T90 Oil Leak

Discussion in 'Vintage Classics' started by Fuseman, Jul 31, 2023.

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  1. Fuseman

    Fuseman New Member

    May 11, 2023
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    3
    Pontefract
    This maybe a silly question but I'm looking for advice as to the likely source a a small oil leak on a 1964 T90.

    After a 10 mile ride there is a small amount of oil apparent at the base of the rear of the cylinder block. It's difficult to see where it's coming from - but it doesn't appear to be from the top end - more likely from the bottom of the pushrod cover or the base of the block itself.

    I wonder if this is a common leak which would allow me to concentrate on sorting that area. Any thoughts appreciated.

    Martin
     
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  2. darkman

    darkman Crème de la Crème

    Oct 26, 2015
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    Tappet blocks rarely leak although oil can leak from the bolt that holds it in the barrel, normally its the top or bottom pushrod seal that leaks. Thoroughly clean the area and ride the bike but keep stopping to have a look and you should be able to tell :)
     
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  3. Fuseman

    Fuseman New Member

    May 11, 2023
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    Pontefract
    Thanks - I did suspect the bottom pushrod seal - good to have your view on it
     
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  4. Iceman

    Iceman Crème de la Crème

    Apr 19, 2020
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    The pushrod tube seal will likely be the culprit, there are uprated seals available and I would go for a set of those.
     
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  5. Fuseman

    Fuseman New Member

    May 11, 2023
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    Pontefract
    The bike also appears to lose a bit of oil from the chain region. It isn't excessive and the guy I bought it from says this is normal for this bike. Does anyone have a view on this?

    If it is normal I won't waste my time trying to stop it!
     
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  6. Iceman

    Iceman Crème de la Crème

    Apr 19, 2020
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    Hi Fuseman, this was true when machines originally came out of the factory, this was due to a combination of things, mostly worn out tooling that caused poor mating surfaces and inconsistent tolerances, leading to oil leaks amongst other faults, however modern gaskets and seals are usually high quality and when used usually eliminate leaks, also a lot of people now use quality silicone to seal chain cases, however this needs to be applied very sparingly, a carefully re built engine will be completely free of oil leaks, what is top quality is the alloy that was used in the engines, often these "battle scars as I call them" can be carefully filed out and finished by various grades of wet and dry paper, then buffed up so they are like new, personally any restoration I complete I like to leave these in place as they all tell a story. Ride safe all from an ageing Rocker.
     
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  7. darkman

    darkman Crème de la Crème

    Oct 26, 2015
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    The places oil can leak from are a chain oiler from the oil tank if its fitted, can be turned off with the screw inside the oil tank. A split in the engine breather to oil tank pipe, unlikely. The oil seal in the primary on the output shaft, these would be for engine oil and the mainshaft to output sprocket oil seal in the gearbox, gearbox oil. None of these are urgent if you don't mide dripping oil.
     
  8. speedrattle

    speedrattle Senior Member

    Feb 19, 2021
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    if its pushrod seals, i generally use clear silicone seal.

    clean it thoroughly all arond and then use probes and paper strips to wind a bead around th eseal junction.

    dont use orange silicone or everybody will know that you are a peasant like me.

    it can last a surprisingly long time

    eventually you will re-do the seals, but you dont have to be in a hurry
     
  9. 66Triumph

    66Triumph New Member

    Jun 22, 2023
    6
    3
    Ireland
    I have a 66 500 and had a similar leak that was cured with a new pushrod seal.
     
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