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Discussion Starter · #1 ·
This morning I’m cruising along about 75 to 80 mph on the highway and the bike starts to act like its running out of gas. I switch the petcock to reserves and I notice I have only 95 miles on this tank of gas. I can’t be out of gas. I stop on the shoulder turn off the bike, move tank bag and look into the gas tank. I have more than half a tank of gas. I try to start the bike and it takes a couple of tries then the bike fires back up and off I go to finish up my ride to work.

My problem is this happens at odd times and I’m not able to duplicate it or know when its going to happen. My thinking is the gas tank is not getting enough air into it to provide gas to the carb, and that is giving me the feeling that the bike is running out of gas.

Do you think the tank bag is causing this issue? Where or how does the fuel tank vent as the gas gets lower in the tank, keyhole?

Keep in mind the fuel tank is a Ca. emissions fuel tank. I have a new fuel line installed, carb and filter was cleaned. This has been an issue for years.
 

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This is where I would start if you haven't already...
 

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Discussion Starter · #3 ·
Outstanding!! thanks. That is one part on this bike that I haven't fully taken apart. I guess I know what I'm doing this weekend. I'm so excited to get this issue put to rest.
 

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This ailment is so common. I have fixed several lawnmowers (Zero turn radius type) with this same problem. Why is it so mystifying?

FOG
 

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Discussion Starter · #5 ·
Not so much mystifying just trying to figure out which way to go. I have been trying to figure out which port on the tank is a vent instead of worrying about the key hole.
I remember a thread a while back that said the key hole wasn't a vent..... but maybe that meant that the key hole itself is not a vent, but the gas cap has a vent.
Half the battle is figuring out the bike is tell me its running out of gas instead of some other problem. 😁
 

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This forum is here to serve, it would be helpful if you helped yourself a bit too. third Item in the How too section is the fix "how to service your gas cap"

FOG
 

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Discussion Starter · #7 ·
Noted.....Didn't realize it was going to be a gas cap issue..... hindsight is 20/20.
 

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As you have a Cali tank, you should also read this:
 
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Discussion Starter · #10 ·
Thanks, I appreciate you pointing that out. I have read those post and performed uninstalling those parts.
 

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If it acts exactly like it is running out of gas, then we can apply William of Occam's "razor" to the problem. It probably is running out of gas. If it runs good otherwise, then fuel flow is the problem. Chinese scooter petcock? Toss it. Clogged petcock screen? Cllean it. Plugged fuel filter? Bin it. Tank cap not venting like it should? R&R per the thread here. Float levels too low? It's a process.
 

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Discussion Starter · #12 ·
Took the gas cap apart and I didn't find any passages blocked. I'm now wondering if the vent tube inside the tank is plugged. I think I am going to run a small wire through it to see if it's blocked.
 

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Took the gas cap apart and I didn't find any passages blocked. I'm now wondering if the vent tube inside the tank is plugged. I think I am going to run a small wire through it to see if it's blocked.
Please tell us you tossed both the flapper valves whilst in there?
 

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Discussion Starter · #14 ·
But of course. I followed the how to.
 

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But of course. I followed the how to.
the flappers get greased up (via varnished fuel) eventually stick and fail to flap causing venting issues. Have you actually test ridden since?
 

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Discussion Starter · #16 ·
Ah good to know. I have not rode it since, I only ride it when going to work and I only go into work twice a week. By the middle of next week I would hope to find out if that was the issue.
I need to get some guitar string and run down the tubes to see which port they come out at.
 

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Do yourself the favor and toss that orange rubber vent piece like the tutorial shows.
Please tell us you tossed both the flapper valves whilst in there?
Yeap, this is the key part of it. It's my experience that those valves simply don't function correctly either due to design or material or both, and should just be removed.
 

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Not to forget that the clear (yellowed) float bowl vent hose has to be open and not pinched along its route.
 

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Not to forget that the clear (yellowed) float bowl vent hose has to be open and not pinched along its route.
Good catch, but this hose could be removed as well (for OP, it's a hose coming from a vent nipple between the carbs, which rotates freely).
 

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Have a small list I will always check when I run into this issue, which I have about a handful of times.

-Petcock (fyi , theres a piece of the petcock that u cant rebuild that can only be replaced in side the small vacuum piece that has the smaller ribbed nipple, I've had this fail before which caused overflow, but I know that's not your issue, but blowing in and out of this piece will allow you to know if it provides the vacuum when needed , best to check imo)
-Fuel lines and vacuum line tank to carb, cant be pinched
-Carb passages and carb bowls cleaning, guitar string thru brass fittings, bottle of berrymans to all passages
-if you have an inline fuel filter , I suggest removing it, I tried to install one and it only prevented proper gas flow causing fuel starvation and not allowing the bowls to fill up under hard throttle.

Carb tune and valve adjustment does good together too. I've had weird stumbles on throttle when I was past routine maintence callings around 20k+

Hope this helps.
 
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