Engine stutter at low rpm

[CanadianBob]

Hello,

I have '07 GSF650 Bandit that I bought new. I have put over 20,000 km on it since driving it off the showroom floor.

In the winter, I put it on the center stand and top the tank right up and add the necessary amount of fuel stabilizer. The battery was replaced last year.

A few years ago, a child came along and I haven't really had much of a chance to ride as much as I would like to. If I am lucky, I put about 500km a year.

Last month, I finally had a moment to go on a day trip with a friend and take in the sites of a nice long journey across the country side. However, when I started my trip, I noticed something weird that has never happened before, the bike stuttered in first gear at low rpm. Switch to 2nd, same thing - stuttering. Like it was running on a single cylinder instead of 4. Every gear stuttered at low rpm. I had hoped it was just bad gasoline but it did this on the entire trip. I filled up twice that day - fresh gas obviously.

When it got above 5000rpm, there were no issues. All gears were good when above 5k. But once it got below that, I had a sudden loss in power. I had the bike for 7 years and never in those years has the bike responded like that below 5000rpm; especially not in first gear. Before this problem occurred, if the occasion called for it (which wasn't very often), I could wind it in first gear to almost red-line, and within 2 seconds I was above 80km/hr before dropping it into second.

The other day, I bought a can of Sea Foam and put half of it in a full tank and ran around town for a few hours, jumped on some highways too; bringing it up to a speed of 120km/hr. At the end of the day, there was very little improvement. The stuttering still remained at low rpm across all gears.

I looked around some forums trying to find out if anyone else has encountered the same thing. I saw some posts that mentioned ignition coil replacement (along with new spark plugs) and perhaps a new fuel filter.

This bike has been solid for so many years. Reliable, dependable and consistent; I want that back.

Has anyone else encountered this problem at low rpm - I would gladly like to hear how you were able to resolve it. Any advice please!

Cheers,
Bob
 

[txbanditrydr]

I'm not much help but I would like to say  to the forum.

If it's fuel injected & water cooled I got nothing.... On the other hand it must be something simple.  Keep us posted when you find something.

[ventYl]

nothing special but:
* take a look at ignition HV cables. mine were unplugging from time to time and your can unplug just right now.
* same for spark plugs. just the matter they don't have enough km does not mean they can't be dead

other than that if it is fuel injected nothing else than running it through diagnostics probably won't help you because without that you can't know what haunts in EFI's head.

[CanadianBob]

Thanks for the advice VentYI.

I did just that.

I pulled the gas tank off last night and put in new spark plugs. I also noticed that 2 of the ignition coils were a bit loose. After about 2 hours of trying to get my fingers around the tight spots and trying to carefully pull each coil out of its socket to replace the plug, I finally got all the new plugs in. Put everything back together and went for a boot around 1am; my neighbors were charmed I'm sure.

Anyhow, it looks like that did the trick. The bike was back to normal, no stuttering at all. I guess it was a combination of bad spark plugs and some loose coils.

Pretty cheap and simple solution indeed.

Thanks again!
Bob