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How to clean a carb

126K views 100 replies 39 participants last post by  Laceycamille212 
#1 · (Edited)
Ok, i've seen this problem come up alot lately....sooo..i thought i'd post a thread on how to clean a carb. now..first off..let me say..not everyone will have the same carb !..sooo..with that being said..let's move on. first..turn your gas off on your tank, next..loosen the intake boot screw to the cylinder, and also the intake boot from the air box to the carb, now..if you own a trx300 ?..( makes no difference what year )..on the right hand side of the carb..you will see a tiny screw holding the side cover on the carb, remove it..next..on top of that same side of the carb..you will see a 10mm nut..this is your throttle cable tie down nut...loosen it...now remove the side cover...reach in..and lift the throttle cam up..as your doing this..lift the throttle cable's end out of the cam...now on the left top side of the carb..is your choke knob..it's a 14mm..loosen it..remove it..becareful not to strip the threads..it's plastic !!..pull the choke out of the carb..you should now be able to remove the carb from the bike ..now..take it over to a good clean..wel lighted area...a nice work bench does wonders !..if you happen to have a bench vise ? ( these come in very handy at times ! )..put the carb in the jaws of the vise upside down..you should now be looking at 4 screws holding the float bowl on ?..if your not..you have your carb right side up..lol. now..remove those 4 screws..lift the bowl off the carb..your now looking at the guts of your carb..there is roughly 3 jets your looking to find ?..your main jet is the tall brass one..your idle jet is the small jet down inside a holder right next to it..there is a starter jet..( on some models..they are on the side of where the rubber plug is )..on some models..they are sitting right where that rubber plug is. now..with a flat head screw driver..remove the main jet from the carb..you can also use a 7mm socket to remove the whole assmebly..this is how i do it...as you will need to clean the whole thing..lay it on the bench..now..with a narrower flat head screw driver..remove the idle jet from the carb..lay it on the bench. now..with a very small screw driver ... a jewlers screw driver works great..or you can even use a small spoke from an old motor cycle wheel..anything that you can use as a punch..thats small enough to tap the float's holding pin out. after you get the float's holder pin out..pull the float and float needle out..becareful not to loose or drop the float needle !..lay it on the bench. now..on one side ( depends on which way you got your carb in the vise ? ) there is your pilot/fuel mixture screw sitting on the outside of your carbs float bowl....as we have mentioned..count the amount of turns you go inwards lightly !.but..in this case..were not gonna cover that..( that part is covered later )..remove the pilot needle..be very careful when you remove it !!..there is a tiny washer that some ppl drop..and the cats drag off..and never see them again !..lol. now..if your lucky ?..when you remove this needle..you will get all the parts out at once !..if your luck is like mine..you always get the tiny o-ring staying in the bottom of that hole !..lmao....if it stays in there..try to dig it out with some kind of pick..a mechanics pick works great !..after you get that out..look to see if you missed any jets still in the carb ?..most times..i leave the starter jet ( the tiny jet that's either where the rubber plug is ?..or on the side where the rubber plug is ?..i hardley ever take this out..as most try to strip out when removing them !..but if you can get it out..all the better !..now..if your carb has that rubber plug..remove it. ..take the carb out of the vise..flip it right side up..remove the 4 screws from the top cover..as you get down to getting that last screw out..the top will want to spring off..this is because it's got a large spring under it..hold the top down..as your removing that last screw..now lift the cover off..remove the spring..lift the main jet's plunger out of the carb..it's round..and has a rubber diaphram around it, now..with your carb spray cleaner..spray down inside the top..all the holes..everything..BE VERY CAREFUL NOT TO GET THIS IN YOUR EYES !!..IT BURNS !..LOL..sooo..please wear safety glasses !!..with your air compresser..blow the carb out really good..every nook and cranny you can stick that air too. ok..now comes the hard part..as this will make or break your carb cleaning..lol. grab your main jet..with some wd-40..and one wire from a wire brush..spray the main jet down..work that wire through the middle of that jet...then with some air..blow it out..if you got a bench grinder...and has a wire wheel on it..this next part is a breeze..if not..your gonna have to do it old school..depending on which way you go..i use my bench grinder with a wire wheel..( faster !..lol ) i clean the outside of the main jet holder..as you can tell..this has a few small holes on the outside of it ??..these have to be cleaned..carb cleaner ( gum out )..and that wire..poke it through the holes..then blow it out with air. now..grab the idle jet..and do the same thing to it. inspect your float needle..is it dirty ?..gummed up ?..if not..leave it alone. if it is..try taking some very fine steel wool..and lighty.. AND I MEAN LIGHTLY..scuff the outside of the needle..do not rub the tip !!!..now comes the easy part..putting it all back together..and i'm sure you know where everything goes ??..if not..main jet goes in tall holder..idle jet goes in right next to that..and if you removed the starter jet..that's easy to see where it goes..now..lay the float assembly back in the holder..slide the float's holder through the tabs..put the bowl back on..flip the carb right side up..slide your main jet plunger back down in the carb..make sure you put the rubber part back in the right way..there is a round outter part..with a tiny hole in the middle of it..slide the big spring down in the top..place the top on..while holding the top down..get a screw started..then put the other 3 in. now..turn the carb back over upside down..remember that jet needle that had the tiny washer that the cat draged off ?..slide the spring on..then the washer that you had to fight the cat to get back..then the tiny o-ring..put the needle down in the carb..turn the needle down all the way..go very easy..do not over tighten it !..if you break the tip off in the carb..your screwed !..lightly seat the needle down in the carb..now back the needle out 2 1/2 turns..count the turns as your watching the very end of the slot in the screw..so you will know when your turns are 2 1/2 turns out. now put the carb back in the bike. i hope this helps everyone out. if you own a trx250..the top of the carb is flat..3 screws hold it on..this is a little different set up. id get into that..but thats another chapter..lol. added : don't forget to clean the float needle seat with some carb cleaner spray and a Q-tip !..very important.
 
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#46 ·
I have read your post on the carb rebuild, and I understand it, but I have a question about the Air cut-off valve, and can't find anything on it with a search. I had to change the choke cable and decided to go ahead and change the throttle cable too. I have a '03 350FM Rancher. I bought it used and it was in great shape and haven't had any problems with it for 5 years, till the choke cable housing on top broke. I have a bunch of experience with carbs and never had any problems but found mud in the carb housing where the choke cable went into the carb, so I decided to clean the whole thing. I went to the manual to get the float level and other specs, and saw this "Air cut off valve in the tear down view. Mine never had this part even on the bike at all. The area was dirty where the part is supposed to be but when I looked closer I found an O-ring so I'm guessing it had one on it at one time. So I guess I'm asking if it is a common thing to remove this part and if it's not there what does it do to the operation of the carb. It has run great since I got it except it was kind of hard to start cold. I have had a few hondas and everyone was hard to start cold so I didn't pay much attention to it. When I found the mud I figured that was part of the reason. I hope you can help me out with this situation. We use this bike for yard maintenance and the cut grass is piling up. Thanks -Foxxy-
 
#51 ·
Hi everyone, sorry to vring this back up, but I do have the trx250x and I know the carb is dirty as all get out. I consider myself pretty handy with things like this but witH this being my first, I'm a bit nervous. Any help on the directions step by step like this would be much appreciated!
 
#52 ·
I guess it's my turn for a carb question
My 96' 300 is not running properly. It stays at my dad's in his shed .. so being winter it's very cold with large temp changes. It won't idle correctly and is hard to start .. seems like the choke is stuck ?? I get it home to my place and in my heated garage it runs fine .. choke come on and off properly. Wonder if it's freezing ? I have a new cable to install and a new choke valve incase I need it. I also might disassemble the whole thing and clean it but just a little nervous of making things worse. Something to note I did as a new I think it's a UNI air filter .. removed old set up and just stuck it on the end of the intake hose in the filter box. Don't thin this is the problem but thought I'd mention it. Ran fine for months after I originally put it on.
Any info helps guys!
 
#53 ·
I guess it's my turn for a carb question
My 96' 300 is not running properly. It stays at my dad's in his shed .. so being winter it's very cold with large temp changes. It won't idle correctly and is hard to start .. seems like the choke is stuck ?? I get it home to my place and in my heated garage it runs fine .. choke come on and off properly. Wonder if it's freezing ? I have a new cable to install and a new choke valve incase I need it. I also might disassemble the whole thing and clean it but just a little nervous of making things worse. Something to note I did as a new I think it's a UNI air filter .. removed old set up and just stuck it on the end of the intake hose in the filter box. Don't thin this is the problem but thought I'd mention it. Ran fine for months after I originally put it on.
Any info helps guys!
start by cleaning the carb, then make sure you drain and flush the old gas out of tank !..then it should run like new !.
 
#55 ·
most times when I pre-set my pilot screw to factory settings ?.I never have to mess with the carb unless I need to idle it up or down ?..and I can do this with the gas tank on the atv.
 
#56 ·
I just clean and put a rebuilt kit into the carb of my 96 300. When I installed the slow jet it seemed to screw in way past what yours did in the video. It also didn't seem to bottom out so I stopped turning it in. It's the same size as the original I took out. The carb in the video is the exact same as mine. Kinda making me curious .. hope I didn't miss something, however I don't think I did. I also hope it's screwed in far enough or for the matter not too far even!
I posted this on the post that has the 3 videos on doing a 91 carb clean. Perhaps I should have posted this here!
Newbie
 
#57 ·
I just clean and put a rebuilt kit into the carb of my 96 300. When I installed the slow jet it seemed to screw in way past what yours did in the video. It also didn't seem to bottom out so I stopped turning it in. It's the same size as the original I took out. The carb in the video is the exact same as mine. Kinda making me curious .. hope I didn't miss something, however I don't think I did. I also hope it's screwed in far enough or for the matter not too far even!
I posted this on the post that has the 3 videos on doing a 91 carb clean. Perhaps I should have posted this here!
Newbie
I did not make a video ???. without seeing your parts from the kit ?..and how you removed everything ?..I can't tell what you did ??..lol. and are you sure your carb is an oem Honda carb ??????..I have seen too many ppl buy china knock-offs from ebay !!..lol.
 
#60 ·
it's brass, it won't break down inside ?, but you can strip out the slot on the top ?. you must make sure you have it screwed down all the way ?..or the carb will not work right ?. take the idle jet back out, tab some grease on the threads of it, then screw it back down in there. you don't have to force it ?..but you need to make sure it's screwed down all the way.
 
#61 ·
I took the carb apart and got it tightened down. I also bought a new choke cable however after over an hour of trying to install It I gave up. It's a Honda part but slightly different then the on that was in it. It has a rubber boot on the end which attaches to the choke lever on the handle bars. I don't see how it would ever go in there. What a time I had getting the other one out and back in. I have the repair manual and I couldn't see anywhere in it explaining how to change it out. I did remove the clip but you almost have to work the playing almost breaking it to get it out. I lubed it up well and put it back In after I couldn't get the other one in. Hopefully there wasn't moisture inside that will work down into the valve which could have been the original issue. I lubed it up well. All seems good when I started it ... just have to let it run and possibly play with mixing screw. Fun fun!
 
#62 ·
lol..its easier and faster to start at the handle bars choke lever !!. you install the choke lever at the bars with the carb's end not together !!..then you install the cable and valve at the carb's end. this gives you enough slack to get the cable into the lever.
 
#63 ·
That must have been where I went wrong. I didn't have it into the carb but I did have the valve on the end. Like I said the cable does seem different on the handle bar end with a rubber boot that seems to be in the way of going into the assembly on the handle bars. I will try doing the new cable again tmr. With the old cable in which seems o slide fine when it's out still seems sticky when accuated. I wonder if I should apply some grease to the valve body to help it move in and out easier. It is a brand new valve.??
 
#64 ·
That must have been where I went wrong. I didn't have it into the carb but I did have the valve on the end. Like I said the cable does seem different on the handle bar end with a rubber boot that seems to be in the way of going into the assembly on the handle bars. I will try doing the new cable again tmr. With the old cable in which seems o slide fine when it's out still seems sticky when accuated. I wonder if I should apply some grease to the valve body to help it move in and out easier. It is a brand new valve.??
that little rubber boot won't stop it from hooking into the lever at the bars. wont hurt to grease the valve before you install it in the carb, don't need a lot though.
 
#65 ·
See pic
I don't see how there is room for the little metal band plus the rubber to fit inside the choke lever assembly. The brass colored part is what the retaining clamp hooks onto. This being said all of what I just mentioned has tk fit inside there ... I don't know it's possible or how it would even be able to accuate. I'll have to look again when I get home from backshift !
 

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#66 ·
See pic
I don't see how there is room for the little metal band plus the rubber to fit inside the choke lever assembly. The brass colored part is what the retaining clamp hooks onto. This being said all of what I just mentioned has tk fit inside there ... I don't know it's possible or how it would even be able to accuate. I'll have to look again when I get home from backshift !
starting at the lever on bars, pull the cable out as far as it will come out, hook the end into the lever, swing it around..fit the cables thin part through the outer end of the housing, you should still be able to slide the housing back and forth to put the metal clip over the plastic housing..and the center part of the clip, clips over any of the grooves on the brass part, the closer the groove to the plastic housing ?, the more the cable pulls from the carb end. sooo..you may need to leave the clip off until you get the choke into the carb, then adjust the clip to grooves. if for some reason the rubber boot won't let you attach it at the lever ?, peal the boot off, no biggie if its not on there ?. but it should work with it on there.
 
#67 · (Edited)
following somebody else and doing the work left behind

got to rebuild rebuilt carb. shop got paid, i pay for a lesson, got to do was not. soo i got a few questions;
1. any difficulty taking out heater assy. in case i want to soak? pilot screw only had one o-ring. the diagram looks like 2 0-rings and a washer. [part-zilla]. 3. rubber plug just about fell out. rot. its not in repair kit. can i improvise? 4. is it necessary to have pump kit? i want to just block that part off with plate and gasket.
i never have used pump when it did work. i blocked it off before, but did not use gas proof gasket, hence weeping gas leak. the pump kit cost $50. dollars that i wont have. Well; enough about my financial burden, can i just block it off? If i can take a shortcut that will work im ready for it. ;~)
 
#68 ·
got to rebuild rebuilt carb. shop got paid, i pay for a lesson, got to do was not. soo i got a few questions;
1. any difficulty taking out heater assy. in case i want to soak? pilot screw only had one o-ring. the diagram looks like 2 0-rings and a washer. [part-zilla]. 3. rubber plug just about fell out. rot. its not in repair kit. can i improvise? 4. is it necessary to have pump kit? i want to just block that part off with plate and gasket.
i never have used pump when it did work. i blocked it off before, but did not use gas proof gasket, hence weeping gas leak. the pump kit cost $50. dollars that i wont have. Well; enough about my financial burden, can i just block it off? If i can take a shortcut that will work im ready for it. ;~)
(1), easy to remove heater from carb, unplug it from the harness first, then use a 14mm wrench to unscrew it. (2), yes, the pilot screw has 2 O-rings, one of them is very tiny, always at the bottom of the pilot needle if your holding the carb upside down ?, the other o-ring that goes on it, slides on the end where the screw slot is, it seals the pilot needle once you have it down in the carb, and set correctly. (3), that rubber plug is very important..you must have it in order for your carb to work right !. if your hurting for cash ?, try this, find an old ink pen, pry the top of the pen out, it's just a plastic piece that is stuck down inside the pen, most clear ink pens still have these, I've never used them ?, but I hear and read people have tried it, and it has worked for them ?, soo..thats a gamble on your part ?. you may need to use something to seal it good down in the hole ?, i'm not sure ??, or it maybe a perfect fit ?. (4), no..you don't have to have the primer pump knob if you don't ever use the primer ?, yes..you can block it off, but make sure you seal it very good !!!. when I am sealing something that comes in contact with oil or gas ?, I use a product called '' seal all '', I buy it at advanced auto parts, it was about 9 bucks a tube ?, some very good stuff !!!.
 
#69 · (Edited)
parts parts parts

i think i got the pilot screw set up right. it only had an o-ring and a spring when i took it out. i got from the outside, o-ring, spring, small metal washer, small o-ring. there is small skinny o-ring, an small slightly thicker o-ring, which is the right one? the air cut valve; how to clean and check it? i dont want to mess it up.
 
#70 ·
i think i got the pilot screw set up right. it only had an o-ring and a spring when i took it out. i got from the outside, o-ring, spring, small metal washer, small o-ring. there is small skinny o-ring, an small slightly thicker o-ring, which is the right one? the air cut valve; how to clean and check it? i dont want to mess it up.
spring goes on first, then small washer, then tiny o-ring. as for the air cut-off valve ?, I never mess with them, they don't fail much at all.
 
#73 ·
i had it right the first time, just didn't explain my self well. thats why i got to do sooo many edits when i write. geting the stuff back out of the pilot hole[ washer, o-ring] when put in wrong, sends me to the part store. small washer dont like to be messed with. bent. pliers flattened/expanded it out an split it when i tried to straighten it. i'm use to myself, so i dont cuss anymore. just smile an go on with it. much thanks again. Ed ;~)
 
#74 ·
i had it right the first time, just didn't explain my self well. thats why i got to do sooo many edits when i write. geting the stuff back out of the pilot hole[ washer, o-ring] when put in wrong, sends me to the part store. small washer dont like to be messed with. bent. pliers flattened/expanded it out an split it when i tried to straighten it. i'm use to myself, so i dont cuss anymore. just smile an go on with it. much thanks again. Ed ;~)
anytime ed :).
 
#75 ·
well; do to impatience[15 minutes more, before i jumped the gun], i destroyed that tiny washer, on the pilot valve. i could only see the finish line, and not wait for the reply to my question. i needed other parts anyway, why my rush, the e-mail would come, Let's skip that part. its too sad. The kit with that small washer it about $17. then add gas money to get it you are pushin $25. thats a lot for stupid. after 60 years i ought to get a break besides a bone. got a i.d. and o.d. for that small washer. I am thinking hardware, radio shack[circuit board washers], things made in japan that are tiny, use tiny parts? if i can find those kid toys from mc donalds etc. i just had throwed those walkie-talkies from 45 years ago. you could stand under a phone line and hear people talk. it was funny back then, but aint much more entertaining then a commercial or a reality show now. //Ed
 
#76 ·
1way valve

how much air pressure should close the one way valve? i wouldn't think it would be much. less than what it takes to close my old one though.
 
#77 ·
how much air pressure should close the one way valve? i wouldn't think it would be much. less than what it takes to close my old one though.
what valve are you speaking of ?..on the carb ?..if so ?..this shouldn't take much. I've never bothered with them, they never go bad in the ones I've dealt with.
 
#81 ·
it seems good so far. it starts better, though there is a hint of skip every so often. it is a lot smoother with gas and shifting. on the asphalt, with slight incline, 43 up, 46 down. road is getting worst, i didnt want to push it much more and i am on very limited funds so i still get front end issues to resolve. i never got past 48 mph 7 yrs ago. found my clymers manual and it has good pictures of carb dismantle, with pilot screw spring and o-rings + washer as you would install them. service manual also has good pictures. neither has timing in the index or any great detail that i have found yet. you would think it would be more important. timing is everything.(Deep) (take a deep moment) in a bit i'll either confirm or deny my progress. time is relevant. ;~)
 
#82 ·
its starts and takes off mostly; then other times; there is that skip, or it does not want to accelerate when i first give it gas, an i think the accelerator pump is not working on the carb or the vacuum advance is not working or maybe the distributor needs turning 3 to 10 degrees... of course that does not apply. i did read in the clymers or shop manual or somewhere that the diaphragm can wear, an mine looks like some wear on that cylinder part of it. near 5000 miles, which means more hours. that is my next move. nothing lasts for ever. //Ed
 
#83 ·
rubber plug missing for carb kit replacement

i had to take carb apart because of float needle sticking a bit. my repair with paper gasket didn' pan out. plug was loosing bits of rubber do to old age. soo i took a brass flat head screw that would fit in the hole, an o-ring, that filed off the top of the screw so it barely put pressure on the o-ring, and i could tighten down the float bowl.
i had a shut off problem also and finally got a new one. something i should have done in the first place. i took the old one apart. the seal/ gasket with the 4 holes was also losing bits and pieces as it finished out its life, and heading towards the carburetor. there is a rebuild kit on e-bay for 9 bucks, its probable made in china, and that says a lot about doing extra work and time when you could just get it done. some get lucky buying from china. bad luck mostly. //Ed
 
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