carb trouble

[SFSPECBIKER79]

today, i went out and started up my xs 1100 80 standard ,factory no modifacations, with rebuilt carbs, 120 mains 45.5 pilots 187.5 air pilot jets, floats set at 125.0 mm, air pilot screws are out at least 2 turns. and the float needles are seating shuting off fuel. no dout... with the fuel bowls empty i turn on fuel, wait 30 seconds start engine without fuel enrichment system. it starts up, idles perfect, revs up red line perfect. after a couple minutes black smoke starts rolling out exhaust. will not idle but will run at and above 4 thou. rpms return to idle engine stops off. try to crank wont start. turn gas lever to off. turn throttle wide open position. crank engine runs but want accelerate more than 1100 rpms. after running at 1100 rpms a minute or so. it will start running perfect again. this is with fuel turned to off position. open fuel up, then it starts rolling the black smoke again,stumbling, will not acceelerate just floods in the 1100 to 4000 rpm range. it will stay running as long as i keep the rpms above 4000 rpms. if you can describe what is happening ,please advise me what i need to do. remember the float valves are shutting off, thanks

[Bigfoot]

Was it running correctly prior to this morning?

[XJOK2PLAY]

Normally, they are supposed to have some choke when starting cold. This allows the enrichener circuit to add extra fuel needed, and will allow the engine to high idle. After a couple of minutes, and as the idle speed climbs, you can begin to reduce the choke. Most of these take a few minutes to warm up, onger if the weather's colder.

The only other thing I could suggest would be something's clogged in your pilots, or the petcocks / float valves aren't opening properly.

Do you have inline filters on your fuel lines?

Sounds like your mains circuits are functioning.

But properly choking when cold starting may be the answer.

[randy]

Your fuel enrichers may be stuck open or not sealing for some reason. Runs with the fuel shut off? Sounds REAL rich to me.

[trbig]

If the float valves are shutting off, it wouldn't be flooding.

So here's what I THINK is happening. If you are indeed letting the float bowls get empty, then sometimes this lets the floats drop far enough that the float needle comes completely out of it's hole. When the bowl refills with fuel and the floats raise up and try to push the float valve up, it gets cocked sideways a bit. The bowl will continue to fill up unchecked and begin dumping raw fuel in. At over 4k rpm, it's running fast enough to use most of the fuel, but it's still going to be running very rich.

Sometimes tapping on the carbs with the plastic end of a screwdriver will jar them enough to get them straight.


Tod

[Bonz]

Yes, I concur that a float is sticking. I would also bet $1 that you have fuel coming back into the airbox, yes? I don't see a float sticking and just flooding the engine, fuel would be coming out the back of the carb(s) as well.

I just cleaned my carbs and I could tell one cylinder was running crazy rich when I fired it up. I left the airbox bottom off (won't run well with it off, but let me see easily if gas was coming out the back side of the carbs) and #2 was dumping gas out the back.

I did the "tap on the float bowl and every other part of the carb" trick, and it settled right in the next time I fired it up, runs like a champ now. Pulls so much better on top and with the airscrews at 2.5 turns out, at the 7,000 feet of elevation I live at it purrs like a kitten at idle now as well. The airscrews were still sealed when I took the carbs apart, and 2 were set at 1 1/4 turns out, 1 at 1 3/4 turn and 1 was at 3 turns.

[XJOK2PLAY]

Sorry for the mistype... I earlier said "opening" when I intended to say "working"... forgive my stupidity, Tod... it was before my morning coffee, and I know better than to do that...
Thanks for helping me speak straight...

Uhhhhh, yeah.... what he said.

[Crazcnuk]

#45 pilots are pretty large, too, with no mods.

How does it run in the top end?

My 80G had 45s in it when I got it, I had to put the 42's in.

I am running the 120mains with no problems.

The other thing to check, carefully, is the needle tubes. They wear out, you have to look and see if there is any 'ovaling' of the hole where the needles go in. If there is wear it causes more fuel to get past the needles at low to mid throttle.

This can be partially countered by lowering the needles 1 notch (if you have adjustable needles). Make sure the washer is on top of the plastic needle retainer, not under it as well, on 80-81 carbs.

[skids]

I have a set of 80 carbies and a set of 81's that were set-up with 110 mains across the board. Also, I think you have a typo in the floats setting. 125mm is of course excessive. Just off the top of my head, 25mm is for 78 and 79 models and it is something like 22 or 23mm for the 80 and 81 models.

[rpgoerlich]

I believe the XS11 80G float height was 23mm +/- 0.5mm.
Ditto on the 45.5 pilots being a tad rich for stock.

with rebuilt carbs, 120 mains 45.5 pilots 187.5 air pilot jets, floats set at 125.0 mm, air pilot screws are out at least 2 turns. and the float needles are seating shuting off fuel.

[Ken Talbot]

Just out of curiosity - you say this is your '80 Standard. Petcocks on standards have only ON, RESERVE, and PRIME positions. How in the world are you turning the fuel on and off?

[petejw]

What the others have said,
but also 187.5 air pilots arent standard as well,
180 is stock, the larger air pilot wont stop it from running tho.
Depending on how the bike ran prior, id be putting it all back to stock jetting.

110 mains
42.5 pilot jets
180 air jets
23mm float heights.

[SFSPECBIKER79]

re carb problem

my earlier post stated the floats were set at 125mm, but i meant 25mm sorry for the errow. i have carefully read all the replies. i have been away for a while went to ohio a few days. im going to change the float settig to 23mm as recomended by one member. by the way when setting float levels with the carbs up side down. i know you measure from the carb body where the bowl fits to. to the bottom of the float which is the top when they are upside down. my question is, do you measure with the little pin in the float needle pressed in or not. one member asked how did i turn fuel off. the answer is, i have a 80 special tank on the bike instead of the standard tank. another member mentioned putting back stock jets,if anybody has some stock jets lying around i would buy them or trade mine if they want to part with them.i also plan on checking the throttle needle valves when i pull the carbs again to check for wear and the present position they are set at. one member said that the float needles were'nt closeing off the fuel. but i have left the fuel on for several days in a row and it did'nt leak out the back of carbs or run into the crankcase. so i have ruled that out. it just seems that the level in the bowls are to high. causeing it to emit the black smoke. like i said the bike runs perfect when its not flooding. i dont think it is the jets because it runs so good when its not flooding.

[Crazcnuk]

Going from 25mm to 23mm would be RAISING the floats. You need to go to ~27mm to lower the fuel level in the bowls.

It's the upside-down part that throws us.

[SFSPECBIKER79]

carb question

when setting float levels,do you measure them with the little needle inside the shutoff valve pressed in or or with it springed out?