Service Bulletin: Triumph 650 & 750 Sump Filter Plug O-Ring
When most folks think of vintage British motorcycles there are many things that come to mind from the infamous Lucas electrics, Amal carburetors, the deep glorious sound of glass packed silencers and so on...
The first thing that usually pops into ones mind whether they’ve owned a British bike or not is there reputation of leaking oil.
The funny thing is they all leak oil..
I mean, it’s the nature of the beast. Wouldn't you agree?
For those folks out there that have put together (or what they thought) was going to be an oil tight Triumph engine, perhaps this little tip might help you solve some of your oil leaking problems.
Allow us to present to you an original Triumph service bulletin dated May 5th, 1973.
This service bulletin gets into minor detail regarding the 70-9336 / E9336 crankcase oil filter drain plug.
This crank case drain plug was fitted to all unit construction Triumph 650 and 750 unit twins from 1963-1982. In all fairness there where 2 different types of plugs used during the 1963-1982 period that we will cover below...
Most models used an annealed copper washer to prevent oil leaks but sometimes the copper washer is simply not enough to seal the oil in the crankcase, therefore you must use an o-ring as described in this service bulletin.
The o-ring as described happens to be the same o-ring that is used on Triumph twin models for the bottom of the pushrod tubes.
|Part Type||Part Number||Material||Measurements (approx)|
|O-Ring||70-7310 / E7310||Viton||1 3/16" (OD) - 1 1/16" (ID) - .093"|
The reason why the factory took use of the 70-7310 / E7310 o-ring is the fact that it fits but it is a "viton" o-ring. Viton material o-rings are excellent for applications where heat, oil and pressure play a major role.
The sump filter plug that was installed on all Triumph 650 and 750 twins from 1963-1982 came in 2 types of conditions. Although this Triumph service bulletin only lists the later 70-9336 / E9336 plug using an o-ring on the early plug 70-5312 / E5312 will not do any harm.
Pictured above is a Triumph sump filter plug (70-9336 / E9336) with the 70-7310 o-ring
|Part Type||Part Number||Year||Model|
|Sump Plug Filter (Early)||70-5312 / E5312||1963-1968||T120 / TR6|
|Sump Filter Plug (Late)||70-9336 / E9336||1969-1982||T120 / T140 / TR6 / TR7|
*Both the early and late plugs do not have a recess to accept an o-ring however it works. Make sure when you install the plug to not over torque the plug as it can deform the o-ring. I personally think Triumph was applying a Band-Aid to a problem that should have been redesigned from the start.
Replacing the copper washer
To switch over from the copper washer select your 70-7310 / E7310 o-ring and insert it over your oil filter plug.
Fasten the oil filter plug into the case and you are done...
Need a plug or an o-ring? or both?
Should you need to replace your oil sump filter or install a new o-ring to put a stop to your oil leaking problems perhaps you should see some of links below that we have compiled for you.
|Parts Link||Part Type||Part Number|
|Link||Sump Filter (Early)||70-5315 / E5315|
|Link||Sump Filter (Late)||70-9336 / E9336|
|Link||O-Ring||70-7310 / E7310|
Thanks for reading
I hope this blog post serves you well.
As always should you have any questions please feel free to drop us comment in the section below.