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So looking for some tips or advice from experience on my new yz250x

im having problems with fouling plugs and the bike seems to be running rich. I've ran 30:1 first tank and now tried 40:1. First half hour I rode the bike easy on some logging roads just to break in like the manual suggested and it ran great until I was coming down hill idling lots and got about 3 good runs through the gears and the bike died with a fouled plug. Before messing with the jetting I tried 40:1 and a new plug which I gapped to.024 instead of the .020 the original was which is still within manual specs. The bike still seems to run rich. Seems good at 3/4 to full throttle but has a sputter 0 to 1/4 throttle. Seems like a pilot issue. I than took the bike to the track warmed it up and did about 10 laps to warm up. I turned in pilot screw until it started to sputter than tried out but turning it out doesn't seem to effect the idle at all. I tried at 3/4, 1, and 1/1/4 turns and doesn't seem to effect it at all. Slight hesitation when you first rev it and on the track is will sputter out of the corners than seems to clear up when you really get on it. Plug is also very black still. I'm riding between 1000 and 1200 metres. Any tips would be much appreciated as I don't want to chase my tail on my brand new bike. Thanks

 

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30 minutes ago, Bcwild15 said:

So looking for some tips or advice from experience on my new yz250x

im having problems with fouling plugs and the bike seems to be running rich. I've ran 30:1 first tank and now tried 40:1. First half hour I rode the bike easy on some logging roads just to break in like the manual suggested and it ran great until I was coming down hill idling lots and got about 3 good runs through the gears and the bike died with a fouled plug. Before messing with the jetting I tried 40:1 and a new plug which I gapped to.024 instead of the .020 the original was which is still within manual specs. The bike still seems to run rich. Seems good at 3/4 to full throttle but has a sputter 0 to 1/4 throttle. Seems like a pilot issue. I than took the bike to the track warmed it up and did about 10 laps to warm up. I turned in pilot screw until it started to sputter than tried out but turning it out doesn't seem to effect the idle at all. I tried at 3/4, 1, and 1/1/4 turns and doesn't seem to effect it at all. Slight hesitation when you first rev it and on the track is will sputter out of the corners than seems to clear up when you really get on it. Plug is also very black still. I'm riding between 1000 and 1200 metres. Any tips would be much appreciated as I don't want to chase my tail on my brand new bike. Thanks

 

I had this problem on a 250 husky. Jetted it till my brains oozed. It turned out my gas level in the float bowl was too high. Gas was sloshing into the cylinder and fouling plugs.  I adjusted the float level and I never fouled another plug. 

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They are jetted rich from the factory, lots of others on here with similar problems. Do a search for jetting threads, but as a rule of thumb you might want to try a smaller pilot jet and or go 1 clip leaner on your needle.

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41 minutes ago, kiwi_rider said:

They are jetted rich from the factory, lots of others on here with similar problems. Do a search for jetting threads, but as a rule of thumb you might want to try a smaller pilot jet and or go 1 clip leaner on your needle.

Thanks kiwi_rider I am thinking on trying that and maybe one size smaller main. 

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I had these problems when I first had the bike and leaned my jetting to this and it runs pretty good with no plug fouling:

Riding from sea level to 1000ft
48 pilot, air screw set at 1 1/2 turns out (still adjust from time to time depending of outside temperature)
Needle: N3CW, 1st clip (top clip)
Main: 178 (tried 175 but seemed too lean)

Edited by sebasYam
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Understand that going from 30:1 to 40:1 actually makes the air/fuel mixture more rich. I have a 17 YZ250X and chased jetting from the get go. Bought it in March. Settled on stock needle 1st clip, 45 pilot, 168 main. Also check you floats. Mine were high and resetting them helped a bunch.

I tried new premix this last weekend and fouled a plug out within 5 minutes.

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17 minutes ago, FITZI6_7 said:

Understand that going from 30:1 to 40:1 actually makes the air/fuel mixture more rich. I have a 17 YZ250X and chased jetting from the get go. Bought it in March. Settled on stock needle 1st clip, 45 pilot, 168 main. Also check you floats. Mine were high and resetting them helped a bunch.

I tried new premix this last weekend and fouled a plug out within 5 minutes.

FITZ16_7 did your 250x come with the jets needed in the rebuild kit/parts kit? I still have to get my rebuild kit from dealer as they couldn't find it when I was there. Thanks

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I got a seperate main, pilot and needle.  In my IM i mentioned two sizes, but meant to say one installed (richer) and one extra in the packet.  Also a spoke wrench and a tool to help with the power valve.  Oh, most important,,, the book.  

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On 7/6/2017 at 2:49 PM, Bcwild15 said:

FITZ16_7 did your 250x come with the jets needed in the rebuild kit/parts kit? I still have to get my rebuild kit from dealer as they couldn't find it when I was there. Thanks

 

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I used to foul plugs often on my x.  Changed jetting to 45pilot, stock needle 3rd clip, 40 power jet, 175 main.  Yamalube 40:1, runs great for sea level woods riding, bike idles great and haven’t fouled a plug since 

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What do u think about a 48 pilot  176  main ..due to my gnarly turbine core 2 .v force 3 set up?  Or do u recommend your settings I ride primarily at 7oo and less quite often under 500 feet..what does the power jet do I am confused with that?

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On 8/13/2018 at 10:30 PM, Craig Steinman said:

 

Sry for the delay.  I got two jets with the bike but I had to order jets.

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On 8/18/2018 at 11:33 AM, Craig Steinman said:

What do u think about a 48 pilot  176  main ..due to my gnarly turbine core 2 .v force 3 set up?  Or do u recommend your settings I ride primarily at 7oo and less quite often under 500 feet..what does the power jet do I am confused with that?

 

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Your around 3500 to 4000 feet. Being 1000 to 1200 meters.You need to lean it out.

Put the following in:

Mj 168
PJ 42
Needle: slot 2 from top.

That will get you right where you need to be... there is a lot of guys running 45 at sea level your not even close to that elevation. Your fauling plugs because your way rich on the pilot.

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