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Help with valve lapping /grinding

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Series3boy Wed, 14/12/2022

Hello

I am looking for some tips and advice with regards to valve  lapping/grinding.

I have been attempting to lap the valves on a 2hp Briggs engine which is fitted to a Webb AB lawnmower. Which I bought as a none runner. To cut a long story short there is pitting on the inlet valve.

The issue I am having is that the valve grinding sticks will not stay stuck to the valves. Which is making the process very difficult.

If anyone has any tips and suggestions it would be gratefully received.

Thank you

Rob

Forums

wristpin Wed, 14/12/2022

I always rub the top of the valve head over a sheet of Emery cloth on the surface plate ( 10mm square of plate glass). Also a “ pneumatic” twizzle stick is useful . Press the plunger place firmly on  valve head and release.  In cold weather it helps to thin the paste down a bit with light oil .  If the valve is bad enough to need the coarse paste , stop and get it refaced .

Sending you a private message.

 

Series3boy Thu, 15/12/2022

Thank you for your advice.

The tools that you have suggested look more promising.

The top face of the valve is very pitted and it was very cold when I tried to lap the valve so wonder if this was why to valve stick would not stay attached to the valve.

 

I have replied to your message. 

Thank you

Rob

 

 

 

 

 

Herby Wed, 28/12/2022

The vacuum lapping tool looks promising I think I might go for one myself.

I've always used the traditional stick with sucky cup on the end and made sure the flat of the valve is as clean and free of carbon as I can get it to ensure a good seal on the stick, if it comes adrift while lapping and gets paste on the stick I clean the valve top and sucky cup with carb spray on a rag, I also use a mixture of lapping paste and thread cutting paste on really bad seats. Be sure not to get any on the valve stem and ensure everything is spotless when you re assemble.

If the valve seat is too pitted you might want to think about set of valve seat cutters but they are quite pricey for a good set.