Carburetor Dripping petrol.

[Mantis]

My last carb done this, I have since changed the carb, and the vacum hose along with a brand new choke.

When I first pull the choke out and start the bike up it drips petrol out the airbox for a little while, any ideas?.

[Foxster]

Coupla thunks...

Sure its petrol? Just a thought that it might be wet from the head breathers fed into the air box - if you have an air cleaner plumbed that way.

Other thought is that its reversion caused by your exhaust system design. This is where you get a kind of blowback of fuel+air out of the carb which hits the air cleaner and then condenses. Common on lots of engines. See it here: EX-500 cams_stock_ reversion @ 7200 rpm.avi - YouTube. Might be able to do something about it with a longer intake like on a heavy breather.

[Mantis]

100% its petrol, it stinks like petrol.

The exhaust system I got on there is a screaming eagle system, I cant remember my carb quite chucking so much petrol out as this one, I might change the bottom of the carb for the breather on the old carb and put it on the new carb and see if that makes any difference.

[banquo]

Is it spitting back through the carburettor (sounds like a backfire through the carb) as you open the throttle?
That's generally caused by weak mixture, so your idle circuit might need richened up, or there could be an issue with the enrichener itself or jetting.
If your carb is stock, and you have open pipes and K&N filter, it will run weak, and would normally be fitted with a Dynojet kit or similar. IIRC that involves opening out the vacuum hole and mods to the emulsifier and needle. I'm not exactly sure, as mine had it when I got it.

Dynojet. No doubt available from your local Indy, if your carb doesn't already have one.

[Mantis]

When I bought the carb off EBay I asked the guy if it had been re jetted and he said it had, it only spit back when I turn off the choke, its alright after a few mins of warming up.

The petrol only drips for a little while, then stops.

It might need the overflow part of the old carb put on and the float might be sticking, this is all I can think of at the moment.

[richardl]

I may know this one! I bet that your bike is either in the sun or very warm...the fumes in the petrol tank expand, and look for an easy way out..hence through the air filter...just crack open the petrol filler cap and if it sounds like someones having a good time...use your imagination...then this should stop the drips. Richardl

[Mantis]

Originally Posted by richardl

I may know this one! I bet that your bike is either in the sun or very warm...the fumes in the petrol tank expand, and look for an easy way out..hence through the air filter...just crack open the petrol filler cap and if it sounds like someones having a good time...use your imagination...then this should stop the drips. Richardl

I'll try that.

The thing is it only does it when you open the choke/enricher and then it stops are a little while when the enricher/choke is pushed in.

I'll try this tho and see what happens.

[Mantis]

Still have the problem going on. Couple of other things I have noticed.

1. It doesnt need much choke to fire up.
2. If you dont use much choke it doesnt do it.

So this smell of an overflow problem to me, to much petrol getting in and it does it all the way to work.

Gonna have to check the float and change that overflow pipe.

[dodgyloner]

I think the float height may be set too high. The carb may be brim full of petrol all the time which could explain why it overflows and doesnt need much choke to start.

If you have the float height set right and the needle is seated/sealing properly, petrol should never come out of the overflow.

[OrangeR]

Originally Posted by Mantis

Still have the problem going on. Couple of other things I have noticed.

1. It doesnt need much choke to fire up.
2. If you dont use much choke it doesnt do it.

So this smell of an overflow problem to me, to much petrol getting in and it does it all the way to work.

Gonna have to check the float and change that overflow pipe.

I seem to remember from another thread that I suggested it maybe best to use the float bowl with the overflow fitted from your old carb, it's a straight swap. Also check what jets you have in there while the bowl is off.

If you have the carb off the bike you can test whether the float is shutting off correctly by blowing into the gas inlet pipe. With the carb upright blow in and as you're doing this slowly turn the carb upside down and your blowing should be stopped be the float valve closing. If you can still blow in with the carb upside down then the float is not closing correctly.

Needless to say make sure all the petrol is out and don't smoke or breath in!!!

I hope this helps,

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