Under 5000rpm tries to stall after 5000rpm its fine!! odd

[Boostinu13]

Hello. So 2 days ago my bike was driven into. I was able to drive it home no worries. Drove it to work and home yesterday no worries at all (45min each way).
Today rode to work seemed fine, changed lanes on mway and slowed down. When I went to speed up it was very sluggish.
Came off the mway to some lights and found it would not want to move. Nursed the bike home and found if it si under 5000rpm then it will stutter and basically do nothing. Even back fire slightlyt. As soon as it hits 5000rpm it takes off like nothings wrong. I was thinking it maybe a lead or spark plug as that has been an issue before (over fueling i think as they get quite black compression testing says both cylinders are good). But no matter what gear or speed if its under 5000 it wont want to ride, as soon as the needle hits exactly 5000 it rockets. Thinking a sensor?

Its fine if I want to launch it everywhere, but id prefer not to haha.


Any ideas? Or things to eliminate. Thanks

[george formby]

If it has carbies I would suspect a split inlet rubber. Failing that, yeah, a fuel / mixture sensor.

Might be worth checking the IUD's and rectum fryer, too.

[nzspokes]

If its carbed then blocked idle jet.

Sent from my SM-G965F using Tapatalk

[nzspokes]

If its carbed then blocked idle jet.

Sent from my SM-G965F using Tapatalk

[Boostinu13]

If it has carbies I would suspect a split inlet rubber. Failing that, yeah, a fuel / mixture sensor.

Might be worth checking the IUD's and rectum fryer, too.


If its carbed then blocked idle jet.

Sent from my SM-G965F using Tapatalk



If its carbed then blocked idle jet.

Sent from my SM-G965F using Tapatalk


Wish it was carb since there is a solution that easy mine is a 2011 the efi or injection model

[FJRider]

Wish it was carb since there is a solution that easy mine is a 2011 the efi or injection model

So you have an eight year old 250cc motorcycle, that red-lines at what RPM ... ???

With how many thousand kilometers traveled so far ... ???

[Boostinu13]

So you have an eight year old 250cc motorcycle, that red-lines at what RPM ... ???

With how many thousand kilometers traveled so far ... ???

33000 and 10500RPM

[Boostinu13]

Forgot to mention. When it first happened I had to leave it in a carpark for 2 hours while at uni.
When i started it back up it sounded fine. (when the issue occurs even idle sounds funky sits at 1500 which is standard for it)

Tonight started it and again fine. Will take it for a test ride tomorrow to confirm it needs to be ridden for ti to occur

[Ginge09]

Might be battery related. Crook battery as a result of the shunt. Battery works the electrical gubbins but struggles until the alt and Reg/rec kick in. 5k might be the threshold at which the alt and Reg/rec power through the battery failing. Just a guess.

Have a look at battery earth, Reg/rec earth and connections to alt. Something might have shifted or a connection might be compromised.

Unlikely that the battery shit itself after a shunt though. More likely that a connection has been damaged.

Give battery full charge and see if it still does it. If not, then you are look for damaged connections, otherwise it will fail again eventually. If it still does it after full charge it might be damaged battery.

[Ginge09]

Just to add. When you leave it sitting, it seems fine ( battery recovers over time). When you use it in anger it fails unless you get over 5k and the alt and Reg/rec overcome the failing.

Am leaning towards a damaged connection. Probably between Reg/rec and battery or alt and Reg/rec.

[F5 Dave]

Try riding it rather than driving. Also keep below 33 000rpm as a general rule.

[Boostinu13]

Try riding it rather than driving. Also keep below 33 000rpm as a general rule.

33000 is how many ks the bikes done not rpm I die at :)


QUOTE=Ginge09;1131135367]Just to add. When you leave it sitting, it seems fine ( battery recovers over time). When you use it in anger it fails unless you get over 5k and the alt and Reg/rec overcome the failing.

Am leaning towards a damaged connection. Probably between Reg/rec and battery or alt and Reg/rec.[/QUOTE]

Thank you. The batteries about a year and a half old tops so hoping the batteries good. I will look at connections. Thankyou for your advice.


Only seems to do it once warmed up. Annoyingly took it for a test ride and it was fine for the first 5-10mins (70ks.open road). Finally started to happen once into the 50k zones. Took it home got on my street (20k gravel road) and bam was fine. Was trying to get the issue to occur to try juggle some connections etc when I got home lol

[Ginge09]

Only seems to do it once warmed up. Annoyingly took it for a test ride and it was fine for the first 5-10mins

Yeah, so it's been left to sit for a while. Battery recovers. You jump on and ride it and it behaves normally until the battery starts to die. Battery is either not receiving charge, or it is receiving charge but not absorbing it.


Finally started to happen once into the 50k zones.

Yeah, when you drop the revs in the slow speed zones the alternator isn't spinning fast enough to overcome whatever failing you have in the battery, or charging circuit.

When you lift the revs it all comes good again.

Crook battery or connections from regulator/rectifier to battery.

As a test, start out riding with headlight on full beam. Ride at below 5000 rpm until it starts to splutter, then turn headlight off completely. If it comes good, then it's electrical. See above.

Alternatively, charge the battery overnight then turn ignition on ( don't start the bike ) and turn on head light. If after 2 minutes the head light is still just as bright ( or nearly ) as it was when you started then the battery is fine. You are looking at an issue in the charging circuit. If the light is dim after 2 minutes then your battery is toast. Only works with a fully charged battery.

Not an exact science but cheap. Just because your battery is newish, doesn't mean it's good.

Or, get a cheap multimeter ($15) from Repco or somewhere. Attach the leads to the battery. You might have to bodge something up with tape so it doesn't conduct to earth, or vibrate off. I use insulated spade terminals attached to a short length (500mm) of wire with mini crocodile clips soldered on the other end. One black wire, one red. The multimeter probes can be jammed into the spade terminals. The crocodile clips attach to battery. You can tape the meter to the tank and go for a ride with this rig.

Otherwise find a mate to hold the probes on the battery while you work the bike controls.

Measure voltage before you start the bike. (12.6/12.7 is good ), voltage after you start and the bike is idling ( 12. 4 to 12.6 is good), voltage when you lift the revs, ( should be starting to charge now so 13 point something, voltage above 5000rpm( max charge could be 14 or more).

Not an exact science but cheap, and now you know how to build a test rig.

Keep at it mate.