I went out to start my cart this evening, It started up then fouled the plug and died. The carb was also flooding. Yesterday I started it, adjusted the idle/low speed needle, let it warm up,and took off down the road. This was the first time in 25-30 years that the engine had been started. It has all new parts in the carb, The arm that controls the needle is adjusted flush w/ the top of the carb body. Oh yeah...Its a Mc 91b1 with a bdc 14 carb. Any thoughts? Thanks ========================================================= First thought..... yep, it's a McCulloch, nothing unusual  Second thought.... you need to provide more info..... what is the popoff pressure? Where are the jets set? Did the duck bill swell up or is it still the same size as when you installed it? Did you pull the plug to see if it is wet? How did you kill the motor when you ran it the first time? If you choked it to shut it off you may have flooded the motor with fuel. Will the carb draw fuel when you crank it over? If it pulls fuel up the line when cranking, does it stay there when you stop or does the fuel run back down the line filling the line with air? Answers to these questions will help in identifying the problem. Regards, Steve O'Hara ========================================================= pop off pressure---dont know low side ---just past 3/4 turn high side---just under 1 turn duck bill is a new elder rubber duck bill (will it swell that quick?) Plug was wet Pulled the plug to kill it Had to cover the throat of the carb to get fuel up the line and to the carb..once it was there it stayed...no air It also had fuel sitting in the carb throat...Plug was soaked also I killed it and started it probley 5 times last night...started right up each time It has good spark and compression Reeds are okay... I took carb apart blew everything out ,reassembled, started it, It ran for maybe 10 seconds and flooded out. thanks ========================================================= Set the low speed needle ( the one closest to the engine ) at 1.25 turns and the high speed needle ( the one furthest from the engine ) at 1/2 turn. Turn the idle adjusting screw out until it does not touch the throttle lever and then screw it back in till it just touches, then one more full turn. To check the pop off pressure you need a pop off guage that you can get at your local kart shop of borrow one from a karting buddy. Hook it to the fuel inlet and pump up the carb to see if it hold pressure... go to about 5 psi first and see if it will stay put. If the carb won't hold 5 psi it either has a bad gasket somewhere or the fulcrum arm is set too high. If the fulcrum arm is too high the leakage from the pressure test will bubble out through the brass dump tube and other fuel orifices in the bore of the carb. You can dunk the carb in a bucket of water to see where the leaks are. If the carb will hold the 5 psi it means the arm is set at the right height and there are no bad gaskets so move on to check the pop off pressure by pumping the carb up until it loses the seal and the needle on the guage drops back to a lower reading. Note the highest pressure point you see on the guage.... that is the "pop off" pressure and it should be no less than 15 lbs. Many kart pop off guages only go to 16lbs so you may find the you peg the guage..... if you do that is fine and you are in good shape on the pop off pressure. Before running the motor again you may want to make sure it does not have excess fuel accumulated in the case as it will cause the type of problem you describe. To assure the case does not have a bunch of fuel standing at the bottom, remove your spark plug and your fuel line. Plug the spark plug cap with a non conductive material or tape over the end with some good tape.... you need to be sure it cannot arc to the engine. With the throttle held wide open and the fuel line and plug removed, spin your motor over with your starter for at least 15 seconds as fast as your starter will turn it. You might want to stuff a rag in where the spark plug goes to absorbe the excess fuel that blows out so you don't make a mess of the motor. Once you have the motor cleaned out, clean the plug with brake cleaner, acetone or some other strong oil cutting, fast drying chemical and re install the plug. Hook up the fuel line and safety wire the connection to the carb. Fire it up and fine tune as needed to get the engine to idle clean and have crisp throttle response without blubbering or starving.... blubbering means it is too rich and you need to screw the low speed needle in to clean it out. Starving.... that kind of waaaa, waaaa sound when you crack the throttle means you are too lean and you'll need to open the low speed jet and possibly the high speed as well. Once you have found a setting that gives you decent throttle response, adjust the idle screw to fine tune the idle to a speed a bit higher than you would expect a chain saw or two stroke dirt bike to idle. When you drive the kart and have the engine at full throttle for more than a couple seconds, if the engine does not blubber or 4 cycle as some folks describe it, back off the throttle and open the high speed needle quarter turn and try full throttle operation again. You want to find the setting where the motor will run clean way up to high rpm and then just break in to a 4 cycle or blubber state at the peak rpm. Good luck! Steve O'Hara ======================================================== okay... I pressure tested the carb...It is blowing air out of the brass tube at the front of the carb bore, it is also leaking out the hole at the back of the diaphram plate. 1---is the brass tube the (main fuel discharge check valve)? 2---if so is it supposed to be hollow? took carb apart again...bent arm down (it is at .020 below carb body) still blowing air through both the same holes. water also entered the inside of the carb ========================================================= OK.... we are getting somewhere. If air finds its way out through the hole in the bottom of the middle plate it means there is a leak in the diaphragm and it must be replaced. The metering diaphragm must seal air out and fuel in for the carb to work properly and consistently. The next problem is the dump tube... the brass dump tube is the main fuel delivery path to the venturi and air can only flow out through the dump tube if the inlet needle fails to seal. Usually, a leaking inlet needle is due to the arm height being too high but you adjusted the arm to below flush so that should not be the problem. Sometimes the arms get tweaked and causes the needle to tilt and it messes up the seal. You want to be sure the fork on the end of the fulcrum arm has both tangs in the same plane and the fork tangs should be perpendicular to the needle when it is in the closed position. You should also look closely at the area of the needle where the tangs touch the needls to assure there is no wear. If the needle is worn, the arm will not settle in the same place each time. For gas, the arm should be flush with the body of the carb and the inlet needle should be able to hold pressure up to no less than 15 psi steady without leaking or "poping off". Does your carb have the rubber tipped inlet needle? Some folks changed to solid metal or nylon and those just don't seal well most of the time. If it is a rubber tipped needle, inspect it carefully to assure there are no dings, cuts, grooves etc. It is a first priority to get the inlet needle to seal and pop off at the right pressure. From there, it is just a matter of making sure the plates are clean and flat ans you have a good metering diaphragm and pumper in the carb. You bought the correct new version of the duck bill so you should have no problems in that area. One last thing to check..... make sure you have the gasket and flapper gasket in the correct sequence under the circuit plate. The flapper goes immediately below the metal circuit plate, then the gasket or gaskets. There are several thicknesses of circuit plate gaskets out there and you can run one or more as long as they add up to at least .040" thick and do not exceed .060" thick. Last bit of advice.... if you use a metering diaphragm with the metal plate in the center held on by a rivet you must run it with the extra gasket to provide enough space under the first plate. Without the extra gasket, the rivit will bottom against the fulcrum arm and the plate above and hold the arm open just enough to leak. Good luck.... if you get the carb set up right it will idle clean, have good throttle response and run well through the full range of rpm without lean spots. The Mac carbs are much maligned.... mostly due to careless mechanics that screw them up. Regards, Steve O'Hara ======================================================== my needlle is rubber tipped...looks pretty good..I will check out the folcrum arm. my diaphram has the metal plate....what extra gasket are you talking about? ======================================================= I need to find out who I can get a needle,diapham,and new arm would be nice, mine is showing wear on one of the tongs on the gaskets for the plate on the carb body... is it.040 w/the plate or just the gaskets. Thanks ======================================================== Try Terry Ives, Vince Hughes or Hansen Duncan for the carb parts. The original metering diaphragm in the DBC 14 carb had a metal plate attached to the fabric with adhesive. The later versions attached the plate with a rivet and that rivet makes the assembly thicker in the critical dimension between the fulcrum arm lever and the plate that covers the diaphragm. To offest the extra thickness in the rivet the later diaphragms were paired up with a gasket that doubled the thickness in the area where the diaphragm is sandwiched between the body of the carb and the center plate. You can use either type and the carb will work fine. The .040" to .060" range of thickness for the circuit plate gasket stack does not include the steel plate.... just the gasket and fabric flapper valve. Regards, Steve O'Hara ========================================================== The arm height can be flush or a little below... it won't matter if you use the right diaphragm. Can you post pictures of the diaphragm you bought? If so, post a pic of the wet side, the dry side and a side view so I can see how thick it is. You can use the old diaphragm to make a gasket by simply peeling the thin flexible membrane off or if it won't peel off then just cut the center out so that all you have left is the gasket portion. Regards, Steve O'Hara =========================================================== Steve, My camera is not working. The diaphram has 2 cardboard/Paper sides w the diaphram material sandwiched inbetween. It has a metal plate on each side of the diaphram material w/ a rivet in the middle. one of the plates has a series of holes in a circle. my old diaphram is the same. I can take it into 2 parts. 1 cardboard......1 cardboard w diaphram material attached. I put my carb together w/ the one cardboard/paper half then the new diaphram,then the plate.etc.etc. I have presssure tested it and it holds at 5 lbs no problem....But it never popped off. My gauge goes to 20 lbs and it did not pop off. It will hold at 20lbs . Got some new plugs.someone had put a campion j2j in it. I asked on the board and Jeff said go w a champ L78. I found a champ L78c (the c is for copper) will that work? also got some NGK B7HS what do you think of these? What should they be gapped at? Thanks ========================================================== I installed a gauge that would read higher on the pop off gauge....it pops off at 29psi and stops falling at 20psi. ======================================================== Sounds like you have the right diaphragm and the arm height is set properly. Now you just need to take the fulcrum arm out and squish the spring down as much as you can to lower the pop off pressure a bit. Try to get it down so it will "spit" at around 20pounds. Spray a little WD40 down in the area of the inlet needle and you'll get better read on the test. Steve O'Hara ======================================================== Thanks everyone....It is now running great, Thanks Steve for all the carb info.

McCulloch BDC Carb problems ..... Setting lever heights and pop-off pressure