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KX125 KX 125 CYLINDER SWAP

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Hi all, ive got a 1995 kx 125 and just wondering what other years the cylinder would fit?? i know theyre different part numbers but that could mean anything. any of you guys know? thanks in advance

 

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95-97 look like a bolt on swap if you use the whole cylinder and matching power valve.  98 uses the same base gasket but a completely different power valve design.  Up to 2002 might fit with the correct power valve linkage.  93 and 94 are similar but the base gaskets are different due to one water passage they added in 95.

I've got a 94 motor coming and I like the 98+ design better.  I'm going to take a shot at installing a 2000 cylinder.  I suspect it can be done.  Sorry for the late reply.  I just started looking into this stuff last week.

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The 94 head can interchange with anything from 94-2002.  The motor I have in my K series right now is a 97 bottom end with an 02 cylinder and a 94 head.  Requires a 92-03 CR125 flat top piston to get the deck height correct.

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alrighty guys and gals, lookin for some insight and seems like this is the place. Picked up the lower end of a motor I though was a 98 kx125. Foolishly stared buying stuff without verifiing the year of the engine. turns out its a 96. lower halves are together with crank and trans, and rotor/stator installed. i have a few bits that are for a 98, since thats what I thought i had. basically I'm wondering about compatibility. I think the rods were different on the 94-97 and the 98-02 motors. the only thing I have for the top end is the power valves for a 98. so not a big deal to get whatever is best to match the bottom. I still need to disect evrything and 100% verify what I've got. but any help is appreciated. 

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97 and earlier use a 106mm rod.  98 on use a 104mm rod.  A 92-01 CR125 piston corrects the deck height when using an early crank with a 98-02 cylinder but it is a flat top which requires either welding and recutting your existing head or finding a 94 head to suit it.

The power valve pull rod in the side case is different but the 98-02 parts swap right over.

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Thanks dan. This is the kind of info i was looking for. So basically with the 96 bottom end it seems the the cylinder from 94-02 will fit, but will need the CR piston for the early bottom/late top with a 94 head. seems easy enough. and 94-97 cyclinder should be good to go with stock piston for whatever year cylinder i get? and obviously the correct powervalve parts. 

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They changed the base gasket pattern in 1995.  A 94 cylinder would bolt on but the 95-02 cases have an extra water passage through the base gasket.  If you didn't notice it during assembly you would surely notice it when you tried to fill the cooling system.

95-02 will all interchange, 95-97 use a more complex and more problematic power valve.  98 was the first year for the modern porting layout and simplified power valve.  I think the 2002 cylinder is the best of the bunch.  The power valve design is significantly improved over the 98-01. 

95-97 all use the 106mm rod so if you run one of those you can use 95-97 pistons.  I think Kawasaki changed the dome height from year to year so the cylinder head has to match the piston.  I never ran any of those, I just went straight to the 98 top end and later to the 02 top end.  Used the CR piston and 94 head on both of those. 

Finding a good 95-97 top end with functional power valves would be difficult.  There aren't many out there without a ton of hours on them, if they do still work they probably won't for much longer.  I wouldn't recommend going down that road.  The 98-02 cylinders make better power and the power valves are much more reliable.

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On 8/6/2020 at 11:06 AM, turbo dan said:

They changed the base gasket pattern in 1995.  A 94 cylinder would bolt on but the 95-02 cases have an extra water passage through the base gasket.  If you didn't notice it during assembly you would surely notice it when you tried to fill the cooling system.

95-02 will all interchange, 95-97 use a more complex and more problematic power valve.  98 was the first year for the modern porting layout and simplified power valve.  I think the 2002 cylinder is the best of the bunch.  The power valve design is significantly improved over the 98-01. 

95-97 all use the 106mm rod so if you run one of those you can use 95-97 pistons.  I think Kawasaki changed the dome height from year to year so the cylinder head has to match the piston.  I never ran any of those, I just went straight to the 98 top end and later to the 02 top end.  Used the CR piston and 94 head on both of those. 

Finding a good 95-97 top end with functional power valves would be difficult.  There aren't many out there without a ton of hours on them, if they do still work they probably won't for much longer.  I wouldn't recommend going down that road.  The 98-02 cylinders make better power and the power valves are much more reliable.

Turbo Dan I know this thread is kinda old but I appreciate your responses to others more then you know..

 

So just to clarify before I start ordering parts

 

I can use a 1997 kx125 bottom end with a 2002 cylinder +power valves, and also use a 1992-03 cr125 piston. And with using that piston I would need a 1994 kx125 head. Is that correct? 

 

I noticed you mentioned having to weld and recut the head, is that ONLY if I don't source a 1994 head?

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That is all correct. Only other thing you will need is the power valve linkage from the clutch cover to the cylinder. 

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4 minutes ago, turbo dan said:

That is all correct. Only other thing you will need is the power valve linkage from the clutch cover to the cylinder. 

And that would be from the 2002 correct?

 

Also would this all still work of I used a 1996 bottom end ? It seems crankshaft replacements are hard to find for 1997...

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98-02 should be the same on the linkage.

I used a 95 and a 97 bottom end.  I'm sure a 96 would work too.  You can use a Pro-X rod kit to rebuild a toasted 95-97 crank.  All of the replacement cranks available are lower quality than stock, some worse than others.  It's probably for the best that they don't offer one for these older KX's.

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8 minutes ago, turbo dan said:

98-02 should be the same on the linkage.

I used a 95 and a 97 bottom end.  I'm sure a 96 would work too.  You can use a Pro-X rod kit to rebuild a toasted 95-97 crank.  All of the replacement cranks available are lower quality than stock, some worse than others.  It's probably for the best that they don't offer one for these older KX's.

Ok awesome

 

Are there any places you recommend to send the 1997 crank out too for a rebuild with a pro x kit?

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Lot of places can do it.  There are two places here in Albuquerque that rebuild cranks.  You might have a local shop that can as well.  Check with bike shops.

If you send it out you can use any number of places.  Mr Crankshaft, Crankworks, Ken O'Connor, Tom Morgan, etc. 

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On 1/17/2021 at 4:01 PM, turbo dan said:

Lot of places can do it.  There are two places here in Albuquerque that rebuild cranks.  You might have a local shop that can as well.  Check with bike shops.

If you send it out you can use any number of places.  Mr Crankshaft, Crankworks, Ken O'Connor, Tom Morgan, etc. 

Turbo dan, do you think I could get a 2001 rod installed on my 1997 crankshaft so it'd be 2mm shorter and then run just the complete 2001 top end cylinder/piston/head +2001 powervalves

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9 minutes ago, turbo dan said:

I don't see why not.

Alright I'm gonna go that route I think,  I appreciate your help 👍

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