Gas Smell

Joined
Jul 23, 2012
Messages
36
Location
western Montana
Bike
'91 ST1100
Ok, before I ask anything I have to acknowledge something that I know is preaching to the choir.

I started riding scooters/motorcycles in the early sixties. Over the years I have owned/ridden many different types and sizes. After doing this work on this bike which culminated in "finally", successfully, syncing. the carbs. (to no fault of the tester, but, testee) I never thought this motorcycle would/could improve in its smoothness, but, it did. It truly is, in my humble opinion, as close to a perfect motorcycle as one could get.

With that said, however, I still have remnants of the main issue why I started this project to begin with, a gas smell. It is still there. It is noticeable, at times, approx. ten min. after I shut down. I did only a cursory look at both the overflow & vent hoses and they appeared ok though I did not pull them. I also did not separate the carbs when I had them off to check the "o" rings(too scared). I did,however, replace all the fuel hoses w/ new as well as a new "glass" filter.

What could/might be the most common guesses? The bike has 52,000mi. though someone has worked on this before me.

Thanks
 

Mark

Gotta make tracks
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70
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Apache Junction AZ
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KTM 525exc
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3768
Re: the thing is

I had a gas smell (and residue beneath) the vacuum shutoff; before I removed it completely.
 
OP
OP
Joined
Jul 23, 2012
Messages
36
Location
western Montana
Bike
'91 ST1100
Re: the thing is

What/where is the vacuum shut-off? Is it a part of the pair system? If so, I did just remove this system. Or, is it the valve that is attached to the right side of the base of the air filter?
 
Joined
Aug 6, 2011
Messages
241
Location
Grand Haven MI
Bike
2004 ST1300
STOC #
8800
Re: the thing is

The vacuum is on the right hand side of the air filter housing, just above the fuel filter. 2 screw hold the unit on the air filter housing
& 4 screws hold the parts together. The Honda manual call this a petcock, some call a fuel regulator with yet others calling this a vacuum shutoff.
This part causes issues on some bikes & people take it out of the fuel system completely.
 
OP
OP
Joined
Jul 23, 2012
Messages
36
Location
western Montana
Bike
'91 ST1100
Re: the thing is

Ok, the valve is gone. I will try the bike this weekend to see...(?)

Thanks
 
Joined
Sep 10, 2011
Messages
2,211
Location
West Michigan
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'98 ST1100
STOC #
8470
Check to see if the clamp on the left hand side of the gas tank that secures the vent tube that connects to the gas cap isn't compressing the tube completely. Mine was, without a doubt. There was no way the tank was being vented properly with the hose compressed. I got a longer screw and locknut to replace the very short original sheet metal screw. The tube is now secured, but not compressed, so I know the tank is vented. BTW, you should be able to test the vent valve in the gas cap by blowing and sucking on a hose attached to the gas cap vent port. It should release in both directions.
 
OP
OP
Joined
Jul 23, 2012
Messages
36
Location
western Montana
Bike
'91 ST1100
Ok, I will check that.

I did remove the "vacuum shutoff" valve which seemed to have helped a little, but, it's still there. Having not had an ST before, are they prone to having this issue? Is it something not to worry about? It seems as though I have checked and re-checked all the possibles. (?)
 
Joined
Aug 24, 2012
Messages
418
Location
Park Ridge, NJ
Bike
1994 ST1100
Talking about gas smell, when I got my 1100 last August, she smelled gas after every start. I don't even know how long this bike was parked before I got it but I assume awhile since tires were half the pressure. I didn't know back than as much about STs as I do now so I didn't pay no mind to it. After 20 years of bike starvation I just wanted to ride. Now she doesn't smell gas at all. Never synced the carbs even thoug I bought motion pro sync tool and want to do it every weekend it's just not enough time for everything.
Just ride for some time and it might disappear like mine did. Unless you find fuel leak than its another story.

Mark
 
OP
OP
Joined
Jul 23, 2012
Messages
36
Location
western Montana
Bike
'91 ST1100
Yes, that is about where I am at. The last 2 1/2 months I have had this bike apart so many times I could do it in my sleep. The only time it smells of gas is approx. 10 min. after I shut it off.

I think now is the time to ride...
 

Slydynbye

Will ride for Pie
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Sep 3, 2007
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Location
Fremont, California
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2000 ABSII
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7331
Yes, that is about where I am at. The last 2 1/2 months I have had this bike apart so many times I could do it in my sleep. The only time it smells of gas is approx. 10 min. after I shut it off.

I think now is the time to ride...
I was hoping you would find the issue, I've got the same thing, I usually park the Bike outside the garage for 30 minutes to vent and dissipate then roll it in the garage manually. SWMBO complains of the fumes if I roll in under power. I sill have my vacuum fuel shut off installed. Let me know if that cures it.
 
OP
OP
Joined
Jul 23, 2012
Messages
36
Location
western Montana
Bike
'91 ST1100
Nope, as you probably read, didn't do it. I have it apart again today just to go through one moreeeeee time. There has got to be something I've missed. I'll tell you this and I've said it before, this thing couldn't run any better though (my opinion).
 
OP
OP
Joined
Jul 23, 2012
Messages
36
Location
western Montana
Bike
'91 ST1100
Well, I may have found the culprits.

A previous owner/s for some reason put a "t" fitting on the lower end of the gas cap vent hose about 6" from the its end and did not put a cap(anything) on the open end. Also, either I forgot or the air filter breather hose became disconnected. So maybe with this combination it could be it. I haven't ridden it yet, but, I am crossing my fingers.
 
OP
OP
Joined
Jul 23, 2012
Messages
36
Location
western Montana
Bike
'91 ST1100
Well, those two "things" did not do it. I have no idea where to go from here other than put up with it. The only thing, this makes me nervous. If it was an exhaust (??) wouldn't be troublesome, but, raw gas???
 
Joined
Aug 16, 2010
Messages
31
Location
Kansas
Bike
2002 ST1100
STOC #
906
I have gone through the same process you have and also have not found the source. I do not know what that open vent T from the tank was for but it was also on my 01 and I capped with no success. I have not removed the petcock but I do not see any residue around it or the amount so I can not see where that is the issue.

Trouble I have had is narrowing down the area where the smell is coming from and it is the smell of raw gas not out of the pipes. Have looked at the gas cap but don't really have anyway to test since it should flow both ways but it is holding some pressure as when I open the cap it releases pressure.

If you do find something please post it as it sounds like there are a number of us dealing with the same issue. By the way what year is your bike? I had a 95 that did not have this issue but my 01 does so I wonder if something is different between the two bikes that would lead to the smell.

Thanks

Greg
2001 ST1100
STOC906
 
Joined
Nov 13, 2012
Messages
45
Location
Netherlands
Bike
ST1100N '92
Mine has the smell also.
Just a thought:
When driving, the engine is hot, but it and all around it is cooled down by air. Then, when stopping, remaining engine heat might warm up some parts containing fuel, with expansion as a result. That could explain the smell and it would be normal and nothing to worry about. Just gas venting.
Since my fuel tank after driving usually has some vacuum, I suspect the vapour source might be the carb bowls
I recall having to do a calculation at school many many years ago about the amount of fuel lost when you fill up the fuel tank to the max in summer, when the fuel is stored cold underground. The loss by fuel expansion was considerable.

Regards, Rob
 

John OoSTerhuis

Life Is Good!
Joined
May 10, 2005
Messages
5,219
Location
Bettendorf, Iowa
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1991 SSMST1100
STOC #
1058
The "T" in the vent line is OEM, all years and models. It's long been thought to provide another route to ambient/atmospheric should the very end of the tube become plugged with road grime or sumsuch.

John
 
OP
OP
Joined
Jul 23, 2012
Messages
36
Location
western Montana
Bike
'91 ST1100
Well, if nothing good comes out of this(smell's end) it is some comfort to know I am not alone with this. We have had such an unusually hot/dry summer I am waiting to see what might happen as the weather starts to cool. I think I would have noticed this last spring, so, I am hoping expansion/evap. could be the issue.
 
Joined
May 6, 2013
Messages
28
Age
63
Location
Wilmington NC
Bike
1991 ST1100
did you resolve this yet. If not, remove the gas tank and the rubber matt if one is still there. See if the bottom flat part of the tank was leaking like mine was. Apparently, back in the day Honda used to the paint to seal the metal tank and as the paint wears away little pin holes appear from the weakened metal. If this is the case, take it to a reputable radiator shop and have them solder the bottom. They fixed mine up beautifully. I then spray painted it with gloss black engine paint and reinstalled the tank. Problem solved. New tank: $583 at Honda My cost $160
 
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