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Sparkplug/piston reading

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Since my last post I have rebuild the top end with a fresh replays and wiseco parts, bottom end had zero play which I was totally stoked about. I now have about 10 hours on the new top end, I plan to tear down and replace rings every 40 hours, and piston every 80. 

So my spark plug confuses me. The ring around it being clean tells me it's running lean, but the insulator being black says rich?

This plug has a day of moto on it, about 3 hours. This ride I switched from Yamalube 2R at 30:1, to Maxima Castor 927 at 32:1, and plan on keeping the castor.

Bike is a 2004 yz250, stock besides a FMF Fatty with a Pro Circuit R304 shorty(yeah I guess the previous owner could decide on a brand).  My jetting is a 178 main, 50 pilot, 50 power, N3EW needle on the 3rd clip. Air screw about 1 turn out. I ride at about 1000ft, 80 temp and moderate humidity. 

I thought the bike was running great, other than a tad bit of clutch slip but that's another story and I have already planned on replacing. 

So my question is, how it my bike really running? I'm assuming rich, as when I look into the spark plug hole with my camera, there is zero carbon on the piston. With yamalube, there was a small circle in the center, and it was this way when I replaced the old top end as well. 

Any input on my jetting, plug condition, and rebuild intervals is greatly appreciated. Thank you all. 

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Even though we are at or near the same elevation, this info might not help much, but here is what I am currently running:

My bike came with a 178 main and a 50 pilot. A couple weeks ago, I changed to a 175 and 48. It was much better. I'm still running the stock needle. I could adjust that some too.

I'm sure I could go lower. Probably a 172 and 45. I might try that combination later. I would really like to get the head squish done before doing any more jetting. It's running fine now, but could be a little better.

BUT, I'm riding tight single track and not doing any WOT riding. Plus, mine is a '16 YZX.

I'm also using a low flashpoint premix oil as well, since I'm doing relatively slow singletrack. 

 

Personally, I would rather be a little on the rich side as opposed to lean. As long as it is not loading up too much or fouling plugs.

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12 minutes ago, dmrogers said:

Even though we are at or near the same elevation, this info might not help much, but here is what I am currently running:

My bike came with a 178 main and a 50 pilot. A couple weeks ago, I changed to a 175 and 48. It was much better. I'm still running the stock needle. I could adjust that some too.

I'm sure I could go lower. Probably a 172 and 45. I might try that combination later. I would really like to get the head squish done before doing any more jetting. It's running fine now, but could be a little better.

BUT, I'm riding tight single track and not doing any WOT riding. Plus, mine is a '16 YZX.

I'm also using a low flashpoint premix oil as well, since I'm doing relatively slow singletrack. 

 

Personally, I would rather be a little on the rich side as opposed to lean. As long as it is not loading up too much or fouling plugs.

Thank you for your input! I have contemplated running one size leaner main and pilot(175 and 48 as you are running). I'm just don't want to be too lean, which I have been scared of by the clean ring around my spark plug, which is why I wanted opinions before doing so. I think next ride I'll throw the smaller ones in and give it a try. 

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927 tends to show up differently than other premix oils on spark plugs if what I've read is true. Probably could drop the pilot or needle down but if it ran great why change anything?

I was running 927 in my bike before switching to a synthetic Rock Oil premix, and the plugs looked like that too when I was working on going leaner with jetting since it is a big bore 295.

 

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6 hours ago, ZP_Yamaha said:

Thank you for your input! I have contemplated running one size leaner main and pilot(175 and 48 as you are running). I'm just don't want to be too lean, which I have been scared of by the clean ring around my spark plug, which is why I wanted opinions before doing so. I think next ride I'll throw the smaller ones in and give it a try. 

Is your bike experiencing any hesitation or rough running at various throttle positions? Do you have a lot of spooge? 

If you change the jets, I would start out with a new plug, for comparison.

Let us know what you discover.

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18 minutes ago, dmrogers said:

Is your bike experiencing any hesitation or rough running at various throttle positions? Do you have a lot of spooge? 

If you change the jets, I would start out with a new plug, for comparison.

Let us know what you discover.

I have zero spooge. I do feel like it hesitates slightly right off the bottom. But if I go another position richer on the needle, it sputters getting onto the pipe. But once on the pipe, and up in the rpms at any throttle position, the bike rips. 

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1 hour ago, ZP_Yamaha said:

I have zero spooge. I do feel like it hesitates slightly right off the bottom. But if I go another position richer on the needle, it sputters getting onto the pipe. But once on the pipe, and up in the rpms at any throttle position, the bike rips. 

Try messing with the AF screw. 

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Not sure you can really judge the plug by the OUTER band closest to the threads.  I think it's really all about the insulator, and that reads a little rich, which isn't a big deal.  You may find if you drop the pilot, you get better response and cleaner running off bottom.  Your transition onto the pipe may be a bit leaner, which you could compensate for by raising the needle.  Seems like you have a good baseline, so you can always play with it and see what you get.  Just change one thing at a time.

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