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2004 500 TBX Carb Rebuild Questions

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I recently removed the carb from my buddy's 2004 500 TBX because it was leaking gas out of the overflow. My research led me to believe that the problem was probably due to debris clogging the needle jet and/or main jet. Once I got the carb disassembled I noticed that whoever attempted to fix the problem before me pinched the carb bowl o-ring crushing one corner of it.

I couldn't believe how much crud I found in the carb. I cleaned it out with carb cleaner then compressed air. I removed all the jets, but didn't touch the low speed fuel screw or idle adjustment knob even though the manual recommended removing them, because I didn't want to affect the carb settings. Simply unscrewing jets and re-screwing them in shouldn't have affected the carb's settings.

I reassembled and reinstalled the carb. I also added an inline fuel filter (can't believe there are 500cc machines out there without fuel filters!!!) to hopefully prevent more debris from entering the carb. The good news is; the fuel leak from the bottom of the carb is gone. The bad news is; now the idle is intermittent. The quad won't idle at all when cold, then once it warms up, it will idle for a while then slowly begin to sputter until it stalls.

I tried adjusting the idle up with the adjustment knob on the carb, but that seemed to have no effect until, very suddenly, the idle would climb very high (too high). I should mention that I rode the quad around my property for 15 minutes and it rides great. The only problem is at idle. There is no bogging or any fuel delivery / fuel mixture issues when riding.

I have considered that by adding an inline fuel filter to a gravity feed system, I've introduced too much resistance, although the filter is one of the least resistance filters I've ever seen. Before I connected it to the carb, I turned the fuel knob to the "on" position and gas flowed out of the filter very quickly, so I doubt that is the problem. Any thoughts?

Anyways, the carb sealed, even with the mangled bowl o-ring, but my buddy wanted me to order another one anyways. It will be here Monday. At that time I'm going to remove the carb again and replace the o-ring. I looked at the service manual, Section 11 (Troubleshooting) for "poor idle". Since I just serviced the carb, I'm going to start my examination there. According to the service manual there are 3 areas of the carb that could cause a poor idle. They are:

1. Clogged jets. I will check those again when I'm replacing the o-ring.

2. Float Out of Adjustment - Section 4 of the service manual says,

"NOTE: Check float arm height by placing the carburetor on its side w/float contacting the needle; then measure with a caliper the height when the float arm is in contact with the needle valve. Float

arm height should be 17 mm (0.7 in.)."

Could someone explain exactly where I'm supposed to be measuring from and to, preferably with a picture? Is it from the top of the float to the carb body? I'm not sure exactly where this 0.7" dimension should be measured.

Another issue, if the float height is out of spec, nowhere in the manual does it tell you how to adjust the float height. In section 11 (Troubleshooting), it tells you to adjust the float height, but nowhere tells you HOW to adjust float height. Can someone tell me how to adjust the float height?

3. Improper Pilot Screw (Low Speed Fuel Screw) Setting - Again, Section 4 of the manual (Carbs) says,

"NOTE: Turn the low speed fuel screw clockwise until it is lightly seated; then turn it counterclockwise the recommended number of turns as an initial setting."

That's great and all, but does anyone know what the recommended number of turns are?

Again, the quad idled fine before I took off the carb. Does anyone have any thoughts other than what I have come up with?

The main thing I am looking for here is how to measure the float height (0.7"), how to adjust the float height and the initial number of counterclockwise turns of the low speed fuel screw.

Any help would be appreciated.


Bill Granger

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the height youre looking for is from the bottom of carb where bowl connects on, to the bottom of the float as it hangs ...

there is a little metal tang from where the float needle hangs,

i would do 2 1\2 turns ... book may say different, but will work better @ 2 1?2 LOL



Edited by oxidized_black

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