06 yz250 fouling plugs


16 replies to this topic
  • RandallF

Posted March 16, 2013 - 01:22 PM

#1

My bike has started fouling plugs every ride! It started about 3 weeks ago out of the blue. It has never done this before. There has been no recent motor, air or fueling mods done to cause this. As soon as I got the bike new in 07 I put a full PC pipe and Delta Vforce reeds and a Twin Air filter on it. I pulled the pilot out a few days ago and replaced the 60 with a 58 and absolutely no change. The clip is in the stock position. I don't have the 07 needle. It doesn't load up in the tight trails. It only fouls on start up. I can ride it for hours and park it for a minute and it will foul. One more thing it wont idle any more on its own and when I pull the choke on a cold start up it has a freakin run away but it will actually start on a cold start first kick no choke. Any suggestions would be great. Thanks

  • mxer928

Posted March 16, 2013 - 02:40 PM

#2

Time for a top end and or reeds

  • RagunCajun

Posted March 16, 2013 - 05:19 PM

#3

Can you explain how a bad top end or reeds makes plugs file idling?

  • capt justin

Posted March 16, 2013 - 05:30 PM

#4

broken reed can let in too much fuel

  • RandallF

Posted March 16, 2013 - 05:48 PM

#5

The top end is tight. I hadn't thought about the reeds. I will pull them out in the morning and look at them. Wouldn't it run bad if it was a reed tho? I'm not saying that's not the problem.

  • Vintage Not Pimpage

Posted March 16, 2013 - 10:47 PM

#6

My guess is RHS crank seal. Had one do the same thing at start up.


  • moto2000

Posted March 17, 2013 - 05:43 AM

#7

Do you mean removed the 50 pilot and replaced it with a 48?

  • RandallF

Posted March 17, 2013 - 06:48 AM

#8

My guess is RHS crank seal. Had one do the same thing at start up.

This was my first thought but wasnt for sure.

Do you mean removed the 50 pilot and replaced it with a 48?

No I think it's a 58 right now. To fat? I orderd a JD jet kit 2 days ago for it. It should be in by Tuesday.

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  • moto2000

Posted March 17, 2013 - 08:12 AM

#9

Stock pilot is a 50.....I usually run a 42 or 45.

Maybe you misread your jet?

  • cameron250

Posted March 17, 2013 - 10:50 AM

#10

Right crank seal or reed !

  • RandallF

Posted March 17, 2013 - 03:49 PM

#11

Stock pilot is a 50.....I usually run a 42 or 45.

Maybe you misread your jet?

I sure hope so!!! You got me second guessing myself. I am going to pull the carb and reeds first thing tomorrow. I will let you guys know what I find.
Thanks for all the help everyone!!!

  • mrjata

Posted March 17, 2013 - 09:12 PM

#12

Antoher vote for crank seal. If the reeds were bad, you wouldn't get much of a intake pulse at all. Like holding a valve open or off the seat. If the reeds don't close, the mixture is blown back into the carburetor.

Just my thoughts, let us know what you find.

  • RandallF

Posted March 18, 2013 - 10:54 AM

#13

Well fellas we can check reeds off the list. They look good as new.

  • mtdirtbag

Posted March 18, 2013 - 11:10 AM

#14

RandallF: I would go thru the carb and check everything, but would pay special attention to float height and needle & seat. Sounds to me like it has a load of fuel after sitting around.

  • RandallF

Posted March 18, 2013 - 12:15 PM

#15

RandallF: I would go thru the carb and check everything, but would pay special attention to float height and needle & seat. Sounds to me like it has a load of fuel after sitting around.

I have the carb apart right now. I ordered a JD jet kit Friday. It should show up tomorrow. I will check the float and seat right now. Thank you

  • Corkster

Posted March 18, 2013 - 01:33 PM

#16

If this was not happening before, I would not change the jetting until you have found the problem. Otherwise you will end up chasing your tail.

Check:

- float level
- crank seal (have you lost gear oil)
- blocked air filter
- adjust idle air screw
- bad fuel batch or mistake in oil mixture
- top end


Having said that, 58 sounds way too big.

Edited by Corkster, March 18, 2013 - 01:34 PM.


  • RandallF

Posted March 23, 2013 - 01:19 PM

#17

Well guys I put the JD jet kit in this morning and started the bike up and it sounded super crisp and and would idle like normal. I let it idle for about 30 - 45 seconds and it didn't foul the plug. I didn't get to ride it due to the non stop rain but so far it's looking good.
I'm now running 45 pilot instead of the 58 also The JD red needle on the third (middle) clip. I will let yall know how she runs in the woods as soon as the rain stops.





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