Removing advance unit retainer nut

[larrynyc]

Hello,

I have a '75 XS650B, about to do a top-end rebuild. I've removed the points on the left side, remove the rod, and have removed the advance weights/springs on the right side.

But I'm stuck on removing the advance unit plate. It seems to be attached by a cogged advance retainer nut. The retainer nut won't budge from the plate at all. I looked up some info, and I *think* the way to do it is to use a screwdriver and hammer to turn the nut:

The problem is, each time I whack the hammer, the blows seem to be absorbed because the retainer nut moves along with the advancer plate as a single unit -- and that moves the cam itself and all its innards (the cam chain and everything else it's connected to inside).

With each whack, I can literally hear everything mechanically moving inside, and feel it all "bounce" back, but the retainer nut won't move independently of the advancer plate.

I've stopped because I don't know if continued blows will do any damage inside the engine. Am I doing something wrong, or is there a better way?

Thanks

 

[5twins]

You are using the correct method - hammer and punch or screwdriver. You might try putting the engine in gear and holding the countershaft sprocket somehow so it can't turn. Some penetrating oil on the nut may help too.

 

[larrynyc]

Thanks, when I get back to the shop, I will try putting it in gear. Last night I already hosed down the nut with PB Blaster, hopefully that will help. Quick question -- I have no clutch cable at the moment (I have a new one on order). Will that hinder my effort to put it in gear? Thanks

 

[TwoManyXS1Bs]

Something else that may help is to pretension the camchain on the frontside, which will remove any cam sloppyness/slack. Simply rotate the crank to about 20° past TDC (any TDC). That'll remove camchain slack at the front of the cam, and may give you better 'whackability'...

 

[5twins]

Not having a clutch cable connected shouldn't hinder putting it in gear. You may need to rotate the countershaft sprocket as you move the shift lever to get the tranny shafts spinning. That will make shifting it easier.

 

[pamcopete]

larrynyc,

It also helps if you hit as many of the slots in the big nut as you can instead of hitting the same one.

 

[larrynyc]

Pardon the delay in replying; I wanted to say thanks to everyone here. I got the nut out with these tips.

It turned out a fat punch worked better than a skinny punch or a flathead screwdriver tip. Here's a photo showing the punch I used that worked (vs the screwdriver)

 

[TwoManyXS1Bs]

Thanx for the followup, larrynyc.
Yes, a flat/broad punch is better since a screwdriver tip will tend to 'cut' rather than 'push'...

 

[fredintoon]

Hi larry,
one of the reasons the screwdriver didn't work is that it had a plastic handle that acted as a shock absorber while the punch that did work was solid steel.

 

[angus67]

...that, and more mass. momentum carried thru the hit.