Flat Spot and Stumbling

I have a 2006 FJR I purchased new. It only has 14,000 miles but it gets ridden regularly, as least every few weeks even in winter, on short 15 - 25 mile trips. It has been serviced regularly. It has always run as it should. About 6 weeks ago, I took it for a ride and, while it was still a little cold, it had a flat spot when I put it in gear and tried to move away from a stop sign. It also seemed to stumble a little bit, even in the higher gears at low rpms. As it got completely warm, things got better but there was still a flat spot and some stumbling. I filled up the tank with fresh gas and that didn't seem to make any difference. I dicided to take the bike in for a complete service. I picked the bike up a couple weeks ago and everything seemed fine. We have been having some snow so I haven't been able to ride until today. Unfortunately, the same flat spot and stumbling was evident again today. The service performed was just the regular oil change, new plugs, etc. so they shouldn't have been tinkering with anything significant. It feels like a fuel delivery problem but I know little about such things. My idle rpm is around 1000 and others who have had a similar problem have corrected it by bumping up the rpm. I can try that but because the flat spot and stumbling appears in all gears at higher rpms, I would imagine there is some other problem here. I will take it back to the mechanic who serviced it but I thought many of you in this forum probably know more about these things than he does. Any suggestions about what is causing this problem?

I would do a SeaFoam Treatment (1 OZ/gallon) for a Tank or so and raise the RPM to about 1100-1200 and then see what happens.

Was this FJR a Calif Smog FJR?

I also had the flat spot, I put a Power Commander and that smoothed things out quite a bit

Your results may vary.

FWFE

....forgot you may need to do this:

https://www.fjrforum.com/forum//index.php?showtopic=11783&hl=recall

I'd swear I've seen where a few people have this issue and fix it with a new battery. The reason this sticks out at me is the multiple 15-25 mile trips. Makes me wonder if the battery can charge in that time.

Just a thought.

I would do the easy stuff first like seafoam, idle check and a TBS. I had similar issues and a TBS made a huge difference.

Do as suggested; fuel treatment, plugs, raise idle to 1100 hot, clean and tight battery terms. Then go into diag mode and check the throttle position sensor. You can do a sweep which is were you can see the #'s on the dash change as you move the throttle. Watch the reading and make sure it is smooth and not jumping or flat spots.

Thanks for the input, guys. No, my FJR isn't a Calif Smog FJR. We had a nice day shortly after my original post so I got some Sea Foam, topped off the gank tank and added the Sea Foam. I took a 100 mile ride and everything seemed to be back to normal, even the mileage. We have had snow since then but today is nice so I took it for another ride. I let it idle a bit more than normal to let it get warm. The problem is mostly gone now. I will put some more miles on the bike and see what happens. My idle is about 1000 rpm when warm so I will try to fugure out how to adjust that. Hope I don't have to remove the gas tank and motor <_< . Access is always to hard on bikes with a lot of beautiful plastic covering everything. Oh, well. I also learned that my favorite Yamaha mechanic, who seemed to have disappeared from his last job, is opening up his own shop so when he gets it up and running I will check with him if things are still running rough. I don't recall receiving anything about TPS recall so I will check into that, too. Thanks for all the help. I really appreciate it.

FJRrambo said:

... We had a nice day shortly after my original post so I got some Sea Foam, topped off the gank tank and added the Sea Foam. I took a 100 mile ride and everything seemed to be back to normal, even the mileage....

...My idle is about 1000 rpm when warm so I will try to fugure out how to adjust that...

Click to expand...

Glad to hear the good news! I keep my idle at around 11-1200 RPM. The adjustment knob (knurled) is just beneath the Tank on the Right Side of the Bike:

https://www.fjrtech.com/getdbitem.cfm?item=28

Thanks 03YiHoSilver, I see it. On my '06, it isn't as exposed as it is on an '03. That knurled knob looks like it is designed to be twisted by hand. If you need a screwdriver to come at it head on, I would have to remove some plastic. I will see if I can give it a twist when we get another nice day when I can ride it awhile and get it warmed up properly. Thanks again.

FJRrambo said:

Thanks 03YiHoSilver, I see it. On my '06, it isn't as exposed as it is on an '03. That knurled knob looks like it is designed to be twisted by hand. If you need a screwdriver to come at it head on, I would have to remove some plastic. I will see if I can give it a twist when we get another nice day when I can ride it awhile and get it warmed up properly. Thanks again.

Click to expand...

If you use a screwdriver, go easy on the pressure. It is possible to push the screw out of the slot of the holder. Been there, done that, had to lift the tank to get it back in place.

(click on image for larger view)

This pic shows the adjuster . . . . . . . . . blow-up of the centre



This one was taken with the plastic sprung out (during my clutch soak episode). If you look at the larger view you can see the bracket is a slot.