Tech Tip: Rocker Box Oil Feed Washers - Copper vs Stato-Seals

Tech Tip: Rocker Box Oil Feed Washers - Copper vs Stato-Seals

So for the past few months you have been rebuilding your motor using the best quality parts and taking your time

Not one step was overlooked or missed as you begin to re-install each component

As you proceed to install your cylinder head and rocker boxes the last step you need to do is to fasten your acorn nuts that retain and seal your rocker oil feed line

High Five

Now that everything is installed you start your machine up and it roars back to life. As you begin to high five your buddy’s in excitement you quickly notice an oil leak coming from your rocker feed acorn nuts

Not only do you have an oil leak but it’s a buzz kill, which is not cool!

Today's Tech

Today I would like to cover a new product we stock that will fix all your rocker oil feed leaks and seeps using our new rubber sealing washers

I will also dive into why cooper washers can leak and also how to prevent future leaks using copper or stator-seals

So what does Classic British Spares recommend? 

Keep reading to find out

Lets dive in

The purpose of sealing washers

The purpose of using a copper washer or a rubber bonded washer (stato-seal) on your rocker feed lines is to keep oil and debris from entering and exiting

Both copper washers and stato-seal washers can achieve an oil tight seal, however the copper washers can sometimes be a bit "pesky" the first or second go around


Why Cooper washers leak


When using copper washers to seal your rocker oil feed pipe you may experience oil seepage or weeping over time

Other times you may not have any troubles or problems at all


Anneal Copper Washer With Map Gas

The most overlooked step is annealing copper washers 

Often times copper washers are not ready to go "out of the box"

Copper washers need to be annealed every time should you begin to reuse a copper washer

When you are preparing a copper washer (this goes for anything copper) make sure the washer is "cherry red" (from the heat) but without damaging or melting the copper during the process... this is called "annealing"

I like to use water to "quench" the washer when done 


Gasket Surfaces


Surfaces on both the backside of the acorn nut, oil feed pipe and rocker box surface need to be flat with no obstructions. Remove any burs and address any high or low spots prior to installation 


Copper Washers On Spindle


We have also found that some copper washers have an I.D. (inner diameter) that is slightly larger than the shaft, this is to allow the copper washer to fit over the shaft

Excessive gaps around shafts can pave a way to an oil leak, it's best to have a snug fit but without causing obstructions or grief when fitting..

Don’t be afraid to tighten the acorn nuts

Triumph for example, had a torque figure (on early rocker spindles (3/8” x 26)) of 22ftlbs!

I personally think 22lbs is too much (more like 5-8 should be more than enough) but you get my point..

Did I mention your copper washers need to be annealed?

Why stato-seals?

Stato-seals are the perfect combination of simplicity and convenience 

Our new rocker oil feed Stato-seals we’ve added to our online parts catalog is aimed to prevent oil leaks and weeps on the rocker oil feed line without the preparation 

How stato-seals work


Stat-o-seal on Triumph rocker box spindle


A stato-seal is capable of sealing better than an annealed copper washer due to the fact a stato-seal remains soft and supple while retaining equal pressure around a shaft unlike copper washers which just “slip over” the shaft loosely as we described further above 

Stato-seals are very forgiving and will seal just about anything 

We have used stato-seals on our builds and in testing and have found that the stato-seal washers seal regardless of the situation or preparation


Pros & Cons


Pro's & Con's

Now that you know how each seal or washer works, lets go over some pros and cons (and my take) on which may give you better results and which part is correct for your application 


Copper washer & stato-seal pros & cons

Below is a pros and cons chart comparing both copper washers and stato-seals together, side by side


Yes - Copper No - Copper  Yes - "Stat-O-Seal" No - "Stat-O-Seal"
Leak Proof ✔️ ✔️
Affordability  ✔️
Reusable ✔️ ✔️ (to a certain degree)
Easy of Installation  ✔️ ✔️
Quality ✔️ ✔️


Which sealing washer is better?

Both copper and stato-seal washers work great - but it depends on your preference

I have personally have had great success with copper washers, I have nothing negative to say about them.. they work with simple preparation

However, I have been told by some of my customers that they have had consistent leaks with copper washers..

For the person that wants a fast and worry free leak, I do recommend going with the new stato washers that we have in-stock should you have the extra money to spare (they are almost double the price)

For the traditional builder, you cant go wrong with copper washers. They work and they are very inexpensive 



Caliper & Washers

 Below is a chart showcasing the full specifications of both copper washers and stato-seal washers side by side

Some manufacturers may have slightly different specifications than what is shown below

 Washer Type I.D. (Inner Diameter) (Outer Diameter) Thickness Fits Shaft
Copper .380" .650" .040" 3/8"
Stat-O-Seal .370" .665" .065" 3/8"

Need new washers?

Copper & Stat-O-Seal Washers For Sale

Need a set of stato-seals or copper washer?

We have you covered should you prefer the traditional copper washers or new stato-seal types

Click on the “click here” text below to purchase your washers today

Washer Type Part Numbers (Triumph & BSA) Link
Copper 70-1335, E1335, 70-0402, E402, 40-0159, 40-159 Click Here
Stato-Seal Works with part numbers above Click Here

Both stato-seal and copper washers listed and described above will work with both Triumph and BSA "domed" rocker nuts - some of the original part numbers where.... 70-1435, E1435, 40-0162, 40-162, and other superseded part numbers.

Thanks for reading

Thank you taking the time to read today's Tech Tip post

We would love for you to join in on the conversation by commenting in the section below

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Ride safe - CBS


  • Brian

    How long will the stato-seal rubber hold up when mounted to the head of the bike? The specification for the buna-n rubber in the washer is 220 degrees *F, but the head temperature on the bike can well exceed that. I know that stato-seal washers can also be supplied with a fluoro polymer insert (the red ones) for higher temperature applications. Do you also carry those?

  • william c harvell

    you guys provide a great service here, I,m glad I found your site and services , I love the Classic british bikes , it,s what a bike should look and sound ,perform like, and the free shipping is a a god send to a guy in the middle of nowhere like me here in Mississippi

  • william c harvell

    Tell Peter he needs to replace his o-rings on drive side ,more than likely thats what,s causing his non-feeding side leak

  • eric roberts

    I have a 1973 T100 R. My rocker oil feed bolts (70-3809) are 5/16 dia. My copper washers (82-1880) have a 5/16 ID. Do you have 5/16 ID copper washers or 5/16 ID stato-seal washers ?

  • Bruce Henderson

    Do you have a Stato-seal for the external oil pipe banjo bolts on a Norton Commando head? Thanks, BH

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