Two destroyed exhaust valves [with pics] - replace valves or entire head?

[tkent02]

Those seats look fine, I'd lap them, leak check them and call them good. Not so sure about how new valves will fit the old seats. Are the valve guides good and tight?

[TopTechRacing]

The pits in that exhaust seat will not hand lap out. If you put a new valve on that seat it will just end up burning again.

[Nessism]

Agree that those pits don't look good. Seat looks wider than the service limit too. I suspect the engine would get down the road for a good long while regardless so it's a judgement call.

[Allie]

This thread has been educational for me, since eventually I'll probably be looking at valves.

And, just, WOW.

Wholly CHIT!

[tatu]

I would give the seats a lick round with a seat cutter, then grind the valves in and call it done, plus, maybe, maybe not, take a gnats cock off the stem like Ed says, depending how much was needed to be removed on the seat 'cut'.
When a valve is "Lapped" it has been ground too far causing lines and steps in the seat and valve. Just sayin......
To take those pits out simply by grinding will take a long time, likely cause Lapping and cause the seat angle to change too much, leading to...overheating, burnt valves. Those valves are probably the worst I've ever seen. Well done.

[Nessism]

I would give the seats a lick round with a seat cutter, then grind the valves in and call it done, plus, maybe, maybe not, take a gnats cock off the stem like Ed says, depending how much was needed to be removed on the seat 'cut'.
When a valve is "Lapped" it has been ground too far causing lines and steps in the seat and valve. Just sayin......
To take those pits out simply by grinding will take a long time, likely cause Lapping and cause the seat angle to change too much, leading to...overheating, burnt valves. Those valves are probably the worst I've ever seen. Well done.

I bought a set of Neway cutters when rehabbing my 1000S head. Pretty nifty tools. Watch ebay and you can find them for cheap sometimes. The seat width is what surprised me when measuring my old head, which only had something like 20k miles on it; all the seats were wider than the service limit. I suspect this spec is a little off in the manual. And speaking of off spec, the valve to stem clearance service limit is unbelievably sloppy in some GS manuals. Suzuki is a little inconsistent in this regard from manual to manual. At any rate, working on stuff like this is the fun part of old motorcycle restoration. Requires some precision and care.

[Big T]

Agree that those pits don't look good. Seat looks wider than the service limit too. I suspect the engine would get down the road for a good long while regardless so it's a judgement call.

Agreed

Valve seats should be narrow. Wider is not better

I'd get the seats cut and lap in the valves

Check the valve guides and replace if necessary

If it takes a lot to get clean seats, trim .25mm from the top of the valve stems to regain some clearance

[TheDuke]

Those seats look fine, I'd lap them, leak check them and call them good. Not so sure about how new valves will fit the old seats. Are the valve guides good and tight?

Didn't notice anything loose with the valve guides (but I also wasn't looking for that)...but how much play is acceptable? No wiggle? I will go out and recheck them if you can give me some guidance.

Also, I took a look at Ebay for the seat cutter and they run around $350...which is way beyond the budget of this build. I will call around to find a machine shop and get a quote to get the seats and new-to-me valves touched up.

So, the general consensus is lapping will not suffice?





On a side note, this....