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Engine sprocket

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Hi all, this is a plea for advice. I'm trying to change the primary chain on my Navigator, but I'm completely stuck with removing the engine sprocket from the crankshaft. I've left it under as much tension as I dare, (using the puller that the OC sell, as picture) but despite several goes with a (small) blowtorch, and blows with a copper block and hammer it seems nowhere near breaking its hold on the taper. I've followed procedures I've read from earlier disussions of this on here - I just wondered if there's anything else to try, or is it just 'more heat and more force?'. Any ideas on the best place to land a well-aimed blow?

Any tips gratefully received!

Mat Humphrey

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Hi Mat

I had the same problem, the thing that freed it for me was a hefty whack on the sprocket itself, as though you are trying to push it further on. The puller was very tight and the whole thing came off with quite a bang.

Best of luck

Tony

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I was surprised how much force was necessary to free the sprocket from the taper when I recently replaced the stator on my Electra engine. I didn't use any heat because I didn't want to risk damaging the crankshaft seal.I just kept tightening up the puller and hitting the centre bolt directly with a hammer,untill it eventually came off.Perhaps the copper block is absorbing some of the  impact from the hammer. I would just keep tighting the puller bolts a bit at a time and giving the centre bolt a sharp tap with the hammer each time.

Good Luck

Frank Anderton

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Hi Mat,

   If you can't remove it using Frank's method, I would then use Tony's as what you need is to distort the taper fit. Tighten up the puller as much as possible, then using a substantial steel drift and a decent engineers hammer, give it a blow on the face between the boss and the teeth. Another method if you can get behind the sprocket is to use a large (12") tyre lever between the sprocket and crankcase using a metal plate to protect the aluminium and give it a sharp levering push again using the puller fitted.

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Mat: I've never worked on a lightweight but I do have plenty of experience in removing bearings, drive gears etc of all sizes from all sorts of shafts, (tapered and straight). The problem is the taper, as the sprocket is tightened on the shaft and key it will have taken up all the tolerance. This plus heat when use will have effectively glued the sprocket on to the taper shaft

All of the above methods are perfectly sound ways of removing any form of sprocket, pully, bearing etc from a taper shaft. Another option you can try is to tighten the puller up as much as possible and apply plenty of releasing fluid then leave it to work for an hour or two. Apply more pressure with the puller and if you fancy give the sprocket a hard sharp smack with a copper mallet. You could try some gentle heat while the puller is under tension but be very careful. Plenty of patience is an asset. Ultimately you may have to bite the bullet and use an angle grinder to split the sprocket but, this IS the last resort.

Best of luck

John

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Thanks for the replies all, I really appreciate it.

Tony - yes, I suspect my whacks have not been hefty enough so far - too tentative to do the business. I may have to stop worrying so much about damaging the sprocket. 

Frank - I 've not tried whacking the centre bolt, so that will be next.

Richard - thanks, also worth a try. When I first got this bike the LH crankcase was punctured behind the engine sprocket - I think someone may have tried that technique before without using the metal plate!

John thanks for your advice as well. I will keep trying with the puller and whacks to the sprocket. As you say, last resort to start cutting things up, but if needs be...

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As others have said, heat is your friend. While not as hot as a blowlamp, boiling water is very good at transferring its heat to bits it contacts very quickly,  which is what you need to happen. With the puller as tight as possible, pour a freshly boiled kettlefull of water onto the sprocket and keep your fingers crossed - this has worked for me with other bikes in a similar predicament. The worst that can happen is it is still stuck and you have to mop out the shed! Oh, and wait for the refilled kettle to boil for another cuppa!

Good luck, George 

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Rather than use a naked flame, a good quality hot air gun that kicks out somewhere in the region of 500 to 600 deg C might also be an option. It will take some time but is much more subtle than a blow lamp/gas torch.

I've used this method in the past on delicate jobs and it worked well but took a couple of hours but at least you don't risk a fire or significantly altering the the heat treatment of the shaft.

John

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Stand to the side when working on this job if the sprocket lets go it will hurt.

My advice is to put as much weight on the puller as you can and hit the centre bolt of the puller with a big hammer ,the shock of hitting the centre bolt will transfer through to the crankshaft and sprocket, if the puller in use it is not big enough get a bigger one, if you resort to using heat you need a lot of heat as quickly as possible, the aim is to expand the sprocket off the shaft, slow heat will just let the sprocket and shaft expand at the same time making it worse.

It would not be the first time that I have failed to move the sprocket and left the puller on overnight only to find in the morning the whole lot on the garage floor.

Tony

 

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I see you are working with the engine in the bike.

Don't forget there has to be an equal and opposite force to the hammer blows. Every large blow on the centre bolt of the puller is reacted by the balls in the timing side main bearing. They in turn are making pits in the bearing races.

Sideways blows on the sprocket are taken by the roller main, which is a bit tougher.

And the heat suggested could take out your crankcase seal.

Your copper faced hammer approach was kinder for the bearings, but it sounds as though you might be in for a new timing side main.

Peter

 

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Over the years, with engine hot & cold, the sprocket creeps up the taper, till its almost seized on.

Tighten the sprocket puller as tight as you can.

Apply Heat.I like the boiling water idea. Never tried it, but will try next time. Lot of heat - all at once. Stand well to one side, as the firmer its on, the further it might fly when it lets go.

If still not shifted, tighten the puller again, then use a steel rod at 45 deg and a hefty lump hammer. Hit the sprocket in the angle formed by the boss & the teeth. Hit it like you mean it! (Your copper hammer is asbsorbing the blow).

Warning - this may not do the main bearing any good - but as someone mentioned above, the shock is mainly absorbed by the roller bearing - rather then the ball bearing opposite.

If you believe, it will come off!

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I've just started working on my navigator engine.  I've started with some work on the primary drive.  After reading through this thread I expected the sprocket would be tight, I wasn't disappointed!  Here are a couple of photos of the puller I've made, quite a massive thing compared with the NOC puller.  These tools need to be as stiff as possible so that the forces exerted by them go in to pulling rather than bending the tool.  I wonder if the OP's problems are due to this?  I chose a 1/2" UNF thread to generate the extracting force, a fine thread that is capable of exerting a high load. The other bolts are decent quality cap heads that hold the body of the tool very tightly against the sprocket  I will, some time, modify the tool to provide a better way of holding it still while tightening the bolt.

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Very impressed with your sprocket puller,John,perhaps two flats 180 deg apart so that you can hold it with a big adjustable whilst you tighten the centre bolt  would help?

 

Frank Anderton

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Thank you everyone for the great advice, really appreciated. Andy I tightened the sprocket puller as much as I could, and then left it for 48 hours as I had no time to work on it (this may have been a bad idea...). When I returned to the garage the puller was on the floor, as one of the bolts that threads into the sprocket had snapped. So that's two sprocket pullers eaten by this thing. John I think you're right, this needs a *very* robust tool, I like your creation.

Nil desperandum, I'll keep trying.

 

 

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The tough  2 leg puller that Norton Birmingham  made for Dominators is still availiable from RGM , this never failed to work for me . Dont know if there is enough room to use it on your bike.  

Nice Piece of work John,

Perhaps a 'c' type spanner with 2 pegs to locate into the socket head counter-bores would be as easy and the nearer to the tightening spanner would give good stability by reducing the turning moment.

Whenever I have made special pullers I try to use 3/8" BSP threads as they have an excellent effective diameter/ pitch ratio producing more thrust/ft.lb. of torque than a normal 'fastener' type thread and with taps and dies available it saves having ti screw cut. You are correct in opting for the finer pitch for the same reason.

Regards

Dick

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Thanks for the compliments regarding my crank shaft sprocket extractor.  I needed to finish the tool off as its being borrowed by another lightweight owner to try and shift a stubborn sprocket.

I've machined a 27mm AF hexagon on it so there's something to react against when tightening on to the shaft.

To fix the tool to the sprocket I use two "V" grade cap head screws to avoid them breaking as has happened to the OP's

John

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Try using a slide hammer , utilising the tapped holes in the sprocket and a screwed length of steel rod about 18 ins long .   It’s never failed to extract my sprocket when used.

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Yes, the extractor bolt broke as you need specially toughened one as stated above.

Skide hammer idea will work on a sprocket that has been off in the last 20yrs or sp - not one that has been there for ever.

Try again with hardened screws, plus steel rod at 45 deg and hefty lump hammer.

I did like the sound of a panfull of boiling water - before the lump hammer trick.

I use the Norton Tool - which you can make for yourself - see photos (sorry, my drawing looks a little squished)engine sprocket puller

sprocket puller 2

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If you use the hot water method as per George Farenden, be sure to drain the crankcase afterward as some water will certainly get in there.

Mike

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Just wondering if the OP has shifted his sprocket yet?

My puller has just pulled it's second sprocket but not before a modification.  As  originally made the 1/4" BSW bolts pulled the body of the puller against the small diameter of the sprocket, its been modded to sit against the face of the teeth diameter.  This ensures that when the the tool is pulling on the sprocket its a true axial force rather than something slightly off axial as the Norton tool will do.

Pullers real need to be as stiff as possible so they do not deflect.  The bolts need to be tough, (not hard), I used "V" grade cap heads, if it was metric 10.9 0r 12.9 bolts.

 

 

 

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