Yamaha QT50 won't run By gbtr6 (Read 7,488 times)

[gbtr6]

I have a Yamaha QT 50 and I put a new carb on it. It ran great at first, but now can only start and run on starter fluid. Not getting gas I think. Any ideas? I may take carb off and clean.

Thanks,
Peery

[Alleyoop]

If your carb has an ENRICHER check that out first it may not be feeding fuel for cold starts. If it does have an ENRICHER did you plug it in?

Also what kind of CARB?? a CVK or SLIDER type carb? SLIDER TYPES have the THROTTLE cable going into the top center of the carb, CVK carbs the throttle cable is attached to a bracket on the right side of the CARB. Reason I want to know is each carb adjustment is different.
Alleyoop

[gbtr6]

Hi,

I've attached pictures of my carb. I would say its a slider type. It has an internal piston with a needle. When I got it, I just put it on, no adjustments. It worked well at first. Leads me to believe its some sort of dirt or debris maybe in the carb. But could be an out of adjustment mixture. Any help is appreciated.

Thanks,
Perry

[gbtr6]

Sorry, forgot pictures.

Attachments:

[gbtr6]

Another picture.

Attachments:

[gbtr6]

Anyone able to help?

Perry

[Alleyoop]

Ok, great pictures, I labeled your carb and yes it is a SLIDER type carb.
So If it only wants to start with starter fluid it is not getting enough fuel and to much air.
I have to ask where is the AIR FILTER.. Is that little black piece the AIR FILTER or is that OPEN ON THE END?? Reason I ask is if it is OPEN it is getting to much AIR you cannot run them without some kind of AIR FILTER to cut down on the amount of air it sucks in.

But if that is a little AIR FILTER then Look at the picture of your carb I labled there are TWO SCREWS. The one on the right near the AIR FILTER is your AIR RATIO MIXTURE screw.
So start the motor up THEN turn that screw CLOCKWISE 1/8 at a time and what you want it to get it to IDLE the HIGHEST. Once you find where it IDLES the highes TURN THAT SCREW 1/16 COUNTER CLOCKWISE.

Now take your time after every 1/8 turn CLOCKWISE wait about 10 seconds to allow the motor to catch up with the new setting. REMEMBER your looking for the HIGHEST IDLE out of that screw.

If after you find the highest IDLE and the REAR WHEEL IS SPINNING then turn the MIDDLE SCREW(IDLE SPEED SCREW) counter clockwise until your REAR WHEEL does not turn or JUST WANTS TO TURN.
Alleyoop

[gbtr6]

Alley,

Thanks for the reply. I don't have an air filter on it now. I will put that on. I'd like to get a free flow filter, but later. I don't think I have the air mixture screw. I think it's just blocked off, I'll look. What is the srew on the bottom bowl on the side? You can see in pics.

Thanks,
Perry

[Alleyoop]

The one on the bottom of the CARB BOWL is your CARB DRAIN SCREW there should be a connector to put a hose on it so when you turn that screw counter clockwise the gas comes out of the bowl.

Well if you have NO Air FILTER that is why you need to cover it to get it to start it is sucking in to much air and not enough fuel. Also you do not want to be running around without a filter dirt will get sucked in and think of it as GRAINS of SAND getting onto moving parts NOT GOOD.
Alleyoop

Alleyoop

[gbtr6]

What setting should my idle speed and air mixture screws be set at from completely closed or screwed in? I put the air filter on, but the foam had deteriorated so I need another one to work properly. I think it's getting gas but may have dirt in the line/carb yet. May take it off and clean it just in case. It still starts and dies. Hoe long should you run it on the 'start' setting before switching to 'run'?

Thanks,
perry

[mikey34]

If I ever come across a scooter that has set for over 6months, OUTSIDE, I always take the tank off and get 2 gallons of gas to wash it out with(take it off, fill it a 1/4 up and shake it, relieve pressure with finger). Then, blow the tank filter out with an air compressor. If it has a diaphragm "petcock", Either change it, or make sure the diaphragm moves back and forth. Then Fuel Filter, Replace it. Check lines for gunk, or just run New gas lines. THEN clean the carb(USE A PIECE OF SPEAKER WIRE FOR THE MAIN AND PILOT JET, PAPER CLIP) make it look Brand New. Buy a new Foam Filter(IF YOU HAVE THE AIR BOX) if you don't, buy something like a "UNI" filter. These engines are USUALLY set up for the STOCK AIR BOX, so with that in mind, try to keep the INTAKE of air close to what it was stock, or tune the carb correctly.

BUT you DEFIANTLY NEED an AIR FILTER

Your in GOOD HANDS with Alley he has helped me out quite a bit!

[gbtr6]

Thanks for the feedback. When I got this from my son at the beginning of summer, it had sat for quite a while. I bought the new carb, cleaned the tank, disassembled the petcock, and put in a fuel filter. I am thinking, in addition to the filter, that some latent gunk or debris has come loose and it may be a good thing to clean the carb.

Perry