Can't start after riding for 15 minutes.

[Blackrain]

Hi everyone! I'm from Singapore! I am riding a 2002 CB750RC42.

I'm facing this problem with my bike. The bike starts fine when it is cold. After riding it for about 15 minutes, I shut off the engine and go off to run an errand. After about 10 minutes, when I return to the bike and start it, it will crank and crank and crank but it won't start. I have to wait for about 5 minutes to start it and sometimes it does and sometimes it doesn't. When it doesn't start, I have to push start it and it will fire up without any issue. I've asked my Mechanic to troubleshoot it but he also can't find out what is wrong with it. Does anyone have a clue to this mystery???

 

[dirtdigger]

does it crank over slow when it wornt start? May want to make sure the battery is in good condition, if battery voltage drops too low while cranking you may not get spark. Beings it will starts right up if you push start it then it sounds like a low voltage issue.

 

[Blackrain]

does it crank over slow when it wornt start? May want to make sure the battery is in good condition, if battery voltage drops too low while cranking you may not get spark. Beings it will starts right up if you push start it then it sounds like a low voltage issue.

It actually cranks very strongly as my battery is new. That's the mystery...

 

[amc49]

If you have picked a substandard amp hour battery then you could have made the problem. No mystery to that. Better batteries cost more money, but just try to teach the general public that. Es imposible senor.

Push start to fire right up says starter drawing current off electronic ignition to not start. Ergo, voltage amp issue of some sort.

Problems showing up in 15 minutes say possible starter increased amp demand from old starter and worn too. Starter gets hot and then doesn't work as well. You think it's turning 'strongly' but engine firing up quickly is part of that same equation and you don't have it. Who cares how strong the starter spins if bike won't start??

 

[Blackrain]

If you have picked a substandard amp hour battery then you could have made the problem. No mystery to that. Better batteries cost more money, but just try to teach the general public that. Es imposible senor.

Push start to fire right up says starter drawing current off electronic ignition to not start. Ergo, voltage amp issue of some sort.

Problems showing up in 15 minutes say possible starter increased amp demand from old starter and worn too. Starter gets hot and then doesn't work as well. You think it's turning 'strongly' but engine firing up quickly is part of that same equation and you don't have it. Who cares how strong the starter spins if bike won't start??

Thanks for the tip. I will look into that.

 

[Dave]

If you have picked a substandard amp hour battery then you could have made the problem. No mystery to that. Better batteries cost more money, but just try to teach the general public that. Es imposible senor.

Look closely at the "Ah", that's the only real indicator of difference, the color and brand are marketing and the price difference is usually for the warranty.

PS If this was a Honda "car" the starter relay would be the main suspect.

 

[Blackrain]

Hi guys! Thank you very much for all the tips here. My mechanic has helped me narrow down the cause of this mystery. We highly suspect it is the pulser coil that is the culprit. Stay tuned as we continue to probe...

 

[dirtdigger]

I dont see how it would start when push starting it and not with the starter if it was the pulser. Still seems like a low volaltage issue to the ignition from a high starter draw but who knows maybe if the pulser was marginal then just a small amp draw what render it dead. Keep us posted.

 

[amc49]

Set the airgap closer, that strengthens the signal. If somebody has an old school needle type analog voltmeter you can hook up to the leads and spin motor to read the blips coming off the sensor. Erratic and something wrong with it. Why I keep those 'outdated' tools, it reads abs sensors and crank and cam ones on cars too. Any two wire sensor. If it has three then a Hall sensor and needs slightly different test.

 

[Blackrain]

Hi guys! The culprit in the end was the pulser coil. Got it changed and the bike is running well! Thanks for all your tips here.

 

[amc49]

Two coils there and you'd think the other one being good would crank bike up but on two cylinders only..................thinking they ohm out at 530 ohms if good.