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Top end build - 86/87? (No part numbers to go from..)

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Need some help here, buy the looks of things I need to do a top end rebuild on my KX250. I picked the bike up very cheap in a bran clearance, its had a hard life - there are no engine numbers apart from the images below! 

 

I have split the engine and got the piston off but there is no part numbers on it either, I have been looking around and I'm pretty sure its an 86 frame. What leads me to believe its an 87 engine is this top image - just underneath the flywheel area..

 

Let me know if the images don't work, thanks

 

20140424_154627.jpg

 

20140424_155956.jpg

 

20140424_160259.jpg

 

20140424_160411.jpg

 

20140423_212015.jpg

 

 

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I have measured the piston BORE and CYLINDER - they are both within a few hundredths of a mm to 70mm

 

According to this http://www.oem-cycle.com/KAWASAKIKX250BIKEID.shtml 

PISTON STD BORE AND STROKE - 70MM BORE X 64.9 STROKE

 

It would suggest I do have an 86 engine

 

Can anyone confirm what the 87 stamped number means? Or is it 78?

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Try http://www.kxriders.com/forums/ There are a few guys with older KXs on there. I know one guy just bought a 87. I know the carb isnt original. My 86 (bought it new) had a round slide Mikuni on it. The Keihin is probably a good upgrade though. Good luck, im looking for another 86 myself.

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Great! Thanks I'll put a post up once my registration is activated. Yes the carb is another part that adds to the confusion (I think the Keihin was used on the 87s). Well once its up and running (and I've had some fun) it'll be for sale :) by then it will have served its purpose. Cheers

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According to the kawasaki parts site the 87 was a round slide Mikuni also. I know the 88 had a Keihin PWK.

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1986

 

rear disc, style of Uni-Trak

 

1987 has the semi-modern airbox, not side airbox, Mikuni round slide carb, shock with built-in reservoir, underneath shock linkage, removable subframe, etc.

 

carb is wrong, as mentioned

 

www.kawasaki.com / OWNER INFO / PARTS DIAGRAMS to see the microfiche

 

Good luck!!

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When you say carb is wrong for my year, does that mean it wouldn't be running as good as the original of that year (86)? Or can it be set up with correct jets etc..

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1986

 

rear disc, style of Uni-Trak

 

1987 has the semi-modern airbox, not side airbox, Mikuni round slide carb, shock with built-in reservoir, underneath shock linkage, removable subframe, etc.

 

carb is wrong, as mentioned

 

www.kawasaki.com / OWNER INFO / PARTS DIAGRAMS to see the microfiche

 

Good luck!!

 

 

That original UniTrak design with the bell cranks was horrible. It actually has a falling rate instead of a rising rate, Kawasaki really blew it with the geometry of that design.

 

That's going to be a difficult bike to source parts for, they didn't sell very well at all.

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Someone upgraded the carb to a keihin PJ carb it is a 38mm I think the 86 stock was a 40mm and this a common mod from this period dg sold carb kits then and they really pushed the keihin then.

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