Piston size?

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Piston size?

Postby hoodoo » 01:22 am Apr 28 2005

I have a 2000 KDX 200. I have owned it for 18 months. Pulled the cylinder off, cleaned the kips. Everything looked pretty good. There are marks in the cyclinder walls but no grooves or gouges, slight brown oil varnish on the cylinder walls. It cleaned up pretty good. Machinist at work is going to measure it tomorow.

The piston is a "C". Does this mean its been replaced? When the bike was brand new in 2000 wouldnt it start out with an "A" piston in it?
I believe the letter designations start with "A" then "B", "C", "D"for stock pistons then you would have to go with oversize pistons. I have a Weisco piston in hand but want to make sure the thing is the correct size for my cylinder. Weisco only makes one size for the KDX as I understand. Proex sells the incremental sizes.

When I bought the bike I did all usual checks, swingarm, replaced the wheel bearings front and back. Replaced the chain and sprockets and rear tire. Put 40 kg xr400 springs in (what a difference) Run a FMF woods pipe &TC silencer, Boyeson 607's reeds(no DF3 yet),Carb is out for RB mods at the moment. Have Protaper SE cr highbend bars with tusk hand guards.
I love this bike. The guys I ride with all have late model CR 250s and I pretty much own them in everything but the sand, (which I hate, only ridden it once), woods and high desert for me.

Tonight I dropped the front end out and the lower bearing is wasted....its the one thing I neglected to do in the past year, glad I decided to look cause its a rusty piece of crap. I will cut it off and replace top and bottom bearings, I wonder if I can get those Hihat bearings at a bearing supply house instead of paying Kawi prices?

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Postby John Cena » 01:51 am Apr 28 2005

I'm pretty sure the kdx 200 normaly comes with a B piston but the difference between B,C are super little. Someone probably changed the piston out.

Prox KDX 200 Sizes
65,95 mm. B
65,96 mm. C
65,97 mm. D
65,98 mm. E
65,99 mm. F

Siezco standard size for KDX 200
66.00 mm.
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Postby KDXer » 01:58 am Apr 28 2005

I ended up getting it cheaper from a dealer than CBC bearing co. It was about $35AU $5 cheaper than the bearing shop.

EDIT... I thought the bore size on the 200 was 66.00mm ???? I was unaware that something with an OD of 66.00mm would fit an ID of 66.00mm.
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Postby fuzzy » 10:47 am Apr 28 2005

I doubt your machinist can measure the cyl acccurately enough to get down to the differences between A-D. These are used to make up for the VERY slight wear in the nikasil plating between top-ends. If the plating looks OK, then 'hone' it lightly w/ some scotch-brite, and then put a 'D' in it. Next time, E. These again are VERY slight. You can run an A in a cyl worn out enough for a F...You can run an F in a brand new cyl(wiseco)...When the clearance is tighter, a slight increase in power will be had. Warming the bike to full temp before riding it is imparitive when using tight clearances.

Wiseco's piston is probably for a 66mm bore, but isn't really specifying the actual diameter of the piston. It will be closest to a D or really more like an F....
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Postby lankytim » 10:51 am Apr 28 2005

Check the cylinder block for a letter stamped on it. As I understood it, the cylinder is categorized as an A, B or C depending on tolerances as it leaves Mr Kawasaki's machine shop. My 1998 KDX200 has a 'C' cylinder, so I put 'C' pistons in it. Maybe I'm wrong...
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Postby Indawoods » 11:09 am Apr 28 2005

Your right Tim...
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Postby canyncarvr » 12:26 pm Apr 28 2005

hoodoo: re;'The piston is a "C". Does this mean its been replaced?'

No. It does not mean that.

re: 'wouldnt it start out with an "A" piston in it?

No.

...I'm just agreeing with the rest of the folks.

Wiseco indeed makes one piston for the 200. Pro-x indeed has different sizes grouped by the alpha designation. You cannot specify which alpha if you order from Kawi. You will likely get a 'B'..but maybe not.

The difference advertised is .01mm which equals approximately 1/2 of one thousandth of an inch.

That measurement (.0005") isn't a huge matter in babbit bearing clearances (rods/mains in most autos)....it matters less in piston-to-cylinder clearance.

Consider there is only one ring size available for all of the alpha/different pistons.

But...might as well do it right if you're doing it.

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Postby hoodoo » 05:08 pm Apr 28 2005

Cylinder is within spec and everything looks good for reassembly. The info was great and it has been an interesting day here at work. That cyclinder head sitting on my desk provokes a lot of interest from the work force. Fuzzy, your right the weisco is closest to a "D" cup.
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Postby Indawoods » 07:15 pm Apr 28 2005

fuzzy wrote: Warming the bike to full temp before riding it is imparitive when using tight clearances.

Wiseco's piston is probably for a 66mm bore, but isn't really specifying the actual diameter of the piston. It will be closest to a D or really more like an F....



When using these forged pistons... always warm fully before putting under load or else you MAY get some piston slap and will wear the cylinder. I've heard 'em rattle in the cylinders before warm. Avoid a cold seizure....
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Postby Indawoods » 07:48 pm Apr 28 2005

Here's another piston question:

Seeing how Weisco's pistons are forged and ultra-lite, are you losing the flywheel effect of the heavier cast Pro-X piston? Is this a nominal amount or does it make a difference? :roll: Hmmmmm......
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Postby IdahoCharley » 11:42 pm Apr 28 2005

Is the loss in flywheel weight effect more than made up in allowing the bike to rev quicker due to less rotating mass? More smiles per mile?

Light weight fender MX fender plus RD sticker plus Wiesco piston, plus KX front end equals = ?????
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Postby KDXer » 12:09 am Apr 29 2005

IdahoCharley wrote:MX fender plus RD sticker plus Wiesco piston, plus KX front end equals = ?????


:shock: You'd have to be on track for a land speed record with all those goodies, Wooden ya ???? :lol:
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Postby John Cena » 12:44 am Apr 29 2005

IdahoCharley wrote:
Light weight fender MX fender plus RD sticker plus Wiesco piston, plus KX front end equals = ?????


:partyman:
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Postby fuzzy » 10:02 am Apr 29 2005

Tim, that C on your cyl means that Kawi put a C in it at the factory. They must plate/hone them, then measure for piston fitment and install what works. The differences in these pistons is VERY small. When you rebuilt, you should've gone to a 'D.' The next time 'E', etc. They do this so you don't have to have a million dollar machine measure your bore between rebuilds.

Inda, you know this to be the case. You just went through this, and your 'B' cyl took an 'F' piston....Right? And you only knew this due to the highly sophisticated equipment you had available.

The difference is sooooo small (.0005"). You can take a bike off the showroom floor, never run, and put a 'F' in it. This will be clearance close to a Wiseco....Maybe this is why some people call them siezeco. They are just trying to actually get you the extra power you're paying for when you buy their stuff. Warming up is critical. The piston really doesn't slap around, but will expand (warm up)quicker than the bore itself resulting in a piston going 5000+ RPM that now doen'st fit in the bore anymore....This is the defenition of cold siezure. Running the slimmest piston clearance possible will make the most power, but you're talking fractions of 1hp here....
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Postby dave04kdx » 01:43 pm Apr 29 2005

Re: CC's comment on "only one size rings for all the different pistons". You are so right ! It's always a good idea to check ring end gap. The last time I did the top end on my 88 one ring had an end gap that was tighter than the manual spec. I had to file the ring to get the ring gap correct.
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