Nu2thahawk

Ok,

Here is a quick run down of what's up and my question. Bike is a 98, 16k miles give or take and had been running fine, though it seemed a bit rich (bike would sometimes die if you were sitting at a red light/stop sign and blipped the throttle. Holding the throttle open and cranking it would restart without problems. Ran great under acceleration, really no problems.

Anyway, bout three weeks ago I went to the gas station to fill up on a sunday, ran fine on the way to the station, ran bad on the way home. Seemed like it was only firing on one cylinder. Higher throttle settings turned out poorer performance (basically had to limp the bike home). Figured on water or contamination in the fuel. Didn't do anything else to the bike but would not restart after shutting it off. It would fire a little and puff smoke out the back but wouldn't start.

Pulled the spark plugs, one was wet and dark (but not horrible) the other was right where it should have been. They both produced a nice fat blue spark when not installed. Replaced both plugs anyway (ten bucks a pop for NGKs sucks btw). I also drained the bowls on the carbs in case there was water in there. Installed new plugs, go to start but really not even firing much at all now. Full choke I did get it to fire a time or two but nothing much.

Now, here are my current questions. if you unbolt the front of the gas tank and lift it up, makes it a bit easier to get to the rear plug, also you can see the shutoff on the petcock under the rear of the tank. I believe I turned this and can't discern on from off. There are markings on the petcock but I see no arrow or anything that should point to on or off and can't tell aside from removing a fuel line and checking for flow (I didn't get to all that this weekend). Standing from the front of the bike and looking toward the rear, I have a square peg type deal on the front of this petcock, which way should this valve be turned for the "on" position (when viewed from the front of the bike, as if looking over the windscreen)? clockwise or counterclockwise?

I had thought this might be a vent problem or something of that nature before but it appears to be more than that, anyone had a similar problem or have some advice on where to start now?

Dave

hawxter996

1st have you opened your gas cap since filling ?

could be clogged tank vent,causing a vaccum.

not sure on position of fuel valve.

Nu2thahawk

Yeah, after this all started I read the boards and saw that others had done that and problem was solved. Not so in my case. Before I changed the plugs, I tried opening the tank and at that point, the bike would fire with the choke on (smoke only coming out of one of the pipes), but it would not start and run.

Since changing plugs I have tried venting, even tried cranking with the tank open but no real difference. I left it sit about ten minutes and tried again. It fired one time but didn't start.

Dave

Thumper

Man i have had my tank off several times and can't remember which way is on, sorry.

Make sure you have the small vacume line on the correct place on the petcock. If not on the right place no vacume will get to the Petcock valve thus no fuel to the carbs, of course that is assuming the petcock is in the on position and not the off position. also make sure you have not pinched the vacume line somewhere when you set the tank back down.

As far as the idling issue before all this started, it should idle at 1200, if it will not then it could be a jetting issue or clogged up low spped jet where the bike may have set for 3 or 4 months with fuel in the carbs. If they sit for an extended period without some kind of gas stbilizer in them the tend to gum the small jet opening. Thi smay be your ssue in that you have to choke it or give it throttle to get it to start, indicating a fuel supply problem on the low speed jet circuit.

Nu2thahawk

The bike idled fine before all of this started, its just that if you were sitting at a red light and you revved the bike a few times, once in a while it would just stall out and you would have to open the throttle while starting and it would fire right back up. This, I think, is totally unrelated to the problem I am having. Maybe just slightly rich on the idle circuit. I haven't removed any of the lines from the petcock or carbs so nothing there has changed and should all be fine (as it was running without problems until I got the gas).

I guess I will just pull a line from one of the carbs next week. I know vacuum plays a part here but should this system flow fuel with gravity? Will it only pump fuel with the motor running?

Dave

RickB

You will need to pull a vacuum (running or use a handheld unit for brake bleeding) on the proper line of the petcock to get fuel to flow out of it - its a safety feature... if the diaphram is bad within the petcock you won't get any fuel flow either...

RK1

You said you drained the float bowls, but what you didn't mention, so I have to ask, did you drain/empty the fuel tank?

Also, the petcock will only allow fuel to flow when opened by vacuum.

98greenchicken

Water in gas is common so I would drain the tank and flush with Heat. You can get it at most auto part stores. After I was sure there was not any water in the system then check to make sure you are getting fuel to the carbs. After that well I have no idea.

Nu2thahawk

No, at this point I haven't completely drained the gas tank. I suppose that is my next step. I had drained (and allowed them to refill/drain again) the float bowls as the tank is pretty full and I didn't want to throw the gas all away.

Can someone check on the petcock for me? what is on clockwise or counterclockwise when viewed from the front of the bike.

I will drain the tank if I need to but I want to make sure gas is on, and flowing before I go through with pulling the tank etc.

Dave

98greenchicken

Try pulling both fuel supplies and cranking her over a bit. I just went through that and when the lines are disconected you get an almost instant flow with a crank or two. Also a good way to flush any water if you use the HEAT stuff. It makes the water soluable and it flows right out.

Anto