My 1998 Dyna has a small leak or drip coming from petcock

disconnect hose at tanks petcock, replace with a longer hose to drain gas into gas can, turn petcock on & let it drain until empty

The diaphragm petcock operates by vacuum.
Sometimes, the vacuum line comes unhooked, cracked or broken.

Check the vacuum line.

Also, the diaphragm petcock sometimes dies, and needs replacing.

The reserve DOESN'T operate by vacuum.

The other line goes to the fuel gauge overflow right next to the petcock vacuum line on the tank. Big nipple on petcock goes to fuel line leading between carb 2 and 3. Small nipple on petcock goes to the brass nipple on the front of carb number 2. The other hose hooks up to the nipple coming from the fuel sending unit and routes down below the battery and ends. It's there in case the fuel sending unit leaks the hose will route the gasoline away from a hot engine instead of pouring out right on top of it. The nipple to the fuel sending unit should be positioned pointing directly at the petcock on the bottom of the tank. In case you don't know what I mean by sending unit it's the big round circle on the left side of the bottom of the tank with 2 wires coming from it.

there are 2 types, one is just a cartridge just like a small oil filter, this one just unscrews like an oil filter, when you replace it there is a round knob that unscrews and becomes a pump, just pump it until it becomes firm then try starting it with your foot on accelerator until engine starts. The other has a filter with a bowl under it, they have a small bolt in the center top of the housing, undo the bolt and the filter will drop free of the housing. these have O rings top and bottom and a bleed nipple off center, loosen the bleed screw pump the pump until air stops coming out the bleed, close bleed nipple then follow the same start procedure. any fuel leaks will stop your engine from starting but do not over tighten either filter because they can be damaged

Your problem is far more serious than something a little Sea Foam will fix. I would guess that your slow speed jet is clogged up or you have a major vacuum leak somewhere. Look for the vacuum hose that plugs onto the backside of the carb and see if it's come loose. But, if your bike is equipped with the vacuum operated petcock and it's evidently working, this is probably not the problem. You could have vacuum leaks at the intake to head junction as well. If the bike was allowed to sit up for an extended period of time, the gasoline left in the float bowl evaporated and left behind the "varnish" that has plugged up the jets. The carb needs to be completely disassembled and all the small passageways cleaned out by soaking it in a commercial carburetor cleaner.

Good Luck
Steve

If your petcock is an OEM unit, all the gaskets will be the same regardless of what type tank it is. If it were mine, I'd replace the vacuum operated petcock with a high quality manually operated petcock like a Pingle. The reason for this is exactly what you're experiencing right now. The diaphragm in the back of the petcock gets a small hole in it and starts to leak fuel or worse yet, won't open and allow fuel to flow from the tank to the carb. They are notorious for this. I've seen too many riders with a full tank of fuel but not drop in the carb. Spring for a Pingle petcock and the problems are over for a very long time.

Good luck
Steve

Sounds like you've got a vacuum leak somewhere. Either your intake seals or the carb seal is leaking air. Have you replaced the air filter housing? On the Evolution and later engines, the carb is designed as a "spigot seal" type carb. In other words, it just pushes into a seal instead of bolting on like the older carbs did. This means that the carb has to be aligned correctly or an air leak can occur around the seal. The air filter assembly is what holds the carb. into the seal and aligns the carb.

If you haven't messed with the air filter assembly there is one other thing that I've seen cause this problem. Your bike has two vacuum operated devices on it. One is the VOES switch and the other is the fuel petcock. The VOES switch is part of th igniton system and the petcock is the fuel valve on the fuel tank. The vacuum comes from either the carb or the intake manifold and is routed to the devices by a vacuum hose. Make sure this hose in connected to all three locations and has no holes in it. The vacuum hose to the petcock is on the backside of the petcock and the VOES is located on the bottom of the frame top tube under the fuel tank near the carb.

I have seen the vacuum operated petcock cause a vacuum leak in at least one occasion. Normally, when they go bad they just shut the fuel off to the carb and the engine won't run. But, I did have one that caused a severe vacuum leak and the bike acted exactly like you're describing. I took the petcock out of the tank. Drain the fuel first, not easy to do with the petcock being vacuum operated. I got a large funnel and held it under the petcock while I slowly unscrewed it. Once you have the petcock out, you'll see four small screws on the back side of it where the vacuum hose connects. Remove the screws and check the diagraphm behind the plate. Be careful, there is a small spring behind the plate. Take the petcock apart carefully so you can remember how to properly reassemble it.

Personally, I would eliminate the vacuum operated petcock and replace it with a high quality manual operated petcock. Like I said earlier, if they malfunction they usually shut the fuel off to the engine. There you are, a full tank of fuel but none to the engine. I'd replace it with an original Harley unit for a 1995 or earlier bike or a high quality aftermarket unit like a Pingle.

You need to find this problem before you ride the bike too much. The lean mixture resulting from a vacuum leak will cause the engine to run very hot.

It could be as simple as a leaking hose, but it may also be a corroded alloy hose fitting nipple.

Get is seen to by a mechanic before it fails completely, causing complete loss of coolant and expensive cooked motor.