250-500cc Spark-Plug Analysis / Carburation

[Hurky]

Hi, I am now looking at sparkplugs to check carburation for years but I still have doubts most of the time. Well if the plug comes out black and oily I know that I'm far off but if I am getting closer I have most of the doubts.

So... I just have made some pictures of the same plug, some with the flashlight and one outside with sunlight, the colour changes pretty much...

The plug had some 120Km on it and the bike runs quite good but I think a little rich, smoking a lot and some hesitation sometimes. From the plug colour it seems ok but a little bit dark in real, and oily on the outer ring...

I have read somewhere that what's really important is the porcelain ring on the bottom, and for checking it right it's needed to cut the metal away... Are this pictures even useful for something without cutting the plug in half ?


Please share your insights.

Thanks.

 

[Nordman]

Maybe little rich, like you think. But overall, i think its in the ok range. But again, its somewhat hard to say when looking at the pics.

maybe this can help.

 

[juicypips]

I would be happy with that a tad rich is good for my state of mind.

 

[NCSteve]

Yeah, I would be happy with that plug and agree, a little rich on the top end is good.
Did you check the plug after doing a WOT run? That is: get the bike up to operating temps by riding, not just warm up, do a wide open throttle run, stop and check plug. You can't just putt around the yard and then check plug if you want accurate readings.

cheers

 

[R-J van Hulst]

In addition if you want to perform a plug check over the full range that you should run the motor on different throttle openings with its normal work load and hit the kill switch.

the motor can run rich at full throttle by the main jet and lean from idle to mid throttle due to the needle and pilot jet

if i see the pictures of the plug in the first post i would not be worried (yet on my other monitor Ooh my ) color setting of the computer

in real life a good one should look coffee brown and dry

Robert-Jan

 

[duggoey]

Its always good to do it with a fresh plug too, that way you see how its running now.

 

[Hurky]

Thanks all for your comments, I think I can lean it a little bit out but I'm pretty close, The bike runs perfect, the only thing I don't like is a lot of smoke in the slow sections. But that is also normal I think with a high flashpoint oil as the Motul 800 is...

 

[ptkatoomer]

I haven't looked at the plug but I'm running my KTM at 50:1 and it smokes like crazy. Seems to run just fine though......