Those Doggone Carbs...

[EVAHank]

Hi, All;
I've been having a problem with 'Junior', my '03 V12. (some of you may remember this from the 'old' Forum). The carbs were leaking, bad. I took it to a friend who owns a mc shop (He restores old Britbikes), and he went completely through the carbs, did a thorough cleaning, inspected my fuel lines (they were ok) and installed a new fuel filter. Everything worked fine until yesterday when she started dumping gas again. I went through 1/2 tank in about 10 miles. It only seems to do it when the motor is running-is there something we missed? Could the fuel pump be leaking? Any help or advice would be appreciated, I'm a V12 'newbie'

Ride Safe & Sane;
Hank, Rusty, & Junior

[Rhinestone Kawboy]

Hank,

I would say first to check the obvious. Do you see any leaking gas when the bike is setting still, idling? Test that on the side stand. Maybe the drain screws on the carb became loose, or someone loosened them (hopefully not). Does the bike seem to running too rich- "loading up" or flooding, lots of black smoke, fouling plugs? You should be able to see gas leaking somewhere, or the bike is running rich. This should tell you where to look. One more idea, since you are used to the FI of the beast, maybe you left the choke on or partially on with junior?

[Chris near Kansas City]

Double check to make sure the excess gas isn't getting into the crankcase.

[EVAHank]

Hi, Guys;
Gary, it took me awhile to find the choke on 'Junior', but it was the first thing I checked. It leaks even while sitting on the centerstand at idle, and the flow rate is such that it seems like it's under pressure (which led me to think about the fuel pump...). I have one cylinder that loads up when the engine is cold, then clears out after about 5 minutes of running. (NOTE: this does not happen all the time!) Also, the leak is intermittant...sometimes I'll go through 2 or 3 tanks of gas, then it'll start again. It's getting me really frustrated!! The first thing I'll do after getting this fixed for good, is do an oil change (She's due for one anyway.) Any ideas would be appreciated!!

Ride Safe & Sane;
Hank, Rusty & 'Leakin' Lena'

[stanj1163]

Hank, I had a similar problem late last season and it turned out to be a stuck float.
Can you tell exactly where the gas is exiting the bike?
If it is running out of the rubber tube at the bottom of the carbs it's probably the same issue.
I was able to isolate which carb was stuck by pinching off the input side of each until the flow stopped. I removed the drain screw on that carb and let it drip until empty. When I powered it back up, no more leak.
Since your bike has had an impact it is possible that there is some loose "scale" in the gas tank clogging up the floats intemittently. You may need to dump and flush the gas tank.
StanJ

[Rhinestone Kawboy]

Hank,

I think StanJ has it right, sounds like you either have a piece of dirt preventing your needle valve from completely shutting the gas intake off when full, or, more likely, a stuck float or needle valve. Think I would check to see if dirt or whatever is in your fuel system, your gas filter should filter that out, unless there is a problem there, but your tank should be clean anyway. If that checks out, then I would suspect a stuck float, or stuck needle valve. I've never had the carbs apart on a XII yet, so am not sure how the needle valves are made, but it they have a little rubber tip on them, I've seen that cause problems after it wears so long with the tip of the rubber curling and causing the needle valve to not seal correctly. You may need to replace the needle valve, or, if it has that rubber tip, see if it's curled and just remove the curl- be careful not to damage or mark the mating surface otherwise if this is the case. After you are sure the tank is clean, maybe you should change the gas filter as good measure if that hasn't been done for awhile, or it appears dirty.

[Wayne and Karen]

I agree with everyone here. I would bet anything the float is sticking or there is a tiny piece of dirt keeping the needle or jet from closing. The leaking situation has happened to me on my 1995 several times. I did run sea foam through the system a few time and 'knock on wood', it hasn't happened at all last summer. Try the sea foam. Also, on mine, the leaking always stopped after a few hours at most. I never lost a half a tank, only more of a continuous drip until it stopped but one thing to consider...if the gas is dripping to the ground as you ride, you could be 'coating' your rear tire with gas which could make things slippery for stopping or turning.

One question I have. Many people have talked about dirty gas tanks, dirt or rust coming off the gas tank and getting stuck in the carbs, etc. How the heck could dirt from the gas tank get past the fuel filter? Whether the filter's dirty or not, old or new, I can't imagine how the filter would allow the dirt to get past?

If you do decide to take off the carbs, I took many pictures of the process of removing them and taking apart the carbs which I'd be happy to share - let me know. One dumb thing I did was go through all the troubel of taking them off and cleaning them but I didn't check the floats or change the needles/jets.

One more thing. As an incentive, if you do take off the carbs to fix this problem, you'll also be able to take off the air jet 'caps' and do that job very easily too. I've pics of the cap removal too.

Good luck,

Wayne

[Bill O]

Everyone is providing great advice. I have one other I recently ran into. First! If you're gonna go through the trouble of taking your carbs off to fix a problem, get some rebuild kits (about $50 for all 4 sets (K&N)).

Now, a few points to help prevent some of the trouble I got myself into, before I learned by my mistakes.

1. The drain screw is for draining the bowl. It rarely is the cause of leaking gas. There is a bowl overflow port that bypasses the drain screw. (I buggered mine up the first time thinking I just needed to keep tighening until it stopped.)

2. Get a machinist ruler with T-Slide (about a couple of bucks). This will make setting the float levels easy.

3. Examine the floats (here is another one I didn't notice until the second time apart) LOOK FOR FLUID IN THE FLOATS.
This is also very rare! But, it has now happened twice during my lifetime. 1st time in my XS750 Yamerhammer. Had metal floats that were solder sealed. One was leaking gas out of it when i dismanteled it. Took awhile, but got it resoldered (after making sure it was empty). 2nd time, two month ago in my Voyager. Voyager floats are plastic and light weight. I had one float that one side must have been absorbing gas for years through a micro sized hole. It was completely full. Being full, it looked the same as the other side and the weight difference was not noticed. What this did was make the float, float less!. The result, bowl over filling, constant slight leak, eventually filling the catch tank. (Cal Model). For you all other models, you're just dumping it on the ground (as stated in previous post). I just lived with it for almost two years.

Sorry for getting winded, but, figured this is the best place to post "Lessons learned!"

Bill

[The Count]

A good trick is to weigh the floats when the carbs are apart to know if they are holding fuel or not. A small hand held postal scale works well for this......

[Ken in Crosby]

My 03' did the same thing with less than 20,000 miles. I opened all the drains and ran the starter so the fuel pump would flush gas through the seats. That solved the problem. I also ran some SeaFoam in it.