Another TIGHT engine sprocket.

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I decided to go into the gearbox and change out the layshaft bearing today. All went like clockwork until I got into the primary and finally to the engine sprocket. I've never seen anything this tight on a shaft. The puller is pretty stout; it is US made and was my dad's for about 50 years. As suggested in another thread, I tried heating the sprocket (carefully to avoid heating anything else) until it produced a bit of smoke. No joy at all. The other problem is the puller wants to go out of line with the crankshaft when under stress. Also tried a new puller from the auto parts store which is stout as well. Same result.

Cussin' the designer isn't getting me anywhere--;) Anyone have any suggestions?

~998cc
 
Cubed ice or dry ice on the shaft after a long soak in penetrant.
When you think you can’t heat the sprocket any more give it another 15 seconds and then give the shaft a good shock with a hammer. Sprocket next.
It takes serious shock to break loose serious binding.
 
They certainly can be tough to remove. I use a drift to shock the sprocket that is a very stout old tyre lever with the end ground so that it will fit between the rows of teeth on the sprocket so that the impact gets transmitted through the sprocket. First tighten the correct extractor as much as you can then give the sprocket a good whack.

Ian
 
I take it you are using a 3 legged puller or suchlike as it belonged to your dad?
You need to buy or make a puller that screws into the engine sprocket then give it some welly
Give the head of the extractor bolt a clout
If that doesn't work apply heat in one spot only to the sprocket and give it a clout
Hopefully that will get it off
Cheers
 
And whilst you are doing it stay calm and think what a great job those blokes made
Machining those tapers so accurately that it's still so tight
Cheers
 
Leave it under tension and walk away. Overnight if necessary. The mechanical gnomes are shy and won't work if you are watching.
 
Leave it under tension and walk away. Overnight if necessary. The mechanical gnomes are shy and won't work if you are watching.

Good morning C.G.

I thought the same and left it under tension all night. Still firmly in place this morning. Being Saturday night, the gnomes were likely at the pub. :cool:
Below is a photo of the puller in place and under tension; it is a combo two or three way puller. The nose of either puller would not mesh properly with the end of the crankshaft. This is why the crankshaft nut is installed; it is holding a sleeve in place that better transfers the puller's pressure/tension. The bolts are grade 8.

The glob of blue silicone on the stator cable shows the primary has been opened before, and the chain looks new. If that is the case, the sprocket had to have been off at some point--yes?

Another TIGHT engine sprocket.



~998cc
 
And whilst you are doing it stay calm and think what a great job those blokes made
Machining those tapers so accurately that it's still so tight
Cheers

Agreed, and I do appreciate the fine craftsmanship of the taper and mating surfaces. However, it seems a splined shaft/sprocket would have done just as well and would be infinitely easier to service.

~998cc
 
Cubed ice or dry ice on the shaft after a long soak in penetrant.
When you think you can’t heat the sprocket any more give it another 15 seconds and then give the shaft a good shock with a hammer. Sprocket next.
It takes serious shock to break loose serious binding.

SUCCESS!! Heated it up again--but more thoroughly and brass drift to the sides of the sprocket--nothing. Then one moderate tap on the end of the puller. Pop! The project continues. :D

Thanks to all who replied. Dry ice was next.....

~998cc
 
SUCCESS!! Heated it up again--but more thoroughly and brass drift to the sides of the sprocket--nothing. Then one moderate tap on the end of the puller. Pop! The project continues. :D

Thanks to all who replied. Dry ice was next.....

~998cc
Brilliant news
 
SUCCESS!! Heated it up again--but more thoroughly and brass drift to the sides of the sprocket--nothing. Then one moderate tap on the end of the puller. Pop! The project continues. :D

Thanks to all who replied. Dry ice was next.....

~998cc

Did it release with a pop or !!POP!!.
I've experienced the same issue and when it finally let go using the same techniques, there was a loud BANG.
 
Did it release with a pop or !!POP!!.
I've experienced the same issue and when it finally let go using the same techniques, there was a loud BANG.

Bob. It was just a "pop!" and the sprocket and puller fell away from the shaft. No bangs to speak of.

Layshaft bearing was pretty tight in the case; heated the case and was still hesitant but came out without trouble using a puller. New layshaft roller bearing is installed in its place. The large output shaft bearing came out fine, but the new one is problematic going back in with the case heated. Tried freezing the bearing-no go either. Might get varied opinions here, but the gearbox case is still in the bike which does make bearing install a little more difficult. Really would rather not pull the whole box but may have too. o_Oo_O

~998cc
 
SUCCESS!! Heated it up again--but more thoroughly and brass drift to the sides of the sprocket--nothing. Then one moderate tap on the end of the puller. Pop! The project continues. :D

Thanks to all who replied. Dry ice was next.....

~998cc
Glad it finally freed up!
 
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