Help, Can't Get This Cover Off (i'm The Idiot)

Good morning, I assume that you removed the shift lever and kick start lever? Remove the center bolt from the points area and the two bolts on either side. Use a rubber hammer to gently tap around the case. There should be a gasket, and due to the age is probably just stuck firm to the cover. Try setting it up on edge and gently tap down and out a bit. Be patient and keep at it. Maybe try a little heat from a heat gun too. Good luck.

 

As you have worked out you have to stop the engine from turning to undo that nut. How you do it depends on how far you are going to strip the engine down.
I completely dismantled a Cub engine some years ago and when I got to this nut I had already removed the head and barrel. I locked the engine by placing 2 wooden battens underneath the piston skirt so that it would lock against them when I turned the nut. Once the engine was locked the nut comes undone without too much drama.

Wood, being softer than the piston is unlikely to cause damage to the piston skirt.

Best of luck!

 

Bracing the motor from turning is the way to do it. You will most likely need an impact wrench to do this with. The impact wrench alone will probably do the trick.

 

Don't know if it is the same as my old BSA B25 was but it looks like an advance/retard unit for the points. Is there a large thread inside you can put a bolt into by a few threads, if so, waggle the bolt round, the adv/ retard is probably held on a taper. By the sound if things you definitely need a manual or you may end up doing more damage. Good luck.

 

I'm stuck on the same job. I've seen in the manual about the need to make a puller using two bolts, but I can't fit a thread gauge into the internal threads to measure them. Can anyone please tell me what size bolts I need to get the cam & backing plate off the shaft? Thanks, Mark

 

It was over 40 years ago but I just found a bolt from my trusty(and crusty) tin and grabbed the first thread, no need to go all the way in, and twisted, wiggled and pulled the advance / retard off it's taper.

 

Can't you check the threads from the bolts you took out of the respective holes?

I no longer have a Cub manual but the threads will either be BSC (British Standard Cycle) which is 26tpi for all thread sizes or BSF (British Standard Fine)

 

Thanks guys, appreciate the replies. I have a bolt that is right for the inner thread - as you suggested there was a bolt there originally. The one I'm struggling with is the larger diameter one visible inside the cam (post 8 above). There was no bolt in there so I have nothing to measure.

 

That is the one I used a bolt I had and wangled it to remove the cam, didn't need to go all the way in.

 

My wangling is no match for yours.... An M8 bolt would just catch in the threads but I couldn't wangle it off.
I'm no expert on imperial threads - so the question is now, what would be the most likely imperial thread size if an M8 goes in about half a turn?