1953 A7 plunger, crankshaft oil seal

[A7restore]

My A7 is fitted with a crank shaft oil seal in the primary drive case. according to the parts manuals and other articles I have read there should be a Shim and an engine sprocket distance piece.

I have found online an engine crankshaft oil seal for an A7 plunger. But when I checked the part number, it is the same as  output shaft oil seal

This is confusing. Is it possible that at some point in it's history my bike has been modified? Has anybody else come across this

[Swarfcut]

 Early engines do not have an oilseal on the crank. Instead they use a close fitting primary drive sleeve and an oil slinger, described as a shim.  Measure the hole in the crankcase. For the oilseal type you need a hole of around 56mm. Matching drive sleeve  measures  around 42mm.

  Seal is the same on all engines. Later S/A design uses a spacer running on the seal, plunger doesn't. Both types use circular shims to align primary chain to the clutch chainwheel.

 I would expect your cases to be BA 7 Series. Previous series ZA 7 have the early no seal design.   67 674 is the seal used, where applicable.  Easy to confuse shims and spacers.

 Online sellers often confuse the gearbox mainshaft primary case seal with the crank seal. Today someone asked  "Is it me?" Answer, NO, it's the rest of the the Junk Food Generation.

 Swarfy.

[muskrat]

G'day A7.
I recently converted my 51 AA7 to the 53 on oil seal. See https://www.a7a10.net/forum/index.php?topic=16831.45 from reply #46 on.
Cheers

[A7restore]

Thank you guys.

I have ordered a new seal, fingers crossed it's the correct one, if not I will measure up and order one from a bearing and seal supplier. The original seal has three punch marks in the case to stake it into place so I will do the same.