well ive been trying to run down this problem for a while now. ive taken the carbs out twice now to clean them. the float needle has no groves in them but still when it sits on the sidestand fuel slowley leaks into the air filter and onto my garage floor and with the price of gas its getting old fast. thanks in advance for any help
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fuel still leaking out of left air filter
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what year bike/ carbs? just went through this on a set of BS38s The steel float needle can "look" good and still leak. Mine were leaking. Under a magnifying glass the "waves" in the needle could be seen, I put in new float valves and seats, problem cured. Thanks to 5twins for mentioning he always replaces float valves on BS38s. The rubber tipped float valves on BS34s are more forgiving, usually if the rubber looks good they don't leak.
Needle jet o-rings I usually always replace on the 38s (because they need it), float valves only if they leak. When you have a fuel leak on a carb, it can only be several things - floats (the float itself or it's setting), bad float needles and/or seats, or a bad petcock. Those 3 things control the fuel supply to the carb. If the carb is overfilling, one of those 3 things isn't doing it's job properly. Sometimes it can be a combination of them.
suiteo
XS650 Enthusiast
Just went through this on my new Keihin carb kit on the left side. Mine turned out to be the float level.
J
J
Not wanting to pull those carbs again I put in new valves, set the height with a digital caliper and checked it with fuel and clear tubes before reinstalling them. reinstalled, petcock open, on the side stand for an hour no leaks. Yes having chatted up 5 twins I did the emulsion tube o-rings and I always shake the floats. If any question I dip them in a cup of hot water, if the float has a leak it will bubble when immersed in hot water.
its a 79 with 38s. do you usually shut off the petcock when the bike is off? i always have left them on. but with it off it has a slow drip. but i guess its time for a rebuild kit to see if that works. it seems like it only leaks when its on the sidestand though
bluebikerblan
Geezer
If you have the stock OEM 78' or 79' vacuum petcocks there is no manual OFF position. Just PRIME/ON/RES and you're dependent on the petcock diaphragm valve closing when the bike is not running (supplying vacuum) and the needle valve seating as well as the float valve not hanging up and overfilling then dumping through the throat vent and into the filter. Possibly the engine as well.....better check your engine oil for the smell of gas
If you're leaking more than a carb bowl full of gas you've got both petcock and float/needle seat problems. Whatever this is a not uncommon problem. As 5twins says above some combination of the petcock not shutting off......floats hanging up.....needle valve or valves not seating.
Does this make sense?
There's also another currently active thread on this same subject with quite a bit of related info.
http://www.xs650.com/forum/showthread.php?t=7677
Check that out too. Blue
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79 has 2 vacuum petcocks with no real "off" position. Figure on petcock overhaul(s) or replacements. Sometimes a cleaning is enough, sometimes it's just a rubber part. A few guys throw an inline fuel valve behind them as a quick cheap fix but there isn't a lot of room.
Oh yeah! Always. Carbs shouldn't leak but they sometimes do.
The floats are not for fuel shut off. They are for maintaining the proper fuel level. The petcock is for shutting the fuel flow off.
YL82
Perpetual Restorationist
I was going to start a new thread discussing my latest...issue with my '76/C ..., but came across this thread which offers several possible causes for fuel leaks along with fixes.
In my situation, the leak appears to be at the junction (air cleaner joint?) between my left carb (BS38) and the (OEM) airbox.
The leak is only on the left carb, the right one is dry as a bone...
The fuel leak occurs at a fairly fast rate. Drip$ Drip$ Drip$
I recently re-built my non-vacuum type fuel petcocks, so I'm fairly confident they are in good shape.
I know I'm facing carb removal (never done this) and cleaning and probable replacement of some parts.
A few weeks ago I recall removing the float bowl drain bolts, washers and Main Jets and noticed that they were coated in green stuff and had a funky smell.
My first thought was fuel residue/varnish... But, the green reminds me of copper oxide that forms when copper oxidizes (due to oxygen) in air. I assume this is a brass piece, which is of course ~63% copper (the balance zinc). I had my carbs empty for several weeks so perhaps it is oxidized copper...
I've included an image of what I think is the tension spring, which is right at where the leak is... This spring is not very tight. I can rotate it with my fingers. Can it be tightened and should it be replaced occassionally?
There is also a clamp to the left of the tension spring that IS very tight.
Oh, I just changed my engine/transmission oil (and filters). No fuel in oil...
Any feedback would be greatly appreciated!
In my situation, the leak appears to be at the junction (air cleaner joint?) between my left carb (BS38) and the (OEM) airbox.
The leak is only on the left carb, the right one is dry as a bone...
The fuel leak occurs at a fairly fast rate. Drip$ Drip$ Drip$
I recently re-built my non-vacuum type fuel petcocks, so I'm fairly confident they are in good shape.
I know I'm facing carb removal (never done this) and cleaning and probable replacement of some parts.
A few weeks ago I recall removing the float bowl drain bolts, washers and Main Jets and noticed that they were coated in green stuff and had a funky smell.
My first thought was fuel residue/varnish... But, the green reminds me of copper oxide that forms when copper oxidizes (due to oxygen) in air. I assume this is a brass piece, which is of course ~63% copper (the balance zinc). I had my carbs empty for several weeks so perhaps it is oxidized copper...
I've included an image of what I think is the tension spring, which is right at where the leak is... This spring is not very tight. I can rotate it with my fingers. Can it be tightened and should it be replaced occassionally?
There is also a clamp to the left of the tension spring that IS very tight.
Oh, I just changed my engine/transmission oil (and filters). No fuel in oil...
Any feedback would be greatly appreciated!
Attachments
Do the overhaul. Use the carb guide, leave NOTHING undone. plan on float valves and several o-rings needing replacing. Nothing else you do will fix it. The spring and clamp do not matter, re the fuel leak. Thank you for reuse of an existing thread.
YL82
Perpetual Restorationist
Thanks, gggGary.
Will do.
Yeah, I was kinda wondering whether there should there be any fuel getting in that "neck of the woods" anyway irrespective of the clamp and spring.
I actually look forward to tackling the carbs for the 1st time on this bike. I've rebuilt carbs on a '05 Yamaha Raptor ATV and an '83 Yamaha RX50K Special, so this will be more of a challenge.
No problem on the thread elongation. I really like the Forum Search function.
Will do.
Yeah, I was kinda wondering whether there should there be any fuel getting in that "neck of the woods" anyway irrespective of the clamp and spring.
I actually look forward to tackling the carbs for the 1st time on this bike. I've rebuilt carbs on a '05 Yamaha Raptor ATV and an '83 Yamaha RX50K Special, so this will be more of a challenge.
No problem on the thread elongation. I really like the Forum Search function.
Nubster
XS650 Enthusiast
Looks like I have a similar issue. The gas literally pours out of the left carb in a stream of fuel until I turn off the petcock. Looks like I'm in for a rebuild, huh?
sgallaty
Antihero
if you have vacuum petcocks, they will drain into your vacuum take-offs on the carb boots.
If you have a bad float needle or dead floats, you'll have the carbs overfill which will do what you're seeing.
The floats/float needles can be repaired almost without removign the carbs from the bike if you've replaced the floatbowl retainers with allen heads. with the original philips heads, no way.
If you have a bad float needle or dead floats, you'll have the carbs overfill which will do what you're seeing.
The floats/float needles can be repaired almost without removign the carbs from the bike if you've replaced the floatbowl retainers with allen heads. with the original philips heads, no way.
Nubster
XS650 Enthusiast
Non-vacuum petcocks.
Still have the phillips heads. Sounds like I will replace those with allens when I get them off.
Still have the phillips heads. Sounds like I will replace those with allens when I get them off.
daniel deblanke
XS650 Enthusiast
not sure which old thread to resurrect - but I am having this problem on my xs650
after I ride something is dripping down from the left airbox / carb juncture.
there is also a little spray on the fairings and chain guard.
the petcocks on my tank have an off position, and the carbs were fully rebuilt 15 years ago by previous owner (my FIL)
the air filter is really greasy.
I'm not sure where to begin.
The needle? the o-ring gaskets?
Bike runs great. top end was rebuilt last october.
after I ride something is dripping down from the left airbox / carb juncture.
there is also a little spray on the fairings and chain guard.
the petcocks on my tank have an off position, and the carbs were fully rebuilt 15 years ago by previous owner (my FIL)
the air filter is really greasy.
I'm not sure where to begin.
The needle? the o-ring gaskets?
Bike runs great. top end was rebuilt last october.
year or which carbs?
