Carburetor virgin

[oVTo]

The carb on my son's XR100 was gummed up and the bike wasn't running well, so I took the carb apart and cleaned the jets up with carb cleaner. This was the first time I 've ever taken a carb apart, and it looks like a very simple carb. After re-assembly, the overflow started pissing gas. The floats seem to be work OK with the bowl off, so I'm not sure why it's leaking. I'm assuming the float bowl gasket is OK because it wasn't leaking before I took it apart. What else should I check for the source of the leak?

[csmutty]

The float needle probably has some crud on it. I'd buy a new needle or make sure you clean the top of the needle with emery cloth.

[Sheppo]

Smutty's pretty spot on here. A little emry cloth should be ok

[trusty_rusty]

Like Smutty and Sheppo said, float needle. If it has a rubber tip on it look and see if it has any indents going around it towards the bottom. If they sit for awhile ive seen that happen quite a bit.

[oVTo]

Thanks for the replies! The float needle does have rubber on top and it looks OK to me (but but everything I know about carbs could fit in a float bowl). Here's a big picture of the needle, and one of the cylinder it goes into. The pin on the top of the float needle moves, but it doesn't seem to expand the rubber tip at all. I guess it's there to allow a bit of pressure on the needle without bending anything. In its lowest position, the float presses the pin down.

If I had to guess, it's probably an assembly problem because there was no leak at all before I disassembled it, and now it's pouring out the overflow. If the needle is sealed (I'm not sure that's true), and the bowl gasket is OK, are there any other ways for air to escape the bowl?

[Stromper]

Sometimes the float brackets get tweaked so they rub on the float bowl.

This prevents correct action including sealing the float valve

Once assembled you should hear the floats go up and down as you turn the carb over, proving they move freely.

I also check float level by blowing into the gas hose port and gently lifting the floats untill you can feel the air get stopped.

In my experience the floats shut off when they are LEVEL when the carb is in its mounting position

[breakdirt916]

dump question : on the bottom of the carb is a screw that (eventually) connects to a hose...this is a drain screw, and this drains out the float bowl...is it tight?

[Stromper]

Yes

For long storage shut off gass . drain bowl prevent varnish glue

Note these are delicate tighten with finger pressure its easy to bugger

[Rambunctous]

Take the float and put it in some gas to verify that it floats. Hold it under to see if it leaks.

[stoinkythepig]

I bet I know what it is. I worked on a bike with the same problem and everything indicated a leaking float valve, but it turned out to be a tiny crack in the side of the overflow tube. I removed the tube, pressed in a new one, and the problem was solved.

To test, remove the float bowl, put it in a vise and ensure it is level, fill it with liquid (water works), blow a little air into the overflow outlet, with your finger over the top of the overflow tube. I bet you'll see bubbles come out the side of the tube. I found brass tubing that fit perfectly at a hobby store.

[Rambunctous]

before you try to start this bike take the plug out and kick it over to make sure it does not now have gas in the cylinder. Called hydralic lock.

[stoinkythepig]

before you try to start this bike take the plug out and kick it over to make sure it does not now have gas in the cylinder. Called hydralic lock.

Good advice, but the carb overflow device on this carb is there specifically to prevent that, and it's working, too well...

[csmutty]

Or buy an xr carb on eBay for $10 haha.

[oVTo]

Thanks for all good advice for things to check. I might have found the problem. After cleaning the jets, I put this one together in the wrong order. Instead of washer, o-ring, spring, needle screw, I assembled it washer, spring, o-ring, screw. The o-ring wasn't in straight and definitely wasn't sealing anything. It broke, so now I have to get a new one then reassemble. Hopefully, that's it. Thanks again.

[Rambunctous]

They keep assortments of o rings behind the counter at Advance Auto Parts

[stoinkythepig]

I think you should fix the o-ring, but that won't make fuel flow out the overflow, it's downstream of the fuel bowl.

[oVTo]

I think you should fix the o-ring, but that won't make fuel flow out the overflow, it's downstream of the fuel bowl.

I was afraid that might be the case. It was a nice afternoon for a ride so I went to Advanced Auto Parts for an o-ring, but they didn't have the right size. The o-ring should be nitrile, right?

I've checked all the suggestions. No luck so far; that's why I was hoping it might be the o-ring.

[gregp]

My guess is that, since it did not leak before you disassembled it, you must have had a re-assembly error. Something is either holding the float down, or preventing the needle from seating correctly. Just dis-assemble it, and put it back together again, this time paying close attention to the float assembly. The little wire clip that holds the needle to the float may have slipped off of the tab.

[Stromper]

The clip opens the needle the "tang" closes it

google sudco