Why are the plugs fouling so fast?

trailqueen · May 16, 2007

I'm getting between 150-200 miles out of a spark plug - is that normal? (this is my first 2t)

I read the thread about why 2t's smoke and someone posted that too much gas in the cylinder will foul plugs. Isn't it the oil that fouls the plugs?

If it's too much gas that's causing the problem, can I change the mix from 50:1 to 40:1 without changing the jetting, or will that cause excessive smoke?

It's an 07 ktm 200 xc-w (great bike!). It's running on a 50:1 synthetic mix. The pilot jet was moved from 42 to 40 and the needle clip was moved up one position. Except for the plug issue, it runs great. Thanks. :cool:

junkjeeps · May 16, 2007

Going 40:1 will make it smoke worse. I would think that 50:1 would be as lean a mixture as you would want. Are you put-putting around all the time or do you wind it out? Other than that, you may need to take a look at your jetting.

2strokerfun · May 16, 2007

Going to a 40:1 mixture probably isn't going to make it smoke one bit more. Both mixtures are lean on the oil. And it will lean your jetting slightly, but probably not enough to fix your problem. I agree with above statement that if you a doing a lot of slow riding, you might need to rejet and readjust needle to lean it a bit.
But really, if you like the way it runs, putting a spark plug in it every 200 miles doesn't seem that bad.

flyingfuzzball · May 16, 2007

50:1 is really lean isnt it

i agree try going to a 40:1

and 200 miles isnt bad my friend's old bike only got like 2 hours (but the thing was messed up soooo.....)

76GMC1500 · May 16, 2007

The bike should never foul a plug. What kind of riding are you doing?

trailqueen · May 16, 2007

I ride typical New England trails - fairly tight woods, tree roots, rocks, etc and a small pit area. That's why the bike is so great - it's light and handles really well through the tight stuff. The area I ride is not that big, so I don't always have it pinned. I 'putt-putt' sometimes. Is that really bad for a 2t? I ride about 65 - 70% on the throttle and the rest just cruising.

Does the plug just 'foul' at any time? So far it's only happened when I went to start it in my garage. What would happen if I was going up a fairly steep hill in the pits? Would it just stall halfway up the hill?

76GMC1500 · May 16, 2007

You should post a picture of one of the fouled plugs. Usually, going up hill gets the plug hot enough to keep it clean. Bikes don't usually foul plugs during climbs. What oil are you using? What heat range is the plug?

scooter1130 · May 16, 2007

If you do a lot of slow speed trails, the best thing I have found is to use either platinum or gold spark plugs. They stopped my fouling problems on a 97 KTM200EXC, and I do a lot of tight trails, and slow riding. Just ask the people that keep trying to get around me so they can move above a snails pace :ride:

I also have run 40:1 since I bought the bike new in 97

snb73 · May 16, 2007

If the bike is in good mechanical order, you might look into jetting it. These may help.

Here are a few jetting links;

http://www.all-offroad.com/DirtBike...rs/BGNov98.html

http://justkdx.dirtrider.net/carbtuning.html

http://www.keihin-us.com/tune.htm

http://www.keihin-us.com/am/_media/pdf/slide_valve.pdf

http://www.keihin-us.com/am/tuning/

http://www.maximausa.com/technical/...gsummer2001.pdf

http://www.powroll.com/tech_specs_jetting101.htm

Some Spark Plug Links;

http://www.strappe.com/plugs.html

http://www.dansmc.com/spark_plugs/s...gs_catalog.html

http://www.ngksparkplugs.com/techin...1000&country=US

http://www.ngksparkplugs.com/techin...1300&country=US

250twostroke · May 16, 2007

if u say it only fouls in your garage, i wouldnt worry when you are actually riding it because like somone else said when your climbing a hill the plug is hotter because you have a load on the motor causing it to work harder and thus getting it hotter. so if u say it is running good and it is only fouling plugs in your garage and not really after you ride it i wouldnt worry about it at all

bruno670 · May 16, 2007

40:1 and 50:1 is an oil mixture. Lean and rich is gas/air mixture. Don't confuse the two. If you are jetted for 40:1 then leave it that way. Changing the oil ratio to 50:1 when you are jetted for 40:1 will make the bike run RICH. Jet it for the mix you are currently running.

84cr125 · May 17, 2007

personnaly, i think 50:1 is way too lean. i would switch it to 32:1 and jet it according to that. as long as your not putting it on trails you should be fine running 32:1, it offers more protection than 50:1, so when the time comes to run it to the bone to passs someone you can be safe knowing that your bike is not going to seize.

rmc_olderthandirt · May 17, 2007

Three tales of plugs and fouling:

I have a two stroke outboard, 9.9 HP. In the 15 years that I have owned the outboard I have changed the plug once. I run 50:1 oil mix, whatever oil is cheap. The motor gets used a fair amount, and it always is operated under fairly heavy loads and up in the higher RPM range. It starts easy and will idle without stalling.

I run 40:1 synthetic oil (Motul 800) in my YZ-125. I have never fouled a plug to the point that it wouldn't run, but when I ride along with my wife on her quad I tend to "putt" and the responsivness of the bike just goes to hell. Every once in a while I have to get up and go for a minute or else it will start bogging so bad I can't stand it.

One of my riding buddies rides a Yamaha WR-250, two stroke, same oil mix, same plug. He has never had a problem (that I am aware of) when we were riding together. A couple of weeks ago we rode together in a club enduro, family oriented event. The enduro runs several loops, reusing previous sections a bit. They stagger the end points, sending the masters the farthest and the novices stopping the earliest. Once the deadline for the last rider has passed we all ride the course backwards, pulling all the arrow stakes and removing the ribbon from the bushes. It was a lot of slow riding, frequent stops, never getting up to speed.

We made it about two miles before my buddies bike just quit from a fouled plug.

If you want the performance from a two stroke then you need to work the engine hard enough to burn the deposits off the plug. If you are willing to "detune" (like my outboard is) then run a hotter plug it will tolerate putt'in around, but you will lose that peak performance.

Rod

trailqueen · May 17, 2007

Thanks for all your suggestions. I'll try the better plugs rather than mess with the jetting. There's houses near where I ride so I want to keep the smoke (and noise) down to bare minimum. :cool:

trailqueen · May 20, 2007

So where do you get these platinum spark plugs? I did a google search but can't find them for the ktm. My dealer is over an hour away so I'd just as soon buy them online. Thanks.

scooter1130 · May 20, 2007

Standard plug BR8ES ($2)
Gold Plug (racing plug) BR8EG ($4)
Platinum plug BR8EV ($6)
Iridium plug BR8EIX ($7)

I use the platinum plugs and havent tried the iridium plug yet, but they are doing away with the platinum and replacing them with the iridium plug. I get them from a friend who owns an auto parts store, so I get them about half those prices. you may find them cheaper, those are NGKs prices.

They are more expensive, but I fint them to be worth the price. I replace my plug once a year, with riding every weekend in tight trails, even though it isnt needed when i do.

Rich Rohrich · May 20, 2007

trailqueen said:
Thanks for all your suggestions. I'll try the better plugs rather than mess with the jetting. There's houses near where I ride so I want to keep the smoke (and noise) down to bare minimum. :cool:

If the jetting is too rich and it's causing plugs to foul, using a plug with a different electrode material will not cure the problem. You'll just be ruining plugs that cost more.

Assuming you don't have an ignition problem or a blown right side crank seal , the proper heat range of plug (regardless of material) and proper jetting are the only "fixes" for the problem.

For many riders the stock plug heat range is "too safe" for slower riding. As a result the plug can't maintain sufficient temperatures to burn off the deposits that build up.
Proper jetting will minimize these deposits and make the plug more tolerant of these temperature swings. A hotter plug will make the engine more tolerant of poor jetting and slow speed riding.

scooter1130 · May 20, 2007

Definitely take any advice you get from Rich Rohrich, he knows a lot more than I do for sure. I was only giving a sugestion of what I found to get longer life from plugs that worked for me.

supajdogg · May 21, 2007

Is it possible to run a plug that is too hot? Will it hurt to run a BR9 instead of a BR8? If I'm a little rich, and can't rejet, will the hotter plug make it run like it's a little leaner?

76GMC1500 · May 21, 2007

9 is colder. It is possible to run a plug that is too hot. Too hot of a plug can cause detonation and/or burn a hole in the crown of the piston.

Why are the plugs fouling so fast?

trailqueen

junkjeeps

2strokerfun

flyingfuzzball

76GMC1500

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trailqueen

76GMC1500

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scooter1130

Paragon Junkie

snb73

250twostroke

bruno670

84cr125

rmc_olderthandirt

trailqueen

trailqueen

scooter1130

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Rich Rohrich

Moderator / BioHazard

scooter1130

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supajdogg

76GMC1500

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