Total loss of power

john_needs_a_bike

john_needs_a_bike

Joined
Mar 2, 2022
Messages
116
Age
64
Location
uk
I was out for a ride today, and was travelling down a dual carriageway when the bike St 1100 1998, began to lose power, the engine stopped and I gradually came to a halt on the side of the road, I tried start g it again but it popped a few times and wouldn't start
I left it for 15 mins, tried again and it started right away, has anyone got any ideas as to the possible cause
 
Sounds like a fuel delivery problem? Hard to check when the bike fixed itself...... I suppose listening for the pump when you turn the key on is the first thing....
 
Roger. said:
Sounds like a fuel delivery problem? Hard to check when the bike fixed itself...... I suppose listening for the pump when you turn the key on is the first thing....
Click to expand...
I agree, I took the chance and road it home around 30 mile and it never missed a beat, problem is I feel I can't trust it now
 
Probably remove it / bypass it and open it up, assuming everyone is talking about the fuel vacuum diaphragm- those tear and there’s repair kits for them or get a new one from Honda…or…just remove it and leave it out as many have done without issue.

Here’s the procedure:

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 www.st-owners.com
 
Erdoc48 said:
Probably remove it / bypass it and open it up, assuming everyone is talking about the fuel vacuum diaphragm- those tear and there’s repair kits for them or get a new one from Honda…or…just remove it and leave it out as many have done without issue.

Here’s the procedure:

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 www.st-owners.com
Click to expand...
I've just read that article, but I had total loss of power, not just limited power because one cylinder was fouled so not sure
 
Could be a simple thing too, blocked / partially blocked vent in the gas cap. Don't know how to test. Next time it happens remove gas cap and see if this solves the problem, then just replace with new cap.
 
john_needs_a_bike said:
I've just read that article, but I had total loss of power, not just limited power because one cylinder was fouled so not sure.
Click to expand...

The vac. actuated fuel valve failure can lead to a total loss of power. The carbs use all their fuel because the valve isn't flowing enough. Especially at higher continuous speed.

However, the "one cylinder fouled" comment adds to the mix.
 
john_needs_a_bike said:
I've just read that article, but I had total loss of power, not just limited power because one cylinder was fouled so not sure
Click to expand...
The "limited loss of power" will eventually turn into a total loss of power if the fuel valve fails. That was my experience when I had the problem and wrote that article.

It started out as intermittent surging (slight loss of power, I would slow down, power would come back, then slight loss again) and eventually it led to a total loss of power because the fuel supply was cut off.

It is pretty simple to bypass that valve for testing purposes, that to rule out the valve as the source of the problem. All you need to do is take off the false tank cover to get to everything you need to touch.

Michael
 
CYYJ said:
The "limited loss of power" will eventually turn into a total loss of power if the fuel valve fails. That was my experience when I had the problem and wrote that article.

It started out as intermittent surging (slight loss of power, I would slow down, power would come back, then slight loss again) and eventually it led to a total loss of power because the fuel supply was cut off.

It is pretty simple to bypass that valve for testing purposes, that to rule out the valve as the source of the problem. All you need to do is take off the false tank cover to get to everything you need to touch.

Michael
Click to expand...
So after total loss of power, does the valve somehow start working again, because it started fine after it had stood for a short time, and I rode it home
 
Something similar happened to me last year in Utah. The original fuel pumps start to go bad and become noticeable when you get low on fuel on a warm day. The pump can no longer handle the higher temps and stops working until cooling down.
There is a thread somewhere on how to check it. You can do replacement aftermarket pumps or spend the dough to buy a Honda replacement.
 
Smudgemo said:
Something similar happened to me last year in Utah. The original fuel pumps start to go bad and become noticeable when you get low on fuel on a warm day. The pump can no longer handle the higher temps and stops working until cooling down.
There is a thread somewhere on how to check it. You can do replacement aftermarket pumps or spend the dough to buy a Honda replacement.
Click to expand...
Tank was full at the time
 
john_needs_a_bike said:
So after total loss of power, does the valve somehow start working again, because it started fine after it had stood for a short time, and I rode it home
Click to expand...
If its the auto fuel petcock... it starts with a small tear in the diaphragm, causing it to not open fully (hence symptom likely noticeable at highway speeds or while trying to pass a car... :oops: )
Once the tear rips further the valve won't open at all... unclear how long this takes...

Img_1789 6x45.jpg

This one was found in a '96 ST1100 which still had not shown any symptoms of fuel starvation at the time...
I found it suspicious during inspection refurb because:
a) dust accumulated at the bottom hole (indicating it was drawing false air through there...)
b) tested the vacuum side and wouldn't hold when sucking on a piece of hose which I'd connected (draw, then plug the hose with the tip of your tongue to see if it's still sealed)

I've made this an annual inspection point ever since.

And ensure to sync your carbs after you've replaced the diaphragm, the leak could have persisted for a while, messing up any previous carb syncing...
 
The valve is leaking fuel from the bottom, can I take the fuel hole valve off and bypass it ?
 

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