05 250EXC suddenly to lean? HELP????

[KTM Mike]

I have an 05 250 exc which was running this jetting:

160 main, 38 pilot, A/S 1.25 out, N3EH needle, -3 clip

Set up like this, it was a tad rich, not bad, moderate spooge. Did not foul plugs.

I recently installed a EE pipe, which seemed to lean it out quite a bit - or else something by coincidence at that exact same time happened. A large part of my concern is ZERO spooge. I mean NOTHIN...ZILCH. I have always felt more comfortable with at least some spooge, so am rather uneasy with nothing.

Should I worry?

More back ground info -

Prior to EE pipe, bike Ran well. EE pipe bike still ran great - no issues. I put EE pipe on the bike when it had oh, 120 hours or so on the clock. I immediately noticed the spooge went away at the first ride with the EE pipe.

Bike has ran fine for a few hundred miles now with the EE pipe on it. maybe a bit hotter it seemed to before, and maybe felt a bit lean. It runs rather crisp - not a burble anywhere. I rode it a 200 miles or so, did not check plug (never thought of it actually). After a recent race, I did pull plug to discover it being rather white - one half was slightly darker though. I just did a top end on the bike - no signs of running lean on cylinder or piston (piston was worn looking though at 135 hours - but not a "oh my, this engine is about to sieze!) Cylinder still had cross hatch visible everywhere.

Anyhow, after this rebuild, I decided I should richen it up a hair given how the plug looked before, so I lowerd the clip one notch (raised needle). AS to 1 out. did a 40 mile ride - some faster trail, 3rd gear, 4th gear occasionally. Pulled plug - a light oily black, not at all dry carbony look. Bike felt good, but I would say still kinda feels lean, and once again, seemed to be running hotter than normal. This plug read was not a throttle chop however...and this read showed richer than the other two noted here.

Tonight I upped the main to a 162. (Was 160 before.). All other jetting exact same as noted before. I left the clip in -4 position for this little test. As it turned out, I did not have a 40 pilot to try..so that was left at the 38.

Rode the bike about 1 .5 miles on a grass track to get it warmed up. Did a couple wider throttle positions straights, then did a oh, 3 or 4/10 mile blast top gear throttle pretty much wide open...the throttle chop, and killed the engine. Pulled plug - just like before if not slightly leaner looking - appears way to lean to me...greyish white is, one half of electrode slightly darker. Absolutely EVERYTHING about this plug reads "danger Will Robinson...to lean".

I did notice the bike smelling hotter than I think it normally does (and when i think about it, some riding buddies over the weekend made a similar comment). I had a BR7ES plug in it, decided to pop in a BR8ES - did a repeat of above...same result, if not looking worse. VERY white tip, or if not white, ashy grey. Electrode ashy grey.

Through all this bike still seems to be running great though. If anything the 162 main makes it pull a bit harder than before when whacking the throttle open.

Now I am thinking about air entering the system from places we dont like it to...as in a left main?? How to check that??...take off side cover spray some WD-40 behind the flywheel?

My next jetting specific thing will be raising the needle yet another step... (but my neighbors are gonna get mad if i do it now..so that will wait for tomorrow.)

HELP! The Loose Moose is just 5 days away...gotta have the bike running properly by then!

 

[KTM Mike]

Yes..this is a 2 stroke. Exhaust control (power valve) should have no impact on the jetting however. Hotter plug would to me, only seem to make things worse, not better..that is why i tried a step colder. But no difference.

I did attempt to see if it was a left main...pulled ignition cover, started bike and while running tried to spray some WD40 in general area of left main seal. I am not so sure I was able to get a consistent enough spray on target (hard to hit when it is behind the stator plate and flywheel!)...but for what ever it is worth...with a steady stream spraying in there, no change on how the bike was running. It it were a right main, I would be sucking in tranny oil and blowing white smoke...so not that.

To listen to the bike sittin on the stand idling...it simply sounds like a well running bike...emitting no smoke at all! (other than at inital start up). I also did put the choke on while it was running at idle on the stand. (and already warm). It stumbled, kept running, started puffing some smoke, then did stall. So clearly it is leaner than with choke on! (As it should be...not sure why I did check that - curious I guess.)

So..my next step...hmmm...just to rule it out, I will buy some new gas, mix it up fresh. see if that could be it (for the life of me i cant see why it would be though). FWIW, I am running Amsoil Dominator (full synthetic) at 40 to 1.

 

[KTM Mike]

I agree it sounds to lean - but why? What changed other than the pipe? Does not seem to me that a pipe change would have that large of an impact on the jetting? I called EE - they said normally their pipes dont require any jetting changes. Raising the needle one notch PLUS upping the main one step seemed to do nothing for it..which is also suprising to me - with those two things done, I would expect to see some sort of change towards richer...but no change at all!

 

[CR Swade]

check your carb boot...they tear very easily. In fact, if you overtighten the clamps, they can cut right through the rubber boot like a knife. Is the carb all aligned in the boot notch, correct angle?

 

[stonethecrow111]

Yes..this is a 2 stroke. Exhaust control (power valve) should have no impact on the jetting however. Hotter plug would to me, only seem to make things worse, not better..that is why i tried a step colder. But no difference.

I did attempt to see if it was a left main...pulled ignition cover, started bike and while running tried to spray some WD40 in general area of left main seal. I am not so sure I was able to get a consistent enough spray on target (hard to hit when it is behind the stator plate and flywheel!)...but for what ever it is worth...with a steady stream spraying in there, no change on how the bike was running. It it were a right main, I would be sucking in tranny oil and blowing white smoke...so not that.

To listen to the bike sittin on the stand idling...it simply sounds like a well running bike...emitting no smoke at all! (other than at inital start up). I also did put the choke on while it was running at idle on the stand. (and already warm). It stumbled, kept running, started puffing some smoke, then did stall. So clearly it is leaner than with choke on! (As it should be...not sure why I did check that - curious I guess.)

So..my next step...hmmm...just to rule it out, I will buy some new gas, mix it up fresh. see if that could be it (for the life of me i cant see why it would be though). FWIW, I am running Amsoil Dominator (full synthetic) at 40 to 1.

id get a fly wheel pullr i got 1 for me 300 exc stroker motor do all the work me self. um dont spray wd 40 wont do any think you need sand paper wet n dry on the magets on the stator.if ya sparks down it will run rich. i would try the ajustment on the exhaust controll ezz the tention off so she grunts out more /coolr plug and take the othr guys addv and try a biggr needl sounds good idear too me too.the pipe will have the engine exrtacting more and run hotr so it might not be so silly too adjust that controll might need a lil more tention on the dam thinkit can effect the way shes burning the fuel .combo may be some jetting some exhaust controll ajusts at the end of it all the pipe will have you plzd im sure im wrapd with the fmf pipe i just put on me 300 . it was run nn n rich i put in coolr plug/ and ajusted the exhaust controll too sute the new pipe and she settn the bush on fire lol :p

 

[KTM Mike]

CRswade - good point. I checked it out...all OK.

Stone - My underlying concern is not "how do I change my power delivery so I like it better", nor was it a concern with spark. My concern is bike used to be jetted fine - maybe a tad rich, but fine. Suddenly that changed dramatically when I went to the EE pipe - it became (what seemed to be) way to lean based on no spooge and white plug tip . The reason for spraying the WD40 around the stator area was strictly to determine if I might have a left main seal leaking - nothing to do with ignition itself. The vacuum from the engine would suck in the WD, making the bike run differently for a second - telling me I had a main seal issue. (which I did not thankfully!) As there had been no change on powervalve set up, and as I really liked the power delivery exactly is it was - plus powervalve really would in no way impact the jetting - no need to mess with it either.

Long story short - after many jetting trials, I got it back where I wanted it. Worked my way up on the main until it got fat again (burble burble) with a 165 main. Then went back to a 162. A bit of fine tuning with Air screw and clip position - seems great now. Pulls strong and clean, no hicups in power delivery, plug is looking like it should. Interesting to note however, even with the main running way fat based on the definete burble in the power plus a rather dark nasty plug - I mean, absolutely clear it was waaaay to rich - I still had no spooge! I guess the EE pipe is somehow impacting that...but no big deal.

Thanks for the replies. Heading for the Moose tomorrow morning with the bike running just the way I like it!

 

[ggr3]

So even after you when to a 162 main, the only way your got your plug looking correct was by adjusting air/fuel and needle clip position?

I ask because I have an 04 KXF250 that I've been having the same problem with. I made quite a few changes to the bike over a short period of time, three of which could be some or part of the culprit.
1. Changed from stock to Dr.D exhaust system.
2. Removed flash screen from air cleaner box.
3. Installed a Boysen Acellerator Pump (going 1/2 turn richer on air/mixture per Boysen instructions.)
I knew I'd be having a adjustment just from removing the flash screen as it now get's all the air it wants. Stock is 172 with a 40 pilot and clip in middle on needle, I was at 178 with stock piolot and needle clip position before making the changes, and now I'm at 190 with a 42 pilot and clip down (richer) 1 notch and plug still looks white and lean.

Last weekend out at the track I went to a 192 main and it started to burble, sputter and pop. I knew I had gone to rich on the main, but the plug still looks white.

Your story makes me want to go richer on air/fuel mixture and drop another notch on the needle to see if I get the same results.

Thanks for the posts and followup!

 

[KTM Mike]

So even after you when to a 162 main, the only way your got your plug looking correct was by adjusting air/fuel and needle clip position?

No, not really, that was simply a bit of additional tweeking I did. Since then I did the Moose, but did fine, actually a tad rich. then a bunch of trail riding with my kids...clearly WAAAAY to rich. I raised clip one notch...much better. I will end up doing some other tweeking as well I am sure.

I think the bottom line with all this really was, I did not really need to mess with it all! (maybe a tiny bit). I was just overly concerned becuase i suddenly lost spooge and wanted to be safe.

Your concerns with your 4 stroke are a totally different animal however than with my 2 smoke....afraid I cant offer any assistance there....

 

[ggr3]

Thanks for the reply!

I have read a couple of posts that say Jetting via plug color can be very missleading, especially on a 4 stroke. (I miss my 2 stroke) Color on a new plug can take quite a bit of time on it before you can realy see the whole picture.

Anyway, will go ahead with air/fuel and needle clip position test this weekend or next and post my findings here to help others with these symptoms.

Until then...