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Discussion Starter · #1 ·
Hello all! I just got my hands on a 03 XR50. The carb is really plugged up and I can't seem to get the pilot circuit cleaned out, so I want to purchase a new carb. I see some 18mm cheap XR/CRF50 carbs on ebay for 20-$30. Do they work well? If so what size should I go with for a direct replacement on a stock bike?



Thanks for the help!!
 

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An XR70 carb/intake will fit your stock bike, but just barely. You will most likely need to play with the jetting, but the 70 carb is more legit than a 50 carb... it has cool stuff like a removable pilot jet!



Any carb thats bigger than a stock carb will require a different intake, as the bolt spacing on the carb side of the OEM intake is too narrow for an aftermarket carb.
 

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both true, but my advice unless u want to fuel a parts pile, go ahead and decide where this build is going. That was my bigggest downfall, but Im planning my next build, the only thing Im not gonna plan from the start is the motor cuz Im gonna frame up build it. But for u r u gonna race it, trail ride, pit bike, or stunt it maybe even motard. But pick a direction firdt before throwing money at it. but a quick fix is gonna b the ebay carb my buddy has one and it worked great outta the box. go figure now rejetting just fired up and ran hahaha
 

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Discussion Starter · #5 ·
Honestly this bike is just for my little boy for now. So just looking for a stock replacement carb. I find it strange, but it seems to be very hard to find a OEM XR/CRF 50 carb on ebay at a good price.



They advertise these 18mm carbs as direct bolt on. Is this not the case? At this point I just want it running good.

 

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I am having a hard tome finding this exact info. :( I did get one of the 18mm $30 ebay carbs (after reading that it would be a nice little mod) only to find that it was way to big to fit the stock intake manifold. Should have realized that from the get go lol. :p Well now I am trying to find out how to make it work but am having a hell of a time finding a manifold to fit. Is there something I am missing? There are some that look close but is it going to be trouble having a 18mm manifold meeting up to a 13mm intake hole?
Thanks

JR
 

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I already bought the carb. I am asking is there any intakes that fit the ebay carbs to the stock engine and are there issues with the bigger intake manifold hole meeting up to the smaller stock CRF50 head intake hole? Is boring it out a good idea?

JR
 

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So I got a intake manifold that matched perfectly carb side and engine side. Now I am having a hard time tuning it (and yes I know it is an ebay carb) lol. I think it is running really rich as it bogs out when given any significant amount of throttle off idle and when I pulled the plug it was very sooty. I have tried all the needle clip settings with no improvement as well as playing a bit with the air/fuel mixture screw. Bike idles great and will run pretty well as long as you ease into the throttle (but no wheelies) :( Can these carbs be jetted and if so does it sound lean or rich to you all?
Any help is appreciated. :)

JR
 

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Well you can't be the first person on this forum to try this carb. If you don't know the brand, post a photo of the carb and ask what others are using for baseline jetting. Then see how your jetting compares.
 

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Well you can't be the first person on this forum to try this carb. If you don't know the brand, post a photo of the carb and ask what others are using for baseline jetting. Then see how your jetting compares.
Oh sorry, I have a stock engine and I am using this carb: 18mm Carburetor for CRF50 XR50 CRF XR 50 Carb ATV U CA02 | eBay

this filter: 35mm Red Foam Air Filter XR50 CRF50 KLX110 Uni AF09 | eBay

and this intake: Carb to Head Intake Tube Fits Lifan Honda CT70 XR50 | eBay
 

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Your bike sounds a bit lean on the pilot. Your plug will only tell you if your main jet is too lean or rich. My bike had this same problem but I have a 24mm mikuni. It had a 35 pilot jet and I went to a 40 and it runs great on bottom and top end. Also you might want to check for air leaks because that will pull more air causing a lean condition as well
 
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