Head On Valve Seal Replacement

One of the most common causes of excessive exhaust smoke on our bikes is worn valve seals. Once you have ruled out other causes and you are sure engine is otherwise sound, you can change your valve seals without removing the cylinder head. This will save the extra time and cost of removal.

This procedure is done with a homemade tool, made from some scrap steel I had in my shop, the adapter from a princess auto valve spring tool and some threaded rod. It took a couple hours to fab and the procedure itself took about 3 and a half hours.

I used Teflon seals with spring retainers from Kibblewhite as they can withstand higher temperatures than the standard Norton seals or the viton seals. The teflon seals are not listed for our bikes but can be found at this link.

After 2 years I have had no excessive oil smoke from the exhaust. These seals seem to hold up quite well so far, but you can use whatever seals you see fit.

Note: The engine will need to be warm to remove the rocker shafts. If you can get the dissassembly done quickly you could ride the bike to operating temperatures before starting; this will save time with the heat gun. If you try to remove the shafts cold you could cause damage so be careful.

Here’s how to do it…

1. Remove gas tank and head steady.
2. Remove the carbs and manifolds.
3. Remove the rocker covers and spark plugs.
4. Remove the central stud for the intake rocker cover.
5. Set timing side cylinder to TDC compression.
6. Fully loosen the valve adjuster.
7. Use an industrial heat gun and warm the cylinder head.
8. Remove the rocker and shaft taking care to note where the tension spring and washer go. Use a magnet to ensure they do not drop into the engine.
9. Rotate the engine 360 degrees and repeat the process with the heat gun for the drive side.
10. Install the tool you made and ensure it rests square on the retainer.
11. Back the piston down from TDC by about 2.5in.
12. Stuff some smooth rope into the spark plug hole , use enough to fill the entire space. Alternatively you can use compressed air.
13. Rotate the engine forwards so the rope puts pressure on the valve face.
14. Slowly tighten the tool onto the retainer. You should see the spring move down. The valve should not move at all; if it does you need to redo the rope again.
15. The retainer will move away exposing the collets, remove these with a magnet and be careful not to drop them.
16. Slowly release the tension on the spring and remove the tool.
17. Remove the retainer and springs.
18. Remove the old seal with pliers.
19. Cut a large plastic drinking straw about 1.5″ long and place over the end of the valve so the collet grooves are covered to protect the new seal.
20. Slide over the new seal and press down till it seats. A deep socket or small pipe can be used for this, but ensure it does not touch or press on the end of the valve.
21. Reinstall the spring and retainer.
22. Install tool and compress the spring.
23. Put a dab of thick grease on the valve collet groove.
24. Put a dab of grease on the end of a small flat screwdriver to hold the collets as you place them in the grooves, ensuring they are fully seated.
25. Release the tension on the tool slowly.
26. Ensure the collets are fully seated before removing tool.
27. Back the cylinder down a little and remove the rope.
28. Lightly tap the valve stem with a plastic hammer to fully seat the collets into the retainer.
29. Repeat the entire process step by step for the drive side cylinder.
30. Heat cylinder head again and reinstall the rockers and shafts with tension spring and washer. (Ensure the flats on the shafts face the proper direction.)
31. Set valve clearance as per the Norton specifications.
32. Reassemble all removed items.

Do this at your own risk – Craig