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T150V Valve stem oil seals and valve end caps

Home Forums TR3OC Members Forum T150V Valve stem oil seals and valve end caps

This topic contains 7 replies, has 5 voices, and was last updated by  Neil Martin 6 months, 1 week ago.

  • Author
  • #7466

    Neil Martin

    Hi, I have a 1974 T150V which has done around 13K miles, have had smoking from acceleration on cylinder 1, there was also a noticeable increase in vibration starting around 3800 rpm so stripped down the rockers and removed barrells expecting worn rings etc. Rings were not worn and well in tolerance.

    Removed the valves, all the valves had valve stem oilseals on them and the valve stems were capped with a small metal cap. I have never seen this before, all my other T150’s have never had this.

    Has anyone ever come accross this before, and why has it been done. Any help with this very much appreciated.

  • #7467

    Martin Rawson

    Valve seals are generally only fitted on the Inlets due to oil being sucked down the guide on the induction stroke. It will mask worn guides up to a point. There are some poor seals out there and the seals that Norman Hyde sells are the type known to be of good quality.

    I would normally inspect before stripping and look for oil running down valve stems or outside the guide through the inlet/exhaust ports to identify guide issues.

    Any sign of ring blow-bye on the pistons. Can you still see good cross hatching on bores and no glazing?

    There is a bit of a flat spot in the power delivery on a Triple starting around 3.5-4.500 r.p.m and a small increase in vibration but nothing severe.It soon smooths out.

  • #7468

    Graham Redrup

    Hi Neil, When I overhauled my T150 & T160 engines I had P & M do the cylinder heads, they renewed the valve seats, valves & valve guides, fitted the caps you mention which are called lash caps as well as seals on the inlets. The reason for fitting lash caps is to help get a bigger contact area with the rocker arm which also has bigger headed adjusters hence reduction in rate of wear, if wear does become evident it is easy to renew the lash caps & no need to remove cylinder head to do it.

  • #7474

    Neil Martin

    Many thanks for the reponses , there is no evidence of blow by on the pistons, the valve on number 1 ex and inlet are well coked up and the seats are rough. The guides are well within tolerance. There is very little history with this bike, so I reckon it is start from scratch, reseat and grind in the valves, replace springs, have the barrels honed, balance up the carbs and see how we go. The bike has only done 500mls in the last 12 years, so there are bound to be a few problems. Just hope I can cure the vibration, I have had tridents all my life, so know how they should respond. Many thanks Neil

  • #7475
    iain strong
    iain strong

    Neil have you checked all the engine mounts bolts are tight??


  • #7476

    Neil Martin

    Hi Iain, I checked all the bolts when I got the bike, and loads of them were loose, all tight now.

    • #7497

      nigel wheatley

      If the vibes are more than ‘normal’ then it could be the clutch and/or the shock absorber in the primary has been put back out of balance. Though as martin says vibes around 3.5k-4k is not unusual – though again worn carbs especially worn sliders can make it worse. Worth having the carbs re-sleeved whilst the engine is down and there’s a helpful video on Utube showing balancing the primary shock absorber drum on the clutch spline


  • #7515

    Neil Martin

    Many thanks for the responses, just to provide an update, the bike had 3 different pistons in it, one was clearly second hand, was 0.5mm smaller in diameter to the other 2. Clearly no. 1 cylinder had holed a piston at some time due to the ally deposits in the combustion chamber and the valve ports. The 3 pistons were all different weights with no. 1 being 30 grams heavier than the other 2. Fuel tank was full of rust and the carbs were a mess as well, choke hole had not been capped off. Fortunatly, the barrels are Ok, and I have just had them honed. Carbs have now been ultra sonic bubbled, Rust removed from the tank, all fuel filters cleaned. Combustion chambers have been cleaned out and valves reground, new valve springs fitted and oilseals removed from the exhaust stems. New set of hepolites fitted. Rebuild in progress. You never know what you are getting until you get into the guts of the bike. Reckon the bike should be fine when finished. Had these bikes for 43 years and never get tired of putting them right.

    All the best Neil

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