Miles per tank? Town riders.

[2KLBUP]

I'm told my Bonnie is unusual on petrol, but in town riding only, I go 145 miles before I hit reserve (3.3 U.S. gallons). Out on the highway, I usually get at least 185 miles before hitting reserve. I've got a 2000 Bonnie 790 with all of the typical mods. It pulls hard, but returns awesome fuel mileage.
Cheers-

 

[bobajobbob]

Are you sure that your tacho isn't showing kilometres not miles?

Thanks the lot for the responses. Everyone seems to be getting significantly better than me from 25-50 miles which seems like an awful lot given that I'm not a total hooligan. My riding is very much stop/start 10 miles to work and back in London traffic so I guess it is down to that. I've also only got 1600 miles on the clock so perhaps it will improve with age.

 

[Bonafide]

I'm told my Bonnie is unusual on petrol, but in town riding only, I go 145 miles before I hit reserve (3.3 U.S. gallons).

Guess that would make a difference. All of mine start sputterin at 2.9 gal

I've got a 2000 Bonnie 790 with all of the typical mods.

A 2000 model? Must be one of them pre-producton kind of Bonnies - I am curious what kind of miles you have on it now?

 

[Echoance]

Are the Bonnie tanks significantly smaller than that of the cruisers? I have an 07 Speedmaster with 5k miles on the clock and usually start looking for fuel at around 130 miles (if I've been playing) going up to 150+ miles. This is combined town riding/long A-road runs.
I usually fill it with 13 litres of normal fuel (not high-octane stuff).

 

[2KLBUP]

To answer you and the above post, the tacho reads in miles. I can go over 200 miles without stopping, have 64 RWHP, and I am not light on the throttle.

My Bonnie was originally a "market guage" machine, when Triumph released the Bonnie to see how well it would be received. I have it on good authority that it was one of the first ever built (quite likely, the 88th). It has 25K on the clock currently.

I have gutted the airbox, run stock Bonnie needles, 18T sprocket, stock carbs, 1.5" ID exhaust, deburred and polished the intake runners, upped the rev limiter to 8400RPM with a 3 degree advance on the timing @ WOT, run 142 Jets, K&N, etc. (all the standard low dollar mods).
The first Bonnies had a different head configuration (crossed coolant lines) and while I'm no machinist or flow bench specialist, nor have I compared old and new heads, side-by-side, I believe the original heads flow better. Also, my Bonnie was equipped with the hottest cams to date, which they incrementally downgraded as the years went on. It pulls like a freight train, and 63 MPG is average for me on the interstate, If I behave for the most part. Riding like an absolute nutter has never returned anything less than 57 MPG. I can't explain how I get these figures, but I do--consistently.

I suspect in the years to come, we will unlock why some Bonnie derivatives get better mileage than others. I do know that keeping your hand out of the throttle, coupled with a free breathing engine tends to generate higher MPG figures. As crazy as it sounds, when the bike was bone stock, I could only return 54 MPG.

Cheers-

 

[2KLBUP]

75-80 miles before reserve? In town ONLY when I ride like a complete nutter, nailing the throttle from stoplight to stoplight, I can always get a very minimum of 130 to reserve. Something sounds wrong to me. I cn fix any carb, but I'm lost with F.I., and can't for the life of me understand your situation. You must sit at the Ton+ frequently, or something is certainly wrong with your state of tune. If you've not replaced your pipes, do so as funds allow (I know you've got MOT, but you should be able to find some free flowing cans that won't raise suspicion--try Norman Hyde), and free up your airbox by removing the baffle (caulk the baffle seam for better overall flow, install a K&N filter, throw the snorkle in the trash, and open up the face plate so that it matches the ID of the filter. Also, Bonnie intake manifolds are some of the worst with regard to casting burrs. Grind or file down the cast lines and burrs, and polish them with emory cloth followed by fine steel wool, and a Dremel power buff. I know nothing of the new F.I., and I don't even know if it has TPS or whether it's tunable, though I have to believe in the right hands, it is. I suspect it's still under warranty, so you might query the dealership as to why your mileage is so foul. Apart from that, if you follow the above advice, you should see a sharp increase in mileage.
Cheers-

 

[derby boy]

When used as a commuter (16 miles each way) I hit reserve at 128-135. On long day rides with only 1 or 2 stops I have gone as far as 170 (3.05 fill) and didn't hit reserve. This never seems to change no matter how many exhaust mods I make. I have 115 mains, 1 shim and 40 pilots. I'm going up to 125's and removing the airbox baffle for the next mod and we'll see where the milage and performance goes from there.

 

[bobajobbob]

Cheers for the posts above. I can confirm that I don't get close to the ton. In fact I rarely exceed 50 mph. Nearly all my riding at the moment is 0-40 and back again stop start. I'm going to talk to the dealer because it sounds like something isn't quite right.

 

[AndyB]

I think there are two reasons why your mileage is so poor.

1. You spend all your time in London. I'm not surprised that with the endless traffic jams and stop-start riding that your bike is hard on fuel.
2. Emissions control. Your bike meets the Euro 3 regulations. Earlier bikes were not hindered by such constraints.

I'll give an example. I drive a car with a very fuel efficient diesel that typically does 60-65mpg. I pay only £35 tax a year on this due to the low emissions, courtesy in part of a DPF (diesel particulate filter) Every now and then however, the engine management system has to clean the DPF, so I suddenly find my fuel efficient car has about the same fuel consumption as a small truck at 30mpg for about ten miles.

So I guess this is in part 'progress' and in part your particular circumstances.

Hope that was helpful for a first proper post on this forum.

Andy

 

[Xchoppers]

Guess it makes sense with the EFI. Running fuel injectors dry = hard to restart.

Actually EFI is easier to restart if you run it dry because the electric fuel pump automatically primes the system after re-fueling.

By the way, I get 110 miles before my warning light comes on.

 

[bikebits]

EFI isn't easier to start if running dry toasts the fuel pump. Some vehicles depend on fuel in the tank to cool the fuel pump. Both my BMW (m/c) and a Dodge truck I had warned that running the tank dry could cause serious fuel pump damage.

 

[2KLBUP]

When you remove the baffle, do not remove the entire thing. On the RH side of the baffle, there is a 90 degree wing that juts forward. Removing the entire baffle will actually jumble the intake charge to the right carb (ask me how I know), and return less power than if you do the following:
Cut the wing off with a Dremel, die grinder, etc., and reinstall it, making sure to glue it in place with Permatex 'Ultra' or some other decent sealant that won't get sucked into your carbs like silicone will, once it begins to pull away from the inside of the airbox.
You will then have a perfect rectangle that is 2" X 6".
It's a great mod, accompanied by the opening up of the airbox faceplate to match the ID of the filter. Make sure to chamfer the lip so it rolls in for better airflow.
Best of luck, and those are very impressive mileage figures. You and I seem to be in the minority.
Cheers-

 

[Xchoppers]

Today my low fuel light came on at exactly 100 miles.
As I often do when I have the opportunity, I was riding fast...

 

[Bonniebret]

You have a reserve light? Is that a UK only or EFI feature? The only way to know you're out fuel on my bikes ... sputter - sputter ..."ahh shit, I'm passing someone" ... sputter, *twist to reserve* ... sput-spu-sp -brrrrraawwwwhhhhh ....

That's the same technique I use Bonafide. It usually happens to me around 125 miles then my next stop is the gas station.

 

[Sal Paradise]

I get 110-125 per tank before hitting reserve. Wish it was more but like the way the small tanks look so I guess you cant have it both ways.

 

[2KLBUP]

I think Andy may very well have determined much of what is affecting your mileage. Hang in there. There will be advancements in our understanding of the new machines, and I'll wager better fuel economy will be forthcoming. Nevertheless, a talk with your dealer never hurts...

 

[Xchoppers]

My other bikes usually get 35-36 mpg.
39-40 on my Bonneville is great to me.
Anything more than the 18mpg I get with my Corvette is a bonus...

 

[jackblack]

EFI model has a bigger tank than the carb models -But has the fuel pump in the tank-- I get 220 kms before the light comes on fulltime...........

 

[bobajobbob]

In my quest for more miles per tank any tips on brimming the tank? I paid £10.16 to fill my bike this morning. The fuel light had been flickering on and off for 5 miles or so. I didn't check the amount of fuel but given that petrol is about 90p a litre at the moment that equates to 11.3 litres which is almost 2.5 gallons. As far as I know the 2008 Efi bikes have a tank capacity of 16 litres (3.5 gallons) so my fuel light appears to be coming on with a very conservative 5 litres left in the tank. Does this sound normal or could my low mileage per tank simply be down to a dodgy or very risk adverse warning light?

 

[Hamr Mark]

250 kms to a tank, I think...I haven't been on her since November...an no light, just the coughing and sputtering that others have pointed out.

You need to get out to the country and let her rip everyonce and awhile. These bikes need to be put through their paces, through all the gears, and meant to be ridden. If you are going to going no faster than 40 km/h, you probably shoulda bought a different bike. A 250cc, or 500cc would fit the bill better I am thinking. To ride a Bonnie no faster than 40km, would be like getting a Street Triple III and not going faster than 100km, or a Scrambler, and not taking it off road. Just my $0.02