reading plugs

how many passes or miles do u guys put on a new plug to get enough color on it so u can tell if u am rich or lean ????
I have been putting on about 1 to 2 miles and the plugs just show signs of tan color at the base of the insulator on all circuits.(I cut the threads off to get a good look)

If you have a picture of what you idea of "tan" looks like, that would help a bunch.

i drive to back rd stop , install new plug. then i ran 3 passes on each of these plugs over a 2 mile strech of rd.i ran wot through all gears ,then killed power and throttle then slowed way down and repeated 3 times.after last pass i do complete chop to stop and remove the plug.i have 147.5's in now and i would like to add some needle but im at #5clip already, so i need to order new emultion tubes.that is as close as i could get for pics.


Post edited by: mark1122, at: 2007/10/22 18:44

Post edited by: mark1122, at: 2007/10/22 18:45

Which one do they look like from here:

www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html

Mine look like this:


Post edited by: CoreyClough, at: 2007/10/22 18:56

my plugs after a few hundered miles look like #20. but that is mostly running on the pilot system and the bottom of the needle,1/4 throttle.
your must have a lot of miles to get that much color?
i'm trying to figure out how much time u should put on a plug.at 1'st i thought 5 or 6 passes wasnt enough but i think thats just because i was too lean to add color . now that i hav goen richer i can get color after 3 passes. so it seems that time is critical.maybe the answer is that i just have to use the same amount of time each test .then at least i can develop a patern. but i guess the only real way to tell would be with an 02 censor to see if all my work is correct in the end.

Mark, I haven't a clue as to what you are attempting to accomplish with your method of checking plugs. The carburetors have three distinct ranges... idle, mid and wot. If you start the bike and idle some, then ride around some and then do a wot run, you burn gas in all three ranges. The plugs will reflect a combination of ranges of operation so if your mains a rich and your pilots lean, then the plugs will reflect only whether you were on mains a long time and pilots a little time.

To set your main jets, you can do a plug chop... Install NEW PLUGS after warming it up and get on wot immediately and then kill the ignition and check the plugs. I normally would suggest that you run wide open in 3rd or 4th only for safety reasons and it doesn't have to be that far. I almost never do a plug chop because I have gotten to where I can gauge the size mains needed based on performance and use of the choke at wot.

The mid-range is more difficult. It is hard to tell if you hit a flat spot whether that area is a lean or rich spot... you can make some educated guesses based on your current jetting and throttle position but an EGA helps here. The pilot circuit is governed by the idle air jet size, the slide cut out and pilot jet and usually, if a bike starts OK and then warms up normally (not too quick or slow) and idles smoothly once warm, the idle stuff is likely OK... I guess you could do sort of a "plug chop" with the idle circuit if you wanted... start bike, get it off choke and idle for 4-5 minutes then shut it down and look at the plugs. You would then adjust pilot mix screws or air screws to compensate for rich/lean look of plugs and if that doesn't get it done, start swapping air jets or pilot jets. Most carbs don't have adjustable (or removeable) pilot air jets but some have a variety of slide cuts outs that can be changed.

Mark,

your must have a lot of miles to get that much color?

113 miles on almost new Iridium NGK's. Working with the stock TK27's Carbs, K&N Pod Filters, Megacycle 478-60 Cams, 4-1 Supertrapp Exhaust(no discs and end cap removed), and ported head.

I see you have smoothebores listed in your signature. Are you working with those?

I have found working with the WOT(7500+ Rpm and up) first, then mid range(3500-7500), and lastly idle circuit is the recommended tuning order.

I also found this information on NGK's Website if you are using NGK Spark Plugs.
www.ngksparkplugs.com/techinfo/spark_plu...nav=31000&country=US

Thanks Cory that was a good read. i am using #9 plugs and i think i will go back to 8's to see if there is any dif.
George i just put the bare minimum in the question above. i do under stand the carb circuits fairly well. i was just tring to get at how much time u need to put on the plug to get a color reading.so i would do several passes on a plug on the same curciut then do the chop.making sure to use the same curcuit only . id say i do the tests the same as u, but i have felt i needed to put more time on a plug to get color. it seams that as i get richer it takes less time.so i was wondering exactly how much time is the right amount of time?if u test any 1 curcuit u only have about 12 seconds on a particular curcit before u run out of rpm so i would just repeat the test about 3 times.that is were i am now. u say u only go through 4th and 5fth gears. so this would represent only about a few seconds on a new plug.so i guess your answer would be that u feel u only need a few seconds on a new plug to get enough color to get a good read on a plug ,right?

If you ride for six months on a set of plugs and look at them and they appear rich, then it is time to do some deduction on which circuit is the probably cause. Since most folks SELDOM ride on main jet only, most of the time, rich burnt plugs usually are the result of the pilot or mid-range being rich (or both). I can see what the main jets are doing on ONE plug chop pass which lasts less than 1/2 mile or so. Once I get into tuning the pilot or mid-range, the long term state of the plugs is more telling. For instance, when setting up VM26 with the pilot fuel mix screw (on bottom of bowl on engine side), it is EASY to set those things rich. The bike will start NICE when they are set a bit rich and idle easily. A month later though, your plugs may show the effects of the richness and need to be cleaned. That is why I invested in an Exhaust Gas Analyzer. It is just hard to tell by feel that the pilot circuit is rich. Lean really isn't usually a problem since the bike exhibits non-friendly symptoms if overly lean in the pilot circuit. Bike starts hard, doesn't sync easily and then bogs on take off or just dies under load.

The pilot mix screws allow PRECISE tuning of the pilot circuit but the air screws allow the pilot jet to meter gas and these carbs tend not to be as fussy setting idle as the air volume changes relatively little when you turn the screws... I think they put the screws on the carbs to give the owner something to do when the bike doesn't run right ehehehehe

The air screw actually makes a difference over time as far as how the plugs look but they are not as sensitive to changes as the pilot mix screws.

The jet needle position can cause plugs to look lean or rich as well. You can usually get a sense of the jet needle being clipped wrong by the bikes performance... Problem with doing a "chop" on jet needle function or even looking at the plugs is that all jet needles have different tapers and their air/fuel mix will be different at even slightly different throttle positions. EGA is the way to go here as well if you can swing one.

i have tape marked off on my grip so i can tell where my slides are during tests. i try to do the mid test at 1/2 .as i raised the needle i could feel more power and the plugs look good after 3 passes. if i retested and did only 1 pass the color would likly be light enough to allow more fuel,(but i am at #5 clip and would need to buy large emultion tubes).this had made the 1/8 to 1/4 cruise range rich so after testing with the air screws out to 3 1/2 turns i reduce the pilots from 135's to 122.5's at 2 1/2 turns and the plugs look good after 300 miles at cruise.i feels good at cruise but the starting is odd now. i used to use full choke and it started right away. now i must play with 1/2 choke.
the carbs feel perfect as daily drivers now George.they are just off a bit when u ask alot from them.i will try the rs carbs soon. i have decided not to spend more $ on these, but i would have love to try the p-2 emultion tube just too see how they worked.if u ever do let me know how they worked out.
I'm haveing trouble with it stalling if i try to dump the clutch at any rpm in a drag race type of launch.i would likely be low on the mid range needle at 8500rpms.it jumps 1" in the air then stalls right out every time. its ok if i slip the clutch hard .i'm wondering if it is still too lean in the mid.

Post edited by: mark1122, at: 2007/10/25 10:07