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Is valve seat lapping required

You would use " mechanic blue " to check the contact pattern.----Then decide if lapping is needed.----Here I would certainly do a quick lapping procedure.
 
Hi,

Just my opinion. I haven't done any head work on a Honda engine before.

But, if it were mine, I'd leak check them with carb spray before doing anything.

If they don't leak, I would leave well enough alone.

Having not done any Hondas I don't know if there's even enough "meat" on the seats to provide for a grind if needed.

I know that there's no mention of valve contact areas or grind angles in my BF20D shop manual. And, while they do list a guide reamer in the special tools section, there's no lapper tool even offered.

If you've already disassembled then yes, use Prussian Blue to check the contact.

Although, you may find having a GOOD machinist give you an evaluation could be money well spent in the long run.

There's alot more to it than most people think.

Good luck.
 
My suggestion for what it’s worth. Since you have it apart I would lap them and check them with high spot “prussion blue”. It doesn’t take long and at least you know it’s correct. Just my thoughts.
 
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