Carb. flooding issue (any help please....)

mapbike · #1 03-14-2010, 07:39 PM

I've got a pretty new engine doesnt have but an hour or so on it and I it just isnt reving up like it should, (PROBLEM) it starts choking down a little so I twist the throttle a bit and it would clear up a little but would choke down at about 1/2 throttle, I can see gas bubbling out of the carb vent so I turn the gas valve off at the tank and as soon as the head pressure from the tank goes down it runs like a top, revs great idles great and will take off and run great overall until I turn the gas valve back on, then it will start flooding down again, I took carb off and bowl off, I noticed that the NTTC carb's have a free floating float unattached to the arm that works the needle in the seat, being that it runs ok at low rpm and not when it is rev'd up, I have come to the conclusion that because of the fairly harsh vibration that the engine has it is causing the float to bounce up and down in the float bowl causing the unwanted extra amount of fuel to be allowed into the float bowl which is the cause of it flooding when it revs up but runns OK under idling conditions. I put 2 different brand new carbs on the engine with the same results, they both run great until the engine is rev'd up then they both will start spitting a little fuel out of the carb. vent and flooding the engine down. anyone have any ideas how to resolve this problem other than just getting a better carb....? sorry so long just wanted to make issue very clear, and hopefully answer as many questions as possible about what I have done so far. Thanks...... in advance,

bairdco · #2 03-14-2010, 07:47 PM

vibration/bumps shouldn't be a problem at all. i hit bumps all day, jump speedbumps, etc.

the obvious answer would be that the plastic float has a crack somewhere and is filling with fuel, thus, not "floating," but since you checked and switched carbs, that's doubtful.

the only other thing i can think of is that your carb isn't level.

is it?

mapbike · #3 03-14-2010, 07:59 PM

yes it's pretty level, no major angle if any, I'm thinking that needle and seat are not holding in either carb. as long as the fuel is shut off to carb. where there is no head pressure from tank it runs fine but as soon as the fuel vale is turned on it will start to flood down with-in a few seconds. just getting to much gas. I guess I need to remove the carb. and take the needle out and make sure that it is sealing of properly. its just odd to me that it run as long as there is no head pressure on th e carb from the tank

mapbike · #4 03-14-2010, 08:08 PM

Well, I'm going out to take a carb apart and check the needle & seat, I will check all gaskets, and make sure carb. is sealing between itself and the intake tube, this has got to be a simple fix, just odd to me that I am getting the same results from 2 different carbs. ???? ):~/

bairdco · #5 03-14-2010, 10:22 PM

when you're turning your fuel off at the tank, the carb is probably using up the gas in the float bowl, it shouldn't have any pressure unless your gas cap's not venting.

which actually, could be the problem.

and what do you mean by "carb vent?"

mapbike · #6 03-14-2010, 11:51 PM

what I mean by carb. vent is the spring loaded valve that is on the same side of the carb as the idle screw, "vent" may not be the correct discription but I am calling it that for lack of knowing anything else to call it, when my engine starts to flood down and I rev it up a little after turning the fuel valve to the off position, fuel will come from that "as I would say Vent", once the fuel is shut off at the tank and the fuel level in the bowl dropps a little fuel stops come out at the "vent" and the engine starts to run like it should, you confirmed something I was also thinking a bit ago about the tank cap not venting, I will loosen it in the morning and start it up and see if there is a difference, if so I would say problem found and then I will go from there at getting it venting again. If you think of anything else please let me know, Thank you for the help and thoughts...

mapbike · #7 03-14-2010, 11:54 PM

It's got to be a venting issue, I just cant see both of the new carbs I have, having the same problem, it will be resolved tomorrow. pressure in tank over powering the floats ability to keep the needle sealed off in the needle seat.

bairdco · #8 03-15-2010, 04:11 AM

do you mean the little button lookin' thing? that's the "tickler." you press that down before you start your bike and it pushes the float down, making fuel go into the carb, for a richer situation when you start the bike.

my bike's modified and has way too much compression, and i have to hold that button down till fuel drips out to start it. otherwise i'm pedaling a block or so.

but with your problem, i can't see how fuel would flow up and actually come out of the tickler (vent.)

it could be as simple as the float height isn't correct. take a look at the tabs... wait. if it does the same with 2 different carbs, i'm going with the tank not venting. vapor lock.

i'm drunk now, so let me know how it works after you tried what you said you were gonna do.

Jumpa · #9 02-04-2012, 11:11 AM

Quote:

Originally Posted by bairdco

vibration/bumps shouldn't be a problem at all. i hit bumps all day, jump speedbumps, etc.

the obvious answer would be that the plastic float has a crack somewhere and is filling with fuel, thus, not "floating," but since you checked and switched carbs, that's doubtful.

the only other thing i can think of is that your carb isn't level.

is it?

A dab of super gluem workd wonders and the gas didnt break it down on my cracked float

Jumpa · #10 03-02-2012, 11:21 AM

"i can't see how fuel would flow up and actually come out of the tickler (vent.)"

Liquid seeks its own level, so as long as the source "Your gas tank" is higher than the vent "carb air filter" it will flow out of it. That is until you get that square pointy check valve to seat proper like