CBF500 ABS - 30 MPG

[PotatoHead202...]

I've got a 2006 Honda CBF500 ABS that I use a lot for commuting through town to work. It's got 66,000 miles on it. In the roughly last 1000/1500 miles it's had the carbs cleaned, seals replaced, new boots, new air filter, plugs and oil/filter.
My commute is about 6/7 miles each way through Reading to work but it is taken on the occasional longer jaunt.
I'm getting quite annoyed/suspicious of the fuel economy which seems to be just over 30mpg. 14.72 litres of Shell V Power (i realise v power is overkill but it doesn't excuse the awful economy) and the fuel light is coming on around 100 miles. Now although I accelerate fairly briskly most of the speed is around 30mph due to it being urban with one or two faster stretches to 40mph.
There is absolutely no discernible loss in power and regardless of how cold it is outside it starts with the choke first time every time and idles without issue.
Chain is adjusted correctly, new T31 tyres, brakes are clean and not binding, standard jets/filter/silencer. It does backfire a bit when I've pulled up to the lights and give it a rev.
Any ideas on what this could be? Worn jets maybe? Valves were done about 2000 miles ago. I'm told from other owners that i should be expecting almost 60mpg - ok, maybe not in town, but 30 is taking the piss.
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Suzuki V Strom 1050XT, Honda CBF500 ABS,

[Easy-X]

30?! May as well get a car! At one time I had a Golf GTI, quite horrifying when I calculated it did 16 to 25 mpg

If it was running really rich I'd have thought you'd have already noticed a significant performance drop-off. That and a heady waft of petrol from the exhaust all the time.

My money's on fuel leaking away somewhere. Notice any patches on the ground when it's left standing? (Dry concrete surface is helpful.)

Nothing while standing? Worth checking the carb bowl overflow pipes while running.
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Royal Enfield Continental GT 535, Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[NJD]

I own the 1000, but don't know much about the little 500. Can the bikes ECU be read for fault codes by your local shop? Can't find a manual with MIL codes for this model, seems odd. Carb's on a bike that has ABS is unique.

Guy on the 1000 forum has mpg issues and a scan found three issues that could all be contributing factors.

At that mileage I'd be careful how much money you're willing to throw at it before taking a cut, or pleading ignorance, and P/X'ing it for something else.

~

You mention the work the bikes had done, but was the bike fine before the carb rebuild or filter change?

If you can remember the last time it ran fine I'd take the work its had done since then one by one. May be unrelated, but maybe not.
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The do it all, T̶h̶e̶ ̶b̶r̶o̶k̶e̶n̶ ̶o̶n̶e̶,̶ ̶T̶h̶e̶ ̶b̶i̶g̶ ̶l̶u̶m̶p̶,̶ ̶C̶h̶o̶n̶g̶ ̶N̶o̶o̶d̶l̶e̶

[Riejufixing]

[Riejufixing]

[Polarbear]

30mpg, Jesus, I get better in my Jaguar.

1st thing, 6 miles will hardly get the bike warmed up properly. How much idling is there when doing that journey?

If you fill it up and go for say a 50 mile ride on decent roads do you still get that mpg?

If you don't have an obvious fuel leak and the exhaust doesn't stink of unburnt petrol then you have the choice of digging deeper, ie spending money on a decent shop checking it out. They will have the gear to check exhaust gasses, air/fuel flow, compression etc.

Or as said, you decide that 66000 miles is a good innings and it's time to change. For a 6 mile commute I's be looking at a small scooter and a bigger bike for fun times only. Some would say push bike, but I'm not a sadist so maybe an electric assisted push bike.
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Triumph Trophy Launch Edition

[wr6133]

Is that 6 miles, cold bike, caning it hard from lights and mostly in 1st?

[blurredman]

Keep track of the mpg properly..

Fuelly.com


Also- Checked the oil level and that petrol isn't getting into the engine when standing?
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CBT: 12/06/10, Theory: 22/09/10, Module 1: 09/11/10, Module 2: 19/01/11
Past: 1991 Honda CG125BR-J, 1992 (1980) Honda XL125S, 1996 Kawasaki GPZ500S, 1979 MZ TS150.
Current: 1973 MZ ES250/2 - 18k, 1979 Suzuki TS185ER - 10k, 1981 Honda CX500B - 91k, 1987 MZ ETZ250 (295cc) - 40k, 1989 MZ ETZ251 - 51k.

[2wheelLover51]

All of the above is good advice. It should be doing 50+ mpg. My 600 does 57 in around - town riding.
I would also check the colour of the plugs to see if it's running rich. They should be pale to light brown (electrodes) not black or sooty.
Is the engine blowing smoke? Check the compression against the figures in the manual. These tests should give an indication of the state of the engine. As blurredman said register with Fuelly to get an accurate figure for the mpg.
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2WHEElLover1951

[PotatoHead202...]

It was bought as a bit of a project for me to learn on and to save the salted roads eating the bmw so I'm keen to sort it myself. It's of no real value to anyone other than me.
There is seemingly no loss of power even with my 106kg weight on it. Still has its power band at around 8,000rpm like all the cb5's do. No blue (or any) smoke at all. Does stink of fuel though I admit.
Someone else had mentioned about needles and emulsion tubes? Also bearing in mind these engines can easily do double of what this one has.
I'll pull the plugs this afternoon for a look. I've never really checked consumption before but I don't think it's changed much and don't really do anything more than 15/20 miles max on it. I may try and take it to loomies or something this weekend to give it a run.
I guess it could be a leak when running but there's nothing after it's been standing.
Don't get me wrong, I'm not after a gazillion mpg commuter scooter, I just don't want it taking the piss.
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Suzuki V Strom 1050XT, Honda CBF500 ABS,

[PotatoHead202...]

So slightly oily plug but also carbon build up . What oil there is seems to be almost coming from above.
No blue smoke, just some steam after a cold start up. Absolutely reeks of fuel around the exhaust though.
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Suzuki V Strom 1050XT, Honda CBF500 ABS,

[Polarbear]

[PotatoHead202...]

Thanks man. Yeah I guess that must be it. Have attached a picture of the L/H side plug (pissing with rain at the moment so haven't had a chance to get to the other side).
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Suzuki V Strom 1050XT, Honda CBF500 ABS,

[jaffa90]

Have you a pair of knickers blocking the air intake?
Is there fuel in the vacuum pipe from the tap to the inlet manifold?
Is the engine oil level rising?
If you like fuel suck the vacuum pipe (to open the fuel tap) to see if the carb/s are over filling.

[PotatoHead202...]

Lol no blocks. Someone has drilled three holes into the airbox at some point for an unknown reason....
Can't really see that it is rising, certainly doesn't seem to be burning any. Will have a go at sucking fuel again lol.
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Suzuki V Strom 1050XT, Honda CBF500 ABS,

[sickpup]

[PotatoHead202...]

Forgot about it to be honest. Only when taking the plugs off today i remembered it. It had a piece of gaffa tape covered over it previously. I know for a fact that the jets are the correct size as when i last took the carb apart i'd intended on replacing them and checked them against the specs in the manual (couldn't get hold of the replacements at the time so put cleaned it and put it all back together).
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Suzuki V Strom 1050XT, Honda CBF500 ABS,

[sickpup]

So you know the air screws haven't been adjusted, the needles
changed or raised, the main jets drilled or anything else then?

[PotatoHead202...]

Not that i'm aware of
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Suzuki V Strom 1050XT, Honda CBF500 ABS,

[sickpup]

[PotatoHead202...]

I've ordered a second hand airbox. Guess parts for the carb is a better way to go than second hand unit price wise
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Suzuki V Strom 1050XT, Honda CBF500 ABS,

[ThatDippyTwat]

[sickpup]

[PotatoHead202...]

An IAM observer with reasonable experience with carbs did a compression test today. Both cylinders perfect. He reckons it's the carb diaphragms?
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Suzuki V Strom 1050XT, Honda CBF500 ABS,

[Robby]

Sickpup already told you how to fix it.

Either buy a pair of rebuild kits, or buy some used carbs.