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valve seat pitting

DimitriT

DimitriT

Forum Sage
Past Site Supporter
How much is too much?

I'm freshening up an old 550 head with some lapping of the old valves
and new seals. This is a head to replace the one currently on my 550.

But I noticed some of the seats are pitted quite a lot. After the lapping
the valves seem to seal well (I'm testing the seals by filling with kerosene
and looking for any leak - not a drop after several days).

Should I worry?

I appears the pits don't span enough of the seat to cause a leak.
 
DimitriT said:
How much is too much?

I'm freshening up an old 550 head with some lapping of the old valves
and new seals. This is a head to replace the one currently on my 550.

But I noticed some of the seats are pitted quite a lot. After the lapping
the valves seem to seal well (I'm testing the seals by filling with kerosene
and looking for any leak - not a drop after several days).

Should I worry?

I appears the pits don't span enough of the seat to cause a leak.
Click to expand...

Pictures of the pits would be nice, but hard to take good ones of something that small. How did it run before you took it apart? Compression? If it doesn't leak now it will probably run OK for a while. Tiny pits will go away with enough lapping, sounds like these are bigger.
If you have the cash get it fixed if it looks that bad to you.
 
If the seating surface on both vavle and head are good and straight and dont looked flared/hammered it should be ok. Use petrol instead of kero to test the seats as im sure it seaps thru spaces better than kero and will get a more accurate result. Maybe a result u dont like but still a result. Test the valve guilds for wear by wiggling the valve side to side wjen its just off the seats. Not sure what the limit is but someone will come along wuth that answer
 
sharpy said:
If the seating surface on both vavle and head are good and straight and dont looked flared/hammered it should be ok. Use petrol instead of kero to test the seats as im sure it seaps thru spaces better than kero and will get a more accurate result. Maybe a result u dont like but still a result. Test the valve guilds for wear by wiggling the valve side to side wjen its just off the seats. Not sure what the limit is but someone will come along wuth that answer
Click to expand...

Seating surfaces are good. I've never run this head. Picked it up of a scrapped bike.
The head it will replace has some damage and a helicoil.

If I'm testing the seal using gas or kerosene, what should I expect? No leaks at all?
A drop or two after a number of days? I've heard of people using a blue dye to check the
seal.
 
Petrol will seap thru almost instantly if it can find a way past. Bearing blue is the stuff ure talking about and works good. Smear some on the valve and insert it into the head, bottom it out and pull the valve out revealing a slight mark on the seat. (hopefully)
 
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