Fuel out the exhaust pipe - is it the choke?

[canuckamuck]

My quad, after a year of instantaneous starting from a push of the ignition, has suddenly become difficult to start. And I noticed, on the last start, that fuel is spraying out the tailpipe . Surprisingly, once started it runs normally. Although once I noticed the fuel discharge I stopped using it.

It is an auto-choke set up with a carb.

What is the diagnoses?

[NeverSure]

Are you sure it's fuel and not water? Can you smell it? Water will condense in an engine and/or a gas tank that hasn't run for a long time.

It could be that your choke is sticking, but you could even have water in your fuel. If the fuel is old I'd be up for draining all of it including the tank and replacing it to see what happens.

Can you shut the engine off right after first seeing this liquid and try to smell it?

[canuckamuck]

It's definitely fuel

[VocalNeal]

Go for a ride and see if it still does it?

If choke is stuck you may get black smoke out of the pipe and it will idle roughly when warm.

[johng]

If you don't have a fuel tap or vacuum valve to stop the fuel at shutdown, it could be that the float valve in the carb has become sticky

allowing it to flood the cylinder and leak out through the exhaust port into the exhaust pipe...would be hard to start as its flooded with fuel.

[canuckamuck]

Go for a ride and see if it still does it?

If choke is stuck you may get black smoke out of the pipe and it will idle roughly when warm.

It idles very nicely once started, even when left a while.

[canuckamuck]

If you don't have a fuel tap or vacuum valve to stop the fuel at shutdown, it could be that the float valve in the carb has become sticky

allowing it to flood the cylinder and leak out through the exhaust port into the exhaust pipe...would be hard to start as its flooded with fuel.

Sounds possible, what's the fix?

[johng]

Turn the fuel tap off , fix the vacuum valve and or fix the float needle valve in the carb

[johng]

Could also just be gunk in the fuel bowl not allowing the valve to shut ...so get the carb thoroughly cleaned

[Gsxrnz]

As others have said - float level is probably the answer. Assuming there is no vacuum valve, if the float level valve is stuck open or just not closing fully, the flow of fuel from the tank is unchecked and depending on the configuration it may run/drain into the manifold, or just raise the level in the carby bowl so that when you push the starter, an excessive amount of fuel is sucked into the engine.

This will make it difficult to start because the build up of fuel will then wet the plug and then be ejected out the exhaust pipe unburned. The best way to check is get the engine running and then close the fuel tap and turn off the engine at the same time. Wait say 12 hours, turn on the tap and start at the same time. If it fires up no problems then it implies a stuck float level valve

I'd try the easy fixes before I take out the carb. First, get the engine running and then give the carb bowl a series of solid taps with a screwdriver handle. This may loosen any foreign objects that are causing the valve to remain open. let it sit for a day and then try to start. If it starts no problem, sweet!!

Second - buy a fuel additive that cleans the fuel system. If the valve is sticking because of fuel "gum", this may well clear it.

Otherwise, pull the carby, take off the bowl, remove the float valve and clean using a carb cleaning fluid. Check the float level and reinstall. Or it may pay to get a carb repair kit as you'll probably need a new gasket as well - the kit will include a float valve so may as well replace it. Give the whole carb a clean.

O

Edited January 20, 2016 by Gsxrnz

[CarolJadzia]

This is a common problem, as long as it's a one off then nothing to worry about. My ZRX11 did it the other day while out. One of the four carb's jammed and I got a big backfire when she started.

The floats are gravity controlled, the chock systems on old British bikes used to be 'ticklers' which where just little buttons that pushed the float down and flooded the engine. The big issues if it happens a lot are failing to start due to wet plug. The risk of the petrol igniting inside the exhaust and hydrolocking where the cylinder fills with fuel and the engine will not crank over.

The whole reason for new bikes being fitted with vacuum taps is to overcome the issue. Old bikes never had vacuum taps. We used to have to remember to turn them off.

All the issue is is that the float has not closed the needle valve for some reason. Unless damaged the probable cause is a little bit of dirt has got through the filters and just stopped the valve from closing.

If you can get the float bowl off it is easy to clean and check, you can normally attach a tube to check the hight at which the valve closes as well, this is measured against the side of the carb body.

Float hight is crucial as it is one of the things that controls the amount of fuel getting to the engine.

[kiniyow]

If the Card don't fix it consider the head gasket

[canuckamuck]

So I was going to wait until tomorrow to get some carb cleaner before I started to work on it. But I figured what the heck I'll try giving the carb a few whacks while the throttle is open. That did the trick, it's all good now.

Thanks for all the posts.

[papa al]

So I was going to wait until tomorrow to get some carb cleaner before I started to work on it. But I figured what the heck I'll try giving the carb a few whacks while the throttle is open. That did the trick, it's all good now.

Thanks for all the posts.

"a few whacks ...open."

Before or after starting?

////Also my father's theory of son raising.////

[canuckamuck]

So I was going to wait until tomorrow to get some carb cleaner before I started to work on it. But I figured what the heck I'll try giving the carb a few whacks while the throttle is open. That did the trick, it's all good now.

Thanks for all the posts.

"a few whacks ...open."

Before or after starting?

////Also my father's theory of son raising.////

Throttle open with engine running. Wife opened the throttle and it tapped with a wooden dowel and a hammer.

[Gsxrnz]

So I was going to wait until tomorrow to get some carb cleaner before I started to work on it. But I figured what the heck I'll try giving the carb a few whacks while the throttle is open. That did the trick, it's all good now.

Thanks for all the posts.

"a few whacks ...open."

Before or after starting?

////Also my father's theory of son raising.////

Throttle open with engine running. Wife opened the throttle and it tapped with a wooden dowel and a hammer.

Yep, a good ol' whack can solve many things, pleased the simple solution worked for you.