Runs fine, then...DEAD

[Shaun_inedmonton]

Hey everyone, I just picked up a '84. It has 25 000kms on it and I've already had to use this site too much to trouble shoot. My bike starts and runs fine, but in 2 out of 4 rides, it has just DIED after about 60kms. The other rides, I did over 100kms. When it dies, I cannot start the bike. If it does start, it will only run a few kilometers before dying again. Carbs are clean, side stand switch works fine, just read about possibly cleaning the kill switch on the rh pod, and only mods I can see are K&N pod air filters and a Kerker exhaust. The bike will crank just fine, but there seems to be no spark. Any suggestions?

[oldktmdude]

  G'day and welcome Shaun. Are you sure that there is no spark because this sounds like a classic case of fuel line routing trouble. When the bike heats up and engine temps rise, bends in the fuel hose, kink and shut the fuel off. The fuel line must be routed as recommended by Yamaha or problems can occur. The other problem that is fairly common, although I'm not sure whether this applies to the early models, is fuel cap venting. Hope this helps.   Regards, Pete.

[jscgdunn]

You might want to check fuel filter  I had an old ford that acted the same

[FeralJuggernaut]

Welcome to the mayhem!   

Judging by your list of bikes, this isn't your first go at troubleshooting...   but I am going to ask anyway.   How does it 'die' when it does?   I'm looking for the sputter sputter, gas starvation slowish death with a surge of unexpected power last gasp?

or

like you have it on the center stand in first gear and drop the side stand, a very sudden silence and no sputtering?

I'll also ask, did you bypass your side stand circuit so it couldn't possibly be the culprit?

How is your battery?  new or newish and you have tested out the voltage with bike off, idle and at 3,000 rpm?  Looked at the wiring and particularlly the ground on the coils?    Check the wiring on the left side from the timing cover and make sure it isn't pinched under or near the oil filter housing.   Usually that will cause an oil leak too, but it has been a culprit before. 

Send us some more details.   If you'll be patient with us, we have a pretty darn good batting average.     

[Flyover Country Joe]

Shaun,
It sounds to me like it could possibly be the fuel cap vent that has plagued many an FJ owner. Next time it dies on you, open the gas cap, and see if you can't get it to start. If that does it, follow these directions  http://www.fjowners.com/index.php?topic=2024.0 If not, keep asking, you'll find great help here.

[andyb]

If it dies, splat dead, I'd personally think electrical.  Coils ceasing to work when really hot or sommat.

If it splutters spits gasps and dies, then fueling is more likely.  Gas cap venting is a prossibility, as is a minor restriction somewhere else in the system (plugged fuel filter type problem, petcock not flowing enough, that sorta thing). 

If it doesn't want to restart after dying, that's not entirely unusual if you mean it cranks like the cases are full of mole-asses.  FJ starters aren't the most robust sorta things, cleaning it nicely usually helps, but an XJR starter is probably the better (albeit expensive) solution.

So, lil moar info!

-how's it die?  Alla sudden, or after a bit of coughing?
-how's it not start?  Not much crankin, or plenty of crankin and no fire?  Some cranking and some fire, but not enough?
-when's it dying?  Particularly on one specific road, once you've gotten things nice and warm and are really starting to pour the coals to it?
-how much fuel has it been having when it dies?  Usually wants to with half a tank, full tank, or oh-hell-I'm-near-out-of-petrol?

First guess with the information given says fuel starvation, probably from improper venting or a very slightly wrong fuel line routing.

[Mike 86 in San Dimas]

If someone has put in an in line fuel filter, remove it. One thing I have gleaned from these fellas is that the early models are very sensitive to fuel delivery from the tank to carb. It is gravity feed, no fuel pump. Line must be routed correctly. On my 86 it was the fuel cap vent that caused same problem.