KDXRIDER.NET

I screwed up a perfectly good cylinder this morning by trying to get just a little extra.

I'm really kicking myself in the a$$ as I knew better , just had a major brain fart and now

I'm going to have to send the cylinder out for a strip / replate.

ONLY ATTEMPT MINOR ALTERATIONS IF YOU HAVE THE CORRECT TOOLS !!!!
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Dam ,,, I hate learning by mistakes :( :(

I AGREE THAT YOU HAVE TO BE VERY CAREFUL
but I wouldn't discourage others from trying it. I ported my KDX cylinder myself with great success many years ago. It was resleeved with an unported barrel. All the ports were made by us (the machine shop guys and me down here in Paraguay). The sleeve metal was crap and would wear down fast so I got to experiment with the porting many times as it was replaced every 6 months. The stock KDX should not have its exhaust or transfers raised though. I made mine lower for better mid range power and preferred that setup.

Jaguar wrote:I AGREE THAT YOU HAVE TO BE VERY CAREFUL
but I wouldn't discourage others from trying it. I ported my KDX cylinder myself with great success many years ago. It was resleeved with an unported barrel. All the ports were made by us (the machine shop guys and me down here in Paraguay). The sleeve metal was crap and would wear down fast so I got to experiment with the porting many times as it was replaced every 6 months. The stock KDX should not have its exhaust or transfers raised though. I made mine lower for better mid range power and preferred that setup.

Thats some of the reason the 220 has so much more bottom as the exhaust and transfers are lower.
Some have the cylinder turned down to lower the ports on 200's.

My screw up was on the intake side. I've heard to never touch the exhaust side.

I used a dremel with right-angle attachment to raise the exhaust .5mm and widened the transfers .3mm on my 2000 kx rebuild i just finished. I used metal putty to even out and angle the flow of my transfers so that they were facing each other instead of one of them blowing the charge straight out of the exhaust port. Since I never rode it before i did this work, i have no baseline lol. I was just evening things up and fixing mismatches. The bike is a literal rocket, so i guess i didnt hurt anything lol.

I can't help my self there is always something you can do to make it just that bit better
When I started that bit was usually worse but after a while you get the hang of it.

This might be pertinent to h series kdx bikes as well: I noticed that on my 2000 kx250 that the main powervalve (its a three piece sliding guillotine on my bike) would hang down into the exhaust stream about 3-4mm when it was supposedly fully open. I really think its a design flaw because my cylinder waa cleaned fully and the valve wasnt getting caught or hung up. I carved out a "pocket" in the exhaust roof that allowed the valve to blend completely into the cylinder roof when it opens. I didnt take pics unfortunately, but it might be worth a check the next time anybody has their 200 or 220 cylinder off. Even 3mm is a big obstruction to be sticking into the exhaust stream. The previous owner of my bike HAD to have been missing out on quite a bit of mid and top end power! Im definitely not tho :)

what I want to know is exactly what was the error you (George) did to the intake port.
that's because you can't screw up the intake porting because it's got a reed valve.

He chipped the nikaseal/electroplating, so the cylinder has to be resealed.

if it's below where the rings touch the cylinder (their total stroke) then it's no big deal.

Jaguar wrote:if it's below where the rings touch the cylinder (their total stroke) then it's no big deal.

I was hopeing that would be the case , but it's not and close enough that I'm not going to chance it.

I'm just kicking myself because this cylinder was low wear and a perfect ring end gap before I touched it :(

The statement about not attempting your own porting was a little premature heat of the moment thought.

I tackled it when tired and my cheap a$$ bits bent like butter.

actually I wouldn't even worry about it if it was below the top edge of the exhaust port. That is because once the port starts to open the seal of the rings is not important because the port is relieving all the pressure that the rings were sealing.

Jaguar wrote:actually I wouldn't even worry about it if it was below the top edge of the exhaust port. That is because once the port starts to open the seal of the rings is not important because the port is relieving all the pressure that the rings were sealing.

I sanded the edges of the factory coating that I'd chipped and may just run it.

I just hate to think it would bother down the road.

$200 + for a good recoat is something I hadn't planned on.

This cylinder is so good that the ring end gap is .008 :)