Help! ST1100 dying on the road, fuel contamination or???

Need some suggestions please.

My 1100's been dying on me lately.

Symptoms- Riding along at highway speed, bike will start to stumble slightly, then speed starts to drop off as if it were running out of fuel. Similar to running out of fuel or to sucking up water.
Coast to a stop and give it a minute, then feed it full choke at which point it will usually start on 1 or 2 cylinders, then eventually clear and run on 4, choke off.

Drained the tank as much as possible. Added methyl hydrate to absorb water, filled with fresh high test and added some Seafoam for good measure.

Problem persists.

Changed fuel filter this past winter.

Bike has 100 km's/60,000 miles

Ideas?

Sounds like my bike when my fuel pump started to go. How is your miles/gal, down a little?

Do you still have the vacuum petcock/shutoff valve?

Twinpine said:

Sounds like my bike when my fuel pump started to go. How is your miles/gal, down a little?

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Mileage is fine.

flyfisher said:

Do you still have the vacuum petcock/shutoff valve?

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I honestly don't know what the setup is on my bike.

Is that a problem area?

Johnny Rocco said:

I honestly don't know what the setup is on my bike.

Is that a problem area?

Click to expand...

That it tis'...........remove the turtle top and right side-cover panel. Follow fuel line AHEAD of fuel filter. Fuel line goes to vacuum valve. By-pass fuel line around it, and plug the vacuum line that goes to vacuum valve shut-off. Problem solved........you can either replace vacuum valve assembly or leave it bypassed as several have done on here. Replace fuel filter with a new OEM Honda fuel filter while your there also.

Seems to be a pretty common issue....look in the st1100 technical forum for it......good luck.........ff

Remove the cutoff valve (pretty simply). If that doesn't fix, probably your fuel pump - especially when you are at less than a half a tank and the outside temps are up. At least that was my experience both times.

Given the symptoms that sounds a lot more like a fuel pump failure than the vacuum valve.

You can do a health check on your pump while it is installed using a multimeter set to current. If you clip one wire to the battery positive, and touch the other end to the terminal on the fuel pump flange with the brown/red wire, you can power the pump and measure current draw. According to Norm, the current draw for a healthy pump should be 1.2A, and they stop pumping much below 0.7A.

I have installed an Airtex pump that (so far) has worked very well.

My experience has been very much like the thread started, and it was the vacuum valve. A quick bypass and he will know for sure.

If you need a used pump? I have one for sale.

For grins, check the side stand spring and switch too. I had stalling/cut out issue going down the road and after some help from the board, found the spring was weak. Replaced the spring and cleaned the switch. Took care of that problem.

Peace and All Good

I agree and am betting on the vacuum cutoff valve.
When you route around it (can be done with existing hoses) make sure you plug the vacuum line.

The by-pass is a 5 minute job when you get the plastic off. Un-do and re-do 2 hose clamps and plug the vac. hose. Use one of the screws holding the valve on to plug the hose. The valve is right beside where your right knee would be under the plastic. It is mounted to the plastic air filter box. As mentioned above, see this:

http://www.st-riders.net/index.php?topic=3919.0

Thanks all for your wisdom and suggestions.

I will start with the valve bypass and see what transpires.

+1 on the Vacuum Petcock. Do that first and see if it makes a difference. My $$$ is that it will!

TerryS said:

You can do a health check on your pump while it is installed using a multimeter set to current. If you clip one wire to the battery positive, and touch the other end to the terminal on the fuel pump flange with the brown/red wire, you can power the pump and measure current draw. According to Norm, the current draw for a healthy pump should be 1.2A, and they stop pumping much below 0.7A.

Click to expand...

It can also be done without using the battery terminal at all. Just remove the brown/red wire connector from the pump terminal, and connect the meter leads between the terminal and the connector. You will need a small male terminal (or thin screwdriver, or other thin metallic object) to insert into the female connector on the wire side.

Looks like it's the vacuum valve.

I pulled the turtle and side covers and saw that the valve was leaking fuel and there is evidence of fuel dripping underneath it.

Following the link Ron provided, I removed the valve and plugged the vacuum line.

I'll go for a long ride this week and see if all's well.

Can the valve be left out permanently?

Thanks again for all the advice.

John

Johnny Rocco said:

Can the valve be left out permanently?

John

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Yes. I and many others run without it.

Johnny Rocco said:

Can the valve be left out permanently?
John

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Yes +1. I've ridden two of ST1100s for thousands of miles without them. It's purpose it to cutoff the fuel in case of a tipover. But I always figure if I have a tipover, I have other things to be more concerned about ... ;-)