2004 yz 125 fouling plugs

I have a 2004 yz 125 and just had a new top end installed, and the day i get it back it fired up the first kick and rode great.  And about a week later i go to ride again but when i get ready to ride it wont kick start but when i push start it it starts up fine and runs just like it normally does.  When i take a break from riding for maybe 20-30 minutes i shut the bike off and turn off the gas.  Then when i hop on to ride again it will kick start and then as soon as it starts up it fouls.  You can rev it as hard as you can and it still fouls.  I run a 32 to 1 mix ratio which is what yamaha recomends.  Please tell me what i could do to fix this problem.  

im wondering if the topend is alright due to the fact that you cant kickstart it anymore...

i would pull the head and have a look inside
either that or do a compression check  
.
.
.

1998 cr125
its better to own nothing worldly and still have your identity
then have the world and no identity
---------------------------------------"We were born of the night. We live in it. We will die in it. But tomorrow there will be light, for those now crying in the night. For those to whom day is denied. To whom death is a gift. To whom life is forbidden."

sounds to me that your loading up the cylinder and it needs  to be leaned out. lean out your jetting a bi and see what it does.  
--------------------
____________________
MIKE
Phoenix, az
(07 yz250)
(99 yz125)


Every bush has its day (sanders, 2009)
Lack of enthusiasm is for the weak and timid. (alex, a.k.a. yz250 forever)

I know a lot about nothing at all. (Maple, 2009)

what do you mean by loading up the cylinder and when you say lean out the jetting  

Basically if you are running your bike too rich, you will load up too much mix in the cylinder and it will bogg your bike dowbn and foul your plug. You are not fouling a plug if the bike still starts with the same plug. First thing you may be able to do is locate the air mixture screw on the carb and turn it out a little more, maybe a quarter tur or so and see if this helps a littel. Jetting your carb correctly take a little time, trial and error. But you should at least make sure you are running stock for your elevation and bike mods. Call a local dealership and find out what stock jetting is for your area (this depending on elevation)from there pull the carb and check the numbers on your pilot, main and clip position on the needle. If you have a hard time locating these, a manual should be your next purchase.  
--------------------
____________________
MIKE
Phoenix, az
(07 yz250)
(99 yz125)


Every bush has its day (sanders, 2009)
Lack of enthusiasm is for the weak and timid. (alex, a.k.a. yz250 forever)

I know a lot about nothing at all. (Maple, 2009)

a.guest7:
I have a 2004 yz 125 and just had a new top end installed, and the day i get it back it fired up the first kick and rode great.  And about a week later i go to ride again but when i get ready to ride it wont kick start but when i push start it it starts up fine and runs just like it normally does.  When i take a break from riding for maybe 20-30 minutes i shut the bike off and turn off the gas.  Then when i hop on to ride again it will kick start and then as soon as it starts up it fouls.  You can rev it as hard as you can and it still fouls.  I run a 32 to 1 mix ratio which is what yamaha recomends.  Please tell me what i could do to fix this problem.

Was it fouling like this before the new top end; or its started doing it after the new top end?

What does the plug look like?  Have you put a new plug in it?  Besides the new top end, any carb work done at teh same time?  
.
Dave H 2006 YZ250
(2008 YZ 125 son)

when the plug comes out the tip looks kinda gunky and oily looking.  But when you put a new plug in, it fires rite up and runs good till you shut it off then when you start it up aftr about 20 minutes it starts then fouls immediatly.