1985 KX80 bore?

[jl22n]

Just got a 1985 kx80 and i new it needed a piston and rings, but it looks like the ring or something came apart insided the engine and the cylinders scored up preety bad. I would like to bore it to 100-105cc. I read something about the cylinders having somekind of coating, and i was wondering if you have to have the cylinder coated? or can i have it bored and honed and put it back together?

[KickassKX125]

Theres not a lot of point of asking about boring an 80 cylinder out to a 100 because you would be in the coolant channels and even if it ran it would run like sh*t so you would need to buy a big bore kit.

But if you want to keep it as an 80 and the cylinder is scored then you send it away for a re-plate or if its really bad, a re-sleeve and buy a standard size piston.

[YurFatMom]

^You can bore out an 80's cylinder to 100cc without hitting the coolant channels, it gets done lots of times for superminis. Now, for a 1985 bike that would be a waste of cash to bore it out like that, because the bike will still be worthless, plus the crank will probably go to hel!.

[jl22n]

doesnt it have the same bottom end at as a kx100?

[05kx125]

no, the gears are a little longer (for example the kx80 would go 20MPH being revved all the way in first gear,: then the kx100 would go 21-25MPH bieing rode the same) only the first 4,5 and 6th gear were changed for the kx100's atleast to my knowledge

[05kx125]

oh **** ok my bad i was shure they did but they dont!

[YurFatMom]

Originally Posted by jl22n

doesnt it have the same bottom end at as a kx100?

They have the exact same bottom end. The only difference is the cylinder, head, and piston.

[KDXGarage]

I doubt a 1985 bottom end is going to be the same as a later year that also had a KX100. Look on the parts diagrams on the Kawasaki.com site to compare part numbers (and make sure you are looking at part numbers, not reference numbers). It's a 23 year old model, so it may be tough to find information on it.

[griffbones]

Those old engines are NOT like the late model KX85's & KX100's. Also the old KX80's didn't have power valves either, so that makes the top and bottom ends different than the late model bikes.

Put it this way, to super mini your top end would cost double what that bike is even worth. Just ride it as is, or sell it and buy a newer model. You can find newer KX85's pretty cheap if you keep your eye open for one.

[YurFatMom]

Oh, I wasnt paying attention to what was going on. I thought we were talking about the newer 80cc bikes. Sorry for the confusion.

[jl22n]

I just bought this bike like 3 days ago for $290 just so i can mess around on it with my friends, and 2 of them have preety much stock blasters a they want to race me when im done, and i want to make sure this thing will be fst enough to beat them, im probably going to but a procircut pipe on it to. I have alot of machines so i could probably do the sleeve myself, im not really sure how to sleeve it yet though.

[KickassKX125]

I wouldn't like to sleeve it myself even if I knew what I was doing, I would send it away, anyway where will you get a sleeve from??

[griffbones]

Sleaving will require you to have a boring bar, rigid hone (not a hand held ball hone), porting tools, and several other machine shop items.

[KickassKX125]

Too complicated, let some little green men in a factory do it !

[jl22n]

is there anywhere that sells new cylinders for a 1985 kx80

[05kx125]

wiseco?

[05kx125]

Originally Posted by YurFatMom

They have the exact same bottom end. The only difference is the cylinder, head, and piston.

no am %100 sure they dont if you can tell me where you got that info from then i would be happy to shut my mouth

[YurFatMom]

Originally Posted by 05kx125

no am %100 sure they dont if you can tell me where you got that info from then i would be happy to shut my mouth

I remember Griff saying that they were, and MXA's article on them sayed that they are a bored out KX85. This is only the mid 90's and up bikes.

[jl22n]

If i bor my old cylinder over 2mm i think i can use it but i took some pictures of the exhaust ports so mabey someone can tell me if they've been widened to much, so i dont rebuild this think and break a ring a ruin the cylinder. If they have been widened to much can i repair them by filling the corners with weld and grinding it smooth again?

[griffbones]

Originally Posted by 05kx125

no am %100 sure they dont if you can tell me where you got that info from then i would be happy to shut my mouth

The early KX80 and KX100 were the exact same bottom ends. Then the late model (power valve model) KX85 and KX100's were the exact same bottom ends.
But the early model KX80 & 100's were different than the late model KX85 & KX100's because of the lack of the power valve on the early models. This is what mainly made the top and bottom ends different between the early and late models.
Also in 2006 Kawasaki changed the stator and rotor assembly in the little KX's, and so I do believe that you must use the correct stator to bolt into the case properly.

So now you can happily shut your mouth!























hehe, just kidding!