KDXRIDER.NET

Hello all,

I know there have been countless posts asking about 1983-1985 Pre Powervalve KDX's

Well I received my piston today for a KDX 175, and it fits perfectly!

The only thing that eve changed to the 200 was the stroke versus the 175

So in short, a KDX175 piston WILL FIT in your KDX200

If you check ebay, there is no shortage of piston kits for KDX 175's

-Linny

There will be a lot more to be different on those 2 pistons than the diameter.
Any piston made for a 66 mil bore will fit but that doesn't mean it'll work.

Start measuring :-)

linny, care to post up measurements? If you don't know which ones are important, then that MIGHT be a sign you should not continue to RUSH into installing it.

Wow way to rain on my parade

I'll bring the piston to the machine lab tonight.

What dimensions do you need and in metric or standard?

We are just hoping it really is a workable piston, as we don't want things like ring pin placement, ring end placement, pin placement, skirt length, etc. to be an issue.

We are at least certain it won't contact the power valves.

Jason wrote:We are just hoping it really is a workable piston, as we don't want things like ring pin placement, ring end placement, pin placement, skirt length, etc. to be an issue.

We are at least certain it won't contact the power valves.

So what do I get if it fits?

Do I get the member of the month award?

You can have one running motorcycle, already at your house. Congratulations.

Dimensions are as follows in metric:

Wrist Pin Hole: 16mm

Window Diameter: 9.4mm

Length from Skirt to edge of Crown: 59.6mm

Length of bottom of wrist pin hole to edge (not the skirt): 4.7mm

Length of bottom of wrist pin hole to skirt bottom: approx 21.4mm-22.7mm (Two measurements)

Top of wrist pin hole to crown: 22mm

Bottom ring groove to top of wrist pin hole: 12.7mm

Top ring groove to crown of piston: 3.55mm

Top ring pin orientation: With the arrow on the crown being 12 o clock, the top ring pin is exactly at the 4 o clock position

Bottom ring pin orientation: Same arrow orientation, bottom ring pin is at the 7 o clock position

"Window" is at the 6 o clock position

Anything else?

Caveat, the piston a Wiseco forged

I think you are A-OK on the piston pins and ring pins / ring ends. That is where the stock ones are. Look on completed auctions on eBay. Someone had a 1983 - 1985 piston on there. You can still look at the pictures.

OD is one thing to have. Uncovering ports, covering ports, not smashing into the head or crankshaft are others. It is hard to say without looking at the cylinder too, I would think.

I do hope it works out. Don't let my cautiousness deter you.

Just a quick comparison between 2 Kawasaki standard pistons for a 175 and a '83-'85 200.

Gudgeon pin to piston crown 175 22 mm
200 24 mm

The ring pins are on the inlet side of the 200 piston and on the exhaust side of the 175.

The skirts are shorter on the 175 than the 200.

The window on the 175 piston is up near the rings, the 200 is lower in the skirt.

It's not gonna work, try a '86 + piston, that's pretty close (and certainly much closer than a 175) then let us know if that works.

Good luck linny :-)

Are your measurements saying the port timing isn't going to work?

I'm saying the top of the 175 piston is 2 mm lower than the 200, that'll lower the compression ratio a tad...would it run ?, don't know.

Those ring ends aren't where they're meant to be, they may end up in the exhaust port, that's not good and would not be pretty if the rings popped in to the port.

Try the 86 piston, to look at (and I've not measured them up) there's the 4 lube holes for the bridge between the exhaust port and the power valve ports in the P/V piston that the early piston doesn't have.

I'll compare the 2 pistons in the next few days, the difference's may be minor.

I'd love to know what would happen with the 175 piston in the 200 though, my 200 has a 72 mm bore so l can't try it for myself, I could be totally wrong.

I'll take the risk and try it.

This is my second A model that I'm building on the back burner as a one day race bike.

So I'm willing to take the risk as I can always sleeve it if it detonates, these things come apart like legos anyways, 4 strokes would be different

The 97 piston that worked supposedly sat 3mm lower than the 200, and the poster said it ran just fine

1mm = 24.1 thousandths, so you're looking at 48.2 thousandths lower than the 200, to me that's not big enough of a difference

My manual says the piston to cylinder clearance is .045 to .072, which is HUGE in the machining world, so I'd doubt that a ring end would get caught in the port

I'll make a build thread for it and we'll see what happens!

-Linny

I think what you are missing is that there is a set distance from the piston pin to the top of the piston. If the height was greater, it would smash into the head the first rotation. CORRECT ME if I am wrong, but he is saying that yours is short, meaning that when the piston goes up, it will mean a huge gap. VERY LITTLE COMPRESSION

I get what you're saying about having little/no compression,

but on another forum (dirtrider/adventure rider?) a poster said they used a 1997 OEM piston that sat 3mm lower than the 200 piston and it ran just fine with plenty of power.

I would like to check the compression on it, but after it's all said and done I don' t think a ring end will get caught in the port. I'd have to look at where the 175 is in respect to the port.

The 175 has a shorter stroke than the 200 so I'm praying that the longer connecting rod/stroke will not cause clearance issues.

EDIT: Just checked the piston and cylinder, the ring pins are at the 4 o clock and 7 o clock positions, so I'm not seeing how the ring ends would get caught in the exhaust port.

The manual also warns about snagging the ring ends in the intake port on install, I think there will be enough clearance with the cylinder mated to the bottom end. We'll see though when we do the full install.

Let us know how it works out. I have 3 85's and 2 of them could use new pistons. Thanks!