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Old 06-16-2002, 05:42 AM
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Removing and Cleaning your XS11 Carburators

Removing and Cleaning your XS11 Carburators
by Maans Smit

Removing the Carbs

I take it your scoot is a standard model. Remove the seat by loosening the two bolts under the left and right sides of the seat and slide them to the front. Pick the back of the seat up and slide it back. Loosen the bolt holding the rear of the tank to the frame. Remove the two vacuum lines/pipes between the petcocks and the rubber carb boots (between the carbs and the engine). Now remove the fuel lines from the petcocks. You don't have to remove the other ends of the fuel lines where they are connected to the carbs. Now pick up the rear of the tank with your right hand, grip it in the middle top front (in front of the filler cap) with your left hand (it's pretty heavy if full of fuel) and remove the tank.

Loosen the two breather pipes between the carbs and the airbox, at the airbox. Again leave the pipes connected to the carbs. Hook the clutch cable from the ring bracket on top of the No 4 carb (you always count carbs/ cylinders/exhaust outlets, etc from left to right as if you're sitting on the scoot). Loosen the thick crank case breather pipe where it is connected to the airbox and tie it out of the way. Sit on the left side of the engine/scoot with a long thin flat screw driver in your right hand. Now put your left hand under the carbs in the middle front and push the connection/ spring action lever to which the throttle cable is attached up to relieve the tension on the cable. Now push the head/knobbie on the end of the throttle cable, that fits into a slot on the spring action lever, from the right hand side out of the lever with the screw driver. Now loosen the four clamps holding the carbs to the rubber carb boots (between the carbs and the engine). Also loosen the four clamps holding the carbs to the airbox behind the carbs. Now this is a trick I do with the airbox to keep it out of the way. First remove the two brackets and bolts on the left and right sides of the airbox where they hold the airbox to the frame. Mine has some corner like brackets. Next, at the top of the airbox there's a bolt/nut/screw holding the V-bracket to the frame. DO NOT REMOVE THE PHILIPS SCREWS HOLDING THE V-BRACKET to the airbox, or you'll have a couple of loose screws/nuts/ washers inside the airbox which is hell to re-assemble. Now push the airbox back with some force and put a thin Phillips screw driver IN FRONT OF the V-bracket into the hole in the frame where the bolt was that held the V-bracket. That gives you some space to move the carbs. I heard some folks actually loosen (not remove?) the screws holding the V-bracket, but I am too scared. I have a buggered airbox to prove that those screws are hell to re-assemble.

Now stand over the bike, grip the No 1 and No 4 carbs with the left and right hands and push the back of the carbs sorta down and then up again to loosen the bank of carbs from the carb boots. I always push the backs of the carbs down and they pop out of the boots. Move the bank of carbs out to the left but check for the spring lever (to which the cable was connected) to get past the top oil pipe connection on the engine. Mine usually come out either with the backs up or down, i.e. at an angle.

Dissembling the carbs:

I like to work cleanly, so I usually first wash the gunk off the outside of the bank of carbs before I start removing parts. The idea is to keep the insides of the four carbs separate. They must go back into the same carb they came out of. So put them in front of you on a biggish piece of clean paper/cloth the way they sit in front of you on the scoot. No 1 on the left and 4 on the right. Now just turn the bank of carbs upside down.

Now you're going to remove the float bowls which are usually the bottoms of the carbs. I like to first spray all screws/nuts/connections lavishly with WD 40 or a similar product to make things easy. Unscrew the four Phillips (or whatever screws - mine came with Phillips and I replaced them with cap/Allen screws) on the corners of each float bowl, slowly lift each one off and put them on the other side of the carbs in line with the carb it came from (so you'll have four carb bodies and their insides in four heaps in the same order they are on the scoot, so you don't mix them).

You'll see the float under the float bowl. It is held by a pin which goes through two posts which are part of the carb body. THOSE POSTS BREAK EASILY. Take a thin nail or Phillips screwdriver and softly tap the pin, from the side without a head, out of the post. You'll see you only have to loosen it a little bit and then you can pull it out from the "head" side. But be careful not to hit the post. If you brake the top part of the post off, you can have it aluminum welded/built up again. Take the pin on which the float swings with, so they can drill the holes the same as they were, otherwise your float will not be level. But rather be careful and not break it. Almost in between the posts under the float you'll see the needle and seat where the fuel enters the carb. Take the needle from seat and undo the seat with a ring or box spanner, rather not a flat/open spanner. When turning/loosening the seat with the spanner, see that you don't pull in the direction of one of the posts. If the spanner slips, you break a post. That's how mine broke. You'll see the seat has a minute dome like plastic filter which usually needs cleaning. In the middle of the float bowl space you'll see a copper/ brass "nut" with a hole through it. That's the main jet and the size is usually written on it. Unscrew it and remember to take its copper/brass washer with it. Next to the main jet is a silver looking screw for a flat screw driver. Unscrew it and take its washer with. Now take a thin flat screw driver cause inside the hole that was covered by the silver/aluminum screw, is the pilot jet which is about 10 mm long with (or without) holes in the side but with pin size holes at both ends.(BTW, on my 80 I could not get it to idle well, and eventually found that one of these pilot jets did not have holes in the side like the other three - so it seems it does matter that they are the same). The standard pilot jets are usually size 42,5. PLEASE NOTE: The pilot jets are also brass/copper and the screw driver slots on top of them mess up easily and then its hell to get them out. I had to drill one out. So when you put the thin screw driver in the hole, put some pressure on it and turn slowly. It helps to soak the jets in penetrating oil before you try and get them out. Especially if they haven't been out lately.

Turn the carbs around, put a thick cloth under them so the posts don't break or get damaged, and unscrew the screws holding the tops of the carbs/ diaphragm covers and remove them, the diaphragm springs and the brackets between the carbs. Slide the diaphragm assembly out (thin rubber like diaphragm with the slide) and needle. REMEMBER: These diaphragm assemblies cost mucho bucks (i.e. terrible wallet trauma), so handle with care and don't spray carb cleaner on them. I try not to even put fuel on the diaphragm. I just wipe it with a cloth dipped in fuel and wipe it dry immediately afterwards.

Turn the carb around again and look in the hole where the main jet came out. You'll see the "main screw" (according to the manual) but its really a seat for the needle in the diaphragm assembly. If it doesn't come out easily, soak it as well with the penetrating oil, and tap it from the bottom of the carb, i.e. the main jet hole, with a thin flat screwdriver (round the sides of the hole so you don't damage the thread for the main jet). Some people pull it from the top with long nose pliers but I don't like to come near the seat (for the diaphragm needle) with a metal object, so I don't scar it.

You don't have to disassemble the diaphragm assemble any further (diaphragm/ slide/needle), except if you want to check at which notch the needle is adjusted for your mid range fuel supply. I believe if the circlip is in the middle notch its standard. In the bottom notch is rich (needle sits higher) and the top notch is lean (needle sits lower - thus closing the hole in the seat more). There are only three notches on the needle. You have to remove a spring clip from the top of the diaphragm assembly to remove the needle assembly. Be careful not to damage the plastic "megody" with the two or three (can't remember) prongs for going into holes. It can go in only one way.

If you look at the inlet/airbox side of the carb body you'll see at 8 o'clock the air pilot jet that can be removed to be cleaned.

On top of the outlet side of the carb (small mouth which connects to the carb boot/engine) is the idle mixture screw (there are other names for this screw) which is the screw you turn to adjust your idle mixture, e.g. when you Colortune. It has a spring round it. First turn it slowly all the way in until it is LIGHTLY SEATED, and at the same time count the turns and write them down per carb (to get your idle mixture adjustment at least back to what it was when you re-assemble the carbs). If you turn this screw in too far it breaks off in the hole and you have a .....time trying to remove the stuck point. So be careful. If you want to get the settings of the idle mixture screws back to standard before you start adjusting with ,e.g. the Colortune, turn it in to a lightly seated position and then 1,25 (one and a quarter) turns out.

When you clean the carb bodies, open the choke and spray carb cleaner into all the holes. let it soak and then blow it out with compressed air. I also throw the jets and other metal insides of each carb in the float bowl and cover it in strong carb cleaner/wonder juice/whatever takes you through the night?? and let it soak for at least 6 to 8 hours. I also found that a wooden tooth pick soaked in carb cleaner helps to clean out the small holes in the pilot jet and other holes. metal things like sowing needles might just scar the sides of the holes. I also normally rinse the carbs afterwards in clean fuel before I start assembling them. Sometimes some of the dirt is blown against a corner or something inside the carb and comes out in the rinse. It's just something I do to play safe. Or you'll have to blow each hole in the carb from both sides with the compressed air.

If you want to dissemble the choke assembly or the bank of carbs further, shout and we'll explain. If your carbs differ in construction, and I believe the later models do, or I have left something out, will someone PLEASE add to/change the above, cause I don't know the new models and could have missed something. BTW, as a side line, I use baby oil (very thin) to oil the grooves in which the diaphragm seats in the top of the carbs, and the slides when I re-assemble the carbs. It works good. The oil doesn't get thick or gunky over time. You could also swipe your wife's machine oil for her sewing machine. Also pretty thin oil.

Hope it helps.
Many miles

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