Tapered Shaft Sprocket Woes

[Crashaholic]

I acquired a 73 250 motor that had a broken counter shaft sprocket. What a crappy sight to see knowing it may not come off without damaging the shaft. Tapered shaft sprocket removal has been a real bugger for some people so I thought I would share my attempt at removing this busted up sprocket.



Made a shield to protect the surrounding area.



Because there wasn't enough of the sprocket left to get a hold of with the Husky puller arms I used two bolts in their place and the mig welder to secure them to the sprocket.

I torqued the puller to 40 ft. lbs, HVA recommends 30 ft. lbs. but I thought it was too conservative after feeling the little force it took to move the wrench. I then applied heat using an oxy acetylene torch for about five mins with no results. Don't worry I had my sheet metal shield in place for the torch even though its not in the photo.



After staring at this thing for 30 mins I thought if I cutoff some of the sprocket, a little on each side, maybe it would expand faster than the shaft and allow the puller to do its job. I used an angle grinder with a cutoff wheel to hack off what I could without damaging the shaft. Looks like a mess at this point.

 

[Crashaholic]

With the same amount of torque I lit up the torch and within 15 seconds of applying the heat the puller and sprocket jumped off the shaft. I don't know but maybe the vibration from the grinder had a role in loosening the sprocket but none the less it was a pleasing moment especially since the shaft came out unscathed.





Seal is toast.





You can see theres not much sprocket on either side. Did this helps speed up expansion before the shaft got hot or did the grinder vibrate the crap out of it? Heck if I know.

 

[Crashaholic]

Obviously this would of been much more difficult if the motor would have been in the frame and removing it from the frame would have been a lot of additional work. Even so I think this could be done while the motor is in the frame as long as necessary steps are taken to insure something doesn't catch fire.

In the early 70's HVA put out a Service Bulletin warning dealers about a run of bad sprockets that would slide onto the shaft farther than normal making them difficult to remove. I think that applying to much torque could also drive a sprocket to far onto the shaft causing a similar problem.

 

[jimspac]

If you split the cases , I know of a few that have replaced the tapered countershafts with splined.

 

[motorick]

Nice job! I wound up cutting the sprocket off, but nicked the shaft. Fortunately I found a 250 5 speed one on ebay so I'll be converting to splined when I rebuild it.

 

[Crashaholic]

If you split the cases , I know of a few that have replaced the tapered countershafts with splined

And miss all this fun everytime I want to change a sprocket? Actually I have a couple of later model six speeds and I was comparing the spline shafts from 74 and 76 and it looks like either will work. Definitely a must do when the cases are apart.

 

[husqyman]

Nice Job. Thanks for sharing, While not on any of my bikes, tips like help give inspiration for similar problems that other's have.
Kev W