Carb problem

[Voice]

Hi, my xs 11 special leaks petrol out my carbs when i leave the tap on, I've cleaned the carbs, tested the float valves and they appear to work on the bench, but still the petrol leaks out. I've even tested the float hight, and its got me beat as to why it still leaks.

Any pointers/ideas?

[tsears]

carb problem

Hi,

How about the floats themselves? Are any of them leaking and never getting to close the float valve? It just takes one, and I've had several over the years do this!

Tim

[sixtysix]

It's 1, or some, or all of the following:

Bad Float needle/seat
Bad Float
On 1980 and newer, bad o-rings around the needle seat.

Plus, you have bad petcocks. Or gas wouuld not flow to carbs unless started (or you are in prime)

Do your self a favor and take the carbs out, then pull the airbox, put the carbs back on, turn the gas on and see what carb the gas comes out of.

Read this: http://www.xs11.com/forum/showthread...=&threadid=142

Read this: http://www.xs11.com/forum/showthread...=&threadid=141

Anything else?

[Voice]

66, ya a star mate.
Its a 79, but I got it imported fron the States (CA I think) and was informed the carbs might be a bit different cos of the emmitions laws or some such thing, but I'll have a look at em with this new info and see what happens.

[woodstoc]

There is a diaphram in the petcocks that operate on vacumn. You might need to replace them. They should not flow gas unless there is a vacumn to the rear petcock fitting unless you are switched to prime.

Of course, even at prime, the float needles should shut off the flow. You have a issue there as well. Could be float or needle seat related.

[Dennyz]

I don’t believe a float/needle type carb 100% of the time shut the fuel off when the bike is on the side stand. This is due to the floats binding when at an angle. This is one of the reasons for vacuum shut off valves.

It is my opinion that a person can fart around with their floats and needles until the cows come home and never be able to completely prevent the carbs from leaking when on the side stand, IF the vacuum shut off valve(s) is bad. Fix the vacuum shut-off valve(s).

[Bob S.]

Voice:

Quit swearing at the Queen and they will work! More seriously,
I have a similar problem with two honda bikes. I have mounted the carbs on the edge of a shelf, removed the bowls, and hooked up a fuel feed from above. I found that the floats appeared to cut off fuel flow at their proper heights. With the bowls on, and still on the shelf, I too found they did not leak, and the fuel level was appropriate (using clear hose attached to the drains and opening the drain taps). Finally, when installed on the bike, and with the bike on its center stand, two of the carbs continue to leak.

If you solve your problem please let me know what you find.
Bob

[Voice]

Hi Bob
Problem solved, well in a fashion that is, the big end went big time yesterday taking crank shaft, the main bearings and 2nd and 5th gear with it, so it's now so much scrap. (going at about 90 on the motorway{freeway?} on my way home last night)

To say I'm pissed off is mild

[Bob S.]

Ouch!!

However, you must have fared OK since you are able to write us.
Glad it was only the bike that went south!
Bob

[TopCatGr58]

Engine meltdown

Well Voice,

So sorry to hear about the meltdown, but you kinda foretold the future with your carb leaking problem. Most likely the fuel leaked past a valve and got into the engine oil thinning it out too much, and contributed to your loss of lubrication and eventual burnup.

This is just an FYI to others that if they have leaky petcocks/carbs and faulty float valves, that they are possibly flirting with disaster.

Again, our condolences!!

[strom]

Well... tell me again how this works.

The engine breathing vent goes to the top of the airbox (fat hose).

If fuel is leaking from the carbs to the airbox, it has to fill the whole airbox till it starts running to the carbs.
And even then there's a drain hole at the bottom of the airbox, a small sponge filter there.

So what's with this gas getting in the oil deal?!

LP

[Bob S.]

I just removed the carbvs from my xs1100 and found that one intake boot had a couple ounces of gas in it. I suspect that, since the intake is lower than the top of the vent hose, a leaky seat would permit flooding into the intake long before gas would flow up the vent hose.

[sixtysix]

Yep the fuel leaks into the carb boot (and this will already be full before the airbox leaks!) and then washes down the cylinder walls past the rings. Of course it only happens if the intake valve is open, on the same cylinder or the carb that is leaking.

At least that is the way I understand it.

[strom]

Ergo, always park on a nearby uphill road... so it leaks into the airbox and when it backfires, it ignites the gas in the airbox and the bike burns to the ground.

LP

[kenkrieger]

I have had some weird stuff with this gas system on my Special,,,,,real Special,,,Every time I have used the Reserve position on the petcocks and then put the bike on the sidestand I have had a leak,,,,never if put on the center stand, however I have had leakage once or twice with the bike on the center stand,all the gas leaked out the little hole under the airbox,and each time checked my engine oil, and have never found any evidence of gas in the crankcase. Usually I just change it,,,,but none ever there,,,,as was said above I have done the dance with the floats and float shutoff valve. I did find a flat spot on the rubber face on the end of each of the shutoff valves, when I did the 10 times triple clean. I took some fine sandpaper and spun them on it at the angle and got rid of the ridge and the leak for along time, but as I said it comes back when its on the sidestand, but only after reserve has been used. I just had the gas tank off two days ago and the petcocks are operating just as they should. They were leaking on and off as well, got the new petcock kit but not had the time to do it yet. The reserve thing makes no sense to me, other than maybe a possible siphon type setup after I turn it back,,,,,like I said it makes no sense. I just turn em off and keep it on the center stand and no more leaks. So far,,,,,lol,more to come no doubt. Maybe its time to rid myself of that Octopus.