shee backfiring

[manalive]

my shee is backfiring what do you think might be causing it????

[AWR]

make sure plugs are good and carbs are in sync

[jasons]

i found this on the mikuni site:::

 

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.

 

 

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.

[drag+6blaster]

I'd check your reeds and reed cages. The screws may have come loose and the reeds got sucked in the motor.. also check for fouled plugs

[Screamindemon350]

Is it both cylinders or just one? I had one that misfired on the right cylinder only even when i switched the plug wires around. The culprit was a crack on the inside of the flywheel near the hub part not on the magnet. I would yank that off really quick before you mess with your carbs. If you switch the plug wires around and it backfires in the opposite cylinder you MIGHT have a problem with your coil or one of the blocks on your flywheel. Your pulse coil could be out of adjustment too. Just some info to get you pointed in the right direction.

Give us some more info on your setup. Any recent mods you did and whether you have a timing plate or not.

Edited July 26, 2010 by Screamindemon350

[manalive]

Is it both cylinders or just one? I had one that misfired on the right cylinder only even when i switched the plug wires around. The culprit was a crack on the inside of the flywheel near the hub part not on the magnet. I would yank that off really quick before you mess with your carbs. If you switch the plug wires around and it backfires in the opposite cylinder you MIGHT have a problem with your coil or one of the blocks on your flywheel. Your pulse coil could be out of adjustment too. Just some info to get you pointed in the right direction.

Give us some more info on your setup. Any recent mods you did and whether you have a timing plate or not.

 

 

Hay scream, This is actually the old one i gave my son. I just put rings in shee. I will try swapping plug wires. I think the carbs are out of sinc. Runs ausome, just need tuning.