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Discussion Starter #1
When I have the gas tank on it's support, the bike idles nice and smooth. The minute I drop it down it idles up and down, stalls pops and is not happy. Where do I start? I put in a new filter, because I had one, thinking that was the problem.

No idea where to start, but it seems like a fuel starvation problem. Is there a screen I should change in the pump?

Help, my GF is getting pissed because she can't go for a ride to try her new helmet!
Mark
 

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There is a sump screen on the pump's inlet. I think I'd check to see if a hose is getting pinched when you lower the tank before going at the pump. If the screen was clogged, I feel it wouldn't matter if the tank was up or down. Only other thing I can think of is a piece of debris falling over the inlet hole at the pump flange when the tank is lowered, but what are the odds of that?
 

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Discussion Starter #3
I did check for a pinched hose. I will take a look at the filter screen for the fuel pump, that maybe the problem.
 

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Last summer on the last day of a week-long ride my friend's '02 ST4s backfired and died leaving a light. The bike had intermittently exhibited some rough running that would clear, then might worsen after rain the prior few days. Bike was trailered the last 100 miles home. My friend somehow discovered the bike ran fine with the tank lifted but would die when lowered, and specifically the last inch or so. Ultimately the culprit was a spark plug wire had worn through and was grounding-out the ignition. You might check that.

Joe
 

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if it's ok with the tank up, it's something physical to do with dropping the tank. ie, hose crimping (check both, i have seen return hoses crimping making them run rich), wiring movement/bending, something being loaded, water in tank moving into pick up.
 

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Discussion Starter #6
I just took the tank off and inspected the pre filter for the fuel pump. There was a piece of felt like stuff on the bottom of the filter and it had a small tear in it too. I also found a bare wire. I do have a replacement pre filter, so that is easy to fix. Can the wire being bare cause a problem?
 

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I just took the tank off and inspected the pre filter for the fuel pump. There was a piece of felt like stuff on the bottom of the filter and it had a small tear in it too. I also found a bare wire. I do have a replacement pre filter, so that is easy to fix. Can the wire being bare cause a problem?
Yes it can. If there is no insulation around the wire it can be grounding out. To check this i would simply wrap it with a significant amount of electrical tape AND move the wire to a new position if possible. If it starts running fine, you know that's your problem.
 

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Discussion Starter #8
Two things going on then...
The junk on the screen and the wire. To repair the wire do you need gasoline resistant electrical wire? Electrical tape with break down in gasoline right? Or do I have to purchase a new pressure reg?
 

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Two things going on then...
The junk on the screen and the wire. To repair the wire do you need gasoline resistant electrical wire? Electrical tape with break down in gasoline right? Or do I have to purchase a new pressure reg?
Unfortunately I don't know where this wire is because your picture is zoomed in. :frown2: Is the wire inside the tank? Exposed to gas you're saying?
 

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Discussion Starter #11
Yes the wire is from the pressure reg to the fuel pump, inside the tank. Replace with what a wire that is gas resistance? Where do I get that?
 

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I don't think the bared wire is a big problem, despite the electricity running through the fuel without a spark source & oxygen there is no safety issue.

Your miss or poor running is as Brad said something simpler.

By all means repair the bared wire with a crimp joiner and find the problem.

It is not advised to lift the fuel tank with a full tank, but you might have to 3/4 fill and see if the problem remains to rule out an internal problem.

Here's a photo of the sump where the screen resides beneath the fuel pump and it is a collector of shit so check it carefully for flaked rust etc

Craig
 

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There was an St on here not long ago. It would cut out , but only with a full tank of fuel it was fine below ½ a tank. Turned out to be the fuel pump.
 

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Discussion Starter #17
Thanks for the info bradblack. I will make a visual inspection to see if it something the dealer missed when they did the 30,000 mile service
 

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Discussion Starter #18
I looked over the bike and discovered when I lowered the tank the support rod was pushing on the spark plug wire. Upon further inspection, the metal cap on the spark plug, was loose. The dealer must have not tightened the threaded part well enough and it has backed out.

So as I understand, the only way you can buy the spark plugs for my ST 3 is with out the metal cap attached. You need to buy the caps separately and attached them to the threaded post on the plug. I will be replacing all four plugs with new ones, I have the ones with the threaded post that require the metal cap to be installed. So my question is, when installing the caps, loctite or what?

Thanks for everyones help!
 

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Hm, I don't know where you're buying spark plugs, but mine always come with the "cap". Even if it's loose in the box, it's always in there.

I installed some of the iridium plugs last time. I can't tell any difference performance-wise between those and the previous plugs, but they had the "caps" with them.

Joe
 

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When I put the iridium plugs in .... it was because I knew they were supposed to be longer life ... an added plus was maybe a bit more performance .... better response .... or maybe just , wishful thinking since I paid so much for them ... ?
Craig
 
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