If you have problems with orginal carb of the 85-87 BigRed or you want little more power to your BigRed, you might buy cheap chinese relipca carb from ebay or some else shop.
I received one of those "perfect fit" carbs from China. I liked to check how those really fit to BigRed and what is quality of product. I had read how those chinese carbs fit perfect to atc250es. But its not fit perfect, it have to say first.
Positive side of Chineese carb.
+Carburetor is cheap and availability is good from Ebay, Amazon and other stores.
+You might got more power (with good jetting)!
-Carb is not ready to run. You need at least some jets to adjust the mixture.
-Carb is taller and wider than orginal. I had to cut about 8mm from intake side of carb body, so that I could use an old air cleaner.
-Cause of size of new carb, you cant use orginal air hose between airbox and framepipe
-You need also other throttle cable than orginal BigRed. You can use Honda TRX 350 Rancher 2000-2006 cable Part Number : 17910-HN5-670. That cable is longer than original but works fine.
My Conclusion is, if you have reasonable original Keihin with all orginal air intake parts, might be better to repair those. I want to keep my BigRed original as could be, and biggest problem of chineese carb is that air intake problem. Original air intake way from frame to airbox is very good.
Cause of that knob, primer pump, original airhose does not fit in.
Fuel line goes from carb to other direction.
Fuel line of chineese carb.
I had to cut 8mm of carb body. Chinese air intake is longer than original.
Original throttle cable doesn't fit
Size of chineese carb is bigger than original Keihin QA. You could have more power from this chineese one. My original Keihin QA01 is with cold start kit 06161-HA8-305.
What ever you choose be happy with your BigRed