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Air pilot screw adjustment question.


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Yeahhhh....ALWAYS better to rebuild OEM.  I've been forced to use chinese junk a couple times due to missing carb on some junk ones I've put back together and they never run as good as OEM.  Even if you get them to run pretty decent they usually last a year or two and the cheap rubber seals fall apart.

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Yup, I'd advocate for the OEM overhaul over an unknown make any day.. Even with worn slides and carb body, they are still a better bet than some of the aftermarket carbs.

As for the initial setting... some aftermarket use their own, different, threads on the idle mixture screw, and different taper. Set it where you like initially  and adjust it once it's going and warmed up.



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If it's the same make and model as the OEM that's a good start, but then they come in different versions for different markets and years as well.. Different markets often have different jets and adjustments.

If it's the same make and model and has the same, stamped in, numbers and letters, it can still be set up slightly differently. Some makes have up to about four variations for a single model and year.. The stamped in numbers and letters are the most specific details, they tell us what jets and setup they have. The general model though can be fitted to heaps of different make and models and have endless variations of jets etc.

Quick question.. the cover on top of your carb, is it squareish with four screws, or an odd shaped cover ?

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The stamped in numbers are done when it's set up for a specific bike and market. The after market carbs don't have the numbers, and are not set up for any particular bike or market, they are just set for a general tune which should start and run anywhere.. 

If the new carb is an exact copy of the original(right down to the threads used for the jets), then you can often swap all the old jets and brass bits, and the slide and needle, from the old carb to the new one to set it up as intended for your market/climate/fuel/altitude..  The idle mixture screws sometimes have different threads though and can't be swapped.. If the new carb isn't an exact copy of the old one though swapping the jets, even if they do fit, doesn't always work so good.

Unless it's the OEM make, and with the same stamped in numbers, it's not really a OEM replacement part.


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Yeah that's what I was thinking..  A weld.. 

That carb is a QB02B or QB02A. The A was fitted from 93-2000, and the B from 2001-2006 models. They both have the same jets and float height, but they will probably have different slide needles and/or emulsion tubes(the brass tube the slide needle slides down into), or possibly slides.

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Yeah, I got screwed when I bought this piece of sh**, $1000.00 down the drain. All I wanted one for was to go through the woods by the house to hunt and fish.  I figured surely it should be good enough for that. But so far it's proved me wrong. That fat bastard I bought it from should be glad there's laws!

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When I got it barely ran the guy said it probably had some junk in the carb. I figured I could clean that out and it would be fine. But, I think it was having trouble starting and staying because It was probably about ready for the chain to jump off then. I've got maybe 2 minutes of actual riding time on it.

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This is something a lot of people get confused about.  The pilot screw (air or fuel) setting in the manual is a starting point.  That's why it's an adjustment not a permanent setting.  No two engines are exactly the same.  And yes new carbs - either installed or in a box - are set at the factory but that's why there's a Welsh plug to remove so you can adjust it.  

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