'90 Katana 600 Valve Stem colors

[dnelli]

I noticed the valve stems looking into the cylinder with the carbs removed, the center two heads valve stems looked more varnished than the outside two heads. Is this typical? Heat Related? Curious...

Bike has about 17K miles.

[maniac1886]

I wouldn't read too much into it. Could be heat related, could have some leaky valve seals. If it runs good and doesn't blow smoke I'd just assume it was fine.

[92xjunker]

The center jetting is different than the outer...I agree with the above.

[dnelli]

The center jetting is different than the outer...I agree with the above.

Actually, the main jets and pilot jets were all identical. I was worried about mixing them up before I read what they each were.

It was more of a theoretical question.....

At the surface, my first thought was that it must be heat related. The outside are likely cooler than the inside cylinders/heads. I suppose it could be valve seal leakage, but why not the outside two then....because they're cooler??

I figured I'd ask and see if someone else has seen this on their Katana's.

My new choke cable came today. I'll install it, the carbs, air box, charge battery and try and fire her up. Thanks!

[maniac1886]

Not necessarily because they are cooler. The valve seals in the middle just could have worn out. I had a pre Kat 750 motor come thru my garage that had some bad valve seals. No rhyme, reason, or pattern, but those valves were definitely darker than the rest of them. And man were they a bitch to clean!