Fuel Economy and Vacuum Lines

The Dark Shadow

The Dark Shadow

Joined
Aug 23, 2022
Messages
321
Age
53
Location
Nova Scotia
EDIT: I should also mention that my exhaust smells rich. Always does, even on my former st13 2005. I thought these babies were set to run lean. If bike is running rich, what are the most regular culprits.

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Okay, so now that my brakes seem good, I'll move back to fuel economy.

At 110kph (about 70mph) the best in getting I'm getting is just shy of 40 US mpg on the flats cruising without acceleration. (This is after odometer correction.)

Other people have reported 44mpg at 120kph (approx 80mph), but I drop to about 37-38mpg at that speed.

It seems that the 5 way tee often gets clogged. I had the shop check the 5 way tee last year when they opened it to replace thermostat (based on the fact that the engine was running cool, with the suspicion that the thermostat was stock open, but in truth they put in the wrong spark plugs with 11.5% too small of a gap!). Even though I asked for the five-way T to be cleaned, the worker only blew air through it and reported it as fine. So I do not know if the five-way t is properly clear or not.

Can the 5 way tee appear to be clean by blowing air through it, but still have enough gunk to obstruct vacuum air flow and negatively impact fuel efficiency...?

Is there a metal 5 way tee replacement...?

Also, even though my wax seal seems to be performing properly, can this get gunked up and negatively impact fuel efficiency...?

Here's the thing... If the bike's optimum fuel efficiency is 10% better than what mine is giving, I want to diagnose and rectify the issue. I don't look at prices of fuels like my wife does... "Oh gas is going up 5 cents tomorrow... gotta rush off to the gas station tonight!" But if the bike (as reviews regularly stated) can go 500km/tank, I want that instead of refueling just over 400km, and it brings me great satisfaction to have my tools in optimal working condition.

Is there anything else that could be checked...? The valve gaps were checked last year and reported to be perfectly within spec.

Thank you again everyone.
 
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I am far than being an expert on the question, but...
I am not sure that blowing air would be enough for cleaning the 5 way tee. The gunk is very sticky, I used a small wire and seafoam to clean mine.
A carb sync is maybe also to consider as a way to optimise your fuel efficiency beside of also affecting the running temp of the engine.
 
Hello fellow Nova Scotian. I've had my 07 since new. Best Mileage is based on 5th gear cruising for a long time. I drove to California twice with a fellow Hayabusa. I got 58 mpg, but I get mid to high 40s here in NS. It's also based on your right hand... mine has 145900km and climbing
 
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The ST1300 has no carburetors to sync. There is a fuel injection sync or something, maybe balance? I've not done that, only read Larry's directions some time back.

You won't clean a 5-way T by blowing through it, except maybe if you use a 150psi compressor for a period of time. I'm unable to verify that, personally.

I may have seen 45mpg once, but I routinely get 42mpg on my '08.

Because I don't ride like an old man, never mind my birthday accumulation.
 
Sadlsor said:
The ST1300 has no carburetors to sync. There is a fuel injection sync or something, maybe balance? I've not done that, only read Larry's directions some time back.

You won't clean a 5-way T by blowing through it, except maybe if you use a 150psi compressor for a period of time. I'm unable to verify that, personally.

I may have seen 45mpg once, but I routinely get 42mpg on my '08.

Because I don't ride like an old man, never mind my birthday accumulation.
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I get the same MPG and I doubt that you can get "real" better numbers if you don't drive the bike specifically to save gas.
Sure ha, no carb on the ST1300, but the process is very similar. Carb-injection sync or balance.
 
The Dark Shadow said:
I had the shop check the 5 way tee last year when they opened it to replace thermostat (based on the fact that the engine was running cool, with the suspicion that the thermostat was stock open, but in truth they put in the wrong spark plugs with 11.5% too small of a gap!).
Click to expand...
That should affect the operating temperature range of the spark plugs, but not the engine temperature.
 
In my Non-expert opinion, the ST likes 3 things for fuel milage 1. high altitude, 2. Heat ( think 95+ deg F), 3. Low humidity. This combination will give you Extreme gas milage. IGOFAR reports constant mpg in the 50's, (lives in the high desert). reduce any of these factors and you will be getting approx 40 mpg. at 75 mph. Just my opinion, I have been known to be incorrect .
 
Your dragging brakes would have certainly lowered your fuel economy.

I'd wait a bit and see if the fuel economy improves before chasing more bandits.

Fuel economy is certainly one of those things that will fluctuate given a lot of factors.... type or riding, distance, wind resistance, tire pressure, wrist twist etc.

Might not be right but I just ride as I wish to and fill up when I need to. Striving for a max economy takes all the fun out of it.
 
I watch my MPG very closely at every fill up. I get between 42-47 MPG.

I live in the Seattle area, and commute 60 miles a day total (round trip). Temperatures range from low 40's in the morning, to mid 60's in the afternoon when I go home. This is what I've learned so far...

Ambient air temperature has a huge impact on MPG. The warmer the weather, the MPG go way up and bike seems to run smoother. I've read that it has to do with the fuels ability to atomize or something. Its way over my head. All I know, is the warmer the better for fuel efficiency.

The overall speed and the engine load placed on the bike have a huge impact on MPG. If I can keep the engine load lower on the bike, obviously MPG go up. Even when I'm at highway speeds, if I'm climbing a hill or going up a grade along the freeway, the MPG go down to around 37 MPG.

I keep the speed between 70-80 MPH for the most part. When I ride over 80MPH, fuel economy goes down. When I keep the bike around 65-70, I get optimum fuel economy.

I check fuel economy at every fuel fill up and reset my odometer to get real data. However, the bikes onboard computer is suprisingly accurate.

Anyways, 42-47 MPG is what I see as pretty normal for most folks on the ST.
 
Tdinova said:
Hello fellow Nova Scotian. I've had my 07 since new. Best Mileage is based on 5th gear cruising for a long time. I drove to California twice with a fellow Hayabusa. I got 58 mpg, but I get mid to high 40s here in NS. It's also based on your right hand... mine has 145900km and climbing
Click to expand...
If I cruise smoothly at the speeds I've given, the results are as given.

To get 58 mpg at 110kph to 120kph seems impossible to me...
 
dlim said:
I watch my MPG very closely at every fill up. I get between 42-47 MPG.

I live in the Seattle area, and commute 60 miles a day total (round trip). Temperatures range from low 40's in the morning, to mid 60's in the afternoon when I go home. This is what I've learned so far...

Ambient air temperature has a huge impact on MPG. The warmer the weather, the MPG go way up and bike seems to run smoother. I've read that it has to do with the fuels ability to atomize or something. Its way over my head. All I know, is the warmer the better for fuel efficiency.

The overall speed and the engine load placed on the bike have a huge impact on MPG. If I can keep the engine load lower on the bike, obviously MPG go up. Even when I'm at highway speeds, if I'm climbing a hill or going up a grade along the freeway, the MPG go down to around 37 MPG.

I keep the speed between 70-80 MPH for the most part. When I ride over 80MPH, fuel economy goes down. When I keep the bike around 65-70, I get optimum fuel economy.

I check fuel economy at every fuel fill up and reset my odometer to get real data. However, the bikes onboard computer is suprisingly accurate.

Anyways, 42-47 MPG is what I see as pretty normal for most folks on the ST.
Click to expand...
Thanks.

I'm very well aware of wind and hills. My mileage is listed as on the flats.

My average from my last few test drives is 37.5 mpg. All highway (except leaving and returning to town).
 
Sadlsor said:
The ST1300 has no carburetors to sync. There is a fuel injection sync or something, maybe balance? I've not done that, only read Larry's directions some time back.

You won't clean a 5-way T by blowing through it, except maybe if you use a 150psi compressor for a period of time. I'm unable to verify that, personally.

I may have seen 45mpg once, but I routinely get 42mpg on my '08.

Because I don't ride like an old man, never mind my birthday accumulation.
Click to expand...
I remember Larry mentioning that blowing through the 5 way T won't clean it. (I asked the shop to CLEAN IT because it builds up gunk, but I didn't ask them to "check it"... Yet another professional disappointment.)

The numbers I gave above are not my average fuel economy numbers. If I lost average city/highway driving, my fuel economy goes to 33.6 US mpg. I do live in a very hilly city, which must be factored in.

But steady cruising at 110kph yields 40mpg. Of course, with a tailwind and downhill, those numbers go up. But headwind and uphill, I'll be getting 32mpg plus our minus depending on wind strength and hill slope.
 
Sidekick said:
I am far than being an expert on the question, but...
I am not sure that blowing air would be enough for cleaning the 5 way tee. The gunk is very sticky, I used a small wire and seafoam to clean mine.
A carb sync is maybe also to consider as a way to optimise your fuel efficiency beside of also affecting the running temp of the engine.
Click to expand...
I had the throttle bodies synched last season.
 
Larry Fine said:
That should affect the operating temperature range of the spark plugs, but not the engine temperature.
Click to expand...
Weaker spark, weaker explosion, incomplete combustion, cooler engine temperature... The engine was building up carbon and varnish, a sign of incomplete combustion.
 
diferg said:
In my Non-expert opinion, the ST likes 3 things for fuel milage 1. high altitude, 2. Heat ( think 95+ deg F), 3. Low humidity. This combination will give you Extreme gas milage. IGOFAR reports constant mpg in the 50's, (lives in the high desert). reduce any of these factors and you will be getting approx 40 mpg. at 75 mph. Just my opinion, I have been known to be incorrect .
Click to expand...
There we go... It's extremely humid here, and cool to cold 3/4 of the riding season. And I love about 60 to 80 feet above sea level...
 
One strange thing I noticed about my mileage is when I’m around 55 mph 5th gear gets lower mileage then 4th gear.

Whether I’m cautious with the throttle or aggressive, by the end of the tank (call it 200 mi.) it gets around 40 MPG. I reset the odometer every fill and calculate. The only exception is when going that whole 200 at 80 mph or more, it’s still high 30’s.

I’ve seen the computer show mid 30’s for a tank and when I calculated, it comes to 40. More road testing is needed.

@The Dark Shadow , certainly cleaning everything and running a few tanks with Marvel Mystery Oil will improve the mileage, I heard a rumor that correct tire pressure helps too. In the end, you’ll get about 40 MPG.

Just my 2 cents and fieldwork. More is needed.
 
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