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pgalligan

Fouling plugs and different power valve springs?

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I have a '19 KTM 250SX with 5.5hrs on it. I did 90min escorting a beginner around a novice trail and the bike was basically idling for the whole time. Immediately after that I did some advanced trails which were mostly tight and technical so still low speed at low revs. When I jumped on the bike again a week later the plug was fouled so I replaced it.

 

I haven't actually checked but based on the spare jets supplied with the bike it looks like it is the standard jetting which is fine for where I ride (temp and altitude) according to the chart in the manual.

 

Just wondering if the different power valve springs, and adjustment of same, has any effect on whether the plug will foul when doing constant low revs? eg. Is it less likely to foul if I use the red power valve spring over the green or yellow springs?

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No it's not based on the spring ,you could just try half a turn out on the airscrew

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On 8/23/2019 at 4:42 PM, pgalligan said:

I have a '19 KTM 250SX with 5.5hrs on it. I did 90min escorting a beginner around a novice trail and the bike was basically idling for the whole time. Immediately after that I did some advanced trails which were mostly tight and technical so still low speed at low revs. When I jumped on the bike again a week later the plug was fouled so I replaced it.

 

I haven't actually checked but based on the spare jets supplied with the bike it looks like it is the standard jetting which is fine for where I ride (temp and altitude) according to the chart in the manual.

 

Just wondering if the different power valve springs, and adjustment of same, has any effect on whether the plug will foul when doing constant low revs? eg. Is it less likely to foul if I use the red power valve spring over the green or yellow springs?

the manual is still rich

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Power valve should not effect plug fouling.

Jetting, oil ratio and the fact that it idled for 90 minutes is a bigger factor.

+1 Air screw out 1/2 turn, but if it starts to surge, turn it back in (too lean)

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The UK one is good STD ,but it's not used to riding around slow ,surprised it didn't over heat

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Look up spankys jetting on tt here, screw what the manual says, it doesnt deal with humidity and such so its just a ballpark. Try a pilot leaner, a clip leaner first, the mikuni can handle a fat main without presenting problems on the rest of the jetting.

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On 8/26/2019 at 9:07 PM, hondaman331 said:

Look up spankys jetting on tt here, screw what the manual says, it doesnt deal with humidity and such so its just a ballpark. Try a pilot leaner, a clip leaner first, the mikuni can handle a fat main without presenting problems on the rest of the jetting.

I've gone 1 clip leaner and 1/2 turn out on the air screw and so far it seems pretty good.

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