back fire
Sep 30, 2005 | 12:35 AM
#2
Extreme Pro Rider
Joined: Dec 2003
Posts: 4,054
Likes: 0
back fire
Originally posted by: scooter1967
i had my NEW AC 500 back fire the other day.
i came to a quiK stop and shut er down and ...***POW***
is this normal or ok for that to happen?
i had my NEW AC 500 back fire the other day.
i came to a quiK stop and shut er down and ...***POW***
is this normal or ok for that to happen?
Sep 30, 2005 | 12:50 AM
#3
Pro Rider
Joined: Jul 2004
Posts: 281
Likes: 0
back fire
Very common on my ATV's and even my snowmobile does it. It is usually a sign that you may be idling to high or you are jetted to rich and when you shut it down, the motor pushes unburned fuel into the exaust system and the hot muffler ignites the fuel. Has your quad ever backfired when you let off the throttle when your cruising down the trail? That to is a sign of a rich condtion.
Sep 30, 2005 | 03:28 PM
#5
Elite Pro Rider
Joined: Dec 2003
Posts: 5,599
Likes: 0
back fire
Originally posted by: CATSKINNER
Very common on my ATV's and even my snowmobile does it. It is usually a sign that you may be idling to high or you are jetted to rich and when you shut it down, the motor pushes unburned fuel into the exaust system and the hot muffler ignites the fuel. Has your quad ever backfired when you let off the throttle when your cruising down the trail? That to is a sign of a rich condtion.
Very common on my ATV's and even my snowmobile does it. It is usually a sign that you may be idling to high or you are jetted to rich and when you shut it down, the motor pushes unburned fuel into the exaust system and the hot muffler ignites the fuel. Has your quad ever backfired when you let off the throttle when your cruising down the trail? That to is a sign of a rich condtion.
Are you using pure gas.. or ethenol blended? If youre filling up in mn, its ethenol blended unless the pump says other wise. Try using a tank of pure gas, and see if it gets better. The blended stuff, is leaner than pure gas, and if you want to continue using the blended stuff...give the mixture screw a 1/4 turn richer, and the popping will stop.
Sep 30, 2005 | 08:18 PM
#7
Elite Pro Rider
Joined: Dec 2003
Posts: 5,599
Likes: 0
back fire
Octane has nothing to do with it.
Its the alcohol that is blended in the gas..that makes the mixtures about 10% leaner than pure gas.
Its the alcohol that is blended in the gas..that makes the mixtures about 10% leaner than pure gas.
Trending Topics
Oct 1, 2005 | 02:46 AM
#8
Extreme Pro Rider
Joined: Dec 2003
Posts: 4,054
Likes: 0
back fire
Originally posted by: hondabuster
Actually its just the opposite. Its a lean condition which causes the pops on shut down or sudden throttle let off.
Are you using pure gas.. or ethenol blended? If youre filling up in mn, its ethenol blended unless the pump says other wise. Try using a tank of pure gas, and see if it gets better. The blended stuff, is leaner than pure gas, and if you want to continue using the blended stuff...give the mixture screw a 1/4 turn richer, and the popping will stop.
Originally posted by: CATSKINNER
Very common on my ATV's and even my snowmobile does it. It is usually a sign that you may be idling to high or you are jetted to rich and when you shut it down, the motor pushes unburned fuel into the exaust system and the hot muffler ignites the fuel. Has your quad ever backfired when you let off the throttle when your cruising down the trail? That to is a sign of a rich condtion.
Very common on my ATV's and even my snowmobile does it. It is usually a sign that you may be idling to high or you are jetted to rich and when you shut it down, the motor pushes unburned fuel into the exaust system and the hot muffler ignites the fuel. Has your quad ever backfired when you let off the throttle when your cruising down the trail? That to is a sign of a rich condtion.
Are you using pure gas.. or ethenol blended? If youre filling up in mn, its ethenol blended unless the pump says other wise. Try using a tank of pure gas, and see if it gets better. The blended stuff, is leaner than pure gas, and if you want to continue using the blended stuff...give the mixture screw a 1/4 turn richer, and the popping will stop.
Ok. I'll bite. Explain your theory on how a lean condition causes a backfire.
Oct 1, 2005 | 04:25 PM
#9
Elite Pro Rider
Joined: Dec 2003
Posts: 5,599
Likes: 0
back fire
I used to think it was rich but after reading this , on the mikuni carb website, I now know its from lean.
4: Backfires in Exhaust
Note:
It is normal for many high performance exhaust systems to moderately backfire or pop when the throttle is closed from mid-to-high rpm. In fact, one should expect a well-tuned high performance engine to "pop" and "crackle" when the throttle is closed at high rpm.
The popping is a result of the air/fuel mixture becoming very lean when the throttle is closed and the engine is rotating well above idle speed. It is also necessary that the exhaust system have rather open mufflers.
Why This (normally) Happens:
1) When the throttle valve is in the idle position, fuel does not flow out of the main system (needle, needle jet, main jet). Fuel is only delivered to the engine by the pilot (idle) system.
2) The combined effect of the closed throttle and elevated engine rpm is to create a fairly strong vacuum in the intake manifold. This vacuum, in turn, causes a high air flow rate through the small gap formed by the throttle valve and carburetor throat.
3) Under these conditions the pilot (idle) system cannot deliver enough fuel to create a normal, combustible air/fuel ratio. The mixture becomes too lean to burn reliably in the combustion chamber. It gets sent into the exhaust system unburned and collects there.
4) When the odd firing of the lean mixture does occur, it is sent, still burning, into the exhaust system where it sometimes ignites the raw mixture that has collected ---- the exhaust then pops or backfires.
Other possible causes:
Air Leaks:
Any source of fresh air into the exhaust system can create or worsen the conditions that bring about exhaust backfiring. The most common entry point is the junction of the header pipes and mufflers. Even a small air leak can dramatically increase the intensity or likelihood of exhaust system backfiring.
A high temperature silicone sealant, as can be found in many auto parts stores, may be used to seal the pipe/muffler junction.
Lean Carburetion:
While exhaust system popping may be considered normal, it is certainly made worse by an overly lean idle circuit.
Be sure that your carburetor's pilot jet is the correct size and that the idle air mixture screw is correctly adjusted before looking for other causes of popping. The procedure for adjusting the pilot circuit is covered in the Tuning Manual.
Ignition:
If exhaust system popping is very loud, irregular and accompanied by loss of power, then you should suspect that the ignition system is not performing as it should. If, for some reason, the ignition sometimes fires at the wrong time, then exhaust popping can become very energetic (loud). Look for failing high tension leads (plug wires), failing ignition coil(s) and especially switches or connectors as possible causes.
4: Backfires in Exhaust
Note:
It is normal for many high performance exhaust systems to moderately backfire or pop when the throttle is closed from mid-to-high rpm. In fact, one should expect a well-tuned high performance engine to "pop" and "crackle" when the throttle is closed at high rpm.
The popping is a result of the air/fuel mixture becoming very lean when the throttle is closed and the engine is rotating well above idle speed. It is also necessary that the exhaust system have rather open mufflers.
Why This (normally) Happens:
1) When the throttle valve is in the idle position, fuel does not flow out of the main system (needle, needle jet, main jet). Fuel is only delivered to the engine by the pilot (idle) system.
2) The combined effect of the closed throttle and elevated engine rpm is to create a fairly strong vacuum in the intake manifold. This vacuum, in turn, causes a high air flow rate through the small gap formed by the throttle valve and carburetor throat.
3) Under these conditions the pilot (idle) system cannot deliver enough fuel to create a normal, combustible air/fuel ratio. The mixture becomes too lean to burn reliably in the combustion chamber. It gets sent into the exhaust system unburned and collects there.
4) When the odd firing of the lean mixture does occur, it is sent, still burning, into the exhaust system where it sometimes ignites the raw mixture that has collected ---- the exhaust then pops or backfires.
Other possible causes:
Air Leaks:
Any source of fresh air into the exhaust system can create or worsen the conditions that bring about exhaust backfiring. The most common entry point is the junction of the header pipes and mufflers. Even a small air leak can dramatically increase the intensity or likelihood of exhaust system backfiring.
A high temperature silicone sealant, as can be found in many auto parts stores, may be used to seal the pipe/muffler junction.
Lean Carburetion:
While exhaust system popping may be considered normal, it is certainly made worse by an overly lean idle circuit.
Be sure that your carburetor's pilot jet is the correct size and that the idle air mixture screw is correctly adjusted before looking for other causes of popping. The procedure for adjusting the pilot circuit is covered in the Tuning Manual.
Ignition:
If exhaust system popping is very loud, irregular and accompanied by loss of power, then you should suspect that the ignition system is not performing as it should. If, for some reason, the ignition sometimes fires at the wrong time, then exhaust popping can become very energetic (loud). Look for failing high tension leads (plug wires), failing ignition coil(s) and especially switches or connectors as possible causes.
Oct 1, 2005 | 11:26 PM
#10
Extreme Pro Rider
Joined: Dec 2003
Posts: 4,054
Likes: 0
back fire
Originally posted by: hondabuster
I used to think it was rich but after reading this , on the mikuni carb website, I now know its from lean.
4: Backfires in Exhaust
Note:
It is normal for many high performance exhaust systems to moderately backfire or pop when the throttle is closed from mid-to-high rpm. In fact, one should expect a well-tuned high performance engine to "pop" and "crackle" when the throttle is closed at high rpm.
The popping is a result of the air/fuel mixture becoming very lean when the throttle is closed and the engine is rotating well above idle speed. It is also necessary that the exhaust system have rather open mufflers.
Why This (normally) Happens:
1) When the throttle valve is in the idle position, fuel does not flow out of the main system (needle, needle jet, main jet). Fuel is only delivered to the engine by the pilot (idle) system.
2) The combined effect of the closed throttle and elevated engine rpm is to create a fairly strong vacuum in the intake manifold. This vacuum, in turn, causes a high air flow rate through the small gap formed by the throttle valve and carburetor throat.
3) Under these conditions the pilot (idle) system cannot deliver enough fuel to create a normal, combustible air/fuel ratio. The mixture becomes too lean to burn reliably in the combustion chamber. It gets sent into the exhaust system unburned and collects there.
4) When the odd firing of the lean mixture does occur, it is sent, still burning, into the exhaust system where it sometimes ignites the raw mixture that has collected ---- the exhaust then pops or backfires.
Other possible causes:
Air Leaks:
Any source of fresh air into the exhaust system can create or worsen the conditions that bring about exhaust backfiring. The most common entry point is the junction of the header pipes and mufflers. Even a small air leak can dramatically increase the intensity or likelihood of exhaust system backfiring.
A high temperature silicone sealant, as can be found in many auto parts stores, may be used to seal the pipe/muffler junction.
Lean Carburetion:
While exhaust system popping may be considered normal, it is certainly made worse by an overly lean idle circuit.
Be sure that your carburetor's pilot jet is the correct size and that the idle air mixture screw is correctly adjusted before looking for other causes of popping. The procedure for adjusting the pilot circuit is covered in the Tuning Manual.
Ignition:
If exhaust system popping is very loud, irregular and accompanied by loss of power, then you should suspect that the ignition system is not performing as it should. If, for some reason, the ignition sometimes fires at the wrong time, then exhaust popping can become very energetic (loud). Look for failing high tension leads (plug wires), failing ignition coil(s) and especially switches or connectors as possible causes.
I used to think it was rich but after reading this , on the mikuni carb website, I now know its from lean.
4: Backfires in Exhaust
Note:
It is normal for many high performance exhaust systems to moderately backfire or pop when the throttle is closed from mid-to-high rpm. In fact, one should expect a well-tuned high performance engine to "pop" and "crackle" when the throttle is closed at high rpm.
The popping is a result of the air/fuel mixture becoming very lean when the throttle is closed and the engine is rotating well above idle speed. It is also necessary that the exhaust system have rather open mufflers.
Why This (normally) Happens:
1) When the throttle valve is in the idle position, fuel does not flow out of the main system (needle, needle jet, main jet). Fuel is only delivered to the engine by the pilot (idle) system.
2) The combined effect of the closed throttle and elevated engine rpm is to create a fairly strong vacuum in the intake manifold. This vacuum, in turn, causes a high air flow rate through the small gap formed by the throttle valve and carburetor throat.
3) Under these conditions the pilot (idle) system cannot deliver enough fuel to create a normal, combustible air/fuel ratio. The mixture becomes too lean to burn reliably in the combustion chamber. It gets sent into the exhaust system unburned and collects there.
4) When the odd firing of the lean mixture does occur, it is sent, still burning, into the exhaust system where it sometimes ignites the raw mixture that has collected ---- the exhaust then pops or backfires.
Other possible causes:
Air Leaks:
Any source of fresh air into the exhaust system can create or worsen the conditions that bring about exhaust backfiring. The most common entry point is the junction of the header pipes and mufflers. Even a small air leak can dramatically increase the intensity or likelihood of exhaust system backfiring.
A high temperature silicone sealant, as can be found in many auto parts stores, may be used to seal the pipe/muffler junction.
Lean Carburetion:
While exhaust system popping may be considered normal, it is certainly made worse by an overly lean idle circuit.
Be sure that your carburetor's pilot jet is the correct size and that the idle air mixture screw is correctly adjusted before looking for other causes of popping. The procedure for adjusting the pilot circuit is covered in the Tuning Manual.
Ignition:
If exhaust system popping is very loud, irregular and accompanied by loss of power, then you should suspect that the ignition system is not performing as it should. If, for some reason, the ignition sometimes fires at the wrong time, then exhaust popping can become very energetic (loud). Look for failing high tension leads (plug wires), failing ignition coil(s) and especially switches or connectors as possible causes.