Carb Problems!

[jaimes-duran]

Hey guys got a problem. The bike runs fine when I ride it. But when I let it sit overnight the air box floods. I kept an eye on it last night and found out there's a small drip of gas coming out of the #3 carb where it connects to the air box. I took the bowl off and made sure the float and needle was clean. What is the problem? How exactly do I clean the needle and seat?

[Ivan]

You don't have any info on your scoot. What's the year and model? The needle and seat change from early carbs and late.

If your needles are not viton tipped, they are very susceptible to dirt, since there is only a small lapped surface to seal. The finest amount of grit will cause it not to seal. Also the floats can hang in the bowls and not float. There is another adjustment for how far the float drops, a little tang that bumps against the float post. Make sure your float doesn't drop too far to hang in the bowl. Also, if its the brass floats, they can leak and sink. Check for fluid in the float.

[jaimes-duran]

sorry about that 79 special all stock I think its on my name

[wingnut]

If you have the original 79 carbs you will have the solid metal needles and brass floats. Its most likely dirt in the needle. Pull the carbs and give the system a good backwash thru the needle valve. Are you running in line fuel filters? They would be a good investment unless your tank is pristine. After you clean up the system level the carbs on the bench and apply fuel to the carbs. That way you will be able to tell if they are sealing before you have to fight them back on the engine. If they still leak you may need a new needle valve assy. It could also be a float hanging up in the bowl. Make sure the float has not gotten tweaked and is catching on the bowl some where.

[mro]

Float needle

Prom once posted about spinning the needle in the seat with a little chrome cleaner (kinda like lapping a valve)
I do this even if the carbs are not leaking when I have the carbs apart for cleaning.

Works for me.

mro

[Ken Talbot]

Remember that you have two problems, not just one. You have a leaking float valve as a number of people have noted. Your other problem is a leaking octopus. If either one of these is working properly, you will not get a leak. If you have a leak, both are in trouble. Fix them both.

[oseaghdha]

sorry about that 79 special all stock I think its on my name

Turn the petcocks to "OFF" at night.

I don't even worry about needle-n-seats beyond the point that they control the fuel just fine when the motor is running.

When the bike is not in service a positive fuel stop at the tank is the best method to keep gas where it belongs.

Vacuum stops are the work of the devil.

[wingnut]

Fix the carb

Dan not to be contrary but I subscribe to the other theory. If the needles are working correctly and shutting off the fuel like they are designed to do, and its not real hard to get them to work correctly, then I have removed the other 2 component failure points. The operator error of forgetting to turn off petcocks or octopus failing to close from the equation. That also reassures me that the carbs are operating as designed and performance is not being affected. Just my 2 cents worth.

[dbeardslee]

Antonio - To clean your fuel valves (needle and seat) you need to pull the carbs and remove the bowls. Carefully remove the float pins. If they've been in there a long time they can be difficult. Usually it's a good idea to spray them with some penetrating oil (I personally like 'Free All') turn the pin a little in the hole using a small side cutter or pliers on the head of the pin (the flat surface) to make sure it's broken loose, and very carefully tap it out using the appropriate size punch and a small hammer. Again, be careful - it's pretty easy to snap a post off if you get too aggressive removing the pins. Once the pins are out remove the floats, and lift the needles out of the seats. Make sure you keep the needles together with the seats they came out off. To remove the seats screw them out with a 10mm socket. The fuel valves have a small screen that snaps onto the bottom that can be removed for cleaning. Make sure the face of the needle and the mating surface are clean and clear of debris - a little gunk between them will keep the valve from sealing. You'll also want to clean the fuel orifices under the valves that lead to the fuel T's. Squirt them out good with carb cleaner, and finish with compressed air if you've got it. Never just put compressed air on the fuel lines with the bowls attached to the carbs. It will increase the air pressure inside the carb and squish your floats. It would probably be best to replace your fuel valves if they're leaking. I opted to use XV920 fuel valves in my '79 as they have the viton tips and a better screen arrangement. When you reassemble don't try to drive the float pin in too far, and make sure you check your float height if you change the valves. Even if you don't change them, it's still a good idea to check them. On a '79 they should be between 24.7 and 26.7mm, with 25.7 being the usual setting. My $.02

[XSokieSPECIAL]

Antonio I opted to use XV920 fuel valves in my '79 as they have the viton tips and a better screen arrangement.

Ahh, cool. I was wondering if there were viton tipped valves available for the 79 carbs.

That's why I'm here on this site. I learn new stuff every day.

[jaimes-duran]

Thanks guys, So I go for a ride and notice how blue my pipes are. What is causing this? Due to the leak on the carb it seems worse. I rode the bike just a little up the road and notice it seems like the fuel from that carb is getting into the muffler because its putting so much fuel in the engine. There is a loud drowning sound in the muffler the more throttle get it. Is this why my pipes are blue? Is my theory right? What can do to fix it?

[jjwaller]

Generally, bluing is from heat. i.e. A LEAN condition!
(I probably should say excessive bluing) Depending on the type of pipe.)
Lean engines run HOT.
Of course, if you are dumping raw fuel into the exhaust and igniting it........

[DGXSER]

Another opinion heard from...

I will add to the group that thinks you should fix all of it. The petcocks leaking will make it difficult to remove the tank withoug losing fuel all over the place, a bad thing! IF you like the Octy valve and want to keep it, then it must work right or you will need to use Prime to run the engine which eliminates the reserve function which can easily lead to you one day pushing this huge hog of a bike up some hill to the petrol station. Another bad thing! And leaking float needle valves means you are not properly controlling the fuel level in your float bowls. Mayeb it will start off as the bike just getting a little rich, but eventually it ends up as you having fuel running out of your exhaust pipes. Been there, seen that happen. And let me assure you, after you fix it, it will take about ten miles or so until you quit foggin up the entire neighborhood. Again, seen it in action. Additionally, you run the risk of now dumping fuel into the crankcase and diluting your oil which wipes out bearings on things like your tranny and or the crankshaft or rod ends. Awful costly repairs to avoid fixing leaking float valves in my opinion.

oseaghdha is correct that as long as your bike is running good and you turn off your petcocks it may nto hurt the bike. But from what your describing you seem past that point already, and I would not want to play in that game of fire to see when I get burned and how badly. Ohhh...speaking of fire....yep it can cause one of those to.

[jaimes-duran]

yes you guys are all right. So how exactly do I fix the problem?

[oseaghdha]

Dan not to be contrary but I subscribe to the other theory. If the needles are working correctly and shutting off the fuel like they are designed to do, and its not real hard to get them to work correctly, then I have removed the other 2 component failure points. The operator error of forgetting to turn off petcocks or octopus failing to close from the equation. That also reassures me that the carbs are operating as designed and performance is not being affected. Just my 2 cents worth.

That's fine. I do not mean to say that you can completely ignore the needles.
My point is that if they seep a bit, it won't matter one whit while you are running the engine, but that could accumulate overnight and get in the oil, or make a mess on the floor. Not only that, you have 4 possible points of failure only considering the needles, plus one for the octo, then two more at the petcocks.

Having had a motor die prematurely (an XV920) due to gassed up oil, I have determined that I will conrol the gas and not rely on passive methods.