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Discussion Starter #1
Sigh. So I just did a VERY thorough de-winter on my 1100, including a carb clean/rebuild. I took out and bypassed the fuel pump and reduced the length of fuel line. It also has a new filter in-line and a near-full tank of fresh gas. With the new fuel setup and clean carbs and new gas, I rode it twice, for about a half hour each time, after warming up, and it ran beautifully, all through the throttle range.

I then changed the oil, made a little whoops (had energy conserving oil in, but didn't run it, drained and replaced with good oil) that I fixed, and it ran fine on open roads for another 45 minutes.

Tonight, I go to ride it, I take a passenger, and it's bogging under throttle. Stalling a bit easily, so I pull the choke back a bit (more gas) and it gets a tiny bit better, but not really. I think maybe the extra weight is an issue, so after I drop off my passenger, I take it out alone, and same problem. When I open the throttle (clutch engaged or not) it has a 50/50 chance of bogging and acting like it's stalling, or of revving just fine. With a load on the engine, it'll power up a bit and then bog back down. I have a clear fuel filter, and it's full of fuel, so I don't THINK it's fuel starvation, although I could try and fill the tank more, but even on reserve it did it. I'd say I screwed up my carbs, but why would it run without issue for so long before this?

I'm at a bit of a loss, I was VERY thorough with the carbs, and the fuel and air filters shouldn't be problematic. Suggestions?
 

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gravity has nothing to do with it. check rubber vacumn lines, and caps.see if the carbs are seated right.mine came loose once.you could check for a vacumn leak with some spray cleaner. i would pull the carbs remove the jets clean all the holes with spray carb cleaner blow out all passages and carefully reassemble.
 

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with no fuel pump, as long as it is full....not 3/4 but full, you should be able to eliminate that as an issue. I'd pull the carb hoses to verify though.

Other than that, you could have something messed up in the carbs, like a needle holder pop out of place....
 

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Discussion Starter #5
gravity has nothing to do with it. check rubber vacumn lines, and caps.see if the carbs are seated right.mine came loose once.you could check for a vacumn leak with some spray cleaner. i would pull the carbs remove the jets clean all the holes with spray carb cleaner blow out all passages and carefully reassemble.
When you say "vacuum lines"... I'm not sure what lines there are. I have the breather to the little filter under the air box, and another breather from the front cylinder head to the same air box. The only other lines are the parts of the AIS system, which I haven't touched. Is there something I'm missing? I suppose I can take the carbs back off (dammit) and check them over, but I just did a complete rebuild and it was running fine. I suppose I could have gotten a loose needle valve, but I feel that would have a stronger effect than just bogging under load. Idle is fairly normal. It DOES smell a bit rich, though...

with no fuel pump, as long as it is full....not 3/4 but full, you should be able to eliminate that as an issue. I'd pull the carb hoses to verify though.

Other than that, you could have something messed up in the carbs, like a needle holder pop out of place....
When you say "not 3/4"... it shouldn't matter so long as there is fuel, right? I still HAVE the fuel pump, but I've seen it eliminated before with no issues, and my lines have little (if any) routing that isn't a nice, easy downward flow. I was NOT looking forward to taking the carbs off again.
 

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Discussion Starter #6
drain the fuel bowls. easier and there might be water in them.i'm not clear on gravity. if the lines go below the carbs some people say the weight of the fuel will fill the carbs.
Ooh. I like this. I did this initially to get the fuel flowing after the rebuild when trying to start it.
 

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Every time I've seen it eliminated there have been issues. I've seen it done several dozen times. Either you need a larger fuel valve going out of the tank or a baffle inside the tank to keep enough fuel in place to drop to the carbs without getting a bunch of air in the lines.

In my 10+ years hanging around all of the forums I've seen all but one or two go back to a fuel pump. Believe me, if Yamaha could have had a great running bike without the additional cost of an electric pump, they would have. At only 3-4 lbs it isn't much, but it's enough to make sure the fuel lines stay full even when the level drops below 1/2 tank. For me, I didn't enjoy rolling into a nice corner just to have the bike sputter and die...then do it again....and again....until I filled the tank full. I could go maybe 45-50 miles running fine.

Come over to the Delphi V Star 1100 Riders forum. We've been going since 1999....have a huge amount of documentation in the V Star 1100 wiki Knowledge Base...and you can search the fuel pump thing and read all about every ones attempt to do without it.....there are more posts there just on the 1100 every day then there are for all of the bikes here.

More power to ya if you can figure it out.....let us know how it goes....
 

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Discussion Starter #9
Mick, if what you say is true, then I'll put the pump back in. When it was running fine, there was a small bubble of air the filter, and now it's gone and totally full of fuel. Maybe the air bubble is blocking flow somewhere, because it does sound mostly like fuel starvation. All the posts I read about pump elimination sound great, but nobody really has long term results, and just because the first couple miles are problem free doesn't mean it's OK in long run. Good thing I kept it and some extra hose.
 

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removed my pump 4 years ago. never had a single problem.going around a curve and loosing power i dont get that at all.if i forget to turn on my petcock i can ride two blocks before it starts sputtering.my fuel line goes as direct as possible to each carb.i have no filter because that would lower the lines making them lower than the carbs
 

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open the pilot mixture screws 1/4 turn more, when i did this on my 650 it started pulling much better, pilot mixture settings affect all throttle positions not just idle and off idle
 

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A couple of years ago I had a Honda Elite 80 scooter, which was strictly gravity fuel flow. I added an in-line fuel filter, said to be for motorcycle use. All seemed well, until it got down to half a tank of gas. It then quit. I eventually got it to a gas station and filled it, then it ran fine. As soon as I got it home I removed the filter and all was well again. I have no doubt the filter added some restriction to the fuel flow. My 250 Star has a fuel pump. I added (upstream of the pump) an inline fuel filter to it. No problems, save one. One winter I drained the carb. Come Spring, I put the fuel petcock into PRIME to fill the carb bowl, and no fuel flowed. The year prior, without the filter, that worked. Absent the fuel pump, I suspect the motorcycle would run poorly if at all with the filter. I agree with the person who said Yamaha would not have installed a fuel pump if it were not needed.
 

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removed my pump 4 years ago. never had a single problem.going around a curve and loosing power i dont get that at all.if i forget to turn on my petcock i can ride two blocks before it starts sputtering.my fuel line goes as direct as possible to each carb.i have no filter because that would lower the lines making them lower than the carbs
running unfiltered fuel might come back to bite you when you least expect it, all it takes is a tiny spec on a float needle and gas will pour from the vent which could find an ignition source and poof
 

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one manifold nipple has the ais vacuum line to it the other has a vacuum plug cap, on mine that plug cap got dry and was leaking causing exhaust popping and lousy performance
 

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wheres the dirt come from?
a little flake of rubber from inside the fuel line will do it, sediment in the tank, a piece of rubber from inside the fuel hose that's connected to the nozzle, dirt or whatever that falls into the storage tank when the cap is opened, empty out an old filter and tell me what you see, crappy dirty fuel is what i usually see, if dirt didn't get trapped in fuel filters we would never have to change em, my friends s10 clogged so bad the truck stopped running, when i removed the filter it felt twice as heavy as the new one it felt like rocks were in it
 

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You're one of the first my friend..... never seen it successful before this.
 
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