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It will run, for a few seconds.



When you push the primer bulb, the fuel comes up to the carb...but it does not stay. It drains back into the tank.

What holds the vacuum in the carb to keep the fuel up?

I think if I can stop the fuel from draining out of the fuel line...problem solved.

But, I have been wrong before.

thanks, Shift

Starvation. The lines may be plugged. There is a small drop in fuel filter in the tank which may be plugged. The line can be bought by the foot. Others here will help I'm sure.

motoman said:

Starvation. The lines may be plugged. There is a small drop in fuel filter in the tank which may be plugged. The line can be bought by the foot. Others here will help I'm sure.

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It has new fuel line.
I ran a temporary line from a squeeze bottle and it ran, holding it above the carb.
. I had to use my finger for the choke.

Shifts, I'm on shaky ground here as I have never really had your problem and have owned only two of the 2 stroke motors. So...I do not know if the carb is just gravity fed or, if the fuel is assisted by vacuum pulses . Seems as 2 stroke the crankcase is only used to pressurize the next charge so maybe gravity. Did you look for the filter? Mine is about thrumb size. and floats in the gas tank with a line on it. Maybe someone with real knowledge will respond to help you. :anyone:

I would make sure there isn't a hole or tear in the primer bulb.
Most shops usually just replace the carb due to the low cost of these carbs.
This should help answer your question, see Primer Operation- Zama - Carburetor Systems and Operations

shiftsuper175607 said:

It will run, for a few seconds.



When you push the primer bulb, the fuel comes up to the carb...but it does not stay. It drains back into the tank.

What holds the vacuum in the carb to keep the fuel up?

I think if I can stop the fuel from draining out of the fuel line...problem solved.

But, I have been wrong before.

thanks, Shift

Click to expand...

Goes like this you push the bulb and that forces the air in the bulb down the overflow tube into the tank.
The primer bulb has a one way valve on it so when you take your finger off it applies suction to diaphram chamber inside the carb which is the equivalent of a float bowl.
This sucks fuel past the two one way valves in the fuel pump and up the tube from the tank with the filter on the end of it.
So all the "primer" bulb really is a manual fuel pump.
Once there is fuel in the bulb there must be fuel in the carb.

If you pump the primer bulb till it fills with fuel and the contents of the bulb drains out then it is time for a carb rebuild or at the very least replacement of the primer bulb & valve.

Go to Walbro http://www.walbro.com/media/21936/SERVICEMANUAL.pdf and download the manual.
Weather you have a Walbro or not they all work exactly the same and Walbro have the best manual with the clearest best explained diagrams.
From the Walbro service page Parts & Service you will see a link to the repair video which is well worth watching.
The previous link to the service manuals is bottom right of the same page.

Cube carbs are fairly simple to understand in theory but a right royal PIA to fix because the holes that block up are tiny.
Time wise I no longer fix them because 1 hr of my service time is worth more than a replacement and 2 hours of my service time is worth more than a new Weedeater and I charge 60% of the standard rate.

If you do decide to have a go, do it inside the house on clean butchers paper, not paper towel or cloth as the fine fibers from either can block up the carb you are trying to fix.
I use canned air ( air brush supplies ) if you drag compressor lines into the house make sure you turn down the pressure no more than 15 -20 PSI or the air can damage the internals or lodge dirt in so hard you will never be able to remove it.

Thank you for the ideas and the link to the Walbro manual.
I have ordered a carb.
carb kit and bulbs

shift

shiftsuper175607 said:

Thank you for the ideas and the link to the Walbro manual.
I have ordered a carb.
carb kit and bulbs

shift

Click to expand...

Installed new carb and new fuel lines and filter. After about 20 pumps the primer bulb filled and I started her up.
I used it a good bit. I need to adjust the idle down.

Thanks for help.

Oh, it is a FS 74, don't know how I missed that.

I'll say it again. Administrators should consider "stickys" at the top of the forum like other forums. When pros like Berts and others take the time to present essential information like above , but it is then "lost" in the archives it is nonsensical. People keep asking the same questions over and over. No matter the original intent of this site the fact is that a lot of people have a lot of problems. With generic stickys responders could then ask if the requester has reviewed them before answering.

DISCUSSION PLEASE..........

Won't work.
I troll through the forum when I come up for a cuppa ( or for the results of too many cuppas ).
I have noticed that most 1st time problem postes put the post in the wrong place and oft your will get 2 or 3 almost in a line with the same problem.
People just do not search the forum so unless they have exactly the same mower and the mower name & model is in the post title they will never see it.
Thanks for the compliment, but I am not a professional, I used to be a metallurgist, then ran a small courier business for 30ish years, retired into wedding car hire then found out I was a better transport manager than financial manager courtsey of the GFC so now I fix mowers

To me a professional is one who is business and earns fees for services. I doubt you work for free. So accept the title.

People would continue to ask the same questions even if there were more stickies. Not to mention this forum would be boring if people weren't asking some of the same questions.

Mikel1 said:

People would continue to ask the same questions even if there were more stickies. Not to mention this forum would be boring if people weren't asking some of the same questions.

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On some of the motorcycle forums I haunt a lot of the general posters keep a list of their own posts and just cut & paste a reply.
There seems to be some sort of competition over who can respond fastest and I am starting to think some of them have text reading soft wear which reads the post then replies with he appropriate response.
Either that or they are the decendants of the Phantom ( he who never sleeps ):laughing:

That's funny at least they are committed it seems. That's better than them telling you to use the search.