:?: Bike not starting when hot. :?:

[swaffs]

I've got a problem with my CBR600 FY, where if I turn my ignition off when the engine is hot (which I have to do every morning to go and get my carpark pass) when I come back out to the bike 2 minutes later, the bloody thing wont start, it's almost as if the battery is not giving enough charge to turn the starter motor.

I can bump start it fine and have done each morning this and last week.

when I return to the bike at the end of the day it starts just fine so the battery is not actually flat (providing I hadn't tried too many times to start it in the morning).

I dunno why but I'm thinking reg/rectifier is overheating maybe?

I hope somene can help me with this as it's doing my head in each morning and I was tempted to pop into the office this morning with the engine left running, but I suspected I would have come out to no bike!! (this is central london)

Anyone any ideas?
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[Black Knight]

My bike needs more fuel to start when hot. I use about 40% of the throttle to start it.

[Scotsman37]

That sounds familiar as my friend had a similar problem and it was rectified by WD40 all the wiring loom connection blocks and it hasn't done it since then.

[Claud 14.7 to 1]

Reg/rec problems.

Contacts/block/wiring not making contact, as Scotsman37 says. Too high resistance in the wires. Earthing possibly, even loose battery terminal contacts could cause this.

Stator and/or wiring.

Seems like the battery is being drained somehow.

Doubt it would be fuel, as it's the turning over power that isn't making it catch.

If I had to guess right now, I'd say reg/rec.

You'll have to hook up a multimeter and start testing the power going back into the battery. It is quite possible the Reg/rec is burning up, as this is exactly what happened to my fault unit. Except the bike would lose all of its charge and just cut out when the revs settled to idle speed, leaving me stranded with no battery power to turn the bike over, in the middle of no-where.

So anyway, hook up the multimeter to the battery, rev the bike up to 4-5,000 and check the charging rate. It should be a healthy 13-15v regardless of what electrics are on. The ultimate test is with ALL the electrics on as it will be operating under max "load".

Also feel the reg/rec mine got very hot after about 1 minute, and until then it was working properly and charging up the battery fine. As soon as it got hot, it gave me the problems. They do get hot by nature but too hot and or too soon means they're faulty. Haynes gives you a test procedure for the reg/rec, although I didn't find it very helpful.

[Ian (GPX)]

swaffs, when it does this, does the starter motor turn ?
if not, check out the solinoid / starter relay. I had the same problem last week.

[Kickstart]

Hi

Very much doubt it is the regulator / rectifier. After all that affects charging, and the battery has loads of charge at the end of the day (and from the description Swaffs gives it seems it is cranking over happily, just that if he does it long enough he kills the battery for the end of the day).

Would be inclined to say that it is fuel vapour. Check for any blocked / misrouted carb breather. Check for a missing heat shield for the carbs.

On carbs the old Weber carbs used to suffer from this. The way round it was to try starting the car with the throttle open a fair way (just back off quickly as soon as it caught). Not sure you could do this effectively with CV carbs but it might be worth a try giving it full throttle.

All the best

Keith
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[swaffs]

OK, when I try and turn the ingine over if it is hot.
IT tries to crank it over but dies after less than a second (like a flat battery)

but there is pleanty of charge because i can keep on trying it (well about 10+ times until it does actually lose charge)

It doesn't actually spin up, it's as if it doesn't have enough power to spin the starter motor.
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[Claud 14.7 to 1]

The battery is flat, but not completely dead. I understood it like that.

It is flat enough not to have the power to start the engine, but has enough to turn the engine over. The battery still would have enough power to turn the engine over for a good while after the charge goes under the "required" power needed to start the engine. Because it is under this "required" amount it won't have enough juice to fire it up. Eventually you'll run it down completely.

I had this: charging problems.

I have heard that if the reg/rec goes, in some cases the bike may cut out due to low battery, then you leave the bike for a while and it'll turnover with full power again. I know it sounds strange and improbably but this happened to me the first time my reg/rec packed up.

I would defo try my test, (same as in a Haynes). It is free and you'll know pretty soon if it's shot or not.

Also best make sure the battery is ok as well, while you're at it.

[Wave2k]

it sounds like the battery is flat, but it isnt
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[Ian (GPX)]

errr! read my 1st post.

[swaffs]

Cheers guys,

Ian can't check this stuff yet as I'm busy at work.

I'l check the voltages tonight and wil then know if the charging system is working ok.
and have a look into the starter relay.

I'm thinking a bettery replacement might be a good choice anyway as it's never been great since I've had the bike. and then I can review the sutuation.

Swaffs
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[EuropeanNC30R...]

The problem is, if it is the reg/rec, it will knacker your new battery in double-quick time.

[swaffs]

I started straightaway when leaving work, but as soon as I got home I tries again and.....

same thing:

took a little video on my phone:
MP4 version

AVI (sound only)

I've a feeling the battery is just getting old and not man enough to start the bike when warm.

Bend came up with good idea to try starting the bike via jumpleads when it is hot.
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[mchaggis]

An off the wall suggestion? It sounds a bit as though the starter is running fine, but being prevented from working properly, perhaps by clearances in the starter mechanism closing up when it's hot?

Obviously, try the jump lead approach to discount my idea, I doubt a starter clutch rebuild would be much fun; hopefully I'm barking up the wrong tree.
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[Kickstart]

Hi

While batteries do recover some charge if left for a while, I would doubt this is the problem. If the reg / rect was Donald Ducked then if would likely not charge the battery at all. Might do as you describe once, but likely that by the time you got home it would be totally flat.

Also it normally needs a fair amount more power to start a bike from cold than from hot. When cold the oil is all thick and results in a fair bit more drag.

It could well be the battery is on its last legs, and a new one might solve the problem but I am not convinced that it is all the problem.

Whatever happens, stick a voltmeter over the battery and see what it reads as you blip the throttle. This will hopefully confirm that it is charging OK.

All the best

Keith
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[Ian (GPX)]

I had a listen to the avi ..... it sounds just like my problem I had when engine was warm, starter motor sounds as if it's not getting the required power to turn it over, check the starter relay out.

It could be the starter motor, it might need a rebuild / replacing, but check the above first.

[swaffs]

[swaffs]

ok just been doing some tests.
Battery voltage was steady at 12.3V when engine off.
and at 14.5V when engine running, dropping slightly with lights/indicators etc on.

so no problems with charging...

I left the engine running long enough for the fan to cut in (hotter then it got today on way home)

and it just started fine for about 5 times !!!!


I then have just been out for a 'spirited' ride for 20 minutes. although the bike didn't get 'that' hot (1/2 way)
I shut the engine off, and then on starting, the starter motor span about 6 times before appearing to go flat.

I whacked the voltmeter on and tried again, this time the voltage dropped to about 5V during the starter motor spinning and it nearly fired.

next attempt at start it did fire...

I suspect it's not enough of a run to test it, my normal commute is 30minutes+ through central london i.e not very fast but lots of little sprints to keep the bike warm!!


I did notice when checking the voltage during the last couple of times trying to start, the the starter motor relay was clicking occasionally, although I suppose that would happen.


??????????????????????????
Thanks for all assistance so far...
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[yohomiesmelly...]

I had a sort of same problem on my TZR125R. Basically, i could start it maybe once in the morning, go to work and then 6 hours later when i was to go home it would crank the engine over but it wouldn't fire. As soon as i bumped the bike it would instantly fire up. I cleaned connections and checked what I could but still the problem persisted.
In the end i ended up changing the battery for a new one and giving it a good start in life on a optimate for about a day letting it maintain the new battery and now my bike starts on a flick of the button and so far i havent even touched the choke to get her running on colder mornings. It seemed that the charging circuit was working well and everything else was doing the required job but the battery just couldn't hold a charge and its cranking capacity (cold or warm) had just diminished completely. I suppose you get some bad ones once in a while

Don't know if it helps

[swaffs]

ukbilleh,
that is just what I'm thinking and discussing in irc now.

I have had issues with the battery before not holding charge after a 40mile motorway blast, but hat seemed to fix it self.
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[Ian (GPX)]