Why does my bike seem to run better when it's cold?

5v3d3b0 · World Chat Champion Joined: 24 Sep 2006 Karma :

When it's cold my bike just seems nippier...That I think is the opposite of the normal thing to happen...

mr.z · World Chat Champion Joined: 04 Feb 2004 Karma :

Cold air is denser than warm, so more oxygen, similar to the effect of nitrous which does what it does it has a higher concentration of oxygen than normal air..
(at least thats how i understand it)
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Finglonga · World Chat Champion Joined: 27 Jul 2004 Karma :

Yep, and they also run better if the air is damp.
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5v3d3b0 · World Chat Champion Joined: 24 Sep 2006 Karma :

Another question...Why does an engine actually need warming up before you hit full throttle? Doesn't quite make sense to me...Does it have to do with the expansion of the cylinder bore or something?

Davo · Davo To The Rescue! Joined: 05 Apr 2004 Karma :

lilredmachine · World Chat Champion Joined: 24 Jan 2005 Karma :

If you punt the bike from cold, the piston will heat up much quicker than the surrounding block. The effect is exaggerated by the oil not being at optimal temperatureand causing increased friction.

Laymans terms, you'll seize the fucker.
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befdelta7 · Brolly Dolly Joined: 24 Aug 2006 Karma :

my bike (listed below) seems to be a lot quicker on accelerating when cold (left over night), seems to have more of a pull for say first mile. but when warmed up just goes normal! same with my scooter when i fitted a malossi air filter would accelerate super quick for first mile or so when started up in the morning then would run normal after that untill next morning.
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Paddy Blake · World Chat Champion Joined: 29 Jun 2006 Karma :

TheDonUK · World Chat Champion Joined: 20 Feb 2006 Karma :

Dom_ · Points Mean Prizes Joined: 02 Aug 2004 Karma :

Nah, my rs50 was definately quicker in winter. My car also seems nippier when cold albeit a lot more jerky as well.

lilredmachine · World Chat Champion Joined: 24 Jan 2005 Karma :

well, as your motor warms up, so will the air around it. This air will be less dense/contain less oxygen per unit than cold air. Hence it will not burn as well as cold air.

It will be a tiny difference, but large enough to cause a large psycological one.
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JonB · Afraid of Mileage Joined: 03 Jun 2004 Karma :

I found my 2 stroke 50 was more nippier in the cold than my 4 stroke 600.
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mark83 · World Chat Champion Joined: 19 Sep 2006 Karma :

Boys boys boys (and girls, if there are any Razz

)

You're neglecting one thing: who cares how cold the air is and how nippy the engine is when your tyres are stone cold and more slippery than a soap bar in a gay prison. (Quite proud of that one actually!!!)
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brooky · Brolly Dolly Joined: 27 Jan 2006 Karma :

Dom_ · Points Mean Prizes Joined: 02 Aug 2004 Karma :

colin1 · Captain Safety Joined: 17 Feb 2005 Karma :

also has something to do with enthalpy. the bigger the difference between fuel and air in, and exhaust gases out, the more energy is released

some vehicles have intercoolers purely to cool down air to get this effect. cold air is denser, so more oxygen in a given volume of air, and also the enthalpy thing
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mark83 · World Chat Champion Joined: 19 Sep 2006 Karma :

Actually, it has nothing to do with oxygen and enthalpy.

In fact, its all to do with the fact that the bike is freezing its nuts off and wants nothing more for the rightful owner to jump on rag the tits off it! Laughing

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TheDonUK · World Chat Champion Joined: 20 Feb 2006 Karma :

befdelta7 · Brolly Dolly Joined: 24 Aug 2006 Karma :

greatmoorred · Nearly there... Joined: 13 Jul 2005 Karma :

Ive noticed this too, my bandit loves it when its cold. Tends to cut out a bit in the summer but never misses a beat when its chilly.

satellite · Two Stroke Sniffer Joined: 30 Apr 2006 Karma :

My dad told me that for every 1 degree you can reduce your engine temperature you get an effective gain of 5 BHP! Now this sounds mad, but he is quite good at that kind of thing and is currently fitting a water injection kit to his car Smile

I don't know if it translates the same for a bike though? (I know a company does a stupidly expensive charge cooled kit for my car too)
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