Plug chop, read this plug

[dirtballer]

I took my "new to me" KDX 220 out for my first real trail ride in many years this past weekend at the closest DNR trails from the Twin Cities. I’m used to old Yamaha XT’s and not too long ago thought I would have bought a DRZ or an XT350 - I think I made the right choice with the KDX! I was amazed by the power the bike has with just stock jetting and the airbox mod. I think it has plenty of power for tight woods riding. I’m 6’2, 170lbs - the pipe and other power mods can wait for awhile, I’ll just concentrate on the suspension and getting it jetted perfectly. I’ve never had a bike that I could lift the front wheel whenever I want. I didn’t find any decent hill climbs or jumps, so I’m not sure how it will do in that respect.

At the end of the day I put in a new plug and tried doing my first plug-chop test down a gravel road. Maybe its just me, but when you get these bikes in WOT in fifth and sixth gear on gravel its pretty spooky :yikes: they seem to wander quite a bit (tires are at 10psi). I’m not sure what the plug is telling me, maybe I’m too lean or I didn’t do the plugchop run long enough….the plug has a little whitish gray powder on it , there is a slight ring that started to form at the bottom of the plug, although, not very dark. Currently I have a 145 main, 42 pilot, airbox mod, clip on 2nd from top. Temp was 78 and slighlty humid. I’m thinking of trying a 150 main next time out. And thinking of doing the plug chop on pavement since gravel gives me the creeps wandering at 70mph. How can you tell whitish soot (good) from grey aluminun (bad), is it pretty obvious?

 

[FruDaddy]

I think it say "JAPAN". It's probably telling you what country it was made in. :nener:

Now for the tuner answers.

 

[whenfoxforks-ruled]

How is the packing? If the air filter to the silencer is not in top shape then the reading is going to be misleading. Looks like the timing is off little.

 

[Hoffies]

No smoke ring , thus I think it is running too hot(too lean). Please be carefull not to keep running it like this, too lean - too hot - meltdown. Did you only do chop at WOT? What does the mid throttle show(needle setting)?145 main seems a bit small to me anyhow! I would go with 150/152 to start off with.

 

[dirtballer]

The "packing" seems fine - just cleaned and oiled the filter, I can blow through the silencer (is there a better way to check it). When I read all the posts on how do a plug chop tests, they basically say go WOT for 20-30 seconds. So, after riding around for a few hours (seemed to be running very good, plenty of power, but i have no baseline since I just bought it) I put a new plug in it, started it up and immediatly cracked the throttle, shifting through the gears (had to let off a tad between gear shifts). I got up to sixth gear - felt like I might loose control on the gravel at any moment - went for about 5 seconds further. let off the throttle, grabbed the clutch and found the kill switch. Did I do it right?

Do these things have a rpm cut-out? Seems like a pretty obnoxious procedure. I would think there should be a way to do it in 2nd or 3rd gear instead, may find a big paved hill to put it under load (I guess that is very important). I'm going to try the 150 main jet next, and see if that makes a differnence, just seems strange that it might need a 150 with just an airbox mod on a bike that is so rich with factory settings - or does that refer mostly to the low and mid part of the throttle? Needle clip is on 2nd from top setting.

 

[whenfoxforks-ruled]

A lot come fat on bottom. Not all by any means. It should have a rev limiter. Thank fully the alleged mods on clipping that wire is very questionable if it really works. There is almost no way of knowing if some fool with tools has been inside a used engine. Till you take it apart and measure, and see what you have, your jetting may be impossible to achieve. And it would be wise to get a leak down test done to assure the bottom is tight. The compression measurement is not real precise, when you do not know what is was just after break in. You check that the number stays the same, when it drops then its time for a rebuild. Read post #4, http://www.dirtrider.net/forums3/showthread.php?t=159938&highlight=spanky's+jetting+guide

 

[steve.emma]

if this plug was brand new just prior to doing the chop test then this wont tell you anything. the whitness is just because its new, not because of how its running. give the plug some ride time before doing the chop test. BTY what heat range is this plug? what altitude are you riding at?

 

[dirtballer]

Its the standard BR8ES plug, temp was 78 F.
I think I just did not spend enough time doing the WOT run. I went on an awesome trailride in Theilman, MN this weekend and at the end of the day the new plug was black, so at least I'm not lean (although it is possible I could be lean on the top end only, since most my time was spent in the low/mid part of the throttle). I did get a feel for mixture screw adjustments over the weekend so that was progress for me. And I did'nt feel like I needed more power anywhere else. Still pulls wheelies with eas ;) Thanks for the link to Spanky's Tuning guide, I'm going to use that next time I do the plug chop. I'll get this jetting dialed in soon enough.

 

[whenfoxforks-ruled]

Cut the plug you ran all day. The length of time is not an issue. A black plug makes me think of 2 things, either burning trans fluid or anti freeze. Not a lot, but some. A leak down test will rule both out. But, water in the fuel and retarded timing can cause the issue also. I like seeing the shiny spot on the electrode tip to run down a little. http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html, look good at the difference between rich and lean. http://www.strappe.com/plugs.html

 

[glad2ride]

How many seconds were you at WOT? You can drag the rear brake to create drag on the engine.

I am guessing you didn't run it long enough. Use a new plug whenever you do it.

 

[dirtballer]

Well, I think I found out why my plug was so dark after a 30 mile ride (mostly tight woods, not WOT)). Today my different size jets came in, so I took out the 145 main and the 42 pilot and put in a 14 8main and a 40 pilot. The only mod I have is a large hole cut out of the airbox lid. I think I was running super rich on the 42 pilot before as it was only 1 turn out (in is rich, out is lean). I thought the rich bottom end feeling and the smoke was normal until now, that's a newb for ya.

Following spanky's tuning guide I found the optimum setting with the 40 pilot to be about 2 turns out. I have yet to do a plug chop to find out if the 148 is a good choice. The acceleration is much more linear now, and the bottom end is so much better. It feels good to start getting the hang of jetting finally.

 

[RMZ450FIRST4T]

I know you wil probably think these are stupid questions, but I just want to know what does WOT mean.

 

[cornishwrecker220]

your plug colour looks a tad little lean to me...i would run a 148 main jet....what air box mod have you done?? what oil & mix are you running??