valve replacement questions

[brs127s]

After looking the parts from the head of my 850 over again, I saw that one exhaust valve is cupped very badly, thus causing it to sit further into the head. This would explain why I had such a hard time getting my cam tool under the camshaft when I adjusted my valves last year.

I am definitely planning on replacing the valve. My question can I just replace one valve, or do I need to replace a pair or all? All the other valves look okay. I haven't had any of them ground yet, but none of the others are cupped like the bad valve. If I only replace the one valve, can I use an aftermarket valve, or do I need to use a stock if not replacing the others?

Thanks,

Brandon

[Billy Ricks]

You can just replace the one. Cupping of the valves is pretty common.

[brs127s]

Thanks Billy.

I want to do everything right, so I won't have to do it for awhile, but I am also trying to stay within a budget. I have looked, but so far, I have found no aftermarket valves for the GS850. The cheapest I have found the OEM valves, if I was to replace them all, would cost me over half of the amout for my top end rebuild!

[Billy Ricks]

Manley may be able to supply you if you haven't already checked with them. Also check out Sudco.

[Billy Ricks]

Sudco doesn't show valves for your particular model, but they may be the same as one of the other models. They may also be able to order them for you.

[brs127s]

I went to Bike Bandit and compared several GS models from 80-83. None of them had the same part numbers as the 850.

[Billy Ricks]

I know what you mean about the cost. 4 or 5 years ago I had my head done. Replaced all 16 valves. Took months to get them from Suzuki. Fortunately a friend of mine with connections got them for me at a deep discount.

[Don Lobacz]

Use a Suzuki valve since the surface has a hardened surface coating. This is one of the reasons that our GS motors last so long. I have disassembled dozens of GS heads and have yet to see a valve that won't clean up with a wire wheel and lapping. Never 'cut' GS valves since the softer metal underneath will wear fairly quickly. Check the valve seat for anything unusual, too.

[Anonymous]

Use a Suzuki valve since the surface has a hardened surface coating. This is one of the reasons that our GS motors last so long. I have disassembled dozens of GS heads and have yet to see a valve that won't clean up with a wire wheel and lapping. Never 'cut' GS valves since the softer metal underneath will wear fairly quickly. Check the valve seat for anything unusual, too.

How much quicker? I just had mine done and they did "cut" them.

[brs127s]

Don,

My buddy from the machine shop was going to grind my valves at the shop, just to get a good mating surface for the valve/seat mating. Is this the same as cutting? Should I not grind the valves and leave them as they are and only grind the valve seats?

Thanks,

Brandon

[Don Lobacz]

Here is the exact quote from the December 1984 issue of Motorcyclist, page 55. It is the GS1000 rebuild article written by Joe Minton that others have mentioned in the forum (right, Keith Krause?).

"Valve job: The only thing you have to do to the valves is clean off the accumulated carbon. The Suzuki's valves and valve seats are made of very hard and wear-resistant materials. If you do happen to find a burned valve, you must replace it rather than grind it. The surface treatment of the Suzuki and other Japanese valves seems to be the secret to their incredibly low wear rate. When you grind the face of a valve, you remove that tough surface and the valve wears very rapidly."

It should be noted that this article was written in 84. This means that 5+ years of accumulated data contributed to these recommendations. It should also be noted that Joe Minton was one of the most technically astute experts of the day.