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02 DRZ250 running really bad - carb question

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My sons 03 DRZ250 has been sitting for a long time...

Gas looked like windex, it looked bad. I drained the gas and made sure the petcock flowed. Took the carb off cleaned it out, the float moves freely and valve works. There was alot of varnish but I cleaned it all out and and put it all back together. New battery and it fires right up. It runs really bad, backfires, popping.

I dont see a fuel filter is there a screen somewhere? I dont have a manual for it. I didnt take the What may I have missed that would cause it to run so crappy?

Carb: Was there two carbs available for these (different years maybe)? I ordered a float valve but the one I got was too small. maybe this has a different carb on it? How can I tell...

Jetting: It had a Yosh full system on it, I put the stock exhaust back on and it has a K&N filter. What would a good starting point be for jetting? Im not going to do any mods to it, I want it quite and stock.

Thanks for any help, Im hoping to make this thing puurr...

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First of all figure out if it is a the pumper carby or the CA vacuum carb. If the slide has a diaphragm attached to it at the top it is a vac, if its got an arm that pulls the slide up attached to the cable pull you have a pumper.

I only know how to work on the pumper. I have had a similar issue with it running like that when the pumper piston jammed. The pumper piston sits in the side of the float bowl and should have a spring under it. This is activated by a rod being pushed downwards that is linked by a cam to the cable pull. If something is missing/jammed or got lots of play this could be your problem.

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Its the vacuum unit. I didnt pull the diaphram apart to clean anything, the slide seemed to move OK. I suppose I should pull the top and diaphram off and clean that end of the carb as well...

They must have given me the float valve for the pumper carb.

Thanks for the reply.

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I have a 2006 with the CA vacuum carb. I have a #15 pilot and a #137.5 main, and shimmed the carb needle .070" with a washer. Header welds ground out, stock muffler and snorkel removed. I put (3) 1" holes in the side (right) of the airbox and one in the top. The pilot jet has such tiny holes in it that it still could be plugged.

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My wife has the CA model with the 32mm vacuum carb. It sat for quite awhile and ran like poo. Most likely due to old gas and sludge in the carb. Anyhow to make a long story short, I ended up removing the carb and cleaned all of the jets and passages and changed the main, and pilot jet, along with adding a spacer under the needle since it isn't notched, per Glenn F's specs. Prior I had opened up the airbox and exhaust, ground the header weld, yet saw only a little improvement. Now this bike runs so well it blows me away. The transformation is beyond worth the effort. You will not regret taking the time to do this.:bonk: GlennF has a post telling you how to do this. This bike can be so much more with a little time and less than $10 in parts.

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I realized as I was taking it apart again the boot going into the cylinder has a big crack in it. Going to order one of those and clean the carb again before doing anything else...

Thanks for the info.

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