scoot only starts after draining carb

[bluefire808]

I have looked all over google and cant find any one that has my issue. My 139qmb wont start unless i drain the gas from the float bowl in carb. Once i drain it i kick it over untill it fill with gas and then i have a chance to start it. Some times it starts great amd fast. Maybe even for days. Then out of no where it wont start unless i drain carb and crank till it fills with gas again. Any one have any ideas? Carb just got cleaned, valves are adjusted and no air leaks in manifold of head or bottom end. Have 91 pump gas with slight octain boost/keeps gas cleaner. I have good flow of gas to carb and if i take vacuum line off carb and suck on it with gas line disconnected the gas runs outfast so i dont think vacuum line or fuel to carb is problem. Help hahaha

[bull]

Welcome to the forum!

My initial thoughts are flooding. But one thing you said is making me question it.

The next time this happens, pull the spark plug and see if it is wet. This will confirm the hypothesis, then we'll know what to look at next.

[cheapeto]

I have a small tube that runs down toward the center kick stand, that has a very small screw in the tube end, that I drain my carbuator bowl of a it's contents, when I swapped the jets.
Maybe you have one also.

[kz1000st]

You should start using a treatment like Seafoam. Obviously the ethanol is getting watery and mucking up the carb. Pour in a few ounces, go for a good ride and the problem may be over.

[bluefire808]

Ok so t make sure it wssnt vacuum lines i replaced all vacuum and fuel lines.also i thought it might be the ethnal gas/was sucking through carb, so the last 2 tanks of gas i used normal gas without ethnal and slight octain boost/fuel treatment to eliminate thst also. I fixed ( hasnt returned yet ) the not stsrting issue. I found i had the air/fuel mix screw way to far backed out. It may very well have been flooding when i tried to start it. One problem solved but another is happening now. Now it keeps RANDOMLY loosing 90% power and almost dying. It happens regaurdless of throttle possitio. It doesnt back fire, it just all of a sudden barely runs like its trying to suck water through or is running out of gas... Like i said it keeps dying out randomly regaurdless of throttle possition but hasnt completely died. It looses almost all power and barely runs for about 5 or 10 second only to REGAIN Full Power after it does this thing where it l tries to die. I checked all wire connecttions and there tight. I have no idea why this is happening

[bull]

what is the brand of the "Octane Booster" that you are using, and how much do you normally add to a tank of fuel?

how many miles did each of those 2 tanks of fuel deliver?

when you "cleaned the carburetor" did you clean and tighten the jets properly? did you pinch, cut or rip any of the seals? or did you adjust the float level or change it in any way, like putting the needle back wrong?

is the "normal gas" you use, regular grade, 87 octane, but still has the 10% ethanol content?

[bluefire808]

Ill find out about the octain boost from my dad as he uses it with non ethnal gas in his crotch rocket.i dont know exact miles but it seemed the same as normal. One tank of gas runs for about 2 hrs at WOT of a average of 35-40mph. I used 2 cans of carb cleaner and didnt hurt any seals in carb. Got every single hole completely clean ( carb only has 4k miles on it and wasnt dirty to start with. As far as propperly screwing the jets back in i beleive so. There in exact same possition and had no issues reinstalling them. When you say needle your talking about needle that goes from diafram into main jet right? It seemed to go back into possion smoothly. I didnt adjust float bowl because it didnt appear to have any adjustability. I did remove the float bowl to clean carb porpperly. The regular gas i used is non ehtenal 91octain that a local gas station sells mainly to people for commercial boats and airplains. Im thinking of blocking off holes to the auto choke incase it keeps engaging randomly, do you think its worth trying as i live in a always warm year around enviroment?

[skyrider]

Since I replaced my carb about 5 yrs ago followed a Scootmembers advice of 1 cap seafoam every tank and haven't looked back until I did a stupid thing by laying down my scoot to change the oil and clogged the petcock, but that's another story,LOL.

Which makes me think that you should check the petcock, pull it off and check the inside of the tank. If me, I would prob get a new carb and petcock for the problems you're describing.

[bluefire808]

Thanks for the reply. I am thinking i may need a new carb also. Tomorrow ill drain tank and check petcock. Ill also add sea foam to gas when i refill it since it cant hurt

[bull]

based entirely on the info you supplied in #7, you are running very rich - way too much fuel-

WAG about 30 or 40% too much

if you feel the way to go, is a new carb, by all means do what you think is right

[bluefire808]

Bull why would thr same carb thst had work perfectly for 4k now be running way too rich all of a sudden?

[bull]

these scooters with GY6's are set 'rich' from the factory - haven't yet checked exhaust gas #s, because of time constraints

adjustable main jet needle style setup correctly will achieve 100mpg gps verified. IF your #s above are using the speedometer/odometer they are typically 20% optimistic. so you are easily 35% off now

higher consumption = running rich

IF you are going to replace the carb, and you don't believe it is running rich-- then why replace it?

[bluefire808]

Im thinking of replacing carb because im slowly relplacing every single part cause some where one of the parts isnt working. If i replace everything ill eventually replace a broken part. Im running a 50mm BBK and have ported polished head with big exhaust and intake valve that come with 24 mm carb. This set up has ran PERFECT for 4k. So changiing needle possition i dont think would help it from being overly rich, also i do.t think changing jets would help since it ran perfect for 4k with good plug color. However when it crapped out while riding just now i turned the engine off and pulled plug and i think it looks bad color (hoever im colorblind so i cant match it up to plug chart. So can you folks tell me whst the color indicates? Also the head and bbk and carb came from scrappy dog scooters. First thing on there page under 139qmb performance. I just bought sea foam and am going to pull off gas tank and check petcock for glogging or anything non normal. However if the plug was the color of being too rich then i doubt petcock was problem

*also i blocked off auto choke so it cant effect engine. It didnt fix problem

[bluefire808]

I just diconnected fuel line into carb and put it into a gas can. Took vacuum line off and sucked till gas started pooring out. I then pinched off vacuum line with plyers to maintain vacuum and it drain entire tank fast without hesitation in flow... Does that i dont need to take petcock off to check it?

[skyrider]

Well, Bull may correct me on this, but I thought the petcock regulated the flow, so if its dirty or not working properly then gas will not get to the carb or not very well. Can't hurt to remove and check it out. I replaced my petcock after my stupid mistake and the carb ran like a champ, didn't need to replace it.

[bull]

Skyrider, you are correct that a petcock can starve an engine for fuel, especially if it is stopped up. the filters in some fuel control valves are inadequate, especially in light of some of the additives people use that are up to 30% ethanol, which can destroy the filter in it and attack the tank coating.

I prefer testing, and repairing rather than just swapping parts, so with the latest information bluefire shared about his SD BBK, the next step for me would be to check the compression and valve adjustment.

[bluefire808]

I just redid valves and have kept up on them regularly. Do u recommend any compression test tools/brand or website u would use? I have never done a compression test

[bull]

my choice for tools is SnapOn, Mac & Cornwell, they are too expensive for hobbyist or casual users

there are plenty of videos on youtube showing how to do the test

[tcthomp66]

Thinking you might also check the air/fuel screw. I'm currently working on an issue with the air/fuel where it will either run or idle at start, but not both. If you have access to the screw, try setting it to 2-2 1/2 turns out, and see if it will idle at start. Then give it some gas and see if the engine actually revs up or bogs down.

My theory here is that you may actually have an air/fuel mixture issue. Try the petcock first (they're about $4 on Amazon), then check this. Good luck.

[bluefire808]

I tuned my air/fuel a few days ago which solved my starting issue. Now it just randomly dies.. compression test snd petcock are my next tasks