Stutter or Loss of Power with load or open throttle - Star Motorcycle Forums: Star Raider, V-Max, V-Star, Road-Star Forum
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post #1 of 48 (permalink) Old 06-09-2016, 02:32 PM Thread Starter
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Stutter or Loss of Power with load or open throttle

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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post #2 of 48 (permalink) Old 06-09-2016, 03:23 PM
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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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post #3 of 48 (permalink) Old 06-09-2016, 03:26 PM
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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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post #4 of 48 (permalink) Old 06-09-2016, 03:37 PM
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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.
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post #5 of 48 (permalink) Old 06-09-2016, 03:47 PM Thread Starter
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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.
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...

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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....
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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post #6 of 48 (permalink) Old 06-09-2016, 03:50 PM Thread Starter
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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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post #7 of 48 (permalink) Old 06-09-2016, 03:51 PM
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when i said vacumn lines all i mean is check whatever rubber parts that could be cracked or loose.
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post #8 of 48 (permalink) Old 06-09-2016, 11:42 PM
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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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--- Striping, lettering and paint by Sick Mick 6* Tree - 2" extended forks 21" front wheel - HK Sideburners - Progressive rear shock Pods Sick Mick solenoid delete - Spring seat - and other stuff

Last edited by Sick Mick; 06-10-2016 at 07:44 PM.
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post #9 of 48 (permalink) Old 06-10-2016, 03:42 AM Thread Starter
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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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post #10 of 48 (permalink) Old 06-10-2016, 05:24 AM
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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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