Question about 2003 Yamaha YZ 125
Our 125 grizzly will start when choked but dies when given gas. My kid ran it out of fuel last year and it did the same thing. The main jet was plugged with gelled gas. This year it acts the same but the main jet was okay. I cleaned up the carb anyway and put it back together. Minor improvement. I have put in a new plug and do not have the air cleaner hooked up right now and it still will not run. I also put on a clear gas filter and can see that there is fuel going to the carb. Any Thoughts?
Take the carburetor apart again, remove the main and idle jets and idle mix screw, plus the float and needle valve. The main jet holds an 'emulsion tube' in--look inside where the slide valve moves, you should see a short brass tube projecting out of the bottom. Carefully push down on that tube with a plastic rod or wooden dowel, it should drop out the hole where the main jet was. Chances are that the tube is dirty and needs to be cleaned--look carefully at the series of small holes drilled into the sides of the tube. These small holes deliver air which is mixed into the fuel passed through the main jet. That air comes from a small hole just inside the intake side of the carburetor. The long needle that sticks out of the slide bottom controls low to mid-range speed fuel-mixture. Check that the 'C' clip on the top end of the needle is in the center groove and that the retainer spring is pressed down the 'C' clip. Now soak the whole carburetor with spray cleaner, then blow out all passages with compressed air. Don't soak the rubber-tipped needle valve from under the float. On reassembly, set the idle mix screw 1-1/2 to 2 turns CCW from CW stop. Adjust for best idle after you get it running and warmed up. I hope this long winded explanation helps!
Posted on Aug 14, 2009
Check that reed valves not sticking and check the pilot jet its prob. half blocked. have to stick a very thin wire through it.
Posted on Aug 12, 2009
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Posted on Jan 02, 2017
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