KDX200 Cylinder ports Condition

[Gittt]

Hi, I'm currently doing a full rebuild on my recently acquired 97 KDX200, and I already know that the nikasil coating is stuffed and I was planning on sending it off to get replated.

I'm pretty inexperienced when it comes to porting on any bike, but even I could tell that someone had attempted porting the cylinder. To me it looks pretty rough, is it even worth replating this cylinder? Or should I begin a search for a new one, they're pretty few and far between down here in Aus so I'm hoping that the current one will be fine.

Just looking for some opinions before I go spending money either way, thanks in advance.

[Chuck78]

Old school porting - the knife edging is done backwards... It's best done in the shape of an airplane wing (rounded edge facing INTO the airstream, knife edge in the exiting side of flow - the opposite of how your example is done), which in the case of the visible main intake ports, no knife edging should exist since the exiting side is the cylinder bore in which the piston ring must ride.

That's not to say this won't work well, but one aspect of it was done in a way that is not considered best in modern times according to decades of research and development.

The porting work is a bit shakey there on the knife edged side, not a straight profile where it perhaps should be, perhaps indicating an amateur's hand at it.

I can't speak for the actual port timing of yours vs stock based on photos alone, because even 1mm of alteration to a port's height can drastically alter the performance, including potentially in a very negative way.
It'd be best to have a stock cylinder to compare to as far as port sizing and timing (heights).

All that being said, this could still in fact be an upgrade in performance over stock....
How'd it run originally?

[kdxdazz]

To me i think it just looks worse than it actually is, that inlet casting area is very uneven from the factory, he's just gone over it with a porting stone to try polish it but you can see he had no idea what he was doing, looks like the ports on the inside of the cylinder are untouched except for his bad chamfering, if it was me I would clean up the 2 knife edge ports with a file and remove any sharp edges, they are prone to cracking in that area
Same with the chamfers, just use needle files to even them up
I'm a big fan of files, I have over 50 in my collection and still feel like I need more shapes and sizes
I got 2 of my cylinders sleeved by serco in Brisbane, was a terrible job, I had to remove the sharp edges myself from the ports with a file