Fuel Leak...

[jmpacella17]

I took this assembly apart (some sort of diaphragm for fuel delivery; between the fuel pump and carbs), and now it is leaking out of this small hole on the bottom (2nd pic). I couldn't find this listed in my shop manual. Anyone have an exploded view of this, so that I can see if I assembled it incorrectly? Any hints in general?
Thanks in advance for your help! -JP

 

[Andrew Shadow]

It is a vacuum operated fuel shut-off valve. Many people remove them completely and bypass them because the diaphragm tears and can leave you stranded.

Have a look at the below for more detail.

Article [11] - ST1100 - How to do an emergency bypass of the fuel valve | ST1100 Articles

The ST 1100 has a fuel valve that is operated by vacuum from the engine. This valve has been known to fail, and like most failures, it won't happen in your driveway - odds are that it will happen when you are a long way from home. The valve usually doesn't fail abruptly and bring you to a...

www.st-owners.com

 

[Andrew Shadow]

Here is some more information for you.

ST1100 fuel shut off valve | ST1100 Related

The Honda parts dealer seems to only have the complete Valve , $ 250 + shiping and taxes . Found this on e-bay . Anyone tried these ? I have not had any problems with the original valve/auto petcock , but trying to stay ahead of the game . Ebay : Petcock Repair Kit Valve ST1100 ST1100AL...

www.st-owners.com

 

[red one]

Or you can replace the whole assembly for $140.00. Don't ask me how I know

 

[rwthomas1]

I just bypassed it. One less thing to fail. Remove the fuel line from the filter, and the valve, then simply put the fuel line from the carbs to the fuel filter. Its so easy its like they designed it that way. Don't forget to plug the now vestigial vacuum line. The argument can be made that if a carb float needle sticks open there would be no way to shut off the fuel, IF the tank is more than half full. Yup. I'll live with that infinitesimal risk. I'm a rebel.

 

[jmpacella17]

Thanks for your help, guys! I think I’ll just go ahead and bypass it then. Ironically, mine failed at the base of our driveway so that was handy.

 

[John OoSTerhuis]

(Dis)assembly order:

 

[mortenk]

It's called a petcock valve. I had one fail in the mountains of Corsica on my 1983 XJ900. Gasoline was pouring onto my feet/sandals. I removed the tank, poured the gasoline into some empty soda bottles (roads were littered with them back then), and then found the culprit. I took the petcock valve apart and found a small tear in the diaphragm. I repaired it with super glue (never leave home without it). It was meant to be a temporary fix until I got back to Denmark, but I ended up riding with this until I sold the bike

 

[ST_SVK]

This was first part which I removed from bike. Put plug into vacuum tube and that´s all.

 

[Uncle Phil]

They've been long gone on all four of ST1100s ...

 

[Oldbikefixr]

Seems my OCD keeps my bikes original unless there is no alternative. I rebuilt the valve on our 1991 about seven years back. The only symptom was a strong gas smell in the garage. The diaphragm had a rather long crack but hadn't any other symptoms that I remember. Did it again two years back when the bike peed gasoline onto the garage floor overnight....I just replaced or rebuilt everything that could have caused it at that point, it was 30 years old at that point.

 

[jmpacella17]

Need some more help on this, guys. I have a related issue, I believe. Since removal of the petcock valve, the bike did not idle consistently. If stopped at a sign/light, the revs would continue to drop down and then stall.

Then I just let it sit for about 4 weeks after Thanksgiving to Christmas (it's been in the 30's here in PA). I tried to start it, and it wouldn't turn over even though the battery was on tender (had plenty of juice, lights were on). So, I tried to bump start it, and the tire wouldn't rotate even in 3rd or 4th gear. I did end up getting it to finally turn over, but it acted like it was flooded. And, then when it did run it seemed to be running on 3 cylinders. So, I checked the plugs, and one was fouled, and it appeared that there was a lot of fuel in that same cylinder (sprayed out when I checked spark...that was exciting .

So, I replaced the plug, started it, and it ran, but did the same thing as before (didn't idle consistently and ran a little rough). I turned it off after running it a little while, parked it in the garage on the center stand, and tried to start it again this today. Again, it wouldn't turn over.

Is it possible, it is hydro-locking? If so, what could be causing this? Does this mean I have a stuck float(s)? Please let me know if you have any insights or things to check...

 

[Uncle Phil]

Any idea if it is the stock fuel pump or aftermarket one?
Some of the non OEM ones put out way too much pressure for the carbs.
I would be surprised if it is hydro-locking.
I'd check spark on all 4 cylinder first - if nothing else, old plug grounded on the engine.
If you are getting good spark, then fuel is the next suspect.

 

[jmpacella17]

All 4 have good spark. The fuel pump is aftermarket (quantum hip-360-ST). Do you think that could be the culprit? Does that meant the petcock acts as a regulator? And if this is the problem, what’s the failure mechanism?

 

[Uncle Phil]

All 4 have good spark. The fuel pump is aftermarket (quantum hip-360-ST). Do you think that could be the culprit? Does that meant the petcock acts as a regulator? And if this is the problem, what’s the failure mechanism?

If it's a Quantum, I can just about guarantee it's putting out too much pressure (6-8 PSI and you only need about 1-2 PSI).

Article [11] - ST1100 - Fuel Pump Replacement | ST1100 Articles | Page 3 | ST-Owners.com

 

[Al st1100]

All 4 have good spark. The fuel pump is aftermarket (quantum hip-360-ST). Do you think that could be the culprit? Does that meant the petcock acts as a regulator? And if this is the problem, what’s the failure mechanism?

the original fuel pump has the regulator attached to it. What were the fuel pressure specs on the pump you used ? only need 3-5psi or close too that. Some of those pumps can be upwards of 30 psi, problem on a carburated bike.

 

[jmpacella17]

I’ll have to double check the pressure specs. If it’s too high, what’s the best way to fix it? Put a regulator in line with it? Put a resistor before the fuel pump? New fuel pump?

 

[Uncle Phil]

I’ll have to double check the pressure specs. If it’s too high, what’s the best way to fix it? Put a regulator in line with it? Put a resistor before the fuel pump? New fuel pump?

You'll need a pressure gauge to check the actual flow to be sure.
Unless you have one, probably cheaper to pick up a fuel regulator on flea bay like I note in my article.

 

[jmpacella17]

Thanks, Phil!

 

[Uncle Phil]

I just went out and looked at the boxes of the Quantum fuels pumps that I have.
They are marked HFP-360 on the box - which is probably the exact same model you have that is 'specified' for the ST1100.
I had a long discussion with Quantum about the fact that their pump was putting out way too much pressure but they never did anything about it AFAIK.
That is why I went with an external pressure regulator so I could adjust it until I got it where it should be.
They did say that using a regulator would not cause a problem with their pumps.