Honda CBF125 - Power related to amount of fuel in the tank?

[Zephyrus]

Hi all,

I've just moved to the UK and thought to myself.. why don't I get a bike.. there's a lot more riding time in England than there is in Canada!

I've only been riding for about a month now on a new CBF125 and I've done ~560miles in that time. I've noticed a trend that the power of the bike seems to be related to the amount of fuel in the tank! Is this normal? Eg.. with a full tank I can get the bike up to 70mph but with the tank on half or less it seems to stuggle around 65mph.. Both examples are on lets say a windy A-road with minimal gradient..is this normal??

Thanks!
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Harlequinn Ink Streams

[Kickstart]

Hi

Shouldn't happen.

While I can think of possible situations where this could happen they would be pretty unlikely (ie, fuel pickup for fuel injection badly positioned and sucking in air sometimes when the tank isn't full)

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[pepperami]

Wow that a new one that I`ve never come across before

The nearest thing that I can think that could possibly be anyway near to those symptoms is a blocked air-hole in the tank cap????
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I am the sum total of my own existence, what went before makes me who I am now!

[locked]

That don't sound normal at all. You still running your bike in?
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on the look out for my next bike....
CBT Passed - 13/09/09 Theroy Passed - 19/12/09 Mod 1 Passed 04/05/10 Mod 2 Passed 14/05/10 - Free to ride ANYTHING!
Motorcycles are perfectly safe as long as you remember they're dangerous.

[Rogerborg]

[kingsknight]

it shouldnt make much difference to your top speed!
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TS50 (sold) NS125F (sold) NSR125R-K (write off after 2 crashes) CG125 (nicked) XR125L-3 (Sold )-: ) DR125SM '11 (sold yay) XL125V '12 (In love with this bike) XT600E '04 (fun on the dirt)

[virus]

had a few bikes seem to run better when ive just filled up, I assumed it was a mixture of a overactive imagination and the cold fuel from the underground storage tank being slightly more dense than warm fuel so more of it can fit into the combustion chamber giving an ever so slightly richer and more powerful mix.


maybe.


Cheers
John
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own: 81 xs1100g...
owned: 85 rat CG (sold), 91 GS500e (stolen), 84 gsx400f (scrapped), 81 z250 (siezed, siezed, scrapped), 83 cb250rs (sold), 84 gpz750r ratfighter (killed) 84gpz400 (sold), '80 cb650 ratfighter (wrote off) 95gsx6/12f ratfighter (killed) 91 xj900 (sold)
stinkwheel Well I just had my hands up a pigs fanny. Which makes your concerns pale into insignificance.

[doggone]

The bike will be significantly heavier and weight distribution subtley different.
You might have more momentum as a result which could help maintain a higher speed in some situations.

[Digitalize]

I've always been told that its because the fuel is gravity fed, and its what i've always accepted, but it does it on a lot of small bikes.
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1998 CB600F Hornet

[Kickstart]