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New to 2 Strokes (250exc): can you foul a plug easily from riding too slow?

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Just trying to figure this out as I'm a newbie to 2 strokes (4 months now)... yet I'm a decent rider (recently won my first hare scramble....vet C class... out of 12 other 2 stroke riders). Anyway, I did some jetting on  my carb recently & the bike was runnin pretty good... yet today in the woods I was cat walking a long, downhill, steep creek bed & was in 1st gear mostly.... not reving it up much but slight revs... finally at the bottom I went to drive away & the bike was feeling boggish... it then died right out w. lots of gas in it. The plug was fouled!! Luckily had a new one. *my buddy who rides a ktm 300 told me that I can idle my bike around the woods all day in 1 st gear & it wont foul a plug.... now is that B.S. or true?? I mean, can I really ride it slow & be ok or do I always have to rev it up high to clear it out?? Im a bit confused. My old bike was an XR 400 & man I never had any engine issues.... at any speeds... this bike seems temperamental..... any help is appreciated.... free coffee to everyone also~

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Edited by cheetah66

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Proper needle selection goes a long way. I have never fouled a plug even in my beginner days where I was never on the pipe and lugged it everywhere. When I first started I read so much about jetting my eyes wanted to bleed. It's payed off though.

Edited by mynewcr250
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Proper needle selection goes a long way. I have never fouled a plug even in my beginner days where I was never on the pipe and lugged it everywhere. When I first started I read so much about jetting my eyes wanted to bleed. It's payed off though.

thanks, Ive been rackin my brain for weeks on this.... itz getting old.  Reading tons of articles here & elsewhere. Just confusing at times honestly. I tried making it leaner via clip on needle, air screw & jets.... its rips my arms off when good but then it fouled the plug unexpectedly & when I looked at the plug it was carboned black all over??? Can that happen in 10 mins??? because before that it rode great for an 1hr....  anyway, im burnt out... falling into carb depression... maybe ill order a pizza & drink a beer... that should solve the problem temporarily.

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Also, am wondering if this matters or affects it: Im running the red PV spring turned in a lot. Bike breathes fire at times... yet sometimes feels choppy/boggish.... maybe the fuel line has some dirt or something... microscopic boilders jamming up the fuel highway in the carb... who knows...  but suicide is never an answer.

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thanks, Ive been rackin my brain for weeks on this.... itz getting old.  Reading tons of articles here & elsewhere. Just confusing at times honestly. I tried making it leaner via clip on needle, air screw & jets.... its rips my arms off when good but then it fouled the plug unexpectedly & when I looked at the plug it was carboned black all over??? Can that happen in 10 mins??? because before that it rode great for an 1hr....  anyway, im burnt out... falling into carb depression... maybe ill order a pizza & drink a beer... that should solve the problem temporarily.

clip position is only part of it. the tapers of the needle are what really matter. once you get the taper right you use the clip positons to fine tune.

 

ktmtalk.com is a very good place for getting info on what youre trying to accomplish. lots of offroad guys there with lots of ktm jetting experience, so they know the OEM needles very well. i would get on there and ask for some advice on maybe picking a needle that will work better for your style of riding.

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Guessing that my carb doesn't have a kit in it, but it's jetted correctly for my area. I can go a very long time without getting on it hard, and it will take a long time before I noticed that it is built up a bit, but usually after a quick run, it cleans out good. so far, I haven't experienced a fouled plug on my ktm yet. was on the same plug for 6 months, and changed it out for a race, so I would be fresh. 

 

 in some ways I would say it's stupid to say "you can go like that forever without fouling the plug" I don't believe that to be true, I would just always expect it to happen, and have a plug to switch it out. but a good running, and jetted bike(I run 48:1) it will go a long ways.

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I have an '04 250 EXC - had since July - have yet to foul a plug. I'm running the recommended chart jetting for my elevation and temps. I run 55:1 premix. I also run a revloc (autoclutch). Just did 80 miles of singletrack over the weekend. My recommendation especially if you like to lug off the pipe - put the yellow spring back in. I just swapped a yellow back in - I had a red spring in there unbeknownst to me from the previous owner.

Running the yellow spring with about 1 thread in from flush - night and day difference! I run 13:50 gearing and 3rd now feels like what 2nd used to. Way more low end torque. This is for tight singletrack. Mainly off the pipe. But twist of the throttle and can be on the pipe whenever I want. But it's very linear and predictable.I personally prefer the yellow spring power curve and IMO is much better for singletrack riding and enduros. This probably goes against what you'll read in many posts but I tried and tuned around both and stick to what worked best for me - yellow spring. I ride woods and want woods powerband. Otherwise I would have gotten an SX.

PS -I run the stock pipe with an FMF Turbinecore2 silencer. Jetting I'm running for 1050 ft, 65F - N3EH needle, 3rd clip position, 160 main, 35 pilot, 1 turn AS. I run 91 oct non-ethanol.

Edited by _LCW_
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Read your jetting chart. It works great if you run pump gas (91) and mix at 50:1. If you are running a spark arrestor your bike will be a little fat so you will need to run at least one and most likely two steps leaner than the chart says. The KTM needles work great IF YOU RUN THE RIGHT NEEDLE FOR YOUR TEMPERATURE AND ELEVATION! That is why KTM sells several different needles just like they sell several different idle jets and main jets. There is no "magic" jetting spec that works at all elevations and temperatures with every pipe and silencer combo.

Does your bike spooge? If it does and you are fouling plugs, most of the time it is because you have to fat of an idle jet. If your bike sputters down low and then hits like a train when it gets on the pipe, you are to fat on the pilot jet and needle.

My bikes can sit and idle for over ten minutes and then go wide open with out any hesitation or smoke at all.

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For 1½ years I rode my stock jetted '12 300XC-w without a problem, even praised the stock jetting on this forum ~ and then I went on a "kid ride"...  10 miles into it and constantly swapping places in the riding pecking order, I got stuck behind an 11 year old on a DRZ-125 in deep sand...  It was a "for the fun of it" ride, so jumping out of the main groove and blasting past wasn't in the cards, plus his dad had the keys to my ride home.  Needless to say I fouled a plug after barely 1 mile, this is the first 2 stroke plug that I've fouled in 10 years (maybe more).  With this bike I've always had a small amount of spooge out the silencer but nothing to cause concern.

 

After fouling the plug I bought and installed a JD jet kit.  Didn't realize how fat the bottom end was jetted from the factory until then, and now it runs so much better on the low end! 

 

Long story short, if your 2 stroke is jetted correctly you should be able to putt around and never foul.  If you are fouling then it's time to re-jet and if your lucky enough to have a bike that JD sells a kit for then I recommend that you buy it.

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I have lugged mine low in the RPMs for a while at a time and never once fouled a plug. Like said before, carb settings will determine if your plug will foul easily or not.. 

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Maybe this is silly, idk. But on my 125s if I set them to idle they will always foul the plug. And I dont lug a 125, at all, on the track screaming all the way. Maybe some can explain this to me, or maybe its just a figment of my imagination.

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Maybe this is silly, idk. But on my 125s if I set them to idle they will always foul the plug. And I dont lug a 125, at all, on the track screaming all the way. Maybe some can explain this to me, or maybe its just a figment of my imagination.

When your throttle is closed to 1/4 throttle you are on the air screw and the idle jet. 1/4 throttle to 3/4 throttle you are on the needle. 3/4 to full throttle you are on the main jet.

Symptoms of being to fat on the idle jet are. A bike that sputters down low, then the mid range hits hard as it cleans out, smokes when it is idling or has spooge and likes to foul plugs. If your bike does any of these you should try a smaller idle jet. If you are more than two and a half turns out on the air screw you should try a smaller idle jet and readjust your air screw.

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Long story short, if your 2 stroke is jetted correctly you should be able to putt around and never foul.

 

 on my 125s if I set them to idle they will always foul the 

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