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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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#5 ·
Thanks for taking the time to write this up for people Shadetree.

I want to see your post how to synchronize your carbs on your Magna's! lol, especially if their a CV type of carb,which I don't think yours are for the year of your bikes.(now those are fun to sync!)
 
#7 ·
it means to tighten it down..as in screw it down to where it stops..this is what seat the needle means.
 
#8 · (Edited)
Congrats. The longest run on sentence at the forums that I have ever seen...lol

Just a joke. I know what shadetree can do and does do. Nobody has to remind me. He and I made a trade after driving 5 hrs one way. He contributed a 96 trx300fw and I contributed lots of green. Relax, it was just a joke. Shadetree and I talk from time to time. If he has a problem, he will let me know! Lol
 
#9 ·
Well we are at it again. 04 TRX400 FA. Can't fix it. Can't stop it from flooding on the idle circuit.
Choke plug was changed. Cable was changed, badly rusted. New float needle. New spark plug.
Rebuilt head. Will not idle. Rev it up and runs not bad. When it tries to idle it fires about every
6 - 8th time around. Shop is so full of gas fumes in 30 seconds you have to leave. This carb was BAD when i got it. Anyone got a used carb for this thing ? Any ideas ? I'm wondering if it is not an ignition problem. Thanks in advance.
 
#10 ·
check your timming..sounds like your timming got off. you say you rebuilt the top end..you may have your timming off on your bike.
 
#12 ·
Just follow Shadetree's instructions. Most ATV carbs work basically the same way.
 
#15 ·
Great write up, thank you for taking the time to share!

I have a 2003 rancher 350 4x4 (if it makes a difference). I just rebuilt the carb with a kit from Moose. I followed the online manual here (that is just a fantastic download).

Anyhoo the "pilot screw" on the bottom of the carb was set at 1 and 1/4 full turn in. I installed the new one at the same setting. My question does anyone know what the correct setting should be? After reading this thread I think I need to open it another full 1 and 1/4 turn.
 
#16 · (Edited)
The initial setting for you carb is 1-3/4 turns out. That's just a starting point and should be close enough to start and run OK at that setting. After warming the engine up, just fine tune the adjustment until you get the smoothest idle. I usually just turn the screw in one direction until the engine starts to stumble and then I turn it the other direction until the engine starts to stumble. Count the number of turns in between stumbles and center the pilot screw in between. Some people will turn it out just a hair more to make it a little richer, but I always just aim for the smoothest idle since the pilot screw does very little over idle anyway. All engines won't have an exact setting, they will differ.
 
#18 ·
Thank you for the tutoring Helmut.

The machine idled pretty good at start up, but I will do as you said once the new rings arrive in a few days.
thanks for the comment..as for your pilot jet screw..i hope you made sure you got all the old parts outta that tiny hole ??..sometimes it's a pain to get that tiny o-ring out..if you left it inside the carb..it will throw your settings out of wack..as for the turns out..helmut has you covered.
 
#20 ·
#23 ·
Thank You Helmut, I already have D/Led that manual.
I am not much of a mechanic so need all the pictures I can get ( and instruction) that manual doe's not have much of a break-down or exploded view of the carb. and I'm not having any luck finding one on the web.
Guess my next move will be to take it to the locale small engine shop, would rather do that than take a chance on screwing something up myself from lack of knowledge.
 
#24 ·
Will this help? It's all I could find.


 
#25 ·
can anyone help?

stock 2000 400ex purchased about a month ago. quad ran great and is deff the best quad ive owned. it was leaking gas out of the hose on the bowl. the screw on the bowl was tight so i was told it was possible the needle valve. so my buddy has this great idea to have me get a rebuild kit and clean the carb all out and then put new jets and needle valve in.

we took it all apart put new main jet and pilot jet in and also a needle valve. the main jet screws into a tube the goes into the carb, we replaced that as well.

my quad now will not idle and will only run with choke wide open and giving it gas and it smokes a lot. can anone please help me as to what i need to do? something obviously is not right!
 
#26 ·
can anyone help?

stock 2000 400ex purchased about a month ago. quad ran great and is deff the best quad ive owned. it was leaking gas out of the hose on the bowl. the screw on the bowl was tight so i was told it was possible the needle valve. so my buddy has this great idea to have me get a rebuild kit and clean the carb all out and then put new jets and needle valve in.

we took it all apart put new main jet and pilot jet in and also a needle valve. the main jet screws into a tube the goes into the carb, we replaced that as well.

my quad now will not idle and will only run with choke wide open and giving it gas and it smokes a lot. can anone please help me as to what i need to do? something obviously is not right!
not sure if you fixed your problem ?..but...your problem is your idle jet ?..or the hole it goes into is stopped up. remove your idle jet..and hold it up to a light, you should be able to see through the center of it ?..if not ?..then it has trash in it. it does not take much at all to stop the idle jet up. spec if your tank has rust or trash in it. the idle jet is the smallest jet out of all the jets..this is why they are a big problem in keeping clean. install a inline fuel filter..this keeps alot of trash from reaching your carb and jets.
 
#27 ·
I just finished rebuilding the carb on my son's 2006 TRX90. The slow jet was completely clogged. It idles now (YEAH) but still runs crappy at the top end. The revs pulse up an down at full throttle and there is an annoying latency between hitting the throtttle and engine response. When I was cleaning up my workspace, I found the part pictured below. Anyone know where this goes?

 
#28 ·
I just finished rebuilding the carb on my son's 2006 TRX90. The slow jet was completely clogged. It idles now (YEAH) but still runs crappy at the top end. The revs pulse up an down at full throttle and there is an annoying latency between hitting the throtttle and engine response. When I was cleaning up my workspace, I found the part pictured below. Anyone know where this goes?
Yes, that's your needle jet. When you unscrewed the needle jet holder, it must have fallen out. The needle jet holder holds it in the carb. The needle jet holder is the part that your main jet screws into.
 
#29 ·
thanks shadetree but does this work for 2000 400ex as well cause i want to clean my carb up too but i think its gonna be a little tricky doing it
 
#30 ·
welllllllll..first..i'm not much into sport atv's ??..buttttttt..most carbs are all the same..they still have the basic parts..idle jet..main jet..and pilot jet needle..the only difference is where they may be located in your carb ?..but they work the same way. hope this helps ya.
 
#33 ·
If I remember correctly, the narrower, longest end goes in first. It should go through and you should be able to see the top of it through the bore of the carb. It will only fit correctly one way. If it doesn't fit snugly in the hole and protrude into the carb bore, turn it around.
 
#35 ·
You're welcome.
 
#36 ·
i recently did a carb cleaning on a 96 fourtrax300 because gas was leaking out the overflow like crazy and it wouldnt idle properly, well now those problems are solved but i messed up somewhere because it wont rev up when the choke is all the way off, when the choke is on it will rev fine but i dont know where to adjust this. please help.
 
#38 ·
Thanks for the info....Im gonna give it a try....I have a 1992 300 Honda TRX 4x4.....Works great when it works..For some reason, your driving along and bang,stops dead...Leave it sit for abit, and sometime starts right up....But lately, hellish to start first thing in the morning....Pump the hell out of it and eventually starts..Once started for the day, starts first kick. But next day, same hasel. Choke cable replaced. Pull plug and its dry....Not drawing its gas. Had no choke cable for awhile and hole was siliconed....Figuring theres a jet blocked with dirt or silicone....I,ll clean it out and let you know...Wish me luck...I've wore out 2 set of starter brushes this year. :(
 
#39 ·
have a 2000 Rancher 350 2x4. It had been sitting up for about 3 years. I put a new battery in it and got it started, but it ran rough. I took the carb off and cleaned it out, pretty much just as described in shadetree's instructions. The engine starts and runs great, but now it leaks gas out of the carb drain. The float and needle looked fine. I took the float off and put it in a cup of gas and it floated just fine, and did not bubble when I held it under. After I put the float and needle back in, I held the float up with my hand and had someone pour a little gasoline in the inlet tube. The gas didn't flow, so that leads me to believe that the float and needle are working as they should. But I still have fuel leaking out of the drain. Any idea what the problem could be?
 
#40 ·
have a 2000 Rancher 350 2x4. It had been sitting up for about 3 years. I put a new battery in it and got it started, but it ran rough. I took the carb off and cleaned it out, pretty much just as described in shadetree's instructions. The engine starts and runs great, but now it leaks gas out of the carb drain. The float and needle looked fine. I took the float off and put it in a cup of gas and it floated just fine, and did not bubble when I held it under. After I put the float and needle back in, I held the float up with my hand and had someone pour a little gasoline in the inlet tube. The gas didn't flow, so that leads me to believe that the float and needle are working as they should. But I still have fuel leaking out of the drain. Any idea what the problem could be?
if your float needle and seat are working like they should as your saying ?..then your drain screw on the bottom of your carb is not sealing ?..this also lets fuel drain from that same over flow nipple on the bottom of the carb..they all are tied together. if your drain screw is working as it should ?..then your float needle is not sealing right.
 
#41 ·
s.o.s....I got a 1998 300 fourtrax ...had it running good then I took off air cleaner lid...it stalled and now it won't start at all...anybody have any ideas where to start looking???????...drained gas out put new gas in same result...it will turn over put just wont fire...have spark even changed plug....help please....thank u
 
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