View Full Version : Carb leaking fuel into airbox

03-14-2012, 11:02 AM
My bike started leaking fuel into the airbox on a cross state trip sunday. cant figure out what it is seems to be happening more at higher speeds. Any suggestions?

03-14-2012, 11:06 AM
How do you know it was 'leaking'? What did you do to determine this? Knowing how you determined this will help us help you.

From the info provided so far:

It's either "fuel standoff" or "reversion".

Is your bike stock? I'm going to assume so since you still have the airbox. In which case it's a little bit of both and is just inherent with the engine design.

Does it leak fuel while the engine is off and sitting? If that's the case tap the bottom of the carb with a rubber mallet to make sure the float isn't stuck.

03-14-2012, 11:14 AM
I was riding about and when I ran out of fuel prematurely I looked at the side of the bike and found gas on the side of the engine, opened the airbox and found a good amount both on the filter and in the bottom of the airbox. Couldn't reproduce the results with the bike sitting. Ran carb cleaner through system. riding around town 30-35mph noticed nothing. Left town and went on the highway. Arriving at next stop the gas is on the side of the bike again.

03-14-2012, 11:19 AM
How dirty/clean is your air filter? How does your boot look?

03-14-2012, 11:29 AM
It was new, just bought the bike from the HD dealer out here. Put about 360-380 miles on it in the last month or two. Had 1008 on it when i bought it.

03-14-2012, 11:45 AM
This is perplexing given it's new, low miles, and the issue only comes up on the highway.

That being said, most all carb issues can be directly related to the rubber boot that connects it to the "manifold". I would replace that (it's a few bucks and very straightforward), don't over tighten it, then go for a long ride and see how it does. Grab an extra boot just in case; or buy Thumpe's Super-Boot and consider it preventative maintenance.

The boot can get hairline cracks that cause all kinds of weird issues and wreak havoc when trying to troubleshoot those issues. First step is always "replace das boot."

i'm still not sold on it not being a stuck float, though. Thump the float bowl with a rubber mallet while you're changing the boot, for good measure.

03-14-2012, 11:58 AM
Alright well I would rather fix it good then fix it twice, where do I get said superboot? And how much.

03-14-2012, 12:01 PM
Forum Member Thumpe (http://www.buellxb.com/index.php?a=member&m=5509) makes/sells them. Also ask him about his other products you may be interested in.

03-14-2012, 03:59 PM
Alright Sounds good will post results after rejetting switching to irridium and replacing das boot.

03-15-2012, 06:13 AM
That doesn't sound like a boot issue to me, sounds like a stuck float. If fuel was coming out into the airbox from the carb then that definitely is it.

Just try tapping the float bowl with the back of a screwdriver and see if you can unstick it. If not just pull the bowl and unstick the float. spray some carb cleaner in their while you are it. This is a common issue, nothing to worry about.

uly luigi
03-15-2012, 06:22 AM
I'm thinking stuck float too, since it started after sucking the bottom out of the tank

03-15-2012, 08:38 AM
Happened before it went empty. Just didn't know till I was on the side of the road.

03-15-2012, 10:42 AM
Stuck float

03-15-2012, 01:35 PM
Well if sticking I want to know why. Oh well changing jets anyways. Install inline filter to keep it cleaner.

03-15-2012, 01:51 PM
Generally dirty carbs. However, carbs are finicky. I have a 1000 4 cylinder carbed cruiser and all hell descends upon the bike when even such as a particle of dust makes it way through past the filter. When a float sticks, the bike barely runs it floods so bad. At least with the blast it just drops right out the intake. Sometimes the just get stuck in the on position. They are very delicate, hence taping the bowl usually unsticks them. Run seafoam through your system regularly and you will be fine.

03-15-2012, 01:52 PM
What jets are you running, what intake and exhaust? What are you planning on changing it too?

03-17-2012, 02:52 PM
Thinking about a 175

03-17-2012, 03:44 PM
Is your exhaust and intake stock?

03-17-2012, 05:26 PM
Completing airbox mod and k&n filter install as long use its out. Unless its a bad idea to rejet before I get the new pipe.

03-18-2012, 12:00 AM

03-18-2012, 09:36 PM
Alright won't do that yet then.

03-21-2012, 06:59 AM
fuel in box solved,floatbowl was sticking. Next airbox crud question, is there generally a coating of oil in the airbox that seeps out the bottom?

uly luigi
03-21-2012, 07:31 AM
That sounds like crankcase breather/PCV valve in the rocker box cover, how many miles did you put on it with it flooding? May have washed/wore the rings enuff to get a little excessive blowby.

03-21-2012, 09:35 AM
I put 700 miles on it in the last 2 months. The odd thing about the gas leak it was only at highway speeds 70+ The oil issue only started a couple weeks ago.

03-21-2012, 11:19 AM
Oil issue is because at stock the PCV valve is vented into the airbox. Re-route it to the ground and let it drip there, or plug it and put a small air filter at the tee and use a cable tie to secure it somewhere. Not an issue either way, comes from the factory like this for emissions control. I think its safer to re-route it though. If you need pics to see what I am talking about, let me know.

Rings will be fine as on the blast the fuel pours out the inlet rather than into the cylinder.