Bottom engine rebuilt-splitting crankcase

[David1977]

Hello , I want to remove a crankshaft from the engine . I am in stage like in photo. Can you tell me what next step follow to split the engine ? thank you

[Groily]

http://archives.jampot.dk/book/Workshop ... .NEILL.pdf

It's all in there, with explanations of all the things you need to know as you go.
Well worth downloading or, better still, obtaining a copy of the book if one comes up.

Having got the top end and timing side off, not that far to go, and if you do things in Neill's order, you'll find it comes apart pretty easily.
With the central main bearing and its carrier, there'll be 'things' you won't have seen in any other Brit parallel twin.

From the pix, looks as if you have a pretty decent basis there, which with any luck will be good all the way through and be very satisfying to work on.
I have two motors just the same yours, one a Mod 20, the other a G9, which get alternated when it's time to fettle one or the other, but they go for absolutely ages - seriously - between rebuilds.

[David1977]

I can not loose this bolt on crankshaft because when I try to loose the bolt the crankshaft is spining around . Is there any trick how to ensure the crankshaft from spining around ?

[les ward]

I remove the pistons, then put a brass bar through the small end of the Conrods, resting it on wood to protect the crankcases.

[Joker_Bones]

20170529_200845.jpg

Norton engine... But as per description in above post

[David1977]

Thank you for the advise. Does the crank bolt has right hand thread ?

[ajscomboman]

You don't have to remove the bolt before splitting the casings.

[clive]

You don't have to remove the bolt before splitting the casings.

I wondered why I had not struggled with this.

[David1977]

I removed all bolts on driving side . Crankcase shoud be ready to split now ? or is there any step what to do now ?

[Groily]

If all the bolts etc etc are out, the timing side should come off, leaving the crankshaft and centre web bearing carrier still in place - attached to the drive side by 6 x 1/4" BSC nuts on studs. When these are undone, and the lower half of the centre main bearing is also removed to get the web off the crank, you will have it - the crankshaft - in your hands.

It is important to understand that there are 2 substantial pins that support the cam followers, with unequal length spacers to keep them in the right spots under the relevant pushrods when assembled. The pins are by necessity a close fit into the timing side case. So the two halves don't usually come apart without some pressure being applied to get the timing side off.
The crankshaft itself needs to be at bottom dead centre to allow the connecting rods to pass through without damage, obviously.

You are almost there - hope you only find good things when you get there. It is CRITICAL (truly, not kidding) that the radii on the big end journals and on the centre main bearing journal have not been damaged, or removed during a previous regrind.
Dimensions are available for standard and regrind sizes and radii in the archives which I mentioned previously, and in a few threads on here too. If the radii are gone or not capable of withstanding a regrind, you are, sadly, in trouble, as the crank will only be good as a very big paperweight!
The crankshaft oilways will need cleaning after removal of the sludge trap screws on each end, and all parts need to be carefully measured. The connecting rod big end eyes should also, ideally, be checked for ovality (especially when hot) as it is a possible point of weakness with alloy rods & alloy end caps. Don't try to get the studs for the big end nuts out of the conrods without identifying and removing the cross-PINS that retain them at the upper ends - or you will wreck the threads. The trunnions and fasteners are, I think, available new still, if need be.