Carbs or something more

[Lou]

I'm a new owner. Bought a 94 st1100 at the end of the summer . It sat while I waited for a registration due to Covid. When I started it after, about 3 weeks on the center stand, I got a significant amount of gas that blew out of my muffler vents/drain holes. This cleared and I didn't have the issue again until today. I was adding stabil for the winter and started it and out came the gas again. Again it cleared but I know this is or shouldn't be the norm. the diaphragms were replaced just before I made this purchase by the previous owner. I have also noticed a little bit of a backfire when the throttle is revved and released.
I'm thinking that maybe the floats are set too high or the float valve or valve seat are leaking by.
Any input to this issue would be appreciated .
Thanks Lou

 

[dwalby]

liquid dripping out the muffler vent/drain holes is usually just water vapor that has condensed, did you smell it to verify it was gasoline and not water?

 

[Oldbikefixr]

Check the diaphragm in the vacuum shutoff valve. It's the flat/round valve that connects with the fuel filter on the right side of the tank. If the diaphragm is ruptured, repair kits are available OR it can be removed. Just search on 'vacuum shutoff removal' via the search function, top right of this page.
I bought a very low mile 1991 which ran great for a bit. One morning I was greeted with nearly a gallon of gasoline on the garage floor. I traced the leak to the V-area under the carbs...wasn't much of an effort to locate it. Drained the remaining gas from the tank and rebuilt the carbs. You can see what all I found/fixed under 'ST1100 refurbishment' that I did last October/November (2021) under the search function. The two primary fuel intake hoses between the pump and aft of the carbs were hardened and split...as were most of the other vent and drain hoses.
Sometimes it isn't the miles but the time that causes problems.

 

[CYYJ]

Hi Lou:

Welcome to our forum community, and congratulations on your purchase of the ST 1100.

Here's a link to a post with photos that illustrates the vacuum fuel shutoff valve. This particular post explains how to do an emergency bypass of this valve if it fails to open... sounds like you have the opposite problem, which is that the valve fails to close. The primary purpose of the valve is to shut off fuel to the engine when the engine is not running, this so that if the bike falls over on its side, fuel does not continue to run (or siphon) out.

ST1100 - How to do an emergency bypass of the fuel valve

Some owners have removed this valve (permanently bypassed it), but my personal opinion is that it is an important safety feature and if the valve fails, it should be replaced. Mine failed at about 30,000 miles, but I now have an additional 140,000 miles on the replacement valve with no problems.

Some other tips for you, seeing as you are a new owner:

1) We have a section in our forum community called ST 1100 Articles. This is a curated collection of the best-written, most useful "how to fix it" posts made over the past 15 years. Make a coffee and settle in for about an hour or two of browsing in that section - it will be well worth your time.

2) The fasteners on the bike that look like Phillips screws are not Phillips screws, they are JIS (Japanese Industrial Specification) screws. The profile is very different from Phillips. If you use a Phillips screwdriver on them, you will chew the heads up and have difficulty removing or tightening the screws. For about $25, you can get a set of 3 JIS screwdrivers. Do a search for "Vessel JIS Screwdrivers" and order a set of 3. If money is tight, just get the middle size, that will meet 90% of your needs. Here's a link to an article with more information: Vessel JIS Screwdrivers Review.

3) Try and get your hands on a Honda Service Manual for the ST 1100, it will be of great help to you. You might be able to get a copy at a Honda dealer (probably about $40), then again, it might be out of print. Sometimes they show up in the "for sale" section of our forum.

Michael

 

[Lou]

Sorry about the delay responding to you all. thank you for the help. I will definitely check out the vacuum fuel shut off.Hopefully this is the issue. With winter setting in, I will try to wait for a day with a little milder weather. Unfortunately, no garage but a shed that like most is very tight. I do appreciate the communities extra help with threads and must have tools, another thing that I was unaware of. I will be purchasing a set of these.
Again, thanks for the quick response. When I finally get to it , I will post the results.
Lou