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Thread: Valve lapping

  1. #1
    Senior Member elime's Avatar
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    I was replacing the base gasket on my parts bike and figured as long as the head was off to lap the valves. For those that don't know what valve lapping is it is sticking a small rubber suction cup on the valve, putting some valve lapping compound between the valve and valve seat and spinning it back and forth. What this does is grinds the surface of the valve and valve seat so they have the same shape and makes for a good seal -- hopefully



    .



    This is my starting picture. The valves have already been removed, lots of carbon, and it looks like the valve stem oil seals weren't doing their job either. Arrows point to the valve seat.







    A little later in the process. Most of the carbon in the combustion chamber is gone and the seats look a lot better.







    A close up of the valve seats.







    Before and after of the valves:



















    The bike ran well but felt down in power. Along with the valve lapping I also installed new rings and valve stem oil seals. Reports to follow as to the results.
    Long live the internal combustion engine!

  2. #2
    Senior Member elime's Avatar
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    I forgot to include the really exciting picture of the head with the valves installed! Also I have discovered a "parts bike" is a bike you buy parts for. I used to think it was a bike one cannibalized then sold the remains to help offset the cost, but I was wrong.



    Long live the internal combustion engine!

  3. #3
    Senior Member jbfla's Avatar
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    Thanks for the explanation, and excellent pictures.



    Jb
    2018 Triumph Street Twin..............2016 CB500F
    2014 XT250 ..................................2008 H-D Softail Deluxe
    2008 SV 650..................................2007 DR 650..

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  5. #4
    Senior Member elime's Avatar
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    I got my TW back together and did a "Hard" ring seating. That is where you accelerate hard followed by a hard deceleration. The idea is the hard acceleration forces the rings into the cylinder walls and the deceleration suck oil up to the ring. I did this for 22 miles today. If the rings don't seat after 20 miles then the cylinder needs to be re-honed. I changed the oil and it was loaded with metal flake so something was going on.



    Before re ringing and valve lapping I could step on the kick starter and just the weight of my leg would turn the engine over through the compression stroke. Very little resistance. Now it is just the opposite. I can rest my leg on the starter and it holds. Also now that the base gasket has been replaced (along with most o-rings and seals and the neutral light switch) my parts bike officially has stopped leaking oil!
    Long live the internal combustion engine!

  6. #5
    Senior Member old mad max's Avatar
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    Congrats............. Now come over and replace my base gasket...... (o; (o; (o;. OMM.

  7. #6
    Senior Member B-dub's Avatar
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    Nice job with the head work, pictures, and write-up. Now you're going to be twice as busy keeping both of the those dubs exercised! I suppose you could recruit some help. Thanks for sharing this.
    My handle is B-dub, I ride a T-dub, and drive a V-dub.

  8. #7
    Senior Member elime's Avatar
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    Quote Originally Posted by omm View Post
    Congrats............. Now come over and replace my base gasket...... (o; (o; (o;. OMM.


    No. I think a better idea is if you come over here. You can even lap dance with your valves!



    Quote Originally Posted by B-dub View Post
    Nice job with the head work, pictures, and write-up. Now you're going to be twice as busy keeping both of the those dubs exercised! I suppose you could recruit some help. Thanks for sharing this.


    Quote Originally Posted by jbfla View Post
    Thanks for the explanation, and excellent pictures.



    Jb


    Your welcome.
    Long live the internal combustion engine!

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