1972/73 750 crankcase

Hi.
There are differences from 72 and 73 750 crankcase?
Thanks.
Piero

The simple answer is yes, there were differences. Somewhere in the 1972 -1973 years the crankcase changed from the earlier style, most easily identified by the plate on the back of the timing side half, to the final style with breather tube in the back of the timing side case. The parts book lists the newer style from serial number 212278 on. Somewhere in here was also the infamous case with the breather at the bottom rear of the crankcase, and no large drain plug at the bottom, but I'm not sure of the dates for it. There were at least four different 750 crankcase designs between 1969 and 1973. I'm sure LAB probably has more detailed info on this question.

Ken

It means that the late 750 cases are the same of the first 850?
Ciao
Piero

lcrken said:

Somewhere in the 1972 -1973 years the crankcase changed from the earlier style, most easily identified by the plate on the back of the timing side half, to the final style with breather tube in the back of the timing side case.

Click to expand...

But, the breather at the rear of the timing case was only fitted to 850 models.

lcrken said:

The parts book lists the newer style from serial number 212278 on.

Click to expand...

Er, no (not for 750)?
http://www.classicbike.biz/Norton/Parts ... _73-74.pdf
750 cases, Group 6, pdf page 17 & 18.

lcrken said:

Somewhere in here was also the infamous case with the breather at the bottom rear of the crankcase, and no large drain plug at the bottom, but I'm not sure of the dates for it.

Click to expand...

Introduced at serial 200000 and continued until the end of 750 production.

Edit:
The hole for starter motor blanking plate was discontinued around mid-'72 and there was an alteration to the machining at the rear of the case (see dynodave link) that also must have occurred around mid-'72.

http://atlanticgreen.com/engcases.htm
"72 and 73-750's........"

Well, like I said, LAB does have more (and better info). I think I confused the pictures of the 850 and 750 cases for some of my comments. I blame my medication. One of the side effects is mental confusion. I should be off it in two weeks, but I'll try to be more careful in the meantime.

Ken

Well.
No differences between 72/73 krankcases.
Ciao
Piero

pierodn said:

Well.
No differences between 72/73 krankcases.
Ciao
Piero

Click to expand...

Well yes there is. The newer (somewhere around 208xxx on) are reinforced in areas of the mounts. See Dynodave's site as mentioned. When they casted over the mag ( or ill propose E start) hole is when this improvement started.

Hi.
Could i join to the left drive 1972 case a 1975 ES timing case.
As far ss i know, it should be possible if you shim the crankshaft timing side.
But, in case, the oil circuit works or must update?
Thanks
Piero

Might be wrong here, are barrel studs spacing and the aperture for the barrel different on the MK3 case when compared to a 750 case.

Madnorton said:

Might be wrong here, are barrel studs spacing and the aperture for the barrel different on the MK3 case when compared to a 750 case.

Click to expand...

Hi.
I dont think so.
Ciao
Piero