pitted intake valve - thoughts?

[Andrew Vanis]

Cleaned up the valves and will lap them next.

Interestingly five of them each have a pit in the area (see marginal picture below) that appears to be the seating surface. Only like 15k on the engine. The exhaust valves look fine.

Thoughts?

I know the 'best' thing would be new valves and before that I'll try lapping and the 'pour fuel in the intake port and see if it holds' Suzuki test.

BTW, if anyone has a few extra intake valves I'll happily pay shipping. 1983 GS750L 16 valve TSCC

https://photos.google.com/photo/AF1QipP42OUdrA6KvM9CXRzoMAayVHSCxh2ZxRCktrlE

[Nessism]

I recommend finding someone with a centerless valve grinding machine and have all the valves cleaned up. If the pitting still remains I'd replace the valve. After the valves are cleaned up then do your lapping work on the seats.

[Andrew Vanis]

thoughts on what causes such pitting?

[Brendan W]

http://www.ultrapartsltd.co.uk/PDFs/Fault%20Finder%20for%20Valves.pdf

I would say something solid got picked up for a while.

[Andrew Vanis]

http://www.ultrapartsltd.co.uk/PDFs/...r%20Valves.pdf

I would say something solid got picked up for a while.

that is a really good article. Since it almost seem slike sharp-edge divots, I'm guessing it was some kind of chemical effect as mentioned in the article about gas flow bypass.

Resurfacing the valves as Nessism suggests may be a good idea (which I won;t do first due to cost and frustration and "where does ti stop" syndrome)

Also with resurfacing there are all sorts of things to consider like vavle depth, seating/mating surfaces, valve stem top length. another very insightful document - http://www.musclecardiy.com/performa...tainers-locks/

[Nessism]

Resurfacing the valves as Nessism suggests may be a good idea (which I won;t do first due to cost and frustration and "where does ti stop" syndrome)

Are you joking? You won't fix your engine right because you don't know when to stop? How about opening up your service manual and checking the valves per the factory supplied service information.

Cleaning up the valves with a centerless grinder is the right thing to do. Or replace the valves with those nasty marks outright. My local shop charged me $20 to do all 8 valves on my bike. Even if it was $100 it would have been worth it.

[Andrew Vanis]

Are you joking? You won't fix your engine right because you don't know when to stop? How about opening up your service manual and checking the valves per the factory supplied service information.

Cleaning up the valves with a centerless grinder is the right thing to do. Or replace the valves with those nasty marks outright. My local shop charged me $20 to do all 8 valves on my bike. Even if it was $100 it would have been worth it.

OK, OK, OK....Just frustrated since the bike ran before I wen on this replace the leaking head gasket goose chase.

The NAPA machine shop said $3/valve so x8 = $24 so not so bad. Other shops were closer to $10 so that was a different story. I'll likely just do all of them including the exhaust ones that look in OK shape.

Since some of them may need serious refacing to deal with the pits, I put an want-to-buy ad for some better valves

http://www.thegsresources.com/_forum/showthread.php?241573-WTB-Valves-Intake-1983-GS750L-16-valve-TSCC&p=2312702#post2312702

since the ones I have with with serious grinding change the displacement and thus combustion characteristics and also may result in different valve stem heights which may actually not be an issue since the 16 valves adjusters have independent adjustments there.

[chef1366]

I'd lap those in and install.
Does not appear to touch the seat.

[Andrew Vanis]

OK.

So found 4 new exhaust valves on Ebay that are on their way.

NAPA is still up for grinding the valves @ $3 each. They are not sure if they can do the smaller EX valves because of their size. The intakes should be large enough for their machine for sure. If their seat grinder would be small enough, they would also do the seats @ $3 each but their seat grinder machine is too big.

Wondering....

Shall I lap the seats with the existing valves and then have the valves ground - or should I just lap the valves and don;t worry about having them ground? Also, on the valves I'll be replacing, shall I lap with the old valves and then put the new valves in?

Should I consider buying a seat cutter and cut the seats as indicated in the manual as opposed to lapping? If so, what diameter cutter shall I get? (the OEM one is like $1,000 so not getting that but it looks like I might be able to get one cutter for about $30 on ebay.) The Ebay options are at the link following (some are like 20mm). What kind of guide would I need? - http://www.ebay.com/sch/i.html?_from...cutter&_sop=15

Is there a general guide to seat cutting I want to look at?

Thanks,

[Nessism]

I've done valve jobs using Neeway cutters and they work great. Those cutters from India are a lot cheaper. You need three sizes per valve, and while some can be used for both intake and exhaust, you can't count on that. In addition you need an arbor to mount the cutter too and a handle. Not a cheap endeavor.

I would try lapping your new/resurfaced valves into the old seats and see how they clean up. Realize, lapping valves should not be an aggressive process so don't sit there and hammer away on the valves/seats more than a couple minutes each valve at the most. If you are not getting a nice clean seat after that amount of time you need to cut them, not lap.