Can't Idle But Runs Again?

[architect]

The other day I was riding and ran into this problem. I had ridden a good 500km before this started to happen. The only thing I recalled doing "odd" was push the bike hard close to the red line. Next thing I know the bike started to sputter like it was losing gas and finally stalls out. It had problem starting right after that. Couldn't get it to start unless I hold the throttle open. I was able to ride it home by holding the throttle partial open during red light so it would not die in idle (RPM will slowly drop over a few seconds until it dies). Even during the ride home I can tell it was looking to stall out. I got home, turned to bike off and tried to start it up again one last time but it would not turn over. I decided to leave it until the next morning.

Next day I started the bike and it kicked in although I can tell it had trouble idling strong. But it kicked in. I took it around the block and finally around the street and it seemed like the more I ride it the better it got. Now the bike "seems" fine. But I want to figure out what the cause of this maybe.

I just bought the bike 3 weeks ago so don't know much about the conditions of it. I suspected dirty carbs but owner said he cleaned them two weeks before sale and can clean them again for me now to prove it. 1988 FZR400 with 39,000KM. Normally it starts up easy on its own. No choke needed at all unless it's below 10 celcius. Like I said put 500km on it since bought with no much issue. Only thing I can think of is i pushed it really hard and fast to the red line but it can just be coincidence too.

Thanks in advance.

[Clanky]

Hi, what you're describing does sound like a temporary blockage in the carbs.

The previous owner may have cleaned the carbs but it is worth checking the state of the fuel tank for rust/dirt and the inline fuel filter. Check that the air filter is on properly as well.

You say the bike is running well again so I would not worry too much about it. I've had something similar with mine before and it cleared up.

[architect]

How does "temporary" work? Did the dirt/object just disappear? I'm just concern it'll keep coming up so I figure I should get to the bottom of it if it's something serious. Or else if what you say is true I'll throw in a can of Seafoam on my next fuel up and call it a day.

I also use Octane 91 without ethanol. Not sure if that's wise for the bike because I hear stories of how high octane sometimes make the bike runs hotter and worst.

[DonTZ125]

It was possibly a clog of rust fines that has blown through into your carbs. I'll wager you have a small pile of sludge in one or more of your bowls right now. If that's what it is, the only thing being cleaned by the Seafoam is your wallet.

Higher octane than needed for the engine characteristics (spark advance, compression, cams etc) makes the bike run off because it burns more slowly.

[Evilchicken0]

Water in the tank or the float chambers or it might be an airlock.
The tank vents through the cap, taking it apart and cleaning it would be a good idea.
I'd take the carbs being cleaned with a pinch of salt, take the float bowls off one by one and clean them out.

[architect]

Looks like everyone is referring to the carbs. I'm gonna get the owner to take it apart and clean them again then. I'll watch him so I can learn for future reference. Last bike I cleaned the carbs on was my Kawi EX 500 and luckily there was only two on that bike. It'll be a good time also to see what size needles are installed too.

[architect]

It was possibly a clog of rust fines that has blown through into your carbs. I'll wager you have a small pile of sludge in one or more of your bowls right now. If that's what it is, the only thing being cleaned by the Seafoam is your wallet.

Higher octane than needed for the engine characteristics (spark advance, compression, cams etc) makes the bike run off because it burns more slowly.

Is ethanol going to damage old parts in this bike? Unless I use 91 octane by Shell there is about 10% ethanol I hear that is the reason people stick with higher octane for older bikes.

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