no gas flow into carbs

so my carbs are now out for the seemingly hundredth time and i'm stumped! last year i had a small fuel drip which meant leaving the bike on the side stand for 5minutes or so at the end of a ride, my "mechanic friend" suggested that over the winter we replace needle and seats and gaskets. Did that but ever since the bike won't run. i've removed all the jets and run a carb cleaner through the assembly, we've checked float height levels multiple times, i've blown air through assembly several times, i've verified floats float etc. As of today the carbs will allow air to flow through but will not accept any fuel from the tank. i've made sure that fuel is flowing through petcock and inline filter by opening to prime and letting it flow into pail so i'm confident problem is in the carbs but i've run out of ideas. figured there was some obstruction in the nipple or tube which feeds the float bowls so removed each needle/float assembly one at atime and blew air through, received a nice spray of gas through each seat but once again when i attach the line from the tank nothing goes anywhere (verified visually by lack of bubbling in clear inline filter and double checking each drain screw in bottom of float bowls) Anyone got any suggestions as to my next step, should i be taking it to someone who knows better than me (and obviously my former mechanic friend)?
Any help is appreciated

 

Well, most people have just the opposite problem with fuel overflowing and running out when they don't want it to. If you take off a float bowl and hold the float up with your finger then let it down a little the fuel will run out. If it does you're in good shape, if not then find what ever is blocking it.
You could have a loop in the fuel line that holds an air bubble that blocks the flow of fuel. I've run into that before and had to straighten out the fuel line. You want it to run straight down to the carbs at and angle and not have any dips in it. If you pressurize the tank it should make fuel flow into the float bowls if there is no obstruction.

 

Just a stupid question, but did you also use the prime setting to get fuel to the carbs? I hate to ask, but... If you are only using the run setting then you might have a bad petcock vacuum diaphram.

 

OK so I'm an idiot! just goes to show that when you get frustrated and spinning in circles it's easy to think you've done what you haven't, my float levels were NOT set correctly therefore no gas could enter as needles weren't opening. Now that I've corrected that problem gas will enter the bowls no problem but alas i still haven't got the bike to start. Presuming I should now verify i've got spark and that i didn't flood it trying to fire it up last night but of course today it's raining and i'm a driveway mechanic with no garage. Thanks for suggestions, they gave me things to watch for in future.

 

I'm going to resurrect this thread, because this just reared its ugly head on my X.

Two or three days ago, I had ridden it to work and back, with no apparent issues (although I thought the coolant temperature seemed to spike after I got off the freeway... but I digress). Today, I get on the road, start heading down the freeway. Get about 5 or 6 miles, and it starts acting funny. Mile or two after that, it started acting like it was out of gas, although there was plenty in the tank. Got off to the side of the road, put it on prime. After a bit of cranking, it fired, and I took off.

Shortly after, it started acting squirrelly again, so I decided to take it back home and get the car. The sequence of events described above happened 3 or 4 more times before I was able to pull into the driveway.

I'm hesitant to blame the carbs, as this happened even with the petcock on prime, but as I think about it, they could be the culprit as well.

You know, this X is really starting to piss me off... can't I just put in gas and oil, and GO??

 

You may just need to sell me your 700. And since it's not running, I want it for cheap!

All kidding aside, I'd also look at your fuel valve to make sure you're not running out of gas because it has malfunctioned. You may need to take it all the way out of the tank to inspect the prescreen, too.

 

I don't profess to be an expert on this bike but it does sound like a fuel starvation issue. If you have an inline fuel filter, is this partially blocked? This would explain why after a period it runs OK again as some fuel is getting thru but not enough to keep it running for an extended period.

Also another thought is tank ventilation, usually not a problem with these older bikes but I have had it where fuel will not flow because the tank vent is blocked.

 

I had this problem at the beginning of the Season.
Checked everything a zillion times.

No fuel flow to the Carbs.
Fuel Starvation
How could this be ... the Fuel Filter was filled with Gas.

Yes it was!
But, the gas wasn't passing through the Filter.
Looked like it; though.

So, I pulled the Filter and blew through it.
Clogged.
Made in China.
Only looked good.
In reality was hardly much of a Filter at all. Just folded NON-Porous paper.

86'd the Made in China Filter.
Installed a Made in the USA Filter ...

... and they all lived Happily ever-after!

 

Great. YOU take the chance of throwing a rod or two and cratering the crankcase. :mrgreen:

These are why I was considering the petcock to be the prime suspect, but I had forgotten about the tank vent. I shall check that as well... if I can find the blasted thing. First on the hit parade is going to be draining the tank and pulling the petcock to check the screen.

Almost new.
Don't know where it was made.
Sintered Bronze.
Bought from Chacal.
Have one just like it on the 750.
Works great.

 

is it possible that the same trouble can happen to just one carb? my #4 was really lean (1,2,3 nice and tan). pulled, bench sync, gauge sync, cleaned plugs-same prob. pulled again ,cleaned #4( thx rick for the proper steps :wink: ).no time for all the carbs. bench.gauge'd,now have a pocket rocket for a bike!.......but #4 plug still clean with a hint of white. 1,2,3 pilots are 3 out,4 ..was 3 now i'm at 3.5 . i read its not good for the motor to run so lean but no choice,car is down too

 

Aaaaaaaaaaaaaaaaaaaand we have a winner!

Started draining on PRI a couple of minutes ago. Noticed that the flow coming out of the hose was starting to slow down... until I opened the cap. Repeated this two or three times, with the same result.

"Dear Penthouse,

I never thought this would happen to me, but..."

 

Good work!

From memory it is an arrangement inside the gas cap, it was on my XZ550 (Vision) anyway.

There's not need to worry about this on my XJ, just the opposite in fact given the strong smell of fuel around the keyhole on the gas cap.

 

Same problem, same solution. You're great Rick!

(Note that out of Advanced Auto Parts, Autozone, and Napa, only the last carries a decent in-line filter, though I guess your mileage may vary)

Edit: bah! forgot to mention that my filter was a seemingly decent bronze filter too, guy above me!

 

Interesting. I had a problem with my cap today as well. It's warmer here, so the gas was expanding. What I was seeing was that even with the petcock on 'On' gas was pouring out. I thought I had a petcock problem (it's new), so I tore into it a couple of times checking and rechecking.

Popped the cap, and I hear the air escape. Hmm... Pulled the cap and cleaned out the passage, no more petcock leak. I haven't ridden it since I fixed that, but I was having a problem hitting a 2K idle after running. Verified the 'clunk' test again, so that has to be it.

Just wanted to share since it was another angle of a gas cap problem.

 

Yep; just take the gas cap apart (it's a rather interesting mechanism, be careful there are springs that like to fly across the room) and clean thoroughly. Use SPARING amounts of lithium grease when you reassemble the latch and it will operate so much better. While you're at it, get a new gas cap seal from chacal (composite rubber/brass) and complete the job. There is an internal o-ring or two on the lock itself but you shouldn't need to tear it down that far.

 

Did you put the floats in upside down the big part goes up (don ask)