rough idle

[harpo]

Put my 05 in for a tune up, throttle bodies sync and new plugs were done. They found a rusty murky layer of gas at the bottom of the tank. I have tried gas treatments to take Ethanol out of the gas, they think that was the cause of the rusty colored gas. I started noticing the bike picked up a rough idle and a drop off of power, kind of like a hesitation when I start off from a stop before the tune up. Well they couldn't find the problem and told me to just ride it and see if it fixes it,so what do you think? It runs great ounce moving.

 

[audiowize]

So you had this problem pre-tune up? Does the engine hesitate while revving in neutral?

 

[Donal]

What is your 'warm' idle set at?

Ideally it should be about 1000 - 1100 RPM.

 

[MrZappo]

Firstly, nothing "takes ethanol out of your gas" . That being said, what were you using to help with the effects of ethanol?

Secondly, if you used stabil or something like that, it makes no sense for them to say that was the cause of rusty crud in your tank.

A layer of rusty crud would only be caused by water (a lot of it) sitting in your tank separated from your gas. This could only be caused by rain leaking into the gas cap or most likely by condensation.

Condensation would only be a factor if the bike sat with a minimally filled tank for an extended period of time in a place with large temperature/humidity swings. And it would not happen overnight.

Either way, if there is indeed a "layer" of anything that is not pure gas, they should have drained the tank immediately and filled it with pure fresh fuel. Running that crap through the injectors etc could cause major problems.

I hope they didn't shrug it off and recommend that.

In any event, I'd drain that tank myself, fill with some top tier gas, say a little prayer and ride. If it is still stumbling after a tank or 2 I'd start looking into other things.

 

[RaYzerman19]

Yes to the above. I'd only add, do not use too much Seafoam or stabilizer..... my lawn tractor didn't run well when I accidentally did that.......

 

[RossKean]

^^^ +1

There is no fuel filter in the system but I would, at the very least, have a good look at the pickup screen on the fuel pump. For that matter, I would remove the pump and thoroughly clean the inside of the tank. Once the **** makes it to the injectors, things get a little more complicated.

 

[harpo]

Thanks for the advice, let me answer some questions. I ride a lot and use Chevron gas most all the time, I have used Startron and Stibil in the past but not lately. The tank was emptied and fresh gas was put in, and the rough idle and hesitation started before the tune up, OH and the hesitation only happens at very low RPM and start off. They set the RPM up to where it should be. Revving the engine and running at speed it has no trouble. Lastly would running a fuel system or injector cleaner be Ok?

 

[RaYzerman19]

They did a throttle body sync..... are the vacuum caps in good condition so there is no vacuum leaks?

"They set the RPM up to where it should be"..... as Donal says, that should be 1000-1100 rpm.

It is always OK to run a fuel additive if you do not use too much. The only time to use too much is when you are intentionally trying to clean the injectors.......... you have to solve your problems first. You have fresh fuel, so it should be OK without an additive.

They also changed plugs....... you may have a plug wire that is not fully engaged with the part that becomes the spark plug cap. To ensure this, unscrew the wire from the cap, trim off 1/4" so you have a clean cut, then screw it back on snugly. Ensure the cap is fully engaged to the spark plug. You also could have a bad spark plug, but that is rare with new plugs.

 

[MrZappo]

If your running chevron, it is already full of additives. It is a top tier gas and has detergents "built in" .

That being said, a small amount of some well respected cleaner like techron or something like that won't hurt. Probably won't do much though.

When was the last time that the bike ran perfectly? And, how many miles on her? What plugs were used?

Is your mileage good?

 

[harpo]

Mileage is good, would be better if I could get my right wrist to behave Lol, as for vacuum, I could only trust that the Yamaha shop had checked and ruled that out. the bike has 33K on it and only started idling rough since maybe mid January. The plugs were standard OEM plugs and the idle is at 1000rpm or better. I know Chevron gas has Techron in it, and that should clean every thing good enough but it was said that there may be a carbon build up on a valve. that seems unlikely because one I ride it a lot and on open road and twisties plus I run good gas in her.