Sump plug Thread

[olympus]

Hi Guys,
Can someone advise me please on the crankcase sump plug hole thread & size.... need to get a helicoil kit

 

[DevonNorton]

Olympus
Assuming you mean the small plug (various part nos. 22850, 06.7824, magnetic 06.4188) the thread size is 3/8" x 16tpi. BSW and UNC are the same at this thread size.
RGM Norton stock 3/8" 16tpi BSW helicoil kits.
Andy

 

[dynodave]

BSW and UNC are the same at this thread size. correct answer=not really


Since your question is on the comando forum. I will answer as such, why?
You have to go back before 1953 to find a seperate drain plug on a NHT. (my 1950 M7 only has a drain plug) The big filter was fitted from then on AFAIK then stopped for the 200000/combat breather series, then all 850 reverted to the big filter AND a drain plug.
As a predominant rule, all new items and parts for the commando era are unified thread. Anything that was carries over from pre commando was generally left with the original thread BSF BSW or cycle mostly on the engine and gearbox. These two morphed from 68 thru 75 as these components were updated with an ever changing mix. The beginning 68 engine was almost entirely BS. Then as an example where the 850 engines were with the most UN fasteners, though a few british threads remained.
Without reservation, the new for 73 850 drain thread is 3/8 UNC and the HEX head is 9/16".

 

[L.A.B.]

As a predominant rule, all new items and parts for the commando era are unified thread. Anything that was carries over from pre commando was generally left with the original thread BSF BSW or cycle mostly on the engine and gearbox.

Without reservation, the new for 73 850 drain thread is 3/8 UNC and the HEX head is 9/16".

As the small drain plug wasn't carried over from "pre-Commando" but only introduced at 200000 then it should've been UNC from 200000.

 

[olympus]

Thanks Guys with a 200918 engine I'll get a 3/8 UNC helicoil

Regards

 

[Craig]

If I was you I would use the ”timesert” kit as reviewed on this forum a couple or so years ago .... I got the kit and managed the fix in an hour or so .... no issues other than you end up buying enough inserts for 4 fixes ..... IMHO much better repair than helicoil ....
Craig

 

[swooshdave]

Thanks Guys with a 200918 engine I'll get a 3/8 UNC helicoil

Regards

Don’t. Helicoil will fail especially on a high use application. Get the Time-sert. I posted a tutorial a few years ago.

 

[swooshdave]

https://www.accessnorton.com/NortonCommando/oil-drain-timesert-repair.14109/