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Discussion Starter · #1 ·
Hi, I am actually rebuilding my heads
I was cleaning my valves using an ultrasonic cleaner (I think I left them in there for about 1 hour in total at 70deg C)
The exhaust valves seem to be clean enough but the intake ones seem to still have some carbon and whoknowswhat buildup on them
I think the surface where the valves meet their seat is ok
My question is should I go one step further and soda blast to remove the remaining buildup or is it not really useful ?
(I believe pursuing the US method won't give any better results than that)

A little precision: these valves come from a junk engine, I believe it has overheated because of the residue in the cooling system and what looked like a failing head gasket.

Nail Brass Metal Copper
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put them in a drill.
a bowl of water and some 2000grit wet/dry paper.

wrap a piece of cloth on the end going into the drill.
fold your 2000grit paper around the end of the valve, keep nice and wet and away you go. pull that trigger on your drill.

Start off slow until your comfortable.
 

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'84 CX650E that is evolving into a GL500
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I'd try cleaning them with a wire brush (hand operated, not powered). I did the ones for my GoldWing a couple of months ago and I cleaned them by spraying them with Tool & Parts Cleaner and then using the brush and all the deposits came off easily.
 

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I use a brass wire brush on a Dremel tool for fine scrubbing jobs.
Do NOT damage the valve seat contact area however, save that for proper gentle valve lapping operation.
 

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I don't think you ever have a good idea of the valve and seat face condition until you start to grind them.

They may look OK, but that doesn't guarantee a fully concentric seal.
 

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'84 CX650E that is evolving into a GL500
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I agree with that. While I was lapping the valves for GoldWing engine I found that several of them only got shiny half way around. I took that as a sign of being slightly bent so I swapped them with ones from my parts engine and those lapped nicely.

I use this kind of brush. I only use a power tool when it is less work than using a hand tool and it is much easier to pick the brush up from beside the vise and make a few passes than it is to dig out the motor tool and a brush for it.
 

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Discussion Starter · #7 ·
I think I've found somewhere on the forum someone soaking his valves in acetone to remove the carbon. I happen to have some, would you recommend this method ?
 

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You should be done cleaning them by now.
Don't be afraid.
Brass brush, stay away from seat contact area, done in one hour tops.
 

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Discussion Starter · #11 ·
Update: A brass wire wheel on a dremel tool is definitely the way to go

I didn't have one so I used a small brass wire brush, soaked them is acetone and brushed them every couple of hours on the first day
they were wayyy better after that
On the next day I repeated the process using mineral spirits instead of acetone and that is the best I could do
I still had some minor black ultracompact deposit on a few of them in the cupped area but overall they looked good

After lapping the intake valves looked brand new but the smaller exhaust valves edges were not as sharp
The 3 cut shape was discernable but they were kind of rounded off (you may be able to spot the difference between the 3rd and 5th pictures)

Now my question is : does the edge of the valve has anything to do with the compression ?
As far as I know it does matter for the air flow mixture and indirectly the efficiency but on the exhaust side I don't really get the purpose of the shape
 
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