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So, I'm a diesel mechanic and automotive technician; however, I don't have a lot of experience with these small engines. I'm working with a 2006 Brute Force 650 4x4i. At idle, warmed up, and choke off, there is a backfire type thing occurring. It sounds like a pop coming from the carburetor. I took the box off and I could see flames in the manifold, below the throttle plate (not your typical Edelbrock flame thrower). So, I took off the carb and looked at the boots; they were ripped and they were replaced. However, that did not solve the cough. So, I took the carb off again and pulled the plug to adjust the pilot screw. I made it super rich, but alas the pop remained (albeit at a much lower frequency). So, I think it must be lean still. So again the carb comes off to clean the pilot jet. There was a little dirt in the bowls, definitely not the worst I've seen, and I proceeded to clean the main and pilot jet as well as inspect the jet needle, diaphragm, and float plunger. Everything looked good and, while I had the carb off, decided to check valve lash--it was good. I then slapped the carb back on, and cuss words ensued--possibly some tools thrown. Anyways, my question is, before I completely rebuild the carb and clean the casting, is there anything else that could be causing this problem. I don't think you can adjust ignition timing on these quads, air filter and box are good, vacuum is good, fuel supply is good, and it's not in limp mode. The popping only occurs at idle (worse at low rpm, and better at high rpm), and when I hit the throttle, the quad ponies up and goes--sounds and performs perfect. Let me know what you think, and sorry for the long post.
 

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The popping is pretty common on these. Mine was doing it mainly at idle as yours did. With the choke ON, it wasn't as bad. Anyways my exhaust header rusted and split down the seem. So I upgraded to full Muzzy Stainless exhaust! A friend who is very good with engines, replaced the jets per advice from this site and I believe put 1 shim on the needles. He played around with it and got a good tune on it. Since he did that, it's been smooth and quiet. Well, the Muzzy is loud but no more popping! LOL! Sorry I don't know the specifics on jet sizes or anything but maybe that gives you a direction to go or someone with better knowledge on carbs can advise.
 

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So, I'm a diesel mechanic and automotive technician; however, I don't have a lot of experience with these small engines. I'm working with a 2006 Brute Force 650 4x4i. At idle, warmed up, and choke off, there is a backfire type thing occurring. It sounds like a pop coming from the carburetor. I took the box off and I could see flames in the manifold, below the throttle plate (not your typical Edelbrock flame thrower). So, I took off the carb and looked at the boots; they were ripped and they were replaced. However, that did not solve the cough. So, I took the carb off again and pulled the plug to adjust the pilot screw. I made it super rich, but alas the pop remained (albeit at a much lower frequency). So, I think it must be lean still. So again the carb comes off to clean the pilot jet. There was a little dirt in the bowls, definitely not the worst I've seen, and I proceeded to clean the main and pilot jet as well as inspect the jet needle, diaphragm, and float plunger. Everything looked good and, while I had the carb off, decided to check valve lash--it was good. I then slapped the carb back on, and cuss words ensued--possibly some tools thrown. Anyways, my question is, before I completely rebuild the carb and clean the casting, is there anything else that could be causing this problem. I don't think you can adjust ignition timing on these quads, air filter and box are good, vacuum is good, fuel supply is good, and it's not in limp mode. The popping only occurs at idle (worse at low rpm, and better at high rpm), and when I hit the throttle, the quad ponies up and goes--sounds and performs perfect. Let me know what you think, and sorry for the long post.
There's your answer ^^^
You opened the pilot screws, added fuel, and the popping got better,
Clean the carb and all parts completely, it probably doesn't need any parts. Stay away from "kits" if it does need a part.
Always make sure the air filter box is fully assembled before making any determinations.
 

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You are running lean. Go to the hardware store get some #4 washers and use them as shims to raise the needles. One under each needle is usually enough but I did have one P650 that need 2 under each needle. Be careful putting the slide back in, it is easy to get the spring in a bind and the slide won't open all the way
 
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