I'M OUT OF FREAKING IDEAS!! THIS BIKE IS DRIVING ME CRAZY!!!

[J-Speed Inc.]

2001 Monster 750 with 12k miles.  Carbs are not getting fuel even though I have done the following:

- Cleaned all jets and orifices
- Cleaned float needles and ensured smooth operation
- Cleaned float bowls
- Replaced fuel pump
- Eliminated vacuum petcock (was stopping fuel flow)
- Verified fuel pump operation by removing output tube and turning engine over
- No fuel leaks anywhere
- Plugs are good

After taking carbs apart, bike will run great then stall.  It seems to me that the float bowls are filling once, then getting stuck.  I've checked the floats for proper operation and they work fine.  How can they be getting stuck after I put the float bowls back on?  Since the carbs aren't getting fuel, they must be getting stuck in the up position.  Bike was running great and I was riding it all last week.

HELP, I'M OUT OF IDEAS!!!

[Slide Panda]

i didn't see a new fuel filter on that list. or was that handled with the pump?

Cleaned the jets - but have you replaced them?

Eliminated Vac leaks?

[Howie]

There is also a fuel strainer at the inlet to the carbs.  Did you check that?

[J-Speed Inc.]

In my experience with carbs, the only reason to replace a jet is if the bike is running poorly even after a clean.  Once the bike starts, it runs great, I just can't seems to get the float bowls to fill back up.

Fuel filter is clean, I ran some air through it to ensure proper flow.

Fuel strainer at the inlet of the carbs has been removed.

[Speeddog]

How's your tank vent?

[ChrisK]

Have you set the float height properly? Proper height is 14 mm. Perhaps those tabs got bent on accident?

[J-Speed Inc.]

Tank vent is fine, bike wont run even with the fuel cap open.

Float height is a possibility.  I'm thinking the brass tube for the float bowl drain may be interfering with the float operation.

[koko64]

It wouldnt be the first time thats happened, worth checking. You angle the bowls in rather than straight on.
If your filter is old dont trust it just because high pressure air gets through, your pump is on it at 3-4 psi max.

[J-Speed Inc.]

UPDATE:

Removed the carbs from the bike and took them completely apart.  Ran air and carb cleaner through every hole I could fine, everything was open and working properly.  Put the carb bodies in my ultrasonic cleaner for 90 minutes in Pin-Sol (this stuff does wonders!) and then put the float bowls and and needle holders in for another 90 minutes.  Everything came out looking nice!  Washed the Pin-Sol off with warm water and re-assembled the carbs.

When I was checking the float heights, I noticed one float wasn't resting on the sping-loaded button at the top of the float needle.  Turns out the spring-loaded button was stuck in the down position.  I was able to get it working again with some PB Blast, now the floats are operating the same.

Could this have caused my running issue?  After the carbs would run outta gas, I could get the bike started with full choke, but applying any throttle would kill the engine.  

I want to verify the carbs are perfect before I install them for the 4th time, this crap's getting OLD!

[jaxduc]

labor of love

[WTSDS]

Are you using fuel with any ethanol in it ?  I had similar issues with a carbied ' bike with Viton tipped needle valve tips. With ethanol added  fuel the Viton swelled up and got stuck in the valve seats. Nearly drove me mad until I saw that the needle valves were getting stuck in the seats, stopping fuel from flowing into the bowls.

[J-Speed Inc.]

All the fuel (except for fuel at boat yards/marinas) has about 10% ethanol, so yes, the fuel has ethanol in it.  When I inspected the float needles, the rubber tips haven't swelled and were moving smoothly in their little cylinder.  The weird thing about all this is when I took the carbs out, both had fuel in them when I removed the bowls, that's what's pointing me to a clogged jet or something.  I think finding this float needle issue was just another issue.

[Howie]

Are you using fuel with any ethanol in it ?  I had similar issues with a carbied ' bike with Viton tipped needle valve tips. With ethanol added  fuel the Viton swelled up and got stuck in the valve seats. Nearly drove me mad until I saw that the needle valves were getting stuck in the seats, stopping fuel from flowing into the bowls.

Something else swelled them.  Ethanol and Viton are very compatible.