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2002 cr 125

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My brother in law purchased a 2002 CR125 back in september. First the bike was set up for motocross but we mainly ride trails. The bike has always bogged on the low end of First and second gear. If we arent "on" the bike all the time it will foul plugs like crazy. We ride at around 1000' elevation, teh bike has a fmf shorty silencer and fmf gold fatty, v force reed cage. That is the mods we are 100% aware of I dont think there are more but could be wrong as this bike runs very strong. Right now the jetting is 142.5 and 32.5. There is also another problem that may be contributing here and I posted a pic of it as well. Any help is appreciated

CRcarb.jpg

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Jetting sounds weird. Stock is 400 and 32.5. It's recommended to go to closer to a 350.

For a PWK38 it would be closer to a 172 and 45-48.

What ratio are you mixing your premix?

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Running 40:1 amsoil dominator. I just got into Bikes a few months ago and will not pretened to know a ton about everything. I have a very good mechanical understanding of how things work, and can do a top and bottem end but thats it

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Running 40:1 amsoil dominator. I just got into Bikes a few months ago and will not pretened to know a ton about everything. I have a very good mechanical understanding of how things work, and can do a top and bottem end but thats it

It's fine, thats what forums like this are for. Try running closer to factory premix ratios which are 32:1(i believe) and put the bike back at factory Mikuni Jetting. I'm not gonna sit here and pretend that I know what the factory jetting is on your bike, but what I do know is factory jetting is always very rich at 60 degrees. usually you need to drop at least, 1 pilot and main jet size, sometimes even drop the needle 1 clip. If you are fouling plugs you are jetted rich. and that Slide looks like it got damaged, you may want to look into a replacement for that.

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I just bought a 2006 cr 125 for my son. It's bone stock including jetting. It has a mikuni carb with a 430 for the main jet, 55 for the pilot jet, and the needle was in the 3rd position. Now,it 's been cold where we ride, approx. 40 degrees F., and I still had to lean the pilot to 35, put the needle in the second from top position ( lowering the needle ) and richened up the main to 440. Also, the float was not set to .300. ( 7.5mm). So far so good. It could still go a little richer on the main maybee 450 due to the cold.

I'm not sure what your bike has for a carb, I do know if it's a kehin, the jet sizes are different. A quick way to see if you are rich on the pilot, is to try and start it when it's cold with out the choke? If it starts, you are to rich on the pilot. Go leaner and start trouble shooting with your air screw around 1 3/4 out.

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