XS runs like crap since running out of gas.

[118R]

I recently bought a 1978 XS11 in mint condition. It was running like a top until i completely ran out of gas(reserve too). I had to have a friend deliver a can and it started readily but now won't idle and almost stalls when engaging in gear. the bike is definitely bogged somehow. I am definitely not a gearhead but would like to avoid taking it to the shop. Any quick fixes I can try before i have to suck it up and spend a few hundred bucks?

there is obviously something wrong with fuel delivery. I thought it could be vapor lock but I'm not great at diagnosing these things...obviously.

Thanks for any feedback,

Brad

[ccogswel]

There will be a Guru that will chime in but if you ran it out of gas I'd say when you done that it sucked up some trash as well. This trash is now in your pilot jet and main jet circuits. You may get lucky and try this. Go to your autoparts store and look for this stuff called "seafoam" Pour this in your tank. I believe you can pour the whole can in. I have done this with no problems but I can't say what will happen for you. This stuff will clean it out if it can get thru.

The second thought would be to take the carbs off and clean with carb cleaner. I'd try the seafoam first.

Either way good luck and let us know how things go.

Oh and next time when you get low on gas you may want to buy some before you run out.

[DavesXS]

I'd pull carbs, pull out pilots and mains, and blow carb cleaner through them.(its easy)

Then add inline filters(2$ ea. at advanced) and then do the sea foam.

If you continue to run with clogged jets the lean condition can and will cause detonation and fry your pistons and valves.

[DavesXS]

Just incase some one doesn't know....

"
Detonation is very destructive. No metals in existence, forged pistons, special head gaskets can withstand sustained detonation. If you hear detonation your best measure is to temporarily back off, before looking for its cause.

Detonation can be caused by the following:

1. Poor/lean Fuel. A fuels octane rating is a measure of its resistance to spontaneous combustion. The greater the octane, the greater the resistance. For extreme boost levels it is recommended you use either an octane booster or some type of Aviation fuel

2. Ignition Timing. Improper ignition timing can cause detonation. A lot of the late model turbo cars have knock sensors built in that automatically retard the ignition when knock is sensed, to prevent damage"

[Ken Talbot]

It won't be vapor lock, Brad. It is most likely dirt that was quite happy to float around in the bottom of the tank until you went to reserve and started drawing from that zone. You might get really lucky with a quick Seafoam treatment, but it is better at dissolving a bit of varnish build-up that can happen over a period of storage.

There's lots of guidance here in the tech pages on taking your carbs out, taking them apart one at a time, and cleaning them out. You'll probably find an accumulation of debris on the fine mesh screen on top of the float valve.

[trbig]

if you ran it out of gas I'd say when you done that it sucked up some trash as well.

Can someone explain this one to me? It's one of those things I've heard my whole life. "Keep the car over half tank or it will suck some trash up.."

All fuel delivery systems that I know of are getting their fuel from the lowest point on a tank... where this "Trash" would likely be sitting anyway. How does running a tank low exacerbate the situation?

Anyway.... you could have dirty carbs, or you may have a stuck flaot valve. Sometimes when the carb bowls get completely empty and the floats drop down completely, the float needles can get cocked sideways a bit and not get to seat. You should have a very rich running motor if this happens. If there's gas in it now, take the plastic handle of a screwdriver and rap on the sides of the carbs. Also, just running it down the road a bit can help.

If this doesn't fix it.... time to do a carb clean. Also.. one last thought... Could you have gotten some bad gas this last time? Water in the can before used for gas maybe?


Tod

[ccogswel]

Hey Tod,

I may be able to shed some light on your thought.
Have you ever poured any gas in a glass and put some trash in it. When it sits for a while everything settles to the bottom. So if you shake it up all the trash floats around. So when you are low on gas all that trash settles lower. So you get trash. This is what was explained to me by my grandfather and it makes since.

But of corse you know that in a motorcycle there are filters inside the tank that help keep most of that junk out. But not all of it. When you put inline filters in I still get junk.

[TopCatGr58]

Originally posted by trbig
Can someone explain this one to me? It's one of those things I've heard my whole life. "Keep the car over half tank or it will suck some trash up.."

If this doesn't fix it.... time to do a carb clean. Also.. one last thought... Could you have gotten some bad gas this last time? Water in the can before used for gas maybe?
Tod

Hey Tod,

From what I understand happens with our bikes is that most folks don't let themselves run out of gas, so they keep the petcocks on RUN. The petcock intake tube for RUN is taller, sits up higher in the gastank, and doesn't have access to the rust and slugde lurking in the very bottom of the tank.

THEN...when a person runs low, and needs RESERVE, they turn the petcocks, and the Reserve pipes are much lower/shorter and allow access to the lowest layer of fuel(AND GRUNGE) sitting in the very bottom of the tank, and it all flows thru the petcock and into the fuel system clogging the works!!

Yes, Brad, inline filters are a must with these older machines and their sometimes rusty tanks, etc.!!!
T.C.

[118R]

Thanks for all the great feedback guys... yeah i guess the moral is don't run out of gas.. thing is the reserve petcock was reversed so regular tank setting is actually reserve. I'm new to the XS and this one definitely doesn't get the best mileage but it is an awesome machine.

[wa407mpp]

That doesn't make sense, there are three settings on reserve, and prime, unless someone has changed to non-stock petcocks. If you ran it empty on prime you probably dumped a lot of junk in your carbs, try pulling the float bowl plugs and holding a baby fool jar under them and see what the gas looks like. If your lucky it might be just watery gas, from the bottom of the tank.

[egsols]

Like everyone else said, most likely dirt has now gotten into your carbs. If not dirt, any condensation in your tank, now water, would also go through when you get too low.

If your tank is still low on fuel, you can check what's in your tank by pulling the fuel line and dumping some of the fuel into a glass jar. That should give you an idea of how dirty and how much water (if any) is in your tank.

[Mississippi]

I highly recommend removing the tank, then remove both petcocks and drain the gas into a bucket to see how much trash and water is still in the tank. Then put some fresh gas into the tank and shake it around and drain it again. On one of my XS1100's the filters on the petcocks were starting to come apart and were not doing a good job of keeping the trash out of the carbs. These filters are still available from Yamaha.

[yadada]

I waited too long to switch to reserve the other day, ooooops.

Float pivot was gunky I think, because the needle was moving around, and I had to work the float back and forth a little.

Put it back together, added gas plus seafoam. Seems okay now. I might need to take them back off though, because I think mine doesn't start as good either. Runs fine though.

[prometheus578]

just a quick comment on those petcock screens.

petcocks have two inlets, as mentioned previously.
for the run position, it's a pipe about an inch high with a mesh screen tube on the top.
when the fuel level falls below the level of the screen, the bike falters and one turns the petcock to reserve.
the reserve inlet doesn't have a tower... just a mesh tube sticking out of it.
anyway... these mesh tubes are plastic and just pressed into the inlet hole of the petcock. they have been known to wiggle loose and fall out. sticking a hose in the tank to siphon out gas... if the hose bumps on of those screens, it'll fall out.
anyway... if the reserve screen is missing, you'll suck in whatever crud is floating around the tank.
pull the tank, remove the petcocks and inspect the screen.

water in the fuel: there's usually a little bit of water rolling around the tank anyway. doesn't cause too much problem, as it stays on the bottom and you normally get more fuel than water when running. run the tank low, and this percentage decreases. run the tank really low, and, depending on the amount of water, you'll get more water than fuel. as mentioned, stick a container(i used a plastic cap from a spray paint can) under the carb bowls, drain then and see what comes out.

vapor lock is when the fuel vaporizes in the line(or fuel pump)due to heat. this is not an issue with our bikes