Engine starts to miss when rear wheel is turned?!

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hearny

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Hi, I have a fz6 s2 08 when i started it up this morning it didnt sound quite right. as i was backing it off the drive and i noticed the engine revs started to idle irraticly but stop when it was stationary. I went for a ride and about 30min it started to do it while riding the bike, it seemed to be missing. Stopped in layby and no problems. Pushed down on handles bars to shake the bike and the bike started to rev irratic again.

Having got home washed and cleaned the bike and investigated futhur by checking electric connections/battery/air filter with nothing out of the ordinary. Checked the computer and there were no faults codes registered. Checked chain slack. I then put is on the centre stand while bike idling and my girlfriend was checking the rear tyre when engine started to idle irratic again.

Any one know why when moving the rear tyre in either direction it would cause the idle/engine to rev iracticly and loose power?. only seems to happen when wheel is moved!

Please help thank you.
 
Shouldnt be related to the rear wheel. Check your neutral safety switch and your kick stand switch. Those may be the problem.

Rear wheel is only output from the transmission. No real input at all.
 
The speedometer receives a signal from that area (Maybe the output shaft?) and the computer may be doing something related to seeing the rear wheel turning. I've gotten my computer into a bad mode and the bike fired funny. I unhooked the battery terminal for a few minutes. Hooked it back up, the computer reset, and it was all good to go.
 
hearny....

It would be good to eliminate the wiring harness through the bars and frame.

Right now, we have two scenarios that may cause the missing you are experiencing.....

1) Bars offset
2) Rear wheel moving

I'd be much more comfortable/familiar with 1 than 2..... wiring flexing to deal with the handlebars moving is much more likely, in my books, than something relating to the rear wheel moving.

Put the bike on the centerstand, and repeat the experiment. If it stutters when you move the back wheel, that supports one line of investigation. If it stutters when you move the bars side to side..... that's another.
 
Hi, the bike has no ABS. i have disconnected the battery for 30min as this normal seems to fix most problems but not this one!
 
After spending most of the nite in the garage! Moving the handle bars has no effect. i have moved every visiable wire and moved it while engine running to see if a electric fault in any of the wires with no luck. i have taken off the air box and battery housing and unplug the main connector and re fitted. i have also unplugged the harnesses in the front left fairing and re plugged. all still not soloving the problem and only happens with the rear wheel moving. Shame the diagnostics is not showing an errror code would make life a lot easier!! I have also checked the center stand/side stand connections and netural saftey switch all working fine as the diagnostics are showing on and off when moving them.
 
There is no ABS on this bike. After spending most of the nite in the garage! Moving the handle bars has no effect. i have moved every visiable wire and moved it while engine running to see if a electric fault in any of the wires with no luck. i have taken off the air box and battery housing and unplug the main connector and re fitted. i have also unplugged the harnesses in the front left fairing and re plugged. all still not soloving the problem and only happens with the rear wheel moving. Shame the diagnostics is not showing an errror code would make life a lot easier!! I have also checked the center stand/side stand connections and netural saftey switch all working fine as the diagnostics are showing on and off when moving them.
 
well if the problem occurs when the bike is in neutral, and you move the rear wheel.. then it seems to me its not in neutral completely.. so gearbox maybe involved..

edit: or anything connected to the gearbox, clutchcable and such..
 
When checking the harness's, look closly for ANY CORROSION on the terminals. I had problems with my 04 FJR (common problem on this one connector). On two terminals a very slight amount of corrosion developed
and caused all kinds of problems. Water followed the line down the connector. Once cleaned and di-lectric grease applied, no problems since.

I'd also make sure you have a fully charged battery, a low battery will cause all kinds of problems. Check voltage across terminals while idling, reving, and turning the wheel backwards (when the bike is acting up).

While apart, put some Di-lectric grease on the terminals. On the ECU connector, very gently tug on the wires to make sure none have come loose. Again, disconnect the main harness and check for corrosion, apply di-lectric grease(preventive maintainance).

I'm thinking you may have a bad ECU if nothing else pans out..

One last thing to check is the TPS. I don't think this would be relayed but is easy to test (see other posts). Make sure you check ALL THE NUMBERS inbetween and that your not missing/skipping any.

Your problem does sound electrical and is quite odd.. Hope this helps.

Scott
 
Hearny,

How consistent is this? Does it happen EVERY time the back wheel turns? Is it completely repeatable? Obviously, it's not related to the handlebar wiring.....

Just to stay objective..... could this be something that is coincidental, and you happen to notice it in this one scenario?

Some of the other 'runs like cr*p' possibilities..... how old is the fuel in the tank?

Has the bike sat overnight recently, with less than half a tank of fuel? It's possible your motor is trying to burn off some water in the fuel.

Other than air or fuel issues (which it sounds like you've taken a good look at already) I would start thinking about talking to Yamaha. If you have a warranty, I would seriously consider excercising that.
 
thanks for all your replies very much appericated. Yes this does happen everytime the wheel is moved. i have fully charged the battery and found the following.

I had left it in diagnostics mode and rotated the rear wheel while in each code. The diagnostic code 01 for the throttle was at 16 to start with but when moving the rear wheel was jumping between 17-21 and i was not touching the throttle.As soon as the wheel stopped back to 16. Also code 06 which is the coolant temperature started to jump every time i moved the wheel but doesnt show this on normal display?

I will in the mean time recheck the wiring harness and look closely at for any corrosion. I am now thinking this is a little more serious so i have managed to get it book in on thursday to yamaha. Will let you know the out come. Still in warranty which i think is a bonus as it could be costly.
 
hearny said:
thanks for all your replies very much appericated. Yes this does happen everytime the wheel is moved. i have fully charged the battery and found the following.

I had left it in diagnostics mode and rotated the rear wheel while in each code. The diagnostic code 01 for the throttle was at 16 to start with but when moving the rear wheel was jumping between 17-21 and i was not touching the throttle.As soon as the wheel stopped back to 16. Also code 06 which is the coolant temperature started to jump every time i moved the wheel but doesnt show this on normal display?

I will in the mean time recheck the wiring harness and look closely at for any corrosion. I am now thinking this is a little more serious so i have managed to get it book in on thursday to yamaha. Will let you know the out come. Still in warranty which i think is a bonus as it could be costly.
Click to expand...

Sounds like there is an effect to your computer occurring from the speedometer signal or a sensor at the output shaft. Where is the speedometer sensor on our bikes? What you've been saying since the beginning is that it only occurs when the rear wheel is turned. There may be more than one sensor at the output shaft and one may have failed.
From your tests it would seem the computer is seeing a throttle position change when the rear wheel is turned. Almost like crosstalk between the sensors. This could also be moisture in a plug connected to the computer or a plug carrying sensor signals. It would be exacerbated if the water had salt which is common during winter.

It sounds like you're on the right track..

This is a very interesting anomaly...
 
I believe the speedometer pickup is at the top of the main engine case (not the cylinder/cylinder head).

To plug in a Speedohealer (which ties into the speed sensor), its located under the gas tank. It is a three wire, with a triangluar shaped WHITE plastic plug (male to female). It would probably be worth your while to find this connector and check it, perhaps follow it down to the block/sensor. The neutral indicator sensor should be in the same general area, but with one wire (shouldn't have anything to your particular problem). Perhaps one of the wires is loose/shorted/broke. Once located, if nothing there is obvious, crank up the bike and manipulate those three wires, see if it acts up/stops, etc. That sensor (short of ABS-which you don't have) is about the only thing related to the rear wheel turning (electrically speaking).

BTW, does the speedometer work ok? With the key on, on the centerstand, (engine OFF) spinning the rear tire by hand should register 5 MPH (or better).

Scott
 
Thanks finally after two days got to the bottom of it. Yes you are right it was the speedo sensor. As soon as i unplugged it the bike was running good again with the wheel turning.
The reason why I did not suspect the speedo sensor was it was actually working fine and giving the correct mph! and no fault code was given.
I presume it was shorting across 2 terminals where it bolts to the engine and it could be due to salt water. I sprayed DW40 around the 3 wires and cleaned them and now working fine. I re done all the tests that i had before and now ok.

Thanks to TownsendsFJR1300 and nccoder for there suggestions and to everyone else advice too to get me back on the road!
 
Excellent! I would strongly suggest loading that electrical connector up with Di-lectric grease... It will keep any corrosion/water from getting in there causing further problems. Its fairly cheap, (about $8.00 in the US for a medium size tube).

ANY connector I take apart, for my bikes (or a customers) I put the di-lectric grease in there. I don't like come backs or do overs...

Again, congrates, learn something new everyday!!

Scott
 
nccoder said:
+1 Great Job! and thanks all for all the other's input on this. This is what makes being on this site so great! :rockon:
Click to expand...

Ditto..i had nothing to contribute to this thread..but was very interested to see the outcome..Much kudos to all involved :thumbup:
 
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