Hard Start In the Morning and Missing Fuel

[3Phase]

The engine has been getting hard to start in the morning after a riding it the day before and a heat-soak/cool-down overnight.

It also seems to be losing fuel from the fuel line and float bowls of the #3 and #4 carburetors. The bike is level and parked in the garage on the center stand. There is no fuel in the airbox or in oil, it's clean.

It's slowly been getting worse and worse over the last few months. Yesterday, it the engine just cranked and cranked and wouldn't start.

The Basic Checks:

Standing battery -- AGM battery, ~13V
TCI voltage with the ignition on, engine not running -- 12.7V
TCI voltage during cranking -- ~11.5V

The TCI is good. I swapped in a spare known-good TCI and it works fine too, once the engine has been started in the morning, so it's not likely to be a TCI problem.

The static and dynamic ignition timing are good.
The vacuum advance works smoothly as does the mechanical advance.

The spark plugs are Iridium plugs gapped to 0.032". They're clean and have less than 2K miles on them.

The ignition coils are the 3 Ohm Accel coils that do not require the ballast resistor so it's been bypassed. The coils throw a nice, hot blue spark that can be seen in full daylight at all four plugs.

The cold cylinder compression numbers #1 to #4: 147/149/150/149 with the throttle wide open.

All of the above seems to point to the carburetors as the most likely suspects so I pulled off the '80G carburetors and put on a spare set of stock XJ1100 carbs.

The 'new' XJ carbs worked fine and the engine fired right up. They still need to be synchronized but they're pretty darn close the way they are now so I went for a ride last night, then put the bike in the garage for the night.


When I tried to start the engine this morning it had the same problem. Before I started the engine I looked at the clear fuel filters and the left-hand filter looked empty.

I started to think about that and after the burning smell finally went away and the dog quit howling I remembered that the fuel lines are overlength and crossed so I can use the fuel tank to synch the carbs. When the left-hand filter is empty it's not #1/#2 carb, it's #3/#4 and vice versa.

Apparently the #3/#4 carbs lose about one fuel line and a small filter of fuel overnight.

Tomorrow morning I'll try putting the fuel taps on Prime for a few minutes and tap on the float bowls to see if the filter fills back up before starting the engine and see if that works or if it's going to fight me the whole way.


It is highly unlikely but not impossible for two different sets of carburetors to lose fuel from the same pair of float bowls so I'm more than a little curious about what's really going on and even if putting the fuel taps on Prime fixes the hard starting problem I still have to figure out where the fuel is going.

It didn't used to do this.

[BA80]

Scott, that fuel is going somewhere, the mother ship didn't fly over and beam it up.

Try clamping the fuel lines over night and see if that problem disappears.

[DGXSER]

The first idea comes to my mind is a seeping leak in you filter or fuel line.

[3Phase]

Thanks, guys!

I got my anti-mothership batteries locked and loaded and just waiting for that sucker to show up tonight! I'll try clamping the fuel lines after I make sure the lines are actually full of fuel and not air.

The fuel taps themselves do not leak and neither do the lines and filters. The lines and filters were replaced in November or December last year because the old lines were starting to harden and the filters were turning that funky color that tells you it's time to get new filters. I forget what it's called but the new lines are that spendy black stuff that supposedly stays flexible and doesn't need hose clamps but I use them anyway because I don't trust fuel lines.

I agree that fuel is going somewhere! but the airbox, oil, and the engine itself are clean. They're not clean so you can eat off 'em or anything but there's no fuel residue anywhere I can find. It's got to get fixed before I ruin the bearings or the engine catches fire and I have to say, "Oh... that's where the fuel was going!"

The engine and carbs don't seem hotter than normal but the only thing I can think of is that the fuel is boiling off or just freakin' leakin' into the manifolds and evaporating before getting into the oil.


Back to the salt mine for me!

[BA80]

Thanks, guys!

I'll try clamping the fuel lines after I make sure the lines are actually full of fuel and not air.

The air isn't disappearing is it now.

[WMarshy]

Did you try throwing it on prime for 10-20 seconds before hitting the start button?

[BA80]

Did you try throwing it on prime for 10-20 seconds before hitting the start button?

Uhm ...Wade.......if gas is disappearing overnight it ain't running short.

Unless a teenager is siphoning it.

[WMarshy]

Uhm ...Wade.......if gas is disappearing overnight it ain't running short.

Unless a teenager is siphoning it.

Greg, what I was getting at was if he cannot explain where the gas is going then how can you fix it?

The slow start issue might be because the low fuel level in those two carbs and the vac petcocks cant replenish it without extra cranking to open the petcock.

To solve the slow start issue put it on prime and allow the level in the carb/line to refill and it might solve the slow start issue.

That being said, if he can solve where it is escaping to then he stands a good chance at solve the start issue as well.

[DGXSER]

Well, obviously it is leaving the line and the filter and presumably the carb bowls, thus the hard start issue. SO, if it is not leaking out the filter, not leaking out the line, then it has to be leaking out the bowl. Is the drain on the bowl leaking a drop or so at a time, not noticeable, but enough to drain over night?

[BA80]

It would have to be leaking from all the carbs to make it hard to start, it would start right up on 3 even if one bowl was empty. It sounds more like a flooding issue to me. That's why I suggested clamping the lines to be certain of no fuel getting from the tank to the carbs via leaky petcocks.

[WMarshy]

I just re-read his original post and he said in the last paragraph that using prime on startup cures the start issue. Gas is going somewhere and sounds like the petcocks are doing their job... gotta be your float valve. Maybe try putting it on the center stand and blocking the front tire and if any gas leaks look for it in the air box..

[3Phase]

Tinms!

There Is No Mothership!

I clamped the fuel lines last night but, again, only one line had fuel in it this morning. The engine fired right up after I Primed the carbs.

Obviously both of the vacuum valves in the fuel taps are holding or science would have been all over the floor this morning.

One of the float needles or seats must have a very slow leak and the fuel seeps out overnight. It's really kind of strange because when the fuel taps are shut off or the fuel line is clamped, the line and filter basically are the same as a hamster water bottle or a straw with a finger blocking one end.

Now it's time to synch the carbs and go for a ride and I'll dig into the '80G carbs when I get back. Holding the Enrichener on the XJ carbs by hand while the engine warms up is a little awkward so I hope I can find and fix the leak(s). If not, someone here on the forum mentioned setting his XS on fire and throwing it down a hill. It's always good to have a backup plan!

[DGXSER]

Did this problem start when you replaced the fuel line and or filter? If so, I would not dismiss them being the problem. New does not always mean there is no problems or cracks, holes, etc.

Like your thinking Scott, for the fuel to get out, there has to be a source for air to get in.

[BA80]

I clamped the fuel lines last night but, again, only one line had fuel in it this morning. The engine fired right up after I Primed the carbs.

So, now you have it narrowed to 2 carbs. That fuel has to be going to the cylinders, the air box, or the earth.

[3Phase]

The hard starting began last November when I had jury duty, of course, and I absolutely had to be there or I'd get in trouble. I usually try to use the kick starter because the engine used to kick over and start very easily even when cold and it saves wear and tear on that infernal starter clutch. When it got difficult to use the kicker I did some basic troubleshooting and pulled the tank to check for leaks. I replaced the old lines and filters while I had the tank off and it didn't help but it didn't hurt, either.

It was still hard to kick start and eventually I had to use the starter to fire the engine in the morning. Once it was started for the day I could start it any time with one or two kicks until the next morning after it sat overnight. Sometimes putting the fuel taps on Prime before trying to start the engine would help, sometimes it didn't. <scratching head> It finally got to the point where the engine just would not start at all so I had to get serious and try to fix it.

No, the fuel really should not come out of a closed fuel line even if I removed the float bowl drain plug so I don't know what's going on with one empty fuel line and filter. The only thing I can think of is the float needle/seat is leaking and the float needle acts like a finger tip when you barely touch the outlet of a water bottle dispenser. The water won't all come out at once but unless you remove your finger and stop touching the dispenser, the air can move up around your finger tip as the water runs out and the bottle will eventually empty itself.

Anyway! The XJ carbs are set and it's time for a ride and I'll mess with the '80G carbs when I get back!