Running problems yz426


5 replies to this topic
  • bmxchamp00

Posted February 16, 2014 - 01:42 PM

#1

My 426 is getting closer to rideable, but when I start it it will get pretty hot quickly and only stay on if I give it some throttle. 1/4 throttle will make it bog though. It idles without any throttle pretty nicely and rides alright but when I pull in the clutch or let it idle after giving it throttle it dies. ??

  • Cooter69

Posted February 16, 2014 - 02:16 PM

#2

If the bike Is getting hot quickly and you are having trouble keeping the bike running your jetting may be off. Pull the plug and see what color it is, sounds like the bike is lean (plug will be white on the tip). If that is the case you will have to rejet the bike and fatten it up so it does not get hot quickly and will stay running at idle after you give it gas.



  • bmxchamp00

Posted February 16, 2014 - 04:44 PM

#3

If the bike Is getting hot quickly and you are having trouble keeping the bike running your jetting may be off. Pull the plug and see what color it is, sounds like the bike is lean (plug will be white on the tip). If that is the case you will have to rejet the bike and fatten it up so it does not get hot quickly and will stay running at idle after you give it gas.




Thank you!

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  • grayracer513

Posted February 17, 2014 - 07:35 AM

#4

The spark plug will tell you nothing about this kind of situation. 

 

Get your idle mixture set correctly, adjust the idle speed, and go from there.  If you can't get the pilot screw adjusted satisfactorily, you probably have a partially clogged pilot jet.



  • bdeemo

Posted February 19, 2014 - 12:43 PM

#5

The spark plug will tell you nothing about this kind of situation. 

 

Get your idle mixture set correctly, adjust the idle speed, and go from there.  If you can't get the pilot screw adjusted satisfactorily, you probably have a partially clogged pilot jet.

Or the wrong size. May I recommend getting a finger twistable fuel screw from tusk for $15? That way you can ride 100 yards, turn the fuel screw a quarter turn, test it out, then ride another 100 yards. If you can't get it close enough try the next size up or down ( depends on your air flow and elevation) on the pilot. Um its super easy to change jets on that carb, just take the bowl drain nut off after turning off gas, 17mm wrench, then take a (8mm i think) socket and take out the main or a screw driver for the pilot.



  • grayracer513

Posted February 19, 2014 - 02:49 PM

#6

You don't get the pilot adjustment done by "riding a hundred yards".  It's done by running the engine at an idle.

 

Read: http://www.thumperfa.../jetting.htm#PJ

 

Also: http://www.thumperta...ircuit-setting/

 

Also, until one becomes somewhat familiar with the inside of the carb, I don't recommend you attempt to change the pilot with the carb in its normal position.  The main is easy enough (until the main nozzle nut comes out with the jet), but it is very easy to damage the screwdriver slots in the pilot jet unless you're using a screwdriver that fits nearly perfectly, and reinserting the jet can be frustrating for anyone, much less the unfamiliar. 







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