Some have asked my how I polish up my kx500 exhaust valves.
So I did one last night as a demonstration and took pics.
Probably one of my biggest things I have to share is not to remove any more material then you have to.
The center flapper is cast steel and has little pin holes and is generally very rough...
The first thing to do is remove the pins.
You can see from this pic that the ends are very worn.
Remember, for ever .001" of wear you loose .002" of lift.
It is not uncommon to see these worn .020" or more
.020" of lift will reduce your port timing probably about 2 degrees and create that annoying KIPS rattle which in turn is creating turbulence from the flapper dancing around. Yes, you are loosing HP if you hear that KIPS rattle.
How to clean and prep your KX500 exhaust valves
- Sandblaster
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How to clean and prep your KX500 exhaust valves
If bikes are for kids I'll never grow up.
- Sandblaster
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- Joined: Thu Jun 07, 2012 3:50 pm
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Re: How to clean and prep your KX500 exhaust valves
The first thing I do is give the center valve a quick run on the wire wheel to knock some of the carbon and gunk off so I can see what I am working with.
That's better...
That's better...
If bikes are for kids I'll never grow up.
- Sandblaster
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- Joined: Thu Jun 07, 2012 3:50 pm
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Re: How to clean and prep your KX500 exhaust valves
Next, it's time to remove those worn out pins.
So I use a Slidegrip, Map Gas, and a vice.
Before you pull the pins out, measure them and record it.
I like to make mine about 1mm or .040" longer then stock per side.
Then, I heat the valve on the thin side of the pin...
Once the valve is hot enough, about 15 seconds, I hook up the Slidegrips and give it a couple of quick slide of the hammer and it pops right out.
So I use a Slidegrip, Map Gas, and a vice.
Before you pull the pins out, measure them and record it.
I like to make mine about 1mm or .040" longer then stock per side.
Then, I heat the valve on the thin side of the pin...
Once the valve is hot enough, about 15 seconds, I hook up the Slidegrips and give it a couple of quick slide of the hammer and it pops right out.
If bikes are for kids I'll never grow up.
- Sandblaster
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- Joined: Thu Jun 07, 2012 3:50 pm
- Location: Eugene, OR
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Re: How to clean and prep your KX500 exhaust valves
There are some guys that will pull the pins out and put the worn end into the valve, or while the valve is hot, twist it 90 degrees.
And that's ok, I just like to replace mine.
I use 4mm drill rod.
And that's ok, I just like to replace mine.
I use 4mm drill rod.
If bikes are for kids I'll never grow up.
- Sandblaster
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- Joined: Thu Jun 07, 2012 3:50 pm
- Location: Eugene, OR
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Re: How to clean and prep your KX500 exhaust valves
Pins out...
A little more on the wire wheel and were ready to get down to some pre polishing.
Because the center valve is cast steel it is very rough.
So I use a hand grinder with a fine flap wheel on it.
Remember... You only need to take of a skim... just break that rough surface texture off.
Don't worry if there are some pits and casting flaws... It won't matter...
A little more on the wire wheel and were ready to get down to some pre polishing.
Because the center valve is cast steel it is very rough.
So I use a hand grinder with a fine flap wheel on it.
Remember... You only need to take of a skim... just break that rough surface texture off.
Don't worry if there are some pits and casting flaws... It won't matter...
If bikes are for kids I'll never grow up.
- Sandblaster
- Posts: 6313
- Joined: Thu Jun 07, 2012 3:50 pm
- Location: Eugene, OR
- Contact:
Re: How to clean and prep your KX500 exhaust valves
As you can see, it looks rough but it's not really that bad
After I get the two surfaces cleaned up, I switch to another flapper wheel which is made from a Scotch-Brite type material.
After the flapper wheels are done I run it on a bench grinder or polisher with a cloth wheel.
I use some green polishing rouge.
So, the more time you spend, the better and smother it will look.
It took me about 20 minutes for the disassembly and polish.
10 more minutes of time would have been crazy
Just go easy with the grinders, less is more.
After I get the two surfaces cleaned up, I switch to another flapper wheel which is made from a Scotch-Brite type material.
After the flapper wheels are done I run it on a bench grinder or polisher with a cloth wheel.
I use some green polishing rouge.
So, the more time you spend, the better and smother it will look.
It took me about 20 minutes for the disassembly and polish.
10 more minutes of time would have been crazy
Just go easy with the grinders, less is more.
If bikes are for kids I'll never grow up.
- Sandblaster
- Posts: 6313
- Joined: Thu Jun 07, 2012 3:50 pm
- Location: Eugene, OR
- Contact:
Re: How to clean and prep your KX500 exhaust valves
Here is about 5 minutes more on the polisher..
As you can see, you get diminishing results.
Sure, it is better and I could get it better yet but for me it's plenty good enough for what it does
Next up is the drum valves.
As you can see, you get diminishing results.
Sure, it is better and I could get it better yet but for me it's plenty good enough for what it does
Next up is the drum valves.
If bikes are for kids I'll never grow up.
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