I took off my tank for the first time a couple days ago and discovered that there was only a fuel line attached to the petcock that I had to remove. I thought there was also supposed to be a breather hose and a vacuum line!

What hoses should be connected to the tank and where should they lead?

As an FYI, my bike is extremely hard to start, but once warm starts easily - I'm hoping the problem is related to this.

 

There should be a small nipple pointing downwards next to the switch housing. There should be a hose connected from this nipple to the nipple on the #1 (far left) cylinder intake manifold. The petcock is supposed to be vacuum operated. This means, as soon as your engine starts turning over and pulling vacuum, fuel should begin to flow. It is easy to test-- take the tank off the bike and suck on that vacuum line. It won't take much effort on your part to open the petcock. Fuel should rush out of the fuel line if it's functioning.

Check this out-- what's connected to the nipple on the #1 cylinder intake? If nothing is connected and it's sucking air -- then you've got a vacuum leak that's causing that cylinder to run lean. My guess is that at some point the petcock failed and allowed gas to flow at all times. Some previous owner discovered this and no longer used the vacuum line.

It doesn't seem like this would cause your hard starting. For that problem, I would troubleshoot the enrichening circuit.

 

Thanks, Berga. When I get home today I will check to see if there is a vacuum line installed on the #1 cylinder intake.

 

You might have an F3 petcock on your F2 tank.

When you say it's hard to start, are you using the choke to get it started?

 

I use full choke, and I usually have to crank it for about 30 seconds in separate 10-second intervals. It seems to only want to start if I apply full throttle, and then it will idle normally afterwards.

It also has an aftermarket exhaust (D&D) that has a pipe going all the way to the headers. Not sure if that would make it run lean. When the bike is warm, you wouldn't know it had any problems at all. It idles well and doesn't have any flatspots or hesitation in the powerband. Occasionally the revs will hang at around 3000 for a few seconds when coming to a stop, that's the only problem I've ever seen.

 

Berga's right, if you don't cap off that vacuum line, your #1 cylinder will run lean and the bike will run like crap. The revs hanging up at 3K after you go off throttle is a symptom of your bike running lean. I would look for a disconnected hose like he suggests, and do a carb sync with all the hoses on.

If you haven't jetted it richer, a full header set should make the bike run lean if it flows freer. You may need to adjust the idle circuit and jetting because of that. Even if you don't have flat spots, you could be down on power due to running lean across the whole range. I would check your plug color too.

 

There is indeed a vacuum line attached to the engine. I will hook it back up to the tank and report my findings.

 

So, my petcock does not have a nipple for the vacuum line. My tank has the two nipples on it further back for the drain and vent tubes, but the petcock only has an opening for the fuel line. So, what should I do with the vacuum line? Block it off, somehow?

 

Yes, all cylinders have that vacuum port. You can just find a bolt that will fit and plug it with that. Or, cut the hose short and plug it with something.

 

Cut the hose short and plugged it with a screw. One problem down! Now to tackle the R/R...