What does back fire mean???
Nov 8, 2004 | 05:13 PM
#11
Elite Pro Rider
Joined: Dec 2003
Posts: 5,599
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What does back fire mean???
The tensioner is on the slack side of the chain...no matter how loose it gets, its still in time.
Backfire in exaust on let off, is caused by lean in the pilot circuit. Either intake leak, exhaust leak, or mixture screw or pilot jet too lean.
This article is from the mikuni website,
4: Backfires in Exhaust
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.
Backfire in exaust on let off, is caused by lean in the pilot circuit. Either intake leak, exhaust leak, or mixture screw or pilot jet too lean.
This article is from the mikuni website,
4: Backfires in Exhaust
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.
Nov 8, 2004 | 06:25 PM
#12
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Pro Rider
Joined: May 2004
Posts: 982
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What does back fire mean???
Thanks dude that helped alot.[img]i/expressions/face-icon-small-smile.gif[/img] I am taking my quad to get dynoed some time this week so there will be a sniffer there to tell me how its running.
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