything while trying to rotate the crank I'd say! And some heat, natch.
I'm sure it will come, if you keep faith with RD's mate Percy wossisname.