How does a motorcycle carburetor work?

Question

I have a seized engine after someone tampered with the carburetor! Initially the problem was that turning the throttle fully would cause the bike to jack.

Answer 1

Motorcycle carbs work the same as any carbs, they mix fuel and air into about a 1:16 ratio. Adjusting it to run too rich (too much fuel) will usually cause it the engine to die. Running too lean (too much air) can cause a number of problems including running too hot and seizing.

Answer 2

Fuel is gravity feed to the carburetor from the fuel tank. At some point it flows through a filter to remove the micron size contaminates. The carburetor store enough fuel in a bowl to control the supply needed. The supply is regulated by a needle valve and a float that goes up and down in the fuel. When the level reaches its maximum, the float is designed to close the needle valve, thus stopping anymore fuel to enter the bowl. The fuel is sucked from the bowl through jets and venture tubes. Works kind of like sucking on a straw. A flap in the lower section of the carburetor opens and closes the amount of vacuum the engine pulls into the engine. This is called your throttle and is hooked to the cable on the throttle that is turned manually by hand to control the speed of the bike. The flap as it is opened allows the straw effect to pull the fuel needed through the jets into the engine. The jets regulate how much fuel to air ratio the engine can handle. The other circuit is the idle control. It is regulated by a needle valve that is adjustable, and controls how much air or vacuum the engine pulls at idle. The carburetor has two sets of Jets. One for the throttle and the other for the idle circuit. The idle circuit is shorter thus allowing it to pull fuel all the time, while the throttle circuit is longer and takes a larger vacuum supply to activate. The regulator between the two circuits works by a spring and an check ball. The vacuum for the throttle circuit will come into play only after the tension of the spring is overcome by pressure from the amount of vacuum allowed into the engine by the throttle plate.
This may be hard to understand, but there are many books you can get at the library that breaks down the system, or you can go to howthingswork.com and see it. I hope this expains what you need to know. As for the engine seizing up, i doubt messing with the carburetor would cause this to happen. Putting sugar into the fuel system could cause this! I feel strongly that the two are not related, and it just happen to show up at the same time. An engine that is near seizing will slow down, and mimic a carburetor that is malfunctioning. Good Luck!

Answer 3

How Does A Carburetor Work

Answer 4

Don't know what you mean by " the bike to jack" but..
If your eng. locked up after someone messed with the carb then the float is set to high and it has dumped raw fuel into your eng. hydrostatic lock. All you have to do is pull the spark plugs out and SLOWLY turn the eng. over by hand a few times (put it in high gear and walk it around) once most of the fuel is out of the cylinders you can hit the starter and blow the rest out, gt the carb fixed and change your oil, gas will go past the rings and into the oil if it as been sitting in the cylinder like that.

Answer 5

Try checking your sump oil level (4 Stroke) or how much oil you have in your petrol (2 Stroke). Your engine should not seize up due to someone fiddling with your carb, it only mixes the petrol with the air.

Answer 6

Sounds like you have an engine problem, not a carburetor problem.

Answer 7

you carb shouldnt have had anything to do with the motor seizing. the only thing a carb does is manage the fuel-air mixture going into the manifold. if it was a four cycle than you didn't have oil in the case. if it was two cycle you didn't have enough oil in the fuel mix.