Join Date: Feb 2010
Location: north little rock, ar.
Liked: 1790 times
how to over haul a trx250 carb ( not for trx250 recon's ).
Ok, as some of you know..i posted a carb cleaning on a trx300 awhile back, and like i said back then..i would do a follow up on a trx250 utility carb..sooo..here you are !..i'll try to cover as much as i can..but i can tell you right now..it's almost the same as the trx300..exceptttttt..with a few changes in carb design..and jet sizes !. ok..ya'll already know the basics of the lower part for the bowl..jets..float..so forth..soo..i'm gonna skip that part..as you should know ??.. onto the process..on the trx250 carb..the main thing that is different..is the throttle cable side...and the top side..these two thing's alone...are the main difference between a trx300..and a trx250 utility carb..on the right hand side of the carb..once you remove it..you will notice there are two seperate parts to the throttle cam..and the top part..which i call the slidder that operates the main jet needle...we'll skip this part for right now..and come back to it..for now..we're gonna start with the top....oh..and i highly say..have a carb rebuild kit before you start any and all work on any carb !!..any way..find you a well lit lighted clean area....have a phillips screw driver..standard screw driver..some gum out carb spray cleaner <--- i use this alot..and i know it works !!. now..remove the 3 phillip screw's from the top..set the top off to the side..pry the old gasket off ( if your lucky enough to still have one on it ? )..throw it away..now..on the top of your slidder cam..you see that phillips screw ??..it moves with the butter fly when you raise and lower the throttle cam..remove it..now..see that plastic thing with a spring wrapped around it..and it's hooked to the upper cam part..and the other end is hooked to the arm inside the slidder..raise the slidder up enough..to pry the spring off the arm inside the slidder..once you do this ?..you should be able to lift the slidder out of the carb's bore. once you get the slidder out..look down in the very bottom of the slidder..see those 2 small phillip screws ?..they can be a pain to remove..if they have never been out ??!!..once you remove them..that metal arm will come out of the slidder..now just push..or dump the main jet needle out of it. if you notice..it has or should have !!..lol..a tiny c-clip..and it SHOULD BE ?!..clipped into the middle groove of the main jet needle..AS THIS IS THE STOCK SETTING!. there are 5 grooves..the middle groove is where your gonna put the new c-clip that came in your carb kit..back on the new main jet needle. new clip on..main jet needle stuck back down into the slidder..start one of those small screws through the metal arm..and try to hold it in place..as you stick it back down into the slidder..get it in..then do the other..once this is done, lay it off to the side. now flip the carb upside down..remove the 4 screws that are holding the float bowl on, remove the gasket from the float bowl..trash it, remove the baffle around the main jet..very carefully..tap out the metal round pin holding in the float, remove the float needle..trash it..lay the float off to the side for now. remove the main jet and main jet holder ( it's the tall one ).remove the idle jet..( it's right next to it )..but down inside the hole, remove the black plastic rubber plug..DO NOT TRASH THIS !!.YOUR GONNA RE-USE THIS..AND IT DOES NOT COME IN A KIT !!. see that small jet on the side of the carb body near where the float was hanging ?..some of these come out easy ?..and some do not wanna budge !..sooo..this is your call..you can try to remove it ?..or leave it ?..i never bother with them..as most never wanna come out..they just strip out when trying to remove them !. ok..so far...so good..now..flip the carb right side up..with the top still off..and the slidder still out..with something small enough..and long enough..stick it down until it rest on the main jet's brass seat..DO NOT USE ANYTHING BIG HERE PPL !!..IF YOU DO ?..YOUR GONNA WEDGE THE SEAT..AND IT WILL NOT COME OUT !. ok..with what ever your using..lightly tap it down..it should fall out the bottom ????. unless you wedged it !!..lol. after it's out ?..on the outside of where the float bowl is..notice the pilot jet needle ?..seeing how your gonna replace all of it ?..we won't worry about the setting's for now..remove the pilot jet needle..when you take the needle out..you should have a spring..tiny washer..and then a tiny o-ring..most washers and o-rings always stays in the hole..you gotta dig them out !!!!..make sure you get them out !!..they are not easy..but it can be done !!..once they are out ?..you should have every part off the carb by now ??..take your gum out carb spray cleaner...and with the straw in it..spray every nook and cranny you see..all holes !!!!..PLEASE WEAR SAFETY GLASSES WHEN YOU DO THIS !!..IT BURNS LIKE YOU KNOW WHAT ! ( don't ask me how i know ! )..lol. spray the jets holes..choke enrichment hole..every part of the carb..top to bottom !. guessing you have a air compressor ?? ( you need to have one right now ! )..comming in behind that carb cleaner..blow out every hole..just like you did with the carb cleaner !!!. now..just start putting it all back together..when you get to the pilot jet ( air fuel mixture needle )...needle..spring..new tiny shinny washer..then new tiny o-ring..there also should be a o-ring that goes on the very screw end of the pilot needle ?..make sure you put the right one on it !!.hold the carb right side up.start the pilot needle..once you get it started..lightly..AND I MEAN LIGHTLY..seat the pilot needle all the way down..when you start to feal the needle get tight ?..DO NOT GO ANY FURTHER !!!..if you do ?..your gonna break the very tip of that needle off in the carb..AND YOU JUST RUINED YOUR CARB !..YOU WILL NEVER..EVER..GET THAT TIP OUT !. once that is done, back the screw out 2 1/2 turns..this is a pre-settings for now..new float bowl gasket on the bowl..remove the main jet from the main jet holder..install the new main jet into the holder..you may want to clean it with some carb spray before you install the jet ?. now slide the main jet seat into the main jet hole, make sure you face it the right way !!, it should have the beveled top side facing down into the hole ?!, now install the main jet. install the idle jet..it's the smaller shorter one..it goes done into the hole right next to the main jet holder. if you removed the very small jet ?..install the new one..now get the float..install the new float needle on it..line the float up..stick and tap the pin back through.DO NOT HIT IT HARD..YOU COULD BREAK OFF THE FLOAT HOLDER TABS ON THE SIDES !!. once the float is in..put your main jet's baffle back in ( if you were lucky enough to have one ? ) black rubber plug back in..hold the carb right side up..start your float bowl..it's easier to do it this way..because you wont loose your bowl gasket !!..once you get the float started...flip it upside down..and finish putting in the remaining screws..snug them..do not over tighten them !! carb right side up..install you slidder..plastic part and spring..then screw on the very top through the cam and throttle lever..spring needs to be in the middle of the pastic ?.and hooked onto the grooves on the ends of the metal arms ?..new gasket..top..3 screws. so far..so good !..now comes the final part..on the right hand side of the carb..where your throttle cable goes..remove the idle screw..your kit should have a new long spring ?..trash the old one after you get it off..new spring on..lay it to the side for now..see that seperate part..where there is a gap ?..and it should only make contact with the butter fly once it rasies so high..your trying to get these two parts to hit each other as close as you can..by doing this..you may need to spread ?..or close the tang gap ?..what happends is..when you use the thumb throttle..you raise the throttle cam..when that goes up so high..it makes contact with the slidder's tab on the top..then it raises the slidder..which..is your main jet..the trick here is..YOU HAVE TO GET THEM TO WORK IN TAMDEN !!!..if you do not ????..then your air to fuel mixture will not mix right !!. once you think you got them set right ?..from the open end of the carb..where the butter fly is...work the cam with your hand..as your doing this..watch the butter fly and the slidder at the same time..your trying to get both the butter fly...and the slidder to open..and the slidder to go up almost at the same time !!!..they really need to be as close as posb !!!!. once this is done ??.install the carb back in the atv..and it will run like a new bike !. if it does not ?..then you did not do something right !!!..lol.f i left anything out helmut ?..feal free too add to this !..lol.
'89 trx350D foreman 4x4...'85 vf700c magna, '03 trx450fm foreman 4x4 , 2015 Yamaha waverunner fx cruiser ho, '05 trx500fm
Last edited by shadetree; 08-25-2012 at 10:24 PM.