92mm KX500 piston right here :-)

[Sandblaster]

Ok, I don't have any yet.....
But, I am looking into getting some.
A 571cc sounds like something I want to build.
I had heard a rumor that they were available so I called Wossner and sure enough they are available.
The only draw back is you have to order 4 at a time.
I can use two of them but I don't need 4.

Now some of you say that it can't be done.
I believe that it can but it will require some extra work.
I hope to explore what is required in this thread.

[Sandblaster]

There are a few things I see that will need to be addressed.
1. The kips wall.
2. The studs
3. The transfer angles
4. The Balance factor of the crank asy.

The Kips wall is very thin as indicated by the arrow.

KX GURU RACING KX500 CYLINDER CUT AWAY 1.JPG (60.66 KiB) Viewed 9103 times

If you want to leave your exhaust port close to the same size as stock then you will need to pre weld the back side of the kips wall then machine it to the correct thickness, then bore.
Of course if you do that you will also need to shorten the length of the center Kips valve.
Which in this case is good because I want to make a few mods to it as well

[foxx4Beaver]

when "bigger", just isn't big enough...eh?

[Sandblaster]

Sometimes you just gotta scratch the itch

[Sandblaster]

Something that I didn't think about came up... at 90mm the cylinders love to crack on a whim... Ask Motorrad...
So the best way to do it would be to sleeve it.
Another issue came up and that is 90mm is as big as you can go without modifying your engine cases
So, I'm experimenting...

Here is where the piston will hit the cases.

kx500 92mm piston.jpg (274.52 KiB) Viewed 8760 times

Another issue is this cavity...
Once you machine enough to clear the sleeve you will open your crank volume into this cavity..

KX Guru Racing 92mm kx500 piston mod 104.jpg (401.32 KiB) Viewed 8760 times

KX Guru Racing 92mm kx500 piston mod 106.jpg (215.39 KiB) Viewed 8760 times

Will that extra volume actually make any difference?
With a smaller bore cylinder it likely would but the KX500 does not respond to crank volume changes as much as smaller bores.
But why worry, we've got something that should take care of the issue...

KX Guru Racing 92mm kx500 piston mod 107.jpg (344.9 KiB) Viewed 8760 times

[Sandblaster]

Some of you know how much I despise this stuff but the alternative is a lot of machining and then welding and this is so much easier.
And remember, it's just there to take up space... it does not have to handle any pressure...

Despite the fact that it is nothing more then a volume filler I want to be sure that it will stay put... Not that it could go anywhere...
I went ahead and cleaned the area very well then added some divots for the filler to cling to..

KX Guru Racing 92mm kx500 piston mod 105.jpg (232.81 KiB) Viewed 8759 times

You can't mess up the proportions of the hardener... you open the cap and squeeze the plunger... it comes out evenly..
Just be sure to mix it thoroughly.... Then apply...

KX Guru Racing 92mm kx500 piston mod 108.jpg (298.23 KiB) Viewed 8759 times

See that little space that did not get filled... uhoh....

[Sandblaster]

Because I didn't get the filler in the cavity evenly I had a hole that was bigger down below then it was on the surface.
So out came the porting tool and I made sure I could get to the bottom of the cavity...

KX Guru Racing 92mm kx500 piston mod 110.jpg (275.91 KiB) Viewed 8758 times

More mixing and applying...
This time I used a zip tie to make sure the filler went clear to the bottom...

KX Guru Racing 92mm kx500 piston mod 111.jpg (271.88 KiB) Viewed 8758 times

[Sandblaster]

I think it's better this time around...

KX Guru Racing 92mm kx500 piston mod 112.jpg (181.97 KiB) Viewed 8757 times

Oh yeah.... ready for some action...

KX Guru Racing 92mm kx500 piston mod 113.jpg (332.34 KiB) Viewed 8757 times