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2000ish XR50 won't run w/o choke on

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A shot in the dark here, I will do my best to describe what is going on and yeah I read everything that I could find with search, no luck.

Bike sat for about a year w/o being run at all, finally got it home to try and get it running for thanksgiving. It is completely stock minus a raised bar kit, motor wise completely stock.

Drained float bowl and put new gas in the bike, wouldn't start. Pulled carb apart and cleaned everything (jets included) with berrymans carb cleaner.

Took entire throttle assembly apart from twist throttle to where the slide goes into the carb, things seemed ok.

bike will now start with choke on but shuts off once I turn choke off. When I twist the throttle the bike falls on its face and just about shuts off. When I let off throttle it will slowly come back to idle, any ideas?

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seems like either the pilot circuit is still clogged or you have a vacuum leak......check the manifold gaskets and o-rings....and soak carb body for a couple hours then blow all passages out with compressed air

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VAcuum leak is possible but unlikely on a here unless a gasket was omitted during reassembly. Before anything, dump the old gas in a safe receptacle, put new fuel in, drain the bowl and give it a go. Old gas can cause all sorts of ill symptoms. If this doesn't correct it then doopsx3 is correct about the pilot circuit I would think. Be sure when you pull the carb, you clean both jets, one is tough to see as it sits deep inside of a tower and can be easily over looked. When cleaning jets, don't slide anything through them or you could damage the shape, just soak and use compressed air.

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The stock XR50 carb does not have a removable pilot jet. Completely disassemble the carb, removing the main jet, air screw, idle screw, float and float needle, and, as stated above, soak the carb body thoroughly. Flush with contact cleaner, making sure you spray it through the two holes to the rear of the carb, where the air filter attaches. You'll see them when you remove the air filter.

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I put all new fuel it in and drained the old gas, I think you guys are correct about something still being clogged. I will disassemble everything, soak the carb body and blow it out with air once done soaking and see what happens. If this doesn't work then will check for any sort of vacuum leaks. Thank you all for the advice!

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I apologize for misinforming you on the pilot jet, all of my knowkedge on these bikes comes from Z50's which are pretty much the same. The air jets are crucial to fuel/air function. As dirtybkr has shown, be sure that your air jets are clean as they are just as important as the fuel jets. As far as an air leak, you should have a gasket in good condition between the intake and the head, an O-ring between the carb and isolator, and a gasket (or o-ring) between the isolator and intake. Also make sure (via parts micro-phiche) that all o-rings are still in place in the carb.

Edited by surveywaters
spelling

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I have had the same problem with my sons 50. I have had the carb off and dissassembled multiple times, and have blown carb cleaner through both of the holes in the back of the carb till a stream comes flowing out of the various passages. I still have the same problem your describing. Let me know if you have any success. I agree with drtbkr188 is the pilot side of the carb but i have been unsucessful

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Sorry i forgot to add to the earlier reply. That i too thought it might be an air leak. So i replaced all the o-rings in the manifold system at the engine side, as well as the isolator and carb side.

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Couple more things to check. dirtbkr help clarify this please A jet needs an emulsifier to properly mix the fuel and air, on the main circuit you have a jet tower that you can remove. Once removed, you'll see a series of small holes covering the side of this tower. These are where the air enters and moves upward to the needle thus creating a turbulent vacuum which draws fuel up through the main jet and forces it to atomize. The pilot jet typically has these emulsifying holes machined directly on to it, since the pilot jet is not removable, (dirtbkr help here) there needs to be atleast one if not 2 small holes in the main ventral of the carb where fuel from the pilot circuit enters and atomizes. Find these and be sure that your carb cleaner is flowing out of here when sprayed through the air jet. Also locate the hole which is regulated by the pilot mixture screw (pms) and varify that it's clear; the pms hole and pilot hole(s) may be one in the same.

One more thing, make sure th vent line doesn't have a bug stuck in it.

Good Luck

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Survey says??????? Hit it right on the nose....if you had a carb with a removable pilot, you would see exactly what he is talking about....non-removable pilot carbs are a beatch to get perfectly clean

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Thanks again for the advice, waiting on some parts that I am sure won't arrive til after thanksgiving. Will let everyone know what's going on once I get the parts I am waiting on.

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As stated above, once you've removed everything from the carb body, when you spray the contact cleaner in to the hole at the 6 o'clock position, the cleaner should come out where the main jet was at the bottom, and out the hole in the center of the carb where the jet needle goes. When you spray into the hole at the 7 o'clock position, the cleaner will (or should) come out the long brass tube next to the main jet orifice, out of a smaller hole near the center hole in the carb body, and also out of the air adjustment screw hole.

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I have run into the same problem on my son's 50. It runs for a while with the coke on, then eventually stalls out. I have cleaned the carb several times and made sure that the passages are clear by spraying carb cleaner through them. I was ready to look for a rebuild kit, but I saw carbs on ebay for $40. I couldn't believe they were that cheap. The OEM ones are about $48, but I'm not sure how much difference there is. One thing that I noticed that was odd was the air cleaners was soaked with oil. I'm not sure if this was a result of running the bike with the choke on for so long. Any advice on the carbs or the oil would be greatly appreciated.

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The foam filter should be oiled, but not soaked. Clean it with dawn or an air filter cleaner, allow to dry and apply some filter oil, squeeze it out real good and it's ready for use. Make sure you're not running too much oil in the crank case.

For all of you chasing a carb issue, due a compression test before spending to much time on it. If your bike runs on choke then shuts off, it could be caused by poor compression.

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Thanks for the feedback on compression testing. I've cleaned the air filter and tried it, but I had the same issue. I'm going to check for a vacuum leak, then try a compression test.

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