Why is the engine firing up through air intake

Angle Fire Bicycle Engine Kits show as one carby

two carbies .with .dual air intake
sounds like a one piece adaptor plate and air filter assembly that can bolt to two single carbies

its a bit of a myth that it will make better power on such a small cc capacity engine


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Sounds like timing belt

Fire, fuel, air. If you're missing one, the engine won't run. You have spark, or "fire" Now check for fresh fuel (a wet plug) and finally air flow to from the air intake filter to the combustion chamber. If everything checks out, you may have a timing issue or internal engine damage.

• Backfiring in internal combustion engines occur outside of the combustion chamber, and are typically the result of an improper air to fuel ratio. This can be caused by a vacuum leak, Idle air control valve, throttle position sensor, oxygen sensor, or just about any part of your emissions contorl system.



• Backfires may also occur before the combustion chamber. One possible cause of this is igniton timing. If the timing is too advanced, the spark plug fires before the intake valves close, causing the combustion to propagate into the intake manifold, further igniting the air-fuel mixture there; the resulting explosion then travels out of the carburetor or intake and air filter. Alternatively, the engine timing may be retarded, in which case the combustion is not completed by the time the exhaust valves open, allowing the combustion to propagate into the exhaust system.



• Improper wiring of the ignition can also lead to timing issues and backfires, or faulty coil or igniton modules.



• Low fuel pressure, clogged fuel filters, and weak fuel pumps could cause a severe lean air-to-fuel ratio with fuel injection systems.



• Missing or damaged catalytic converters can result in backfires out the tailpipe, but very uncommon, and usually only applies to engines set up for race applications.

Backfiring in internal combustion engines occur outside of the combustion chamber, and are typically the result of an improper air to fuel ratio. An overly lean air-fuel mixture (i.e. an overabundance of air) can lead to a failure to ignite in the combustion chamber, also called a "misfire". The unburnt fuel then enters the exhaust system, where hot components can cause the fuel to ignite unpredictably. Alternatively, rich air-fuel mixtures (i.e. an overabundance of fuel) can result in incomplete combustion, again causing unburnt fuel to enter the exhaust system.
Backfires may also occur before the combustion chamber. One possible cause of this is timing. If the timing is too advanced, the spark plug fires before the intake valves close, causing the combustion to propagate into the intake manifold, further igniting the air-fuel mixture there; the resulting explosion then travels out of the carburetor and air filter. On many small marine engines, a screen is placed over the intake of the carburetor as a flame arrestor, to prevent these flames from escaping the intake and potentially igniting fuel or fuel vapors in the enclosed sump or bilge of the boat, causing a fire or explosion. Alternatively, the engine timing may be retarded, in which case the combustion is not completed by the time the exhaust valves open, allowing the combustion to propagate into the exhaust system.
Additionally, improperly adjusted carburetors that create a lean condition during acceleration can cause the air fuel mixture to burn so slowly, that combustion is still taking place during the exhaust stroke, and even when the intake valve opens. The flame front can then travel up the intake and cause a backfire. In this situation it is conceivable that there is a backfire occurring in the intake manifold and exhaust manifold simultaneously.
In both cases (combustion occurring before and after the combustion chamber), the result is a sharp pop, which is colloquially referred to as a "backfire". However, for troubleshooting, engine mechanics more strictly define an ignition of fuel within the engine exhaust system as an "afterfire", while a "backfire" is this same process taking place in the induction system.

I am assuming the engine is gas..
Have you checked base fuel pressure with a gauge ?
Does the engine use a MAF sensor in the air intake ?

Probably blew your intake manifold gasket that would cause the antifreeze to enter the intake also a blown head gasket would cause the same symptoms as to the module I'm not sure could be the computer or the abs pump

Hi, try to sart the engine with your hand ( or someone eslse) covering the air intake of the carburator. If the engine gives you signs of firing, then you probably have a ail leak in you fuel sistem (betwen carburator and the engine) wich is giving you a wrong petrol/air mix.
Goog luck

Backfire in an automobile engine typically results from various malfunctions related to the air fuel ratio. Backfiring can occur in carburetor engines that are running lean where the air-fuel mixture has insufficient fuel and whenever the timing is too advanced. As the engine runs leaner or if there is less time for the fuel to burn in the combustion chamber, there is a tendency for incomplete combustion. The condition that causes this is a misfire. The result of a misfire or incomplete combustion is that unburned fuel or flammable hydrocarbons are delivered to the exhaust manifold where it may ignite unpredictably.


When starting an engine, timing that is too advanced will fire the spark plug before the intake valve is closed. The flame front will travel back in to the intake manifold, igniting all of that air and fuel as well. The resulting explosion then travels out of the carburetor and air cleaner. A common air filter will allow the gases to escape, but will block the flame front. On many small marine engines, no air filter is used, but a screen is placed over the intake of the carburetor as a flame arrest to prevent these flames from escaping the intake, and potentially igniting fuel, or fuel vapors in the enclosed sump or bilge of the boat and causing a fire or explosion. Improperly adjusted carburetors that create a lean condition during acceleration can cause the air fuel mixture to burn so slowly, that combustion is still taking place during the exhaust stroke, and even when the intake valve opens. The flame front can then travel up the intake and cause a backfire. In this situation it is conceivable that there is a backfire occurring in the intake manifold and exhaust manifold simultaneously.

Good luck and hope this helps, check the carburetor settings to make sure it's not running too lean and the timing . Keep me posted, be glad to help you get your RV running 100% again.