Anybody with any good experience jetting and reading plugs, I have an issue. I have an intake on my Predator much like the Rath or Hot Seat K&N on the stock tube. My filter may be a little bigger. I have jetted with a 180 main Mikuni jet, a 200, and also a 210. The 180 was really white on the plug. The 200 has a nice color, but only on one side!?! The other side is still light, almost white. I bumped up to a 210, and the colored side got darker, but the light side still didn't change. Should I not worry about the side thats not changing and just go by the color of the side that is getting color? What's going on? I thought it should change color all the way around? Thank you for any input or advice!!

 

First off, I can't believe you have a 210 in that thing. I only run a 165 and it runs great. I can't really help you with the 2 sided thing. Hozed or modquad will probably know though.

 

Wow, strange. Are you burning pump gas?

 

Yes, burning 92 pump gas. The plug is kinda new (about 1.5-2 hours on it) so maybe that has something to do with it. The old plug had color all the way around, although I didn't have my intake or new HMF on it at the time that it was in there. The old one had about 100 hours on it so when I put the new intake/exhaust on, I replaced the plug too. Keep in mind the filter I am running is a big sucker; I hear Hot Seat recommends a 200 with their kit, and this filter is at least that big if not bigger. The 200 seemed to run really good for me, and the color was about perfect on the side that had it. It was suggested to me that maybe the colored side has something to do with how its facing in the engine, ie exhaust valves. Not sure what that means to me in terms of am I ok or still need to adjust something. Perhaps I just need more time on the plug? The 180 would pop up on top, and when I put in the 200 that went away. No popping with the 210 either. Just runs hard to the limiter. Thanks for your help!

 

The plug color on one side is normal on a stock head. Tune to the side that has color and do not worry about the other side. 87 octane will increase timing slightly and make more power also.

 

Hey thanks! I haven't ever tried 87 or 89 octane. May have to give it a shot. Do you know if the rest of the plug will get color in time? Like I said, it only has maybe 2 hours on it, but the colored side did get darker (a bit too dark) when I went with the 210 jet. I liked the color and how it ran with the 200. Thanks again!

 

plug reading info

 

One side of the plug will always have more color. tan on one side and clean on the other and your jetting is spot on. Lower octane fuel burns faster and has the same effect as advancing the timing. The Predator runs best on 87.

 

Thanks for the article. Pretty good reading, with lots of good info.

SP700Racer, I guess I'm pretty close then with the 200. At any rate, it seems pretty far fetched to me that I may be too lean with a jet that big. This is my first time messing with this stuff, and although I can learn pretty quickly, without prior experience it makes it tough to know what's ok and what's not. Have you observed this "one-sided color" phenomena in your machine?

Thanks again for your help guys!

 

Yes, mine does it also. after having the head ported and unshrouding the plug area it's not as
bad, but it is still more color on one side. All Preds do it. Just the way the head is designed.