Tech Tip: Triumph Twins Crankshaft Oil Feed Seal (Low Oil Pressure)

Tech Tip: Triumph Twins Crankshaft Oil Feed Seal (Low Oil Pressure)

If you're experiencing low oil pressure on your Triumph twin we highly suggest that you stop riding your machine and start reading this blog post before damage occurs.

Today's tech tip just might fix your problem and or save your engine from premature failure.

This $12 part that usually causes low oil pressure is called a crankshaft oil feed seal and might just be your problem.

I recently had a similar problem on my own Triumph TR6R when an oil seal went kaput.

I have first hand experience of what usually causes low oil pressure and how to fix it.

So let's go over the low oil pressure fix in detail below.. you can use the information below for vintage Triumph twins including the Bonneville, Tiger, Daytona down to a pre-unit Thunderbird (6T).


What does an oil feed seal do?


 Timing Gears - Triumph

 Oil feed end on a Triumph unit crankshaft. This is the area where an oil seal will slip over. Notice the hole? That is where oil is fed through the crank end.


So the crankshaft oil feed seal fits into the timing cover and seals around the crank end to direct oil through the crank.

There are different manufactured seals on the market today, most work pretty well but some do not.

Its important that the oil seal functions correctly because the seal is the only component that will prevent oil from sneaking past the crank end which will cause low oil pressure.


What type of seal do I need?


There are two (2) types of oil feed seals that Triumph use to offer back in the day. Each seal is used for the same application but used under different circumstances.

When selecting the seal inspect your crank end spigot. If the shaft appears to be in good shape select the standard seal. If the shaft is grooved and shows signs of pitting or wear choose a -.020 seal.


Standard seal (70-4568 / E4568)

The standard oil seal was originally produced by Pioneer which featured a metal outer casing. This seal happened to be the same seal that was used as a contact breaker or advance unit seal.

This particular seal should be used if your crankshaft oil feed spigot does not show any signs of pitting, rust or grooves.

If your spigot appears appears to be in good order, use the 70-4568 / E4568 seal.

You can always take a seal and slip it over the spigot to check the "fit".

click here to purchase the standard 70-4568 / E4568 seal.


-.020 oil seal (70-6387 / E6387)

The reason for -.020 seal is to help achieve a better fit on the crank feed end.

To use this seal you're crank end either has a groove (caused by an old or worn seal) or had been reground by a crank grinder to eliminate the groove.

Typically a crank grinder will remove material or "turn" the oil feed end to get the groove out of the spigot.

Click here to purchase the -.020 70-6387 / E6387 seal.


What causes low oil pressure?

As briefly stated above, the oil seal works in such a way that it seals and prevents oil from escaping around the oil feed spigot. When oil escapes, you loose oil pressure.

Some seals on the market where made to hold only 7 pounds of pressure which causes oil to blast past the seal. Now a 7 pound rated seal is not good for the crank but it is acceptable for the contact breaker or advance unit housing as they use the same seal.

Although the 7 pound seal is under the same part number but made to a different spec we have clarified which seal to use based off your application when you are ready to purchase a seal. Click here for more information.


Triumph Timing Cover Crankshaft Seal And Timing Cover Seal Orientation

 Triumph timing cover seal orientation


Installing the oil feed seal the wrong way will also give you low oil pressure. This problem is actually very common.

Many folks do not take into consideration of which way the seal is supposed to be installed.

Since the seal is suppose to hold oil pressure around the end feed shaft it must be installed the correct way.

The photo above shows the correct way to install the seal. The back should be facing the crank while the spring should be facing the opposite.


How to check oil pressure

There is only 1 way to check oil pressure on a vintage Triumph twin and that is with an oil pressure gauge. However, not all models can accept an oil pressure gauge.

Using an oil pressure gauge will allow you to monitor you're engine PSI rating at idle and at riding speeds.


Triumph Oil Pressure Gauge


The gauge shown above is a unit that we stock on our site for Triumph twins. Using this gauge you can clamp it onto your 7/8" handlebars and watch exactly what your oil pressure is doing. Fittings, line and gauge are all included.

Click here to purchase your Triumph oil pressure gauge



  • Check your timing cover or crankcase to identify if your engine can accept an oil pressure gauge.
  • If your engine can accept a gauge make sure you have the proper fittings to install the gauge


If all else fails

If your crank seal is new and is installed correctly and you're oil pressure is still low I would recommend the following:

  1. Change the oil - use a 20W-50 multi-grade oil
  2. Clean and ensure that your oil pressure relief valve is properly working
  3. Clean and inspect your oil pump - replace if necessary
  4. Clean and inspect all oil lines - feed and return lines


Thanks for reading

I really hope that this blog post has given you some better insight of why your Triumph twin might have low oil pressure. There is a lot of talk online about low oil pressure.. most assume the worst but many times it could be as simple as a seal.

Should you have any questions regarding this post please feel free to comment in the section below and we will comment accordingly.

Thanks for reading and ride safe!


  • ando

    thanks shipmate, pefectly clear explanation, ill get on with it tomorrow going for a coupla pints in the jawbone tavern

  • ando

    thanks shipmate, pefectly clear explanation, ill get on with it tomorrow going for a coupla pints in the jawbone tavern

  • ian jonescould

    could you tell me witch is the oil feed pipe under the engine it is the right feed block but the pipes have been cut short thanks Ian

  • Andy Griffiths

    So how will people know when to fit an under size seal if the crankshaft isn’t grooved? (i.e. it’s been ground)
    What is a good crankshaft measurement for an OEM seal?

  • Gerry O'Brien

    Hello, My pre unit Tiger is concerning me re the new PRV being closed at tickover when the oil is hot. I’m using 20-50 Classic oil. My crank end is grooved so the seal interests me. I think you are saying I can leave the bush and crank alone and just press a seal into the cover. Is that right or is there a need for a circle which means a circleclip groove needs to be machined. So is it simply push seal in place? Thanks

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