Article [11] ST1100 - Fuel Pump Replacement

[Smudgemo]

My "keeper" ST got a new Honda pump, but the one I decided to sell got the Quantum pump plumbed into the original regulator. I didn't end up riding it much, but it seemed to work normally. This was the hack where you remove the old pump, thread the regulator with a tap and the pump nipple with a die. There is a photo in this part of my thread:

$300 '97 ST1100 Refurb Thread | ST1100 Related

Sometimes I just can't stop working on something, and sometimes I can't stop thinking about working on something. So after a nap and some dinner, I hauled the luggage up from under the house to get a look at what I'm going to be working on soon. I'm just going to say it - I hate working with...

www.st-owners.com

 

[Uncle Phil]

Just an update on the Quantum fuel pump setup -
Still working fine with no issues as it should - and about 10,000+ miles with this setup.

 

[harmdive]

A very helpful thread. Thanks for posting. I am trying to get my ST up and running after sitting for 11 years. The fuel pump has died so need to replace that and will see if I can get the bike started. I tried to get the carbs off to have a look inside but to be honest trying to get 30 year old rusted in screws that I can't see is proabably going to take more time than I want to spend on it so might have to get a 'proper' mechanic to look at it with all the right tools etc. Hopefully I can get the thing started with a bit of seafoam in it to clear the carbs; if not it will have to be looked at by someone else! I sprayed some carb cleaner into the air intakes and it did turnover and had a bit of life so that's good!

 

[Bobcp]

Just an update on the Quantum fuel pump setup -
Still working fine with no issues as it should - and about 10,000+ miles with this setup.

I am considering doing a similar modification but whenever I enquire about the adjustable fuel pressure regulator (same design as yours) installation I am told that the regulator must be mounted horizontally to work correctly.
However, if I remember correctly, the photo of your installation shows the regulator mounted near to vertical.
I just wondered, please, if you had changed the regulator position to horizontal since your initial installation ?
I'm guessing the constraints of space may well prevent horizontal installation.

 

[Uncle Phil]

I am considering doing a similar modification but whenever I enquire about the adjustable fuel pressure regulator (same design as yours) installation I am told that the regulator must be mounted horizontally to work correctly.
However, if I remember correctly, the photo of your installation shows the regulator mounted near to vertical.
I just wondered, please, if you had changed the regulator position to horizontal since your initial installation ?
I'm guessing the constraints of space may well prevent horizontal installation.

Two of mine have been running in the 'vertical' position for thousands of miles.
I got mine on EBay and I didn't see anything about 'position'.
In fact I am in the process of having some brackets made (rather than my homemade setup).
They will bolt into the holes where the cutoff valve goes (I got rid of those years ago) and then the regulator will 'hang' beside the petrol tank.
The only issue is you may have to 'precurve' the fuel line so it doesn't kink.
I just got some fuel line for fuel injection systems that seems to be less prone to kinking.

 

[Bobcp]

Two of mine have been running in the 'vertical' position for thousands of miles.
I got mine on EBay and I didn't see anything about 'position'.
In fact I am in the process of having some brackets made (rather than my homemade setup).
They will bolt into the holes where the cutoff valve goes (I got rid of those years ago) and then the regulator will 'hang' beside the petrol tank.
The only issue is you may have to 'precurve' the fuel line so it doesn't kink.
I just got some fuel line for fuel injection systems that seems to be less prone to kinking.

Many thanks for your response and information which is appreciated.

 

[sleazyrider741]

Hi, I am new to Pans and bought a bit of a pup. One of its many issues is fuel supply and, judging by the posts on this forum, I am not alone.
I tested my flow and got 500ml in 15 secs which explains why the carbs are overwhelmed.
I followed the advice from Uncle Phil etc and removed the fuel tap and put a chinese made regulator in its place. Still got the same flow on the minimum setting so moved to plan B.
I took a brave pill and removed the pump from the tank. Not sure who made it but def not Honda. Obviously there was no pressure relief like on the OEM so I decided to make one. Got a valve, rated at just over 2psi, a y-piece and some hose and clips for less than the cost of the cheap regulator.
After installing back in the tank I did a flow test, this time 200ml in 15secs and the lovely sound of the excess fuel going back in to the tank rather my sump or exhaust. Hopefully will have the weather for a road test this week and will post the outcome.

 

[Uncle Phil]

Hi, I am new to Pans and bought a bit of a pup. One of its many issues is fuel supply and, judging by the posts on this forum, I am not alone.
I tested my flow and got 500ml in 15 secs which explains why the carbs are overwhelmed.
I followed the advice from Uncle Phil etc and removed the fuel tap and put a chinese made regulator in its place. Still got the same flow on the minimum setting so moved to plan B.
I took a brave pill and removed the pump from the tank. Not sure who made it but def not Honda. Obviously there was no pressure relief like on the OEM so I decided to make one. Got a valve, rated at just over 2psi, a y-piece and some hose and clips for less than the cost of the cheap regulator.
After installing back in the tank I did a flow test, this time 200ml in 15secs and the lovely sound of the excess fuel going back in to the tank rather my sump or exhaust. Hopefully will have the weather for a road test this week and will post the outcome.

The key I found was if you have too much fuel pressure, the ST1100 will crank fine without using the 'choke' (which is technically a fuel enricher'.) - especially when it is cold out.
As I said, I played around with various pressure settings and 1 1/2 PSI seemed to be the 'sweet' spot but 2 psi shouldn't make that much difference.
Glad you got it sorted.
Are your in Oxford as in the area of the University of Oxford?

Uncle Phil - Ireland 2010 Day 11 - My Day At Oxford

 

[sleazyrider741]

The key I found was if you have too much fuel pressure, the ST1100 will crank fine without using the 'choke' (which is technically a fuel enricher'.) - especially when it is cold out.
As I said, I played around with various pressure settings and 1 1/2 PSI seemed to be the 'sweet' spot but 2 psi shouldn't make that much difference.
Glad you got it sorted.
Are your in Oxford as in the area of the University of Oxford?

Uncle Phil - Ireland 2010 Day 11 - My Day At Oxford

Thankfully not in Oxford itself but fairly close. Looked like you had a good trip. Pity they didn't take you to Charlbury when you were in Burford. Burford to Charlbury would wake you up after the A40. You will just have to come back and do it properly. I did think you were traveling a bit light for touring. See pic below for proper touring luggage.

I figured the pressure was the problem but don't have a guage so had to measure flow. In theory as soon as the pressure gets to 2 psi the relief valve opens and allows the excess to flow back into the tank. I am going to use the regulator as well. As it is the flow is 800 ml/min which is lot closer to the 640 ml/min that Honda reckon it needs.

 

[Uncle Phil]

Now here's when I am 'properly' packed out -

 

[ST1100Y]

Looks like SWMBO came along on the trip (AKA trailer tongue on the bedroom closet...)

 

[sleazyrider741]

Now here's when I am 'properly' packed out -

Now thats what I call packing. I am glad I'm not the only one who doesn't know when to stop adding stuff.