yamaha kt100s not sucking up gas thru the carb.

[yamahakt100]

ok i got an amazing deal on a racing go kart made by kustom kart shop in brick new jersey.

i believe the go kart and motor is from the late 80's,

i got it for $200 with the pit stand and tons of extra new parts.. the kart is in immaculant condition.


the guy i got it from ( 70 yr old man ) said it has not been started in several years but every year before he put it away he said he drained out all the fuel and ran the motor till it died so the car would be clean with no fuel in it.

well i put all new hoses on and tried to start it and it will not suck gas up thru the hose coming from the gas tank going to the carb.

it will start if i spray gas directly into the carb while starting it but even then it wont suck up any fuel from the fuel line coming from the tank.

i know the line is not clogged cause if i pull off the gas line from the carb and point it down towards the floor gas comes pouring out.

but when i connect it back to carb and try to start it you can see the gas just sitting still in the fuel line and not moving up to the carb.


can anybody please help me and tell me what to do.. i will post pics of the kart and motor shortly..

thanks.. and im also new to this site.. hope to stick around for a while..

 

[OzFab]

Welcome to the forum, good score

Suggestion #1: Ring the old guy & ask him how he used to do it.
Suggestion #2: Is it gravity fed or pump fed? If it's the latter, it won't pump fuel unless the engine is running IIRC.
Suggestion #3: Wait for anderkart to chime in, he's our resident racing kart expert

 

[yamahakt100]

Welcome to the forum, good score

Suggestion #1: Ring the old guy & ask him how he used to do it.
Suggestion #2: Is it gravity fed or pump fed? If it's the latter, it won't pump fuel unless the engine is running IIRC.
Suggestion #3: Wait for anderkart to chime in, he's our resident racing kart expert

ok thanks bud i appericate it.. and honestly i dont have the ol guys number anymore i picked this up last month but havent had time to mess with it due to working on my new house.

and 2nd im not sure if it gravity fed or pump fed.. wouldnt someone more knowledgable no what it is just by knowing the motor is a kt100s ?

 

[OzFab]

im not sure if it gravity fed or pump fed..

Looking at the setup in your other thread, my guess is there's a pump there somewhere.

wouldnt someone more knowledgable no what it is just by knowing the motor is a kt100s?

Hence suggestion #3

 

[bighead]

It has a pump. follow the gas lines until you see it. make sure all the hoses are hooked up. If you can start it with gas in the carb and the pump still not pick up fuel I am thinking the pump needs cleaned.

 

[yamahakt100]

if it has a pump where is it ? on the carb ? cause i dont see any electric wires coming from the tank if there were a pump in tank. and there is only 1 hose that comes from the tank and goes to the carb.

is the fuel pump the "diagram" ( think its spelled wrong ) thing thats build into the carb somwhere ? the flat gasket that pumps the gas ?


and also i noticed gas leaging from under the tank just now while i was outside.. so i drained all the gas out will remove tank tomorrow when its light out to inspect it.

would a leak in the gas tank cause the carb to not suck any fuel ? im not sure how bad the leak is cause it was under the tank mounted to the frame but it looked like quite a bit of gas that it almost soaked a t shirt i used to wipe up the gas.

 

[bighead]

The position on your tank tells me there is a pump. It will not be electric I do not think.

If the pump is not in the fuel lines then yes it on the carb.

Do you have to pulse hose hooked up? Thats a hose that goes from the pump or carb to the engines bottom end cases? Thats your pulse hose that works the pump.

Here is how mine looks. My pump is that square part you see on the carb. The clear hose under the carb is the pulse hose.

 

[yamahakt100]

yes i have a pulse hose hooked up. it looks tho like my pulse hose is in the spot where your blue hose going to the gas tank is and my gas hose is where your pulse hose is.

when i got the go kart. the pulse hose was already hooked in place where it sits now and with metal wire twisted on it to hold it in place.

the main gas line was disconnected and ziptied to the frame when the kart was stored.


the way the pulse hose on my engine is tied with metal wire at each connection end i dont think it was put back wards.. ( i could be wrong ).

 

[bighead]

yes i have a pulse hose hooked up. it looks tho like my pulse hose is in the spot where your blue hose going to the gas tank is and my gas hose is where your pulse hose is.

when i got the go kart. the pulse hose was already hooked in place where it sits now and with metal wire twisted on it to hold it in place.

the main gas line was disconnected and ziptied to the frame when the kart was stored.


the way the pulse hose on my engine is tied with metal wire at each connection end i dont think it was put back wards.. ( i could be wrong ).

I cannot help you any further without be soild advice. I will let the race kart guys take over.

Best to take pics and post them up for sure. Then go from there.

I can say for sure the setup in the pic above is in a working kart. Are the carbs the same?

 

[anderkart]

Your carb has a built-in fuel pump, the diaphragms in your carb probably need to be replaced. If it still has a Walbro brand carb, you can buy a carb kit for under $10 here: http://www.fastech-racing.com/yamaha-kt100-parts/
If its a Tillotson Carb, you'll find carb parts here: http://www.out2win.com/catalog/tillotson.html#parts

If your tank is leaking you'll need to repair or replace it, but another common cause of not pumping fuel is a rotted/leaky pickup hose (or a plugged strainer) inside the fuel tank. You should probably replace all your fuel lines and filter, be sure to wire or zip-tie each end so they wont leak/suck air. You can buy clear racekart fuel line at either of those 2 links I posted above.

 

[yamahakt100]

im not sure what model carb it is.. i will take some good detailed pics and post them up.. thanks.

 

[yamahakt100]

well i didnt take pics yet but after looking at the pic posted above and i also did a google image search for the kt100 engine and in every pic i see on google images it apears to me that the hoses on my kart ARE BACK WARDS...

i will try to switch them and see what happens.

also im just dumb founded on why the pulse hose would have been strongly tied to the wrong spot on the carb with metal twist wire... why would someone purposely put the hose in the wrong spot and tie it good. ?

 

[anderkart]

Someone might have installed a different brand or model carb on your engine. When you post a pic of your carb, be sure to post any brand/model info you find printed on the carb too.

KT100's usually just use the fuel pump feature built into the carb, but sometimes guys instal a pulse fuel pump between the carb and tank to help out. I didnt see an external fuel pump in the pics you posted in your other thread. Does your kart have one?

 

[yamahakt100]

Someone might have installed a different brand or model carb on your engine. When you post a pic of your carb, be sure to post any brand/model info you find printed on the carb too.

KT100's usually just use the fuel pump feature built into the carb, but sometimes guys instal a pulse fuel pump between the carb and tank to help out. I didnt see an external fuel pump in the pics you posted in your other thread. Does your kart have one?

after looking better at the carb it is a WALBORO carb. it says it right on it..

and it looks like the pump is built into the carb. so im assuming my wires hoses were wrong..

also noticed a crack in the plastic gas tank where the gas shut off valve screws ito the plastic tank. i removed the valve and used some plastic 2 part epoxy in the tube to seal the crack. now just have to wait for epoxy to dry and then put it back together and see if the tank leaks.

if the tank dont leak i can try switching the hoses opposite of what they were when i got them and see if it will then suck up gas from the tank.

also thanks for the quick responses guys..

 

[anderkart]

Theres some good KT100 carb info here: https://www.pegasusautoracing.com/document.asp?DocID=TECH00038

 

[sexyvicta]

had this exact problem myself on a kt100. Fuel lines were also hooked up back to front. Then it still didnt work...diaphram in carb was toast. fixed that and went fine.

yours probably are too after siting for so long. ours had only been siting for about a year. rebuild kit is about $30