Jump to content
Sign in to follow this  

80's KX125 56mm piston compatibility

Recommended Posts

Hi All,


I have a KX125 which i'm trying to get going, it's basically a collection of parts from many KX125's from around the mid 80's, I think most of it is 1986 and the engine should be all from either an 85, 86 or 87 bike (Varies from part to part). The problem I have is that I don't have a piston for it at all, it needs a new rod but that's fairly straightforward because they all had the same rod from about 81 up to the late 80's apparently, or at least the same rod will fit.


What's the difference between the pistons? I'm fairly sure the barrel is 85 or 86, but according to the internet the pistons are different, will it matter if I put an 85 piston in an 86 barrel or vice versa? I'm not fussed about losing a bit of power as long as it works, the bike's basically a cheap hack to have some fun in the woods on, i have no intention to restore or race it!


It's a 56mm bore, which from memory I think stayed the same up until the 90's, but I heard they changed the gudgeon pin size and crown shape over the years.. Someone said something about the 87 having a port in it, anyone know how I can check i have an 87 barrel? Assuming an 87 barrel means an 87 piston required.


Any help or advice appreciated :)


In the meantime I'll continue to ask google. 

Share this post

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this