Starting a bike with a flat battery

[Freddyfruitba...]

My battery loses charge when the bike's left unused and I do make use of a smart charger to keep it topped up. But sometimes I do forget - like just now - going out for a run; was all geared up, sat on the drive pointing at the road, pressed the button... nothing. Nada. Zip. Sweet fuck all. So have just put the bike away again, stuck it on charge, and come back into the house in a strop.

Question: are there any easy options to get the bike going quickly under these circs? I'm not on a hill here, and am no longer young/strong enough to try bump starting 200+ kg of bike. If it was the car, I'd have just got the jump leads out and gone round to chat up Janice next door, but as far as I know, jump starting a bike from a car battery is likely to fry my electronics innit? I imagine the same thing applies to those power pack devices? Apart from keeping a spare bike battery permanently on charge in the garage, does anyone have any cunning solution to this?
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KC100->CB100N->CB250RS--------->DL650AL2->R1200RS->R1250RS

[Polarbear]

Practically, with a modern bike it can be real hit and miss if they start and run OK from a bump start. They are so power reliant.

Wifies ER6N would not run with a flat battery. If it fired it would pop and bang but not run properly.

Nowadays I have one of those small starter battery things. It will start anything. I've used it for a car, bike and even my boat. Just leave it connected till the engines settles down and is running properly and off you go.

edited to add - I have never ever fried any bike, car or hamster, jump starting from one to another. As far as I am concerned 12v is 12v and it will jump.

https://www.batteryfocus.com/wp-content/uploads/2019/07/GOOLOO-1500A-Peak-SuperSafe-Car-Jump-Starter-.jpg
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Triumph Trophy Launch Edition

[Nobby the Bastard]

You'll have a job to bumpstart a FI bike because they invariably need the fuel rail pressurised to start and the bike won't pressurise it until you press the starter.
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trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Triumph Sprint ST 1050

[Riejufixing]

[WD Forte]

I've used a car battery on a bike manys the time
jump started too* and as PB says, 12v is 12v

I'd be more concerned over the health of the battery as
letting them go flat can sulphate up the plates.
Starting should be easy enough but how well is it holding charge?
It may be fine but I'd suggest keeping an eye on it




* I even used a CX to top up a failing Transit battery when it was
struggling to turn the engine over on a frosty morning
Top up, not start! I hasten to add, it wasnt dead flat.
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bikers smell of wee

[Kawasaki Jimbo]

I've got a small, easily portable jump starter which does the trick.

Regarding blowing electrics, as I understand it a flat battery, a starter motor, etc. will only draw what it needs. The spare battery doesn't force feed anything, so electrics won't be blown. The exception might be when using a car battery with the engine on, where the bigger alternator might cause damage. However, I've done this loads of times without issue before I learned it might be a risk. A running car engine isn't necessary anyhow.

I've also bump started my 2003 R1 quite easily although the FI is probably a primitive version.

[stinkwheel]

No problem using jump leads from your car battery to start your bike. Just don't have the engine running when you do it.

To be safe, if you are worried about a voltage spike from the bike upsetting the car electrics, disconnect the terminals first so you're just using it as a big cranking battery.

Both batteries are 12v, the car one just holds more charge.

The problem arises if your bike reg/rec tries to regulate the car alternator output.

I used to keep an old car battery charged up in the workshop. It was too dead to turn over the car but would spin the bike over like a good-un. It got nicked by gippos when I left it outside though.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[1198]

Why has nobody asked yet about Janice? Pictures of?
Disappointed.

[xX-Alex-Xx]

[Freddyfruitba...]

Thanks all, that's good to know - will jump start off the car next time then!
Battery was at 11V yesterday but the starter motor didn't want to know. All fine today after an overnight charge.

[Suntan Sid]

[Blah blah]

Trying to start a bike with a duff / weak battery can sometimes stuff the sprag bearing as well, which isn't a cheap and easy fix !

I'd buy a new battery.

[Nobby the Bastard]

I'd rather find out why the battery is going flat before I start wasting money.
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trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Triumph Sprint ST 1050

[Riejufixing]

[bacon]

When my brother scrapped his old focus I kept the Bosch battery. It's not huge by car standards but it is in bike standards. I just jump from that when needed.

So get on the hunt for a freebie battery to leave in the garage.

[megaross]

Nothing wrong with jump starting a bike off a car or a jump pack. Ye olde bump start is the king though.

I remember coming out of a mates house about 2am and my tiger not starting, below freezing so standard "Early warning sign" of a duff battery but less than ideal when you want to go home and get some kip.

Took me about 10 tries but managed to bump start it on a dead flat bit of road, also helped a mate bump start his ZZR1400 (that's a 2 man job). You definitely can bump an EFI bike - it depends how dead the battery is. If it's got enough voltage to run your electrics but not enough to power the starter it'll go on a bump.

I've got jump packs and a few "Questionable but good" batteries in the garage and a baby jump pack (like a power bank) but tbh I've never needed to use any of them on a bike.

Anyway - if your battery is going flat after being sat for a few weeks replace it, it's on it's way out.
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'07 Tiger 1050