I have a 1275 crank but cannot remember if it is large or small journal and the only number I can see on the crank is ESC1X does this number mean anything?

That is a forging number. Look closely at the webs for a stamped on number.
If it is a big journal Oz crank it should have 12G1505 on there somewhere.

Otherwise, measure the crankpin diameter. 1.750" or slightly less is big journal. 1.625 or slightly less is a small journal.

_________________
DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

I have found a similar number it is very faint looks to have been almost removed for balancing but the numbers I can see are 12G128* the last number is ground off and can't be read. Also what should the end float on the primary gear be?

Sounds just like my crank, 12G1288, the last 8 was barely noticeable! Small journal!

Cheers Shane

_________________
If it's not a Cooper S, the mini was designed to be modified!

Yep it's a small journal.
Primary gear endfloat- I aim for .004-.005".

_________________
DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Just a Note, On the large journal Crank, You Will often find 12G1505 OR 12G1505A Cast in the crank.
not stamped

_________________
" A Hundred Years From Now It will not Matter what my Bank Acount Was,
The Sort Of House I Lived in, Or The Kind Of Car I drove ... But The World May Be A Better Place
Because I was Once Important In The Life Of A Child"

What is the difference wit 1505A and 1505 ?
Always wondered that.

_________________
DID I MENTION THAT I AM THE BEST SUPPLIER FOR MINI ELECTRICAL PARTS AND REPAIRS?
"Let us remove your "SHORTS"

Lucky i'm rebuilding this engine it's pretty shagged, at the moment primary gear is .015, and the end float on the crank is .0098.

If you are going to rev it, I'd want .006" crank endfloat, minimum. I built my 1360 with the recommended .003" the first time, after 3 laps at a Wakefield Pk track day the oil pressure went south. It almost spun the centre main shells, and I had to regrind the S crank to clean the centre main journal up. It has .007" endfloat now, all is good.

_________________
DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

small journal cross drilled, large journal not. Well that's my experience anyway.

_________________
The bitterness of poor quality (or Crappy Workmanship) remains LONG AFTER the Sweet Taste of Low Price is forgotten.

Mine was cross drilled too, I thought it was done on a rebuild, maybe!
Maybe it was a factory job.

Cheers Shane

_________________
If it's not a Cooper S, the mini was designed to be modified!

Some small J cranks were cross drilled when new, the later ones were not.

_________________
DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

What is the standard primary gear thrust washer size I'm not sure if the current one is worn or if the engine was built incorrectly the previous time.

I do not think there is any difference, Also sometimes the A is there but not very clear

_________________
" A Hundred Years From Now It will not Matter what my Bank Acount Was,
The Sort Of House I Lived in, Or The Kind Of Car I drove ... But The World May Be A Better Place
Because I was Once Important In The Life Of A Child"

There were lots of sizes selectively fitted.
Karcraft now lists them from .122" to .128" thick. Matt Read `TheMiniMan' also gets them made up in Brissy.

Note the steel `C washer/clip' wears more than the thrust washer, you can turn it over once to extend its life or go buy a new one.

_________________
DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.