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Advice : Would you reuse these exhaust valves?

  • Thread starter Thread starter mackjas
  • Start date Start date
M

mackjas

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Hello All,

I am fairly new to the forum been mostly getting info from previous post. I have been going through my 1980 GS100G engine and discovered a bit of carbon build up on the pistons and valves. The pistons and intake valves have cleaned up well but the exhaust valves still don't look to good after spending a couple weeks on and off in Berryman's Chem-Dip and hit with a brass wire brush on the grinder. Please take a look at the photos, would you recommend replacing the valves or can they be reused?

http://s304.photobucket.com/user/jamackin/embed/slideshow/


Thanks you,
Jason
 
Hi Jason and welcome to GS land :)
They look OK to me.........however ( there is always a however ) the questions to be answered are ;
are they straight, what is the wear like between the stems and the guides and are they sitting flat on the seats. All the info for this should be in the service manual which if you haven't found it yet should be here http://members.dslextreme.com/users/bikecliff/
 
Those look okay, clean them up and see how they are then. Do check the things Brendan mentioned.
 
They look averagely-used. Lap them in and see if they seat properly.
 
I'd soak them in carb dip for a day or so then wire wheel the head. Then find some shop with a centerless grinder and have them faced.

BTW, if you decide the valves aren't good I have a brand new set (almost): 4 exhausts & 2 intakes + new valve springs.
 
I say they show lots of speckling and one even looks rather burnt to me. If it was my they would be replaced with NEW ones and the valves seats would be recut..not just a simple lapping session..but then again my theory is "its open so why not spend the money and time to do it right and only need to do it ONCE".
 
Thank you for all the insight. I am kind of thinking Chuck might be right just to replace them while I've got it open. The way they look in the photos is after carb-dip and hit with the wire wheel, multiple times. I will see how they sit and look per the service manual but I may be interested in your exhaust valves Ed. I'll contact you with a PM if so. Thanks again for all your help.
 
If you dipped them AND ran them SEVERAL TIMES on a wire wheel and they look like that...well i would say they are toast. On the one picture I can only clearly see the seating line on one valve!!!

If you cant find a reputable shop to recut the valve seats, then I would suggest you PM Rapidray and get him some really good and clear close up pics of the seats. Have him give them a going over. If you run a finger nail around them and it gets caught in spotted areas or otherwise look like they have freckles and such then they need serviced.

Maybe take some good pics of the valve seats so we can see them as well.


This is the 1000G manual on Bikecliff ...see the cylinder head and valves sections for specs and info on what they should be like.

http://www.mtsac.edu/~cliff/storage/gs/GS1000.pdf

Link to website home page....click on all the links as they will lead to many many more areas of collected info on carbs, rebuild tutorials for many other parts of these fine bikes, and enjoy.

http://members.dslextreme.com/users/bikecliff/
 
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The margin on your valves looks good. That means there is a good bit of meat still on them and a quick clean up pass with a centerless grinder will have them looking spiffy in no time. I've used Costa Mesa R&D to clean up some valves in the past and they do fine work. Just about any shop with a centerless grinder should be fine though. As for the seats, you need to make a similar assessment to that of the valves. Most people just lap in the valves with grinding paste and call it done. A quick clean up pass with a cutter is better though if there is deep pitting. I've got a set of Neeway cutters in the appropriate sizes for the 1000 head which work well for touch up work. PM me if you get to the point where you think that would benefit your head and we can figure out something from there.

 
That, of course, depends on the seats conditions...which is why i said to post up some good pics of the seats. If they are burnt and pitted you can lap all you want till your arm falls off and youre not gonna get a good seating valve.

I cant quote the specific angles off the top of my head, but they have to be right for the valve to go all the way into the seat in the first place..and then for the contact surface to be the right angle and width to ensure proper seating and heat transfer.
 
I would give them a light lapping, install them and add mineral spirits to the combustion chamber and see if they leak, If they don't leak then use them. Worse case scenerio you bring the head and the valves to a machine shop and get a quote to get the valve face's cut as well as the seats, what do the intake valves look like?
 
The intake valve look good after a cleaning, they don't have the spotting like the exhaust.
 
How do the edges of the pans feel? Run a finger nail down the chamfers to the bottoms and see if you detect any lips the nail snags on. If there are snags they are hammered. I amm no expert but the manual doesnt say the valves are grindable..far as I am able to find. Some claim they are.....
 
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