84 ez-go gas back fires

[dwon5]

runs good is fast but back fires when you let up on the gas. just paid 440 for it so if any one can give some advice it be great.

[madoc1]

dave box has a solution for this. i bet he will be on sooner or later.

[Dave Box]

A backfire is an explosion in the exhaust system. The only way this can happen is if you have fuel build up in the exhaust AND an ignition source. So you need to find out why you have too much fuel first. First you should ensure that the throttle butterfly is fully closed when you release the accelerator. Unfortunately the only visual way to be certain is to remove the carburetor, but you can be fairly certain by observing the throttle arm in the top of the carburetor. Whilst you are there make sure that there is a spring between the arm on the carburetor and the throttle cable stop.
As far as ignition goes there are two possible sources. One, of course, is the spark plug itself. The ignition is designed to turn off when the throttle is released and the spring is there to ensure that the throttle closes BEFORE the spark is turned off thus exploding any residual fuel in the system. The first issue then is to ensure that the spring is set correctly, and it may well be worth experimenting with that. Another source of ignition is carbon build up on the piston. During normal use this will glow red hot and cause, what is known on a 4 cycle as, run on. Now modern fuels have largely eliminated carbon build up but 2 cycle engines are running a nice oily mix and carbon build up is a pointer to running your engine at the correct ratio i.e. 128:1 or one ounce of oil to one gallon of gas.

Of course there could be other explanations and it is difficult (at least for me) to diagnose problems without touching and feeling. All I can say is that this is what I would do.

1. Check the operation of the microswitch on the throttle. You do not want it operating half way down the pedal travel as this would mean that as you backed off you could end up with the ignition off but the throttle partially open. The engine will continue to rotate and suck in fuel that doesn't get burnt but rather collects in the exhaust pipe. When you press the pedal again the gas in the cylinder explodes and sets fire to the gas in the exhaust pipe.

2. Check the throttle butterfly and the arm/spring operation. You want the throttle to be closed with say half and inch of pedal travel left before the pedal is fully up (and the microswitch still on).

3. I think that I might be tempted to BBQ the muffler. It kind of a long shot but it is an easy task and it will certainly not hurt anything.

4. If all else fails I would remove the cylinder head and see if it is full of coke. If you do need to de-coke it then use a blunt tool as the piston and head are soft materials. Any gouges will heat up red hot and you will be in the same position as if you had not de-coked it.
I hope that this helps but please keep us appraised of your prgress.
Dave

[dwon5]

thanks I'll do what you'al suggested and let you know the results dave

[racin161]

DAVE you must have this answer on SPEED DIAL. NOW thats funny. Great job keep up the good work.

[firestop2]

What does BBQ the muffler mean? I have heard it a few times.

Thx

[Dave Box]

Because a two stroke engine runs a mixture of gas and oil over a period of time a thick residue of oil will build up in the muffler. This will eventually start to block the air flow preventing the engine from expelling the exhaust gasses and reducing the performance of the engine. Eventually the muffler will block completely and the engine will stop running.

The solution is to light a big fire and place the muffler on top. After some 30 minutes the oil residue will heat up to its flash point and start to burn. You can see when you are this temperature as there will be a jet of flame from both ends of the muffler. Now you just keep the muffler in the heat for another 30 to 60 minutes and let the fire go out. When cool gently tap the muffler to remove the ash and you are done.

This is also a good reason to run your mixture at the correct ratio of 128:1.

Dave

[firestop2]

Thanks for the info. I learned somthing new!! No need to do this with a four stroke then..