fouling plugs...maybe too rich???

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YZmoto915

Member
Feb 25, 2007
15
0
hey guys, im back with yet one more dee duh dee question, and ths one deals with spark plugs, i have fouled out 2 plugs in the last 3 rides, and im kinda getting sick of paying $6 a pop for new ones, so my question is, am i fouling them out because i am runing it too rich (32:1) and maybe should be running it at 40:1??? any help will be great, thnks, joey.
 
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Chili

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Apr 9, 2002
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Barring any mechanical issues then you likely need to lean the jetting out. Don't chase poor jetting by changing your ratio.
 
7

76GMC1500

Uhhh...
Oct 19, 2006
2,142
1
You don't have to buy a new plug every time it fouls. You can clean them with a wire brush and a little solvent. We need to know more information about what you're doing when the plug fouls. Are you putting around on single track trails or are you running the thing wide open? What heat range is the plug you're running? Is your bike losing oil from the transmission?
 
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just_a_rider

Member
Jul 25, 2006
394
1
You also don't need to be buying 6$ plugs, run the NGK-BRES 7 or 8, they have a thicker electrode that resist fouling a lot better than those NGK's with the skinny one, those are good plugs as long as you stay on the PiPe.
 
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elcamino12sec

Member
Jan 16, 2006
412
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If you are fouling plugs you must not be running it very hard. You will be fine with 40:1 ratio. You can use a b7es plug too. My old bike use to foul plugs all the time when I would ride with my girlfriend. I ended up installing a b7es plug the days I would ride with her and never had a problem. With her I never got out of 2nd gear so using a hotter plug was easier than changing jetting every time I went riding with different people. I sold the bike to a co-worker with the b7es installed and to this day (6 months ago) he has never changed it and says the bike is running just fine.
 
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DLHamblin

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May 27, 2005
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Just remember that 40:1 is actually richer (fuel wise) than 32:1 (more gas; less oil). If you are fouling because you are too rich then going to 40:1 is making it even richer.

As mentioned in the other posts there are numerous reasons for fouling; so with some more detailed info (type of riding etc) you can get better answers.
 
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YZmoto915

Member
Feb 25, 2007
15
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ya i just figured out that running it at 40:1 would be richer, as you can tell i dont really know much about bikes, but i think what i am going to do is change to a br8 and lean the jetting, from a 460 to s 450...but lets see how that goes and if i have more trouble i will be sure to let you guys know cuz u guys are such great help. thanks...joey.
 
7

76GMC1500

Uhhh...
Oct 19, 2006
2,142
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Do you have your bike set so it will idle? If so, try backing down until it only idles for a second or 2 after you let off the throttle.
 
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adam728

Member
Aug 16, 2004
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76GMC1500 said:
Do you have your bike set so it will idle? If so, try backing down until it only idles for a second or 2 after you let off the throttle.
Click to expand...

And why is this?

My 125 will idle all day long just fine and has never foulded a plug. I've let it idle 5-7 minutes at a time, no problem.
 
7

76GMC1500

Uhhh...
Oct 19, 2006
2,142
1
Because you have to run 2-strokes really rich on the idle circuit to get them to idle. AND!!! 5-7 minutes of idle will definately foul a plug. Turn that screw in until it no longer idles and then add a little until it barely idles. This is the optimum setting.
 

robwbright

Member
Apr 8, 2005
2,283
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Not true. I haven't fouled a plug on my E.G. 144 and I can let it idle for 20 minutes. Might be a bit rich, but it's not fouling plugs. Was able to do the same thing for years with a CR80 back in the 80s. Dad's 1994 CR125 will also idle for a long time with no plug issues.
 

BSWIFT

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Nov 25, 1999
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Remember that there is more than one reason for proper jetting of a two stroke. Preventing fouling is the most prevalent reason. The next or best reason is throttle response. Getting the bike down to barely staying running at idle will likely give better "off idle" response. This only effects the first 1/8 or the throttle but is very important in getting the other 7/8's dialed in.
 
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adam728

Member
Aug 16, 2004
1,011
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My bike idles, and doesn't foul plugs, yet you tell me that's impossible? I have mine set up for best throttle response. If I go even 1/4 turn leaner on the air screw I'll get a bog off the very bottom. The pilot is one size leaner than stock. It will idle as long as you ever need it to, and does not seem to load up at all when doing it. Like I said, never fouled a plug.

There are many ways/reasons to get a bike a particular way, there is no one right answer, and definitely not when you start talking "in general" for 2 strokes. There is no optimum setting that covers all bikes, riding conditions, and setups.

I know many desert and dune guys run very rich on the bottom end of things. They are almost never in that RPM range, so it doesn't really effect performance. But after an extended high RPM run that rich idle circuit helps to pull more heat from the cylinder and piston crown when they lift off the throttle.
 
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mtk

Member
Jun 9, 2004
1,409
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Before the pissing contest starts, remember that all carbs do not function the same and some of the older models use circuits for more than one purpose. For example, the Keihin PJ carb on the CR500 has the enrichener and idle curcuits together (if my memory serves me) and that can cause problems with jetting in some circumstances.
 
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