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Discussion Starter #1
hi guys...i know there are many carb threads relating to the older models..however i find myself in a similar situation now with a newer model carb...the bike wont start or run unless its on choke..i've never had this happen before, i have 3 disc models outside that I've stripped and cleaned without issue, we've had monsoon rains here and usually i just drain the fuel, open the carb give it all a good clean and away we go..but this time not so good!i'm guessing there is a problem/blockage with the pilot jet because adjusting the mixture screw make no difference, it pops n backfires with the choke in and runs sweet with it out..swap a carb from another bike and its all good so i know its this particular carb.....ive soaked all the parts over night and blown everything through with the air line, could it still be slightly blocked?i don't have any spare pilot jets, can someone tell me a site that sells them, i think i might get some as back ups for future, anyone uprated this jet already??cheers
 

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Sounds like the lean condition is due to an obstructon somewhere. May not be in any of the metering jets or orifices, but rather possibly in one of the passeges, like one from mixture needle to throat of carb. Could you confirm that compressed air was sucessfully flowing through all the passages, not just the jet orifices?
 

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hi guys.....".the bike wont start or run unless its on choke............,i'm guessing there is a problem/blockage with the pilot jet ...........it pops n backfires with the choke in ......... could it still be slightly blocked?......
Your guess is correct. The pilot jet/circuit is still blocked.

Remove the pilot screw and pilot jet.

Check the hole in the center of the jet to make sure you can see light through it.

This is a photo of the main jet...posted to give you an idea of light through the hole.

The pilot jet hole is much smaller.




With the pilot screw and jet removed, spray carb cleaner into both holes.

There is a tiny hole in the throat of the carb where the spray should come out.




Wear eye protection. The spray may splatter back towards you.

You can purchase new jets online from Partzilla or you local Yamaha dealer.

While you are at it, check that ALL the holes in the emulsifying tube are clear.




jb
 

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My bikes are 2014's, I've had several blockages in the pilot jets after letting them sit for as little as 1 month. Some hard obstruction forms in the jet I think from the gas formula. I used a piece of stranded copper wire to clean one and tried soaking one in vinegar overnight. Now I have #34 pilot jets. It's good to have replacement pilot jets because the hole is so small. I may buy gas welding orifice cleaning wires. Try seafoam too.

Screenshot_2017-04-19-11-51-18.png
 

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Discussion Starter #6
its seems to have cleared now, used a pin and lots of air gun action, installed it and worked like normal, didnt seem to be and different looking through the jet but i guessing the smallest particle will have an effect.


thanks for the assistance

p.s.... don't get sea foam here, what is it?
 

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