Topic: Tappet hole threads galled

[jackhammer50]

[img]galled thread 1.jpg/img]
I need to adjust the valves on my 1972 CB500.  So while removing the tappet covers I found two of them very difficult and one of them refused to come out.   After heating the valve cover and freezing the tappet cap with dry ice, then using an 18 inch ratchet handle the darn thing finally came out.  However it galled the threads in the valve cover.  Any idea on the size of the tap needed to chase these threads?

Thanks!

[70CB750]

M30x1.5 - enco would have it but it will be expensive.

You can use tap like M10x1.5 as thread repair tool, basically you comb out the imperfections.

Or get a new valve cover.

[BobbyR]

You may have to do some searching here, but there was a fella that had a nice tutorial on cleaning up the threads on wheel bearing hub. He used a normal sized tap with the same thread pitch and was able to slowly reform the threads. It was very clever and bears looking at.

[robvangulik]

There are thread files on the market for( relatively) little money

[jackhammer50]

Thank you for replying.

I tried 70CB750's suggestion of using a like threaded tap of a different size...I used a 10MM X 1.5 tap and just sort of 'combed' the inside of the tappet hole with it held  at 90 degrees to the hole.   It took an hour but worked great.  In fact it worked perfect!  You would never know the hole was ever damaged.  Great trick to remember!
Thanks again.

[70CB750]

Glad it worked!

Not my trick anyway, learned it at a machining site and it saved my bacon few times too