Engine starts but then dies

[Taras]

Hey guys,
I just purchased a fine looking bobber, obviously based on the xs400. Took it for a spin a couple of times, runs like it supposed to until today. Went to the gas station, filled her up, started but then the engine died after a couple of seconds. Started again, died. And again.

I tried with the choke fully out, died. Tried putting the fuel switch to prime, died.

I know the battery is not that good, but as long as it starts it shouldn't be the battery right?

Any suggestions?

Thanks,
Taras

 

[bcware]

The first time I put a fair amount of new gas in my old tank it released a lot of rust. It is very possible that you just clogged something in the carbs. Test the battery with a meter to see if it's good. You can drain a little fuel out of the float bowls. Collect the fuel in a container of some kind; if it's dark or yellow-colored you know it has a high rust content.

 

[Requiem]

The first time I put a fair amount of new gas in my old tank it released a lot of rust. It is very possible that you just clogged something in the carbs. Test the battery with a meter to see if it's good. You can drain a little fuel out of the float bowls. Collect the fuel in a container of some kind; if it's dark or yellow-colored you know it has a high rust content.

probably your carbs are clogged up, take them off the bike and clean them thoroughly, and check out your gastank as well

 

[Taras]

It sure sounds like a logical explanation, but the tank was restored and was completely rustfree. The gas is also clear.

Removing the carbs, is that an easy job? The bike is stranded at the gas-station quite farm from home

 

[HoughMade]

Taking off the carbs is not that big a deal, but you don't want to do it and try to clean them in a parking lot. Find a friend with a truck or trailer and get it home.

Sounds like clogged carbs to me or some other form of fuel starvation. The easy way to check that is spray some starter fluid in there and if you can keep it running longer than it has been by spraying that, it's a fuel issue. If that does not make any difference, it's a spark issue. As I said, my money's on fuel.

 

[Taras]

Alright, thanks. Gonna try that out!

 

[bcware]

"Restored" is a relative term. Even if you inspected the gas tank by looking inside it, you will not be able to see any rust on the walls or roof. The inside of my tank appeared quite clean from what I could see in the hole, but as soon as I put a gallon or more of gas in it I found some

It just seems like quite a coincidence that everything was running fine until you filled up the tank.

 

[cafedan]

+1

 

[drewpy]

if you have electronic ignition, and the battery is not at its best. you will have problems keeping the engine running.
you need a good battery to maintian the charging system and feed the ignition.

you need a new battery anyway, so get one and eliminate that part before stripping down the carbs!

 

[OliverB]

Ok, first you have to determine if fuel is flowing freely to the carbs. Could even be a problem with your vacuum fuel tap (valve) on the bottom of the tank. If the tap is the original type, it is caused to open by vacuum when the engine runs or opens when put in the "Prime" position to allow fuel to freely flow. Disconnect the hose at the carbs with the tap set to the "ON" position. If no fuel, that is good so far because it at least tells you the tap is not leaking. Turn the tap to the "PRIME" position and fuel should start to flow. If it does not, you have a problem with the tap, filter or tank. If fuel does flow when the tap is set to "PRIME", start the engine with the hose still disconnected. When the engine starts to run, fuel should begin to flow from the hose when the tap is set to "ON". If fuel does not flow from the hose, something is probably wrong inside the fuel tap. There are tap rebuild kits available for about $25.

Drewpy, our resident expert, is right on about a strong battery. I would recommend an AGM type battery - often called "Maintenance Free" - because they discharge on standing at a much slower rate and tolerate abuse better than a standard liquid acid battery. The AGM design battery still uses liquid acid but the acid is absorbed by a mat and does not slosh around inside the battery. NAPA, if they are in your area, sells AGM type batteries that have a full year over-the-counter free replacement. Many other stores offer only a 6 mo. warranty. AGM is not a brand but is a type of construction and is priced a little higher than standard batteries.

However, if the engine is cranking strong when you attempt to re-start it, your immediate problem is not the battery.

 

[52judeblacklightning]

You've already had a lot of good replies, but I do want to let you know that I got a 1981 XS400 last summer and I had a number of similar issues that I solved.

1)battery is WAY more important than you might think. It's not like a car battery, which is more forgiving. The battery will only recharge while moving the bike, and it's critical to good performance. My first thought when I read your post was "replace that battery, you've got nothing to lose".

2) Clean your carbs. Replace all your main jets/pilot jets. I soaked my carbs in a solution of 1 part Pinesol to 2 parts water, for 2 days, and by golly, it WORKED! I also replaced the carb holders. Guess what? My bike runs now! NOTE: remove all jets and rubber parts before soaking.

3) I also had a problem with the petcock. It had a constant slow leak, and the fuel was overflowing the floats and getting into the oil tank somehow. Once I got a universal fuel tap and fitted it, this problem ceased. Oil is now as it should be.

My advice: start with the battery, then do the carbs (it's not very complicated to take them off/put them on- but helps to have someone with you who's done it when you do it for the first time). Good luck!

 

[Taras]

Thanks guys for all the replies. I'll start working my way trough them!

/T

 

[lhaolpa]

I might also advise using an inline fuel filter.Make sure that it is for gravity feed systems,and that it is clear and large,so that it will hold lots of trash. lha

 

[jigm400]

great tips guys, now its just time to get a friend with a truck to help you pick up the bike.

 

[Taras]

Just picked up the bike from a shop and they stated that something was wrong with the ignition and also the ground cable from the battery was a bit glitchy.
Seems to run beautifully now. Thanks for all the tips though!

 

[OliverB]

Fantastic! Well, it is really hard to diagnose long distance and sight unseen.