Fuel Pressure Regulator

oilspot

oilspot

Joined
Jun 8, 2023
Messages
68
Age
59
Location
Savannah, GA
Bike
2006 ST1300ABS
Hello Fellow Riders! Been a while for me, I've had a lot going on and finally getting back to riding and tuning. My bike runs pretty good, but I'm suspicious of my past work on my throttle bodies (has it been a year already?).

Anyway, a while back I put McCruise on my ST and while I had it opened up I decided to clean the 5-way connector and replace all those tiny vacuum hoses. It took several tries and peeking at the factory manual to do my best to get everything put back together. It runs fine and I love the cruise control for the long highway trips - it really helps with my hand cramps (but I rarely take my hands off the bars). My only real concern/indication that I may have screwed something up is the fuel economy. I was rock solid at 48 mpg prior to the modifications. Now I am rock solid at 38 mpg. Boo!

So I have a feeling I am going back under the fuel tank to have a look around and confirm everything is where it should be - and no leaks or cracks on any rubber stuff. It's a 2006 with slightly less than 50k miles...
I don't think anything is leaking "out" that I can see, but I'm going to be much more diligent in inspecting everything this second time below the air filter... So logic is a vacuum leak potentially

Three questions:

1. The bike came almost completely stock except for a TurboTom fuel pressure regulator. Is that good or bad? A local motorcycle friend said go back to stock because the ST really likes stock parts. I think a new pressure regulator is about $60 so I'm willing to change it if it is "better" to run stock. I cannot find any info about TurboTom.

2. I used generic 3.5mm vacuum hose on the throttle bodies and the 5-way connector looked fine (no junk inside that I could detect) - I have a spare 5-way just in case I need it. Should I order Honda hose? Would Silicone vacuum hose be superior?

3. Would it be worth changing out any O-rings on injectors and/or fuel rail while I am in there?
 
I put the Turbo Tom regulator in almost 100k miles ago and my fuel mileage is consistently in the mid 40s. A more likely culprit is the thermostat. There is a lot of information about this on this forum. My mileage dropped into the 30s and it was my thermostat that was stuck partially open.
 
Should you dig down below the gas tank again, consider lengthening the hoses to position the 5 way Tee above the throttle bodies. This has been a suggested mod to make cleaning the Tee easier next time.

What does your temp gauge show when you are riding the bike? It should go from room temp to one bar in a matter of minutes after starting, and run at a solid 3 bars (not 2 or 4) within a few minutes or a few miles (say starting from 50ºF).
 
My bike temp seems normal, high idle when cold, warms up fast and is solid 3 bars. The fan periodically cycles as needed to maintain cooling at stops or low speed.
 
I don't have enough experience with the fuel pressure regulators on these bikes, but I'm still suspicious of the vacuum hoses and the potential for a misconnection or leak. But I'm grasping at straws. Lean would be more common with a big leak and lean would probably be noticeable in performance and probably use less fuel. I'm not anxious to venture back under the tank, but its a good rainy day activity... It may not be for a few day; but I will post an update once I've had time to dig into this.
 
My bike takes 35/mpg. I've checked vacuum hoses, cleaned the injectors, replaces the plugs, fuel pump, air filter... nothing.
Will call Lary if he can shed the light on.
 
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