2007 g29 backfire like uncle buck!!!!!!!

[jeremy85]

So new to me cart, about 6 weeks now, I use it daily to be bop around town.

Stock except a tweaked governor, 22 mph.

After she been running for a mile or so and nice and hot, I'll come off the gas, and after decelerating to around 3-6 mph, BOOM!!!! HUGE UNCLE BUCK GUNSHOT BACK FIRE!

It doesn't happen all the time, but maybe once a day, I scared some dogs on a walk today, and that's not what I want happening.

It also did this before I tweaked the governor.

So what's up? Possible things to look at?


https://www.youtube.com/watch?v=7RFoY6B6mY8

[Golf cart guy]

Start by cleaning the carb, change the 3 carburetor gaskets, make sure the manifold is flat. 99 percent of the time that will fix your issue

[cgtech]

Throttle blade not closing all the way? Throttle cables holding throttle open just a little?

[jeremy85]

Originally Posted by Golf cart guy

Start by cleaning the carb, change the 3 carburetor gaskets, make sure the manifold is flat. 99 percent of the time that will fix your issue

So you think it has an air leak and that's causing it to backfire?
Can you explain your thoughts and reasoning please sir?
Purely to increase my knowledge. Thank you!!!

[jeremy85]

Originally Posted by cgtech

Throttle blade not closing all the way? Throttle cables holding throttle open just a little?

There's just a bit of slack with the pedal all the way up, and yes, it does appear the blade slams all the way shut.

But even with it all the way shut, wouldn't it still pull fuel from the idle jet?

On a side question, does this ignition "cut off" if the cart is moving(not yet stopped)when the accelerator pedal is all the way up and trip the micro switch to kill the engine at a stop?

Or does it only kill the ignition when pedal is all the way so the micro switch is tripped AND stopped?

Purely for my own knowledge. Thanks!!!

[meimk]

Yamaha uses a "stop switch" at the bottom of the gas pedal - under the floor. With the pedal up the spark is shut down as well as power to the starter generator. It doesn't matter if the engine is still spinning down to a stop or not. Check to see if someone has set up the idle screw on the carburetor. Even if the throttle seems to slam shut, if could be just closing against the set screw and leaving the plate open just a bit.

[Golf cart guy]

Originally Posted by jeremy85

So you think it has an air leak and that's causing it to backfire?
Can you explain your thoughts and reasoning please sir?
Purely to increase my knowledge. Thank you!!!

So I work on atleast one back fire golf cart everyday. So with the way your cart is acting, it is receiving fuel while the ignition is off, and then when you step back on the throttle and the ignition turns back on, it is igniting that fuel at the wrong time. So they question becomes how is that happening? Did the cables get messed with and the throttle is staying open? could be but I see that more with a club car than Yamaha. So I find that most carbs need cleaned every few years and just a little tiny piece of dirt leaving the needle valve open a bit will cause a slight amount of fuel to leak in and cause your issue. There is a bunch of stuff that I just do on every backfire that I come across and I have a 99 percent success rate of fixing it. So I just do the same stuff every time and the cart will run better as well as not backfire.

No if you come to a complete stop and then it backfires.....different story.

[jeremy85]

Originally Posted by Golf cart guy

So I work on atleast one back fire golf cart everyday. So with the way your cart is acting, it is receiving fuel while the ignition is off, and then when you step back on the throttle and the ignition turns back on, it is igniting that fuel at the wrong time. So they question becomes how is that happening? Did the cables get messed with and the throttle is staying open? could be but I see that more with a club car than Yamaha. So I find that most carbs need cleaned every few years and just a little tiny piece of dirt leaving the needle valve open a bit will cause a slight amount of fuel to leak in and cause your issue. There is a bunch of stuff that I just do on every backfire that I come across and I have a 99 percent success rate of fixing it. So I just do the same stuff every time and the cart will run better as well as not backfire.

No if you come to a complete stop and then it backfires.....different story.

Awesome dialog thank you!! I have a lot to think about now as I start to tinker with it. I've owned many machines that may forget how to idle after sitting some, haha, and I know a carb cleaning is due, never had a backfiring machine ever, with a cart never idling, and always starting and stopping the engine, its just a little different than what im used to. I have taken the floor board off and cleaned out the dirt and lubed up the pedals, so I did discover the switches, and also noticed if I just crack the pedal open a lil it stays idling, so was just wondering how the ignition exactly worked, so thank you for the explanation.

And funny thing today, I parked it in the garage, it was completely off for about 3 seconds........ BOOOOMMMMMM HONEY IM HOMMMEEEEEEEE!!


I gotts fix this thing before the muffler explodes!!

[slonomo]

I had this when the float is sticking and allowing extra fuel into the bowl. This causes a little overflow and it can get into the intake and into the cylinder, filling the cylinder with fuel, then when you put the ignition back on....BANG.

The issue of a backfire after it is off is from fuel leaking into a hot cylinder. Sometimes there is a little carbon deposit that acts like a piece of lit charcoal, stays hot. When the fuel leaks into the cylinder, the hot carbon will ignite and cause the BANG.

Not sure if this helps, just things to check. Check the float needle/seat for dirt or debris. A tiny blade of grass always does it.

[fastbasser]

Originally Posted by Golf cart guy

So I work on atleast one back fire golf cart everyday. So with the way your cart is acting, it is receiving fuel while the ignition is off, and then when you step back on the throttle and the ignition turns back on, it is igniting that fuel at the wrong time. So they question becomes how is that happening? Did the cables get messed with and the throttle is staying open? could be but I see that more with a club car than Yamaha. So I find that most carbs need cleaned every few years and just a little tiny piece of dirt leaving the needle valve open a bit will cause a slight amount of fuel to leak in and cause your issue. There is a bunch of stuff that I just do on every backfire that I come across and I have a 99 percent success rate of fixing it. So I just do the same stuff every time and the cart will run better as well as not backfire.

No if you come to a complete stop and then it backfires.....different story.

OK, I read you post and obviously saw the last statement. What is the cause if it backfires after you stop? I have my cart "wire tied" and assume this is part of the problem..