Fuel System Frustrations (I think) ... Causing me to be Depressed!

I am having a intermittent problem that I would love to get some input from other folks. About two months ago I jumped into addressing a sudden occurrence that remained persistent. Symptoms where "very low power", "low idle", "loud popping" and "terrible gas mileage" (per bike computer). So I dug into the bike and input from this site and my Honda service manual (details listed below). The main effort was to replace the fuel pump and filter.

After doing this service the problems went away and everything was peachy keen and happy again! My spirits were lifted and me and the bike were off again to hit the road.

However last night while on the interstate the same symptons re-appeared and of course it was in the dark and there was heavy construction and barrels everywhere. I had to use a lot of throttle to keep up my speed. I pulled off the highway to head home via country roads and had to really use a lot of throttle to not stall at intersections. On my final stretch home I got so frustrated while riding I simply pulled in the clutch and pulled the throttle back to take the tach toward redline. It was totally a moment of anger but at that moment the power returned and the bike jumped back to normal and the rest of my ride home was fine. I parked it back in the garage and it purred like it's former self.

This morning I start it up. No problems. I let it idle in neutral and come up to temperature. I seems a bit rough but it's ok. Then the idle starts to dip down from 1,000 rpm slowly to about 600 rpm. So while still just sitting there I carefully pull back the throttle and take it up to about 6,500 rpm. It then abruptly jumps up to red line at which point I release the throttle. It then settles back into the proper 1,000 rpm idle and it sounds smooth again. I leave it to idle and after about ten minutes it begins to creep down to about 600 rpm again. I repeat this cycle several times. It will stay at proper idle for a few minutes but eventually drift downward.

Service Work done by myself per all the steps in my Honda Service Manual

1. Serviced the upper tank
   
   ​
   ​
   emptied / removed / cleaned / installed upper tank. Replaced all hoses per manual recommendations
2. Serviced the lower fuel tank
   
   ​
   ​
   removed fuel pump and cleaned out lower tank. It was already pretty clean.
3. Serviced the fuel pump assembly
   
   ​
   ​
   carefully and gingerly removed fuel pump assembly from lower tank. Replaced fuel pump with http://www.highflowfuel.com/i-14521145-new-intank-efi-fuel-pump-honda-st1300-2003-2013.html. Also replaced the fuel filter, fuel sock "thing" and the gasket.
4. Serviced the air box
   
   ​
   ​
   carefully and gingerly removed / cleaned the airbox and replaced the air filter.
5. Serviced the coolant
   
   ​
   ​
   Did a complete coolant flush (while all the tupperware was off)

What about the 5 way t connector and hoses? have you checked those? might have gunk.

This sounds like a problem with the vacuumed lines and the 5 way tee as mellow suggested. When you do a throttle body sync. You have to hold the throttle open a few seconds to enter a code once this is done the bike will then go back to smoothly running and idling again. Sounds like this is what you were accidentally doing trying to keep it running. I would remove the mailbox and replace all the vac lines with new ones and do a tb sync. I bet this will fix your bikes issues. You should also look around under there to make sure mice have not built a home or chewed anything. Standing by the white courtesy :call: if needed.

Thanks for the fuel pump info

Oh the dreaded 5 way t connector and hoses. So help me out here. Are those located UNDER the throttle bodies which means I would have to remove the throttle bodies to get to them.

If so I also have the annoying coolant drip which I understand also requires the removal of the throttle bodies to get to.

randmun said:

Oh the dreaded 5 way t connector and hoses. So help me out here. Are those located UNDER the throttle bodies which means I would have to remove the throttle bodies to get to them.

If so I also have the annoying coolant drip which I understand also requires the removal of the throttle bodies to get to.

Click to expand...

No and no.. it's in the throttle body area between them but not under.. you remove the airbox and you'll see them... For the coolant leak you won't need to remove them either, assuming that is where the leak is coming from.

Great article here from John:
https://www.st-owners.com/forums/showthread.php?38212-ST1300-1st-Significant-Service-Coolant-Thermostat-Starter-Valve-Synch-amp-Other

and his pic while doing a sync, all the hoses are going to the 5way t

Normally I'm a "Yes" sort of guy but those were two very welcomed "No"'s.

So I can remove / clean the 5-way thing with only removing the airbox? Darn I was just down in there ...

Mellow said:

No and no.. it's in the throttle body area between them but not under.. you remove the airbox and you'll see them... For the coolant leak you won't need to remove them either, assuming that is where the leak is coming from.

Great article here from John:
https://www.st-owners.com/forums/showthread.php?38212-ST1300-1st-Significant-Service-Coolant-Thermostat-Starter-Valve-Synch-amp-Other

and his pic while doing a sync, all the hoses are going to the 5way t

Click to expand...

So THAT'S what those T-handle thingys are for...

Good Ridin'
slmjim

randmun said:

So I can remove / clean the 5-way thing with only removing the airbox? Darn I was just down in there ...

Click to expand...

I've actually never had the chance to do that but have had the airbox out before so yes that should be good enough. Check the hoses as well for any cracks and be mindful to check the elbow hose that connects the upper and lower fuel tanks as it can be a dangerous situation if that does have a crack... if the bike is over 5 years old might even be a good idea to replace it as well. Sorry to keep adding to the list, just telling you what I'd do.

Replaced the big hoses from the upper to lower tanks per the service manual. The new one was a lot "newer" than the original so that was a good decision.

I had looked at that picture before but never thought to read the detailed text with it that highlights the 5-way T.

The 5-way tee is #5 by the F-46

For coolant hose access the service manual dictates removing the throttle body but the easiest way is to remove the radiator and a frame crossmember behind it.

When I got my ST, it was a minor coolant dripper and always smelled of coolant. I just tightened the worm clamps on the hoses in the vee and that has stopped it for almost a year. I do expect I will be back in there at some point though. That was too easy...

Another thing to check into. Take a look at your exhaust on both sides of the bike especially the area where the pipe expands out into the catalytic converter (between the driver and passenger footpegs). If one of the pipes has started to blue out then I suspect you have a possible ignition/coil problem on that side...

Your symptoms seem pretty severe for just a clogged 5 way tee but Igofar has way more experience here than I do. I would have thought that it might be a tank venting issue causing fuel starvation. Time will tell. Replacing the vacuum lines and cleaning the tee is required maintenance on these bikes anyway. Good luck.

So follow-up on my fuel system issue. Rode about 200 miles over the last two days. Mixture of expressway, country and city. Also quite a chunk in severe rain (don't know if that impacts fuel systems). Anyways I had four individual incidents where the idle went from 1000 down to 600. All four were approaching or sitting at intersections. The simple solution in each was to pull in the clutch and pull back to the throttle to about 5,500 upon which the rpm's would jump up to about 8,000 and then I would release the throttle and it nicely settled back down into the proper idle until it happened randomly again. This was sporadic and you could not predict when it would or would not occur. After each incident the power and gas mileage (per computer) would return back to it's normal parameters.

About 100 miles of those 200 miles where with my wife as pillion. I told her ahead of time the bike might "act up". Later I asked if she noticed anything and she said she did not. So the ride qualities to her where not noticeable as long as I 'popped' the throttle during these moments.

So I'm glad that it's not cutting back on my riding time, but am I just kidding myself. I probably won't have the time to "open up" the bike again to get to the vacuum hoses as work will not permit for several more months. I really hope to stumble along and not lose out on the best time for riding in Ohio.

Scooter posted
Another thing to check into. Take a look at your exhaust on both sides of the bike especially the area where the pipe expands out into the catalytic converter (between the driver and passenger footpegs). If one of the pipes has started to blue out then I suspect you have a possible ignition/coil problem on that side..

Attached are right and left pictures of my exhaust. The bike at 71K on the odometer. Does it look "blued out"?

They're both well beyond blued out....I don't recall seeing st13 pipes that heat-damaged before. Both banks (coils) appear to be firing, but fuel to air ratio appears outta whack. I suspect your ECU is going into limp-home mode due to some sensor issues (should have a FI light blink sequence), or the vacuum lines or 5way tee are intermittently plugged.

I have never experienced an FI light turn on (except when I initially turn on the key for a few brief seconds and with no blinks) during my ownership since 2012 and put on about 10K miles.

When I replaced the fuel filter (beginning of this posting) it was severely blocked. I tried to blow thru the filter and only a small amount of air came through vs. the new filter was totally free flowing.

Is it possible that the blocked fuel filter could have caused the bluing? And since the pipes are stainless steel can I just use some of the "barkeepers friend" that I use to clean my stainless steel sink?

I don't see how a blocked fuel filter would create that--bluing comes from excess heat generated in the catalytic converters (from unburned hydrocarbons getting into them). A restricted fuel filter would result in less fuel, not excess fuel.

What mileage (calculated, not displayed) is the bike averaging?

Yes, you can use bar keep on them, many of us have done so to take off the slight bluing tinge that is common. But I expect it will be only partially effective on yours.

Let us know what you find.