1990 FZR250 misfiring

[Big Dog]

Pulled engine cover off, found a few gears there... aaand, couldn't see anything out of the ordinary.. no gears were worn, no gears showed any signs of chips/cracks, no metal in the cover or near the cover. Just wiped everything down to give it a bit of a tidy and put back together. Still happens. Just sounds like the starter is spinning freely without grabbing onto anything, then it'll make a tonne of clunking and it'll catch on and then start up.. I need to learn how to play with bikes properly..

Sounds like your starter solenoid to me.

To test try and reproduce the spinning sound, then tap the starter motor with a heavy object (I would use my trusty rubber mallet) if it suddenly engages there is your issue. If not and it slowly winds up you are not getting enough voltage to your starter.

Check your battery, connections etc.
Test any relays etc between battery box and starter.

I have never had this problem on a bike but had similar on a number of 20+ yo cars.
Always been the solenoid gummed up or burnt out or a faulty earth from the starter.

Is problem present when engine is already hot?


Stupid phone / Tapatalk, apologies in advance.

[ducatilover]

Sounds like your starter solenoid to me.

To test try and reproduce the spinning sound, then tap the starter motor with a heavy object (I would use my trusty rubber mallet) if it suddenly engages there is your issue. If not and it slowly winds up you are not getting enough voltage to your starter.

Check your battery, connections etc.
Test any relays etc between battery box and starter.

I have never had this problem on a bike but had similar on a number of 20+ yo cars.
Always been the solenoid gummed up or burnt out or a faulty earth from the starter.

Is problem present when engine is already hot?


Stupid phone / Tapatalk, apologies in advance.

The starter doesn't have a throwout solenoid like a car though, it's a constant mesh system with a sprag clutch on a gear between the starter and flywheel usually.

[Big Dog]

The starter doesn't have a throwout solenoid like a car though, it's a constant mesh system with a sprag clutch on a gear between the starter and flywheel usually.

So most likely the starter taking to long to get up to speed?
(Assuming op is correct that everything looks good in the sprag clutch? And is in fact looking at the right part? )

Stupid phone / Tapatalk, apologies in advance.

[Steve Gauge]

my guess starter motor if it was solenoid (separate unit ) starter motor wouldn't engage .
Also with the back firing issue these bikes have big issues with cracking inlet rubbers .

[ducatilover]

So most likely the starter taking to long to get up to speed?
(Assuming op is correct that everything looks good in the sprag clutch? And is in fact looking at the right part? )

Stupid phone / Tapatalk, apologies in advance.

The sprag clutch is bolted on behind the flywheel, so one assumes the OP hasn't removed the flywheel yet.
I haven't yet seen a starter that doesn't spin fast enough to engage a sprag clutch yet, but I have seen plenty of worn roller/rotors and porked casings/races



And Steve Gauge is very much correct about the intake boots on these, or any older Jappa

[bogan]

The sprag clutch is bolted on behind the flywheel, so one assumes the OP hasn't removed the flywheel yet.
I haven't yet seen a starter that doesn't spin fast enough to engage a sprag clutch yet, but I have seen plenty of worn roller/rotors and porked casings/races



And Steve Gauge is very much correct about the intake boots on these, or any older Jappa

I don't think sprags even have an activation speed as such, just any torque in that one direction should be enough to engage em. On my busted vfr one I found it would engage correctly at the start, but then slip and disengage at higher rpm.

[ducatilover]

I don't think sprags even have an activation speed as such, just any torque in that one direction should be enough to engage em. On my busted vfr one I found it would engage correctly at the start, but then slip and disengage at higher rpm.

Yeah you can often make them engage at very low rpm until it hits compression stroke