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03 kx125 is doggy


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Well the 03 KX125 I bought for the sun to ride with me is a little bit of a dog and now I know why.

Today in the interest of checking the condition of the piston and ring etc. i took the top end off.

Unfortunately what i found was not only a scuffed piston with a stuck ring, but the chrome is ripped off the exhaust divider bridge and about 1/4 inch up the cylinder above the exhaust port.

So my question is,,,,,

is the cylinder ruined?

should I just replace the cylinder or have it repaired?

should I send it to Eric Gorr and have it repaired/ bored to 144cc?

Would would you guys do?

Thanks in advance

Jay"RZ"

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a big bore would be cool. but to keep it simple it can be easily repaired. very easily. Just have some nikasil put in and you will be good to go. My 04 motor had the same stick ring sheered piston when I bought it. Its just that the people run the piston too long and it gets too much clearance and it ruins the thing. Just put a new one in and replate the cylinder and ride. In which case you prob paid too much because I paid 1000 for my 04, but I think the guy thought dirt bikes were throw away items, so he gave it to me basically.

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I have a many good 03 KX125 engine parts including the cylinder, new wiseco piston, new crank, new rod kit, new gaskets, new reeds etc. Previous owner bought a ton of new replacement stuff before finding a crack in the cases by the output shaft bearing behind the clutch.

I bought it for the roller, so need none of this stuff.

PM me for more information.

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It depends on how much you want to spend. The cheapest route is to just have it re-plated and stick a new piston kit in. $300 or so and you're up and running.

The next step up would be to have the repair work done by someone like Eric Gorr, and have it ported while you're at it. A good port job (and Eric is very good) is by far the best bang-for-the-buck when it comes to two-stroke engine mods. Half the cost of a pipe with twice the performance improvement, plus you can somewhat tailor the power curve.

The next step above that would be to add a big-bore. Add another couple-hundred dollars for that. FYI, everything I've read and the bikes I've ridden say that 134 kit performs better than the 144 kit. The 134 mimics the stock power curve, just more of it. The 144 adds a lot more low-to-mid but takes away some rev on top.

And if you really want to go hog-wild, you can go all out and add a stroker crank to the big-bore, and take it all the way to 167cc. But bring your wallet for that one.

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