Yamaha F2.5 carb adjustments

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Feb 16, 2017
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So I recently bought a 2003 F2.5 and whenever I rev it up it would bog down a bit, however if I pulled out the choke a bit it would be fine. So I took apart the carb and cleaned it out and it was dirty. The fuel filter was a mess, I used some fine wire to clean jet ports and compressed air. seems to be running better but if I pull out the choke 1/4" it runs a bit better, the air screws/ fuel screw. how do I adjust that? It seems to have a brass plate with a small hole in it covering the screw adjuster. do I remove that small cover? does it turn or pull out? Also if it runs a bit better with the choke out just a bit does that mean I need to turn it out(lean) or in (rich). thanks folks, I've run seafoam through it as well to clean any residue on internal workings
 

ondarvr

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The screw located under the plate is for low speed only, it won't do much at high RPMs. You drill, pry, stab or gouge at it until it comes out, then turn it either way until you get the best performance, normally it's just a small amount, if you need to turn it more than that it means the carb's still dirty.

​If it bogs at high speed and choke helps, it means it's running lean, so there's most likely still gunk in the carb, it's not uncommon to need to clean it a couple of times to get it all out.
 
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Thanks, right now its just low speed issues. the higher rpms is good. This is the second time I've cleaned it but just to be sure I ordered all new jets and fuel filter. the adjustment screw is the last thing for me to check. Love this form always sound advise, thanks again
 

ondarvr

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I have never had to buy new jets, they can be easily cleaned, the passage ways for low RPMs in the carb are typically the issue
 

99yam40

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If you never pulled the pilot adjustment screws out you never cleaned all of the passages.
count the number of turns in to lightly seated before taking them out so you know where to get them back to.
after cleaning properly
 
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If you never pulled the pilot adjustment screws out you never cleaned all of the passages.
count the number of turns in to lightly seated before taking them out so you know where to get them back to.
after cleaning properly

I'm attaching a pic of the carb, would you say number 15 or #5 is the screw you're talking about? I don't know how to remove the cap for #15
 

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99yam40

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run a self tapping screw into the hole you said was in there and pull with a pliers. just be careful not to damage the Pilots screw or move it ,so you know what it was set at
 
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99yam40 ondarvr thanks guys, got the pilot screw out and soaked the carb with everything removed. used carb cleaner before putting it back, then turned the pilot screw 1/4 maybe less to adjust and now its running perfect. turned it to the rich side and no more need for the choke out when running, Thanks for all the help I'm sure ill be asking more questions as I go.
 
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