Why are bikes less responsive when the engine is cold?

Answer 1

The heat helps the fuel/air mixture vaporize better and the oil thins as it heats creating less drag.

Answer 2

The answers that guardrailjim and bob gave are pretty good and I would say I'd have to lean more to bob...the jets and airway passages in a carburetor are sized to give the proper air/fuel mixture with the engine at full operating temp. and are not large enough to supply enough fuel for the cold dense incoming air which is being compressed by a cold piston making the engine run "lean" (notice how they bog when you try to rev them cold like it does when it's running out of gas)requiring the air to be "choked" to compensate until it heats up. Some choke systems like on motocross bikes don't choke the air, they allow the engine to draw an extra amount of fuel to rich-en the air/fuel mixture and this is what a fuel injection system does but automatically controlled by a computer. But once at operating temp. by the time the air is all the way in to the cylinder and being compressed by a hot piston it's much warmer and much less dense no longer needing the richer mixture.

Answer 3

actually the reason for this is like everything we know. The carburettor is the bit of the motorbike which mixes the fuel with air. The fuel comes the tank, through a fuel tap which lets you turn the fuel on or off, then into the carburettor. Normally, we leave it up to gravity to get the fuel from the tank into the carburettor – we don’t need to pump it.
The main purpose of the carburettor is to ‘spray’ the fuel into the air stream which passes through the carburettor. This creates a very fine mist, so that each bit of fuel is surrounded by lots of air which it can react with once it reaches the cylinder. It’s no good having big blobs of fuel, because only the fuel on the surface will be exposed to oxygen.

Answer 4

I would assume the bike uses carbureators, not fuel injection. The bottom line is that the gas isn't being mixed perfectly with air. Details:

In order for gas to burn it must be mixed with air. Carbureators are a relatively crude way to do this. They're designed to work best when everything is warm. They have ways to do it differently when things are cold (the choke is one), but these are add-ons and they don't work as well.

Fuel injection uses a computer to measure temperature and figure out how to mix gas and air well at any temperature. Cars used to run mediocre when they were cold, too. Now that all cars have fuel injection they run much better when cold.

Answer 5

Why are you groggy when you get out of bed in the morning,people fail to realize that machines are made from the same principles as the human body and is as susceptible to some of the same problems as us humans.Warming up a vehicle before running it is a very practical habit to use and a practice that can give you savings in your pocket and longer life of your engine.Modern vehicles are made with a system that is known as the open and closed loop system,this system recognizes when the vehicle is at an optimum operation temperature to give the ideal fuel mixture,so that you can conserve fuel and work more efficiently,similar to when you are running and get what is called (a second wind) ,bikes and cars are employing the same technologies so that there is more attraction to buy them in the consumer market for fuel economy .

Answer 6

Hey dude, the thing you asked was a very common phenomenon, however be assured it would be thing of the past in a few years....
So now let me answer ur question.
I suppose u have a good knowledge about the working of bike engines(which would help in better understanding of the topic, if ur knowledge is limited, u can contact me on my id :- [e-mail] ,i would be happy to explain.)....so when the bike is cold i.e. the heat is not sufficient to burn the fuel completely. to put it in a simpler yet technical way, the spark produced by the spark plug is not sufficient to burn the charge (air fuel mixture) completely. hence the response of the engine is slow. once the engine reaches the normal working temperature, the temperature inside is sufficient for the propagation of the flame. hence, good response...

Answer 7

Heat expands and cold contracts. I learned that in school LOL
When the pistons heat up and expand, they make a tighter seal between them and the cylinder. When the cylinders expand, the bores push out towards the center, further tightening up the seal between the piston and cylinder walls. The tighter the clearance between the piston & cyl, the more compression is obtainable without blow-by past the rings.
Think about it...when the piston & rings and cyl wear out, the performance of the engine goes down.
Also the cold oil is harder to flow through the engine, making it harder for the engine to work. Try pushing "play-doe" (cold oil) through a screen, then measure the speed of water (hot oil) through the screen and compare the speeds to each other. Thinner requires less force to move through tight areas.

Answer 8

Everything is less responsive when cold. Think of when you needed to get the key in the door when your hands were soooooooo cold. Or when you tried to smile when your mouth was half frozen!

It's the same for motorbikes and cars, they need to warm up before they can run to their full potential.

Answer 9

Think of a bike as a beautiful woman and you'll see why...

Answer 10

Just like a woman. You have to kick it a few times to get it started.