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2003 CRF450R please help

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I have had this bike for about a year and a half it ran fine until summer started and then everytime i snapped or rolled on the throttle just a little it wants to bogg or shut off. It works fine if i roll on the throttle real slow but when i twist the throttle to fast it boggs out. I know for sure the problem is not my valves because i have had it in the shop 5 times in the past couple months. My guess is, is that it is the carburator. I have a big gun exhaust on it and Z&M cycles tell me to keep it at stock jetting, but big gun exhaust tells me i should run a 178 main jet and a stock pilot. I dont know what to do If anyone can tell please HELP ME i havent been able to race or fully ride all summer this is my first four stroke and so far i dont like it due to this problem.

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That is too bad, that you don't like the bike. Maybe if you left it stock you wouldn't be having these problems?

It sounds like you have: contamination in your carburetor, partially plugged accelerator pump, pilot jet problem, or air leak.

The easiest fix is to take off the 17 mm drain plug out of the bottom of the carburetor. See if there is any sediment or water in it. See if that makes a difference, if not go from there.

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Well, I think you may have toasted your bike. So let me tell you the best thing to do at this point. Clean it up a little. Drain all the fuel out of it. I will send you $450 ( one dollar per cc which is a great value) and you can give the bike to my delivery guy to take it off your hands. After all you really can’t try to sell it with the shape she is in.

Kevin

03 450R, Trail ready. Best bike in the world, but is lonely in my garage by herself.

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Take the carburator off, take it apart, clean it and blow air through the jets, put new gaskets in it and a new accelerator pump kit. Make sure the float level it set correctly.

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I'd try installing a 55 leak jet in the carb. Its a $7 part that requires removing the float bowl to install. It seems that it took Honda a while to figure this out, as the 55 leak jet is standard on my 06 450. My 05 CRF 250 ran exactly how you describe before I did this mod. It cured it instantly. I was about to replace the leak jet on my 04 450 (#70 leak jet stock, I believe), which also has a mild version of the problem you are describing. I decided to replace the entire bike instead :D .

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Gosh! These answers are shaking my confidence in these guys!

I have a Big Gun Race Exhaust (loud, a little better on the bottom & mid) on my 04 and was told the same- stock jetting, which was wrong- it bogged big time when opening the throttle liberally. Big Gun is on the nose. I installed a 178 Main Jet and she runs great. Carb cleaning and checking fuel screw is good practice, however.

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