ST1100 Vacuum Fuel Shutoff Repair sequence help needed

I recently had the problem where the bike shut off under high speed and would start up on the side of the road after a bit of a break. I replaced the fuel filter which did not solve the problem. After doing some searching here I found it could be the fuel shutoff diaphragm. I ordered the K&L kit and took things apart this morning. The bigger rubber diaphragm had about a 1/4 long tear in it.
As I'm taking it apart the spring fell right out and now I can't figure out how it goes back together. I read the report at this link but without pics I'm kinda lost.. https://www.st-owners.com/forums/showthread.php?1711-ST1100-Fuel-Shutoff-Repair

I understand how the 2 rubber diaphragms fit together with the small metal piece inside. Does the spring sit in the recessed hole in the piece that has all the tubing ports or does it side inside the two halves that go together before you place it on the ported piece? I think the latter is right as the spring seems to sit better in the flatter piece. The only thing with this is that the spring sits against the bigger diaphragm directly.

Hard to explain I know. Here are some pics below as to how it might go together 2 different ways.

It would have been easier to just get rid of it,that's what I did, sorry I can't be of any help with your question.

I've run my 01 for many thousands of miles without the device as have many others here. The space taken up by the vacuum cut off works pretty good to hold an in line fuel pump too.

Leave it off, plug the small vacuum line and put a good fuel filter there. That's what a lot of us do.

Well I already figured it out on my own. Took it out for a test ride and it seems fine. The bypass is an option if this does not work out.

Glad ya got'er up 'n running.

I've never had mine apart but understand the need for a fuel shut-off to prevent fuel from gravity feeding past the carb float valves and contaminating your engine oil.....making for very expensive repairs.

The ST is fairly new to me and also my first bike with a fuel tank that is not in the conventional (gravity feed) location on the bike. On all my other machines I make CERTAIN that the fuel is OFF when the bike is not in use and have replace any vacuum operated valves with manually operated valved. I realize that this is not an option on the ST due to the placement of the valve (without drilling a big hole in the faux-fuel tank at least)

I don't know how much fuel will actually gravity feed into the ST without the fuel pump running but I'm certain that some part of a full tank will since that's the reason Honda went to the expense of fitting this valve in the first place.

I know that many...well most long-term ST owners have removed this valve but, in my view at least, it should be necessary to provide an additional valve between the fuel tank and the carbs rather than relying on the float valves alone.

WHEW !....Now to try to answer your question.

The general way these valves work is for the spring to holed the valve CLOSED so fuel can not flow.

Then when the engine starts, manifold vacuum acts on the diaphragm to OPEN the valve and allow fuel to flow.

Either by studying the valve or by attaching a few bits of tubing and simply sucking and/or blowing through the lines you should find the combination that allows the valve to work as intended.

Hope this helps, let us know.

Ray

Good point, Ray, about the gravity feed but the majority of the ST gas is below the carbs. Also many of us have found the float bowl shut off valves are strong enuff to prevent siphoning. I've had not problem over many thousands of miles without the vacuum valve.

ak85lp said:

I ordered the K&L kit and took things apart this morning.

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And did the K&L diaphragm actually fit the housing? I'd two of those buggers here, oval like an Easter egg there was NO WAY of getting them sealing in the housing rims...
I'd to get replacements (for the replacements...<grrr>) at http://www.nrp-carbs.co.uk/ which where perfectly made however, literally a 'drop in' fitment.
I too advocate for that automatic fuel petcock as important safety device, you don't want to find your mount parked in a pool of combustible liquid one day...

float bowl shut off valves are strong enuff to prevent siphoning.

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Siphoning ! ...... Of course.

I should have thought of that. The if the carbs are below most of the fuel the valve acts more as a "siphone break" (but likely doesn't allow air in the lines like a real siphon break would) or just a stopper valve.

So, theoretically, you could siphon a LOT of fuel into your crankcase if the carb float valves go bad.

find your mount parked in a pool of combustible liquid one day..

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The thing is that you will not find a pool of fuel under the bike. If so, something amiss would be obvious. The fuel will just fill up the crankcase and it will look (if you check) like your oil is overfull. With the sight-glass version of the dip-stick on our bikes, you'll just see the sight glass full and may not give it a second thought.

I know most people have not had a problem with this but with 4 carbs you have 4 times the chance that one float valve will go bad or a small piece of debris will lodge in the valve seat and hold the valve open.

I have seen engines ruined due to fuel dilution into the crankcase. I'd certainly like NOT to have this happen on my machines.

ladder106 said:

The thing is that you will not find a pool of fuel under the bike.

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well, some did... the carb bowl overflow drain runs just behind the side/kick stand... temperature change due to leaving the vehicle parked in the sun in combination with a petcock bypass... and if above that all the needles/jets are leaking... whilst I doubt that much 'syphoning' could actually occur, most of the ST1100 tank sits below the carb level, only the filler neck sticks out there.
YMMV, I however see to keep the auto valve in functional state.

DOT regulations dictated the existance of auto- fuel shut-offs on scoots. +1 on ST1100Y suggestion. Fuel run-over on a hot motor in case of a tip-over would NOT be an option you wanna be involved in! Fix or replace at first oppertuinity if temp. by-passed to get ya' home IMO IS the best choice. Way to many odds against you as it is when we throw a leg over these scoots and hit the start button.

Literally thousands, probably 1000000s of miles on st1100s with out any one reporting a siphoned gas issue.
just get rid of the shutoff valve.

Brant said:

DOT regulations dictated the existance of auto- fuel shut-offs on scoots. +1 on ST1100Y suggestion. Fuel run-over on a hot motor in case of a tip-over would NOT be an option you wanna be involved in! Fix or replace at first oppertuinity if temp. by-passed to get ya' home IMO IS the best choice. Way to many odds against you as it is when we throw a leg over these scoots and hit the start button.

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jes now ye've got me worried lol, I removed mine when eliminating poor running problems, but it turned out the coils were bad,replaced them and all was fine.
Just never bothered replacing the shut off valve, which I'm fairly sure was working a 100%. might just stick it back in and see how she runs.

I replaced the stock fuel shut-off valve with a mechanical check valve. I didn't like the idea of not having some type of fuel shut-off and I also wanted to add some additional restriction to flow since I installed the low pressure Delphi auto fuel pump to get rid of the factory plastic unit.

Mark said:

Literally thousands, probably 1000000s of miles on st1100s with out any one reporting a siphoned gas issue.
just get rid of the shutoff valve.

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#1 on that!

... probably 1000000s of miles...

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For those that can't or didn't count the "0's", that is millions. I'll lay claim to about 200,000 of those millions. I've had more problems with flat tires and/or tip overs.

I was just going on what I consider the Guru of the ST Jon O on what he said here:

https://www.st-owners.com/forums/showthread.php?29593-ST1100-Fuel-Pit-Cock-Problem-Or-is-it&p=312449&viewfull=1#post312449

ak85lp said:

I was just going on what I consider the Guru of the ST Jon O on what he said here:

https://www.st-owners.com/forums/showthread.php?29593-ST1100-Fuel-Pit-Cock-Problem-Or-is-it&p=312449&viewfull=1#post312449

Click to expand...

I remember at the time there was a lot of pressure in the tank when removing the cap, so like it says on this link, I removed the 'doohickey' rubber in the cap to let the vent pipe work better, so according to that thread me having removed the shutoff valve won't be a problem.

So I went on-line shopping for a repair kit....thought I'd have a spare or maybe two on hand. Just in case.

Can't find 'em anywhere. There's one on eBay for $54.00 . Weren't these about $20 a while back?

Also, they appear to also have been used on the GL1500s. Is this true?

If anyone can suggest a place to purchase these for a reasonable price, I'd be obliged.

Ray