yz 125 wont hold idle, and dies after revs!!!


YZmoto915

Member
Feb 25, 2007
15
0
hey guys i am new to motocross and i have a 2001 yz 125, and i have had some trouble getting it started , but when i do it runs fine, but it dies after slowing down from 3rd gear, it just boggs out, and i believe it is running to rich, so basically my 2 questions are 1.) what shoudl i do about the bogging out. and 2.)wht should i run my oil:gas ratio...so any advice will help. as for the bogging out i believe it is just a gummed up main jet from changing the oil type, so we will see about that!!!

thanks, joey.
 

76GMC1500

Uhhh...
Oct 19, 2006
2,142
1
I had a bike that would foul plugs if I tried to open the throttle. It turns out it was a bad crankcase seal. I slowly opened the throttle until it let me run WOT, and then everthing was good to go, after running at WOT for a while.
 

adam728

Member
Aug 16, 2004
1,011
0
Hard starting and no idle? Clean the carb, it could be as simple as a clogged pilot jet. If you've cleaned the carb and the problem persists then my next guess would be reeds.

Of course, if the top end is past due than nothing you do will matter till you get that taken care of!

As for oil/gas ratio, I'd stick to 32:1 or more for a 125, depending on how it gets ridden.
 

rmc_olderthandirt

~SPONSOR~
Apr 18, 2006
1,533
8
The first step is to decide what oil mix you are going to run. Make your decision and stick with it because changing the oil mix changes the jetting requirements in the carburtor.

The next step is to clean the carburetor really well. Many people don't understand what this entails, it is a lot more than taking the float bowl off and wiping the insides out. You need to remove all the jets and soak the carburetor in a really strong cleaning solvent. Note that this stuff is so nasty that your mother/wife will kill you if you spill it in the garage, so do it outside! Then rinse in water, blow out all the small passeges with compressed air.

Next you make sure that the float level is correct. You will need a manual to get that information, but a manual is something you should really have anyway.

Next you make adjustments on the metering jet. This is the needle that is operated with the throttle cable. It will have a small clip and numerous slots that it can be adjusted to. Sliding the metering needle down will lean out the mixture, moving it up will richen the mixture. Try it in several locations and pick what works best.

Next is to adjust the idle mixture. Get the bike idling as slow as it will then adjust the mixture for best idle. If it is idling too fast then adjust the idle speed screw (different than the idle mixture) and then adjust the mixture screw again for best idle. Repeat as necessary.

When things are working reasonably well put a new plug in, ride it hard for a while and then pull the plug and inspect. The center insulator should have a light tan color to it. If it looks wet then you may be running too rich, if it looks ash white you may be running too lean, either of which may require a change of the main jet. If the plug looks oily then you might be running too cold of a plug.

Rod
 

YZmoto915

Member
Feb 25, 2007
15
0
thanks for all the help, it happened to just be a pouled plug, dee da dee, haha but yeah if anything happens again i will be sure to refer back to this, thanks again. joey.
 

KX250Dad

Member
Dec 4, 2006
204
0
it happened to just be a pouled plug, dee da dee, haha but yeah if anything happens again
Joey... not to burst your bubble, plugs don't just foul and even at that a fouled plug is not a "bad" plug. Be advised, I doubt your troubles have past and suggest you follow the posts provided or it is likely the issue will return.
Good Luck...
 

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