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Hey Folks. I got my son an 03 trx90 to get him into quadding. I have an issue I am looking for help with. I recently rebuilt the carb and afterwards I cant get a consistent idle out of it. It idled fine before I rebuild it. The idle is supposed to be set at 1600rpms however when I adjust the idle to or near that range when I let off the throttle the idle hangs for 5-10 seconds prior to returning to the 1600 rpm range. way too much and too long to deal with. When I go to adjust the idle screw, even the smallest turn will cause the idle to drop to the point of stalling. Sometimes I can get the idle adjustment close to where I want it but within 5 seconds it drops way down and then stalls out, especially after feathering the throttle a bit. The fuel/air mix screw has been adjusted in several different positions and has not helped the issue. I then ordered another rebuild thinking I may have gotten a faulty one. Same issue. I ordered another piston slide and needle thinking that might be the issue. Same problem. Compression is good, new plug, tappets are adjusted, intake boot is good, all the intake seals/gaskets are good. The vacuum lines to the air suction valve are good. WHAT AM I MISSING!!!!
 

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Are you sure the carb is original or not a Chinese knock off?i bought my nephew a raptor 90 and when I took the carb apart to clean it it was a fake.just a thought....the numbers stamped into it didn’t match anything I could find...
 

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Discussion Starter #3
All original. I'm stumped. Funny thing is when I googled it, in 2005 another person posted the exact same problem in but never had any responses....just my luck.
 

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Hey Folks. I got my son an 03 trx90 to get him into quadding. I have an issue I am looking for help with. I recently rebuilt the carb and afterwards I cant get a consistent idle out of it. It idled fine before I rebuild it. The idle is supposed to be set at 1600rpms however when I adjust the idle to or near that range when I let off the throttle the idle hangs for 5-10 seconds prior to returning to the 1600 rpm range. way too much and too long to deal with. When I go to adjust the idle screw, even the smallest turn will cause the idle to drop to the point of stalling. Sometimes I can get the idle adjustment close to where I want it but within 5 seconds it drops way down and then stalls out, especially after feathering the throttle a bit. The fuel/air mix screw has been adjusted in several different positions and has not helped the issue. I then ordered another rebuild thinking I may have gotten a faulty one. Same issue. I ordered another piston slide and needle thinking that might be the issue. Same problem. Compression is good, new plug, tappets are adjusted, intake boot is good, all the intake seals/gaskets are good. The vacuum lines to the air suction valve are good. WHAT AM I MISSING!!!!
Do you anyone with the same carb so you can swap and see if the issues switch bikes?
 

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Sounds like there's some debris hiding somewhere in the pilot circuit. Take the carb back apart & shoot some brake clean through every hole you find & make sure it's coming out the other end. Recently had a carb that wouldn't run right & it ended up having a plugged air bleed.
 

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Sounds like there's some debris hiding somewhere in the pilot circuit. Take the carb back apart & shoot some brake clean through every hole you find & make sure it's coming out the other end. Recently had a carb that wouldn't run right & it ended up having a plugged air bleed.
+1, what Scrappy said. Something is more than likely plugged in the carb. Or if you use pump fuel ethanol might of got the best of your carb.
 

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Discussion Starter #8
Sounds like there's some debris hiding somewhere in the pilot circuit. Take the carb back apart & shoot some brake clean through every hole you find & make sure it's coming out the other end. Recently had a carb that wouldn't run right & it ended up having a plugged air bleed.
I have been through it twice. Compressed air, brake clean, I also put it in my ultrasonic cleaner. Still no change. I just replaced the fuel filter thinking it may be that, no keeping a consistent flow of gas. Same...
 

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Discussion Starter #9
I cant see it being anything else...I may just drop the 150 on a new carb so I can finally sleep at night....ha ha
 

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The jets on these minis are very small I had to clean the raptor carb more than once to get it running right,take a single strand of an old clutch or brake cable a push it thru the pilot hole back and forth to make sure it’s open.hold it up to natural light and see if you can see light thru that tiny jet..if you see light you know the passage is cleared..
 

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Discussion Starter #14
So I pulled the carb off again and cleaned it. When I did I had the opportunity to look through the carb from the front of it to the rear. I did notice that there is what looks like a small brass ferrule at the base of where the needle and slide drop onto. It is positioned on the bottom of the carb but is about an 8th of an inch proud of the bottom air flow chamber. I don't know if this would interfere with air flow and/or the venture...…...is it supposed to be proud of the base of the chamber?
 

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The little brass part your referring to is called the needle jet & yes it does stick up into the venturi a little... I still think you have a blocked passage in your carb... I had issue's with my son's e-ton carb & ended up buying a Chinese replacement. Had the same problem with the Chinese carb but than found a tiny piece of casting flash that had broken off & ended up blocking the pilot jet passage way. Got the tiny piece of aluminum out & problem solved.
 

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Discussion Starter #16
Well, looks like I am going in for disassembly #4. Ha Ha. I should really be focusing on the pilot circuit correct? The one passage from the pilot jet to the carb? Its channeled at and angle but looked clear. Sent a small wire into it too. I will try again though......I'm OCD about my stuff looking good and running right...….
 

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Discussion Starter #17
I know a lot of people fix the problem and never leave feedback as to how the issue was fixed or if ever was. I hate that. We are here to help each other out. As previously stated I said I may buy a new carb. I bought a brand new OEM Honda carb and it fixed my problem. The moment it went in all the idle/power/engine consistency problems went away. Amazing the quality that goes into these carbs. The slide and slide assembly came with it too. I was never able to get the idle to adjust correctly with the old carb. With the new carb I can precisely adjust it both high and low with ease. Thank you everyone with all the help..
 
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