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Discussion Starter #1 (Edited)
Hello everyone,

I recently got my hands on the old cx500 custom 1980 that I used to ride when I was in high school. My sister had it at her place for about 6 years and it hasn't run in almost 3 years. Before they put the bike away it ran perfectly. The carbs had been cleaned, the clutch plates were changed, the antifreeze was flushed and refilled, the spark plugs were changed and maybe more. The spark plus have spark, the motor turns, and the electrical system seems fine.

I just finished cleaning the rust out of the gas tank and we wanted to try and start it up but the gas wouldn't flow to the engine(we checked the spark plugs for deposits). The petcock is open, the fuel line and filter aren't clogged, there are no bubbles in the fuel line and we didn't want to risk taking out the carbs since we are beginners and I don't have a shop manual.

I really want to get this bike running, does anyone have a good idea what might be wrong?

P.s. The fuel filter was clean before we de-rusted the tank and still is so I don't think rust got through.

Thanks

Update:

I confirmed that gas gets into the float bowl and there isn't a problem with the gas tank.
I took the carbs off the bike and i noticed that a little switch in the back of the carb seems like it wants to open the throttle slightly when i try to turn on the bike but it doesn't reach.
Also could having the idle set too low cause this problem? I don't know if it was since my stepfather messed with it as soon as i took the carbs off.
From what i understand the float must be working otherwise no gas would get to the float chamber. So the next step to check would be clogged jets? I think that's the last thing that could block the gas apart from not getting any air through the carb?
 

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Check the float bowls for fuel - there's a screw on each bowl that, when loosened, will let fuel out of the drain nipple on the bottom of each bowl. It's preferable if there's a hose on that to dump the fuel below the bike. That will tell you if there's fuel getting to the carbs.

Manual or vacuum petcock?

Also, pop your country into your profile and bike model into your signature - that can help with diagnosing.
 

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Discussion Starter #4 (Edited)
I'll check it tomorrow after work.

I think it's a manual petcock since it should be the original and the gas flows from it when the fuel line is disconnected from the carb, but I don't know how to tell the difference
 

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Discussion Starter #6 (Edited)
Check the float bowls for fuel - there's a screw on each bowl that, when loosened, will let fuel out of the drain nipple on the bottom of each bowl. It's preferable if there's a hose on that to dump the fuel below the bike. That will tell you if there's fuel getting to the carbs.

Manual or vacuum petcock?

Also, pop your country into your profile and bike model into your signature - that can help with diagnosing.
I checked the float bowl like you said and gas gets there in both carbs without any problem.

My petcock is a manual one.

I also tried to prime the cylinders a few time like a mechanic told me to (since i'm planning on changing the oil after anyway) but it only burns what i put in the cylinder and then stops.

I'm thinking that my next step is to take it apart and do a thorough cleaning. If so do i really need a float measure for when i put it back together or can i improvise something?
 

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This is a long but simple shot ... start the bike with the fuel cap off . If the cap ventilation is dirty and blocked a vacuum will build up in the tank preventing free flow of fuel to engine via perfectly good carbs .
 

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Discussion Starter #8
Update:

I confirmed that gas gets into the float bowl and there isn't a problem with the gas tank.
I took the carbs off the bike and i noticed that a little switch in the back of the carb seems like it wants to open the throttle slightly when i try to turn on the bike but it doesn't reach.
Also could having the idle set too low cause this problem? I don't know if it was since my stepfather messed with it as soon as i took the carbs off.
From what i understand the float must be working otherwise no gas would get to the float chamber. So the next step to check would be clogged jets? I think that's the last thing that could block the gas apart from not getting any air through the carb?
 

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