Push start an efi bike
 

Assuming you have a slope, traction and the strength, can you push start a modern, efi bike in the time-honoured 'push, run and jump' way?
I assume if the battery is completely flat then probably not (didn't work on a 660Z for me), but what about if the starter packs up? A less likely scenario I know, but just wondering.

thanks

Chris S

Yes, providing there is enough voltage in the battery to power the electronics. I would say there is no chance with a flat battery.

This also includes the fuel pump.

have jump started mine a couple times when battery was too low to turn over the starter ... but obviously had enough to power the electronics and fuel pump.

If its a packed up starter, then there should be no problem as long as the battery is fine

Depends how far and how long you can push it for. If the battery is flat, I'm not actually sure if you could try and generate enough for the pump and electronics from using the generator while the bike is moving. I think if you got a tow in a high gear, you might just get going.

Obviously getting a tow on a bike is risky but there are 'safer ways' to do it.

NEVER tie the rope to the bike. Wrap it around the headstock a few times and hold it with your hand on the bars. That way if things get 'Ropey' (excuse the pun), you can take your hand off the rope and it will unwrap and go free.

If the battery was completely dead I don't think you'd get it going just by solo pushing. If there was just not enough power for the starter motor but you had the warning lights etc then pushing would work - it has for me a few times (but with the help of a hill!).

It does depend what you're pushing though - if you're talking 600 single or similar, then I don't think you have a hope. Even with valve lifters and everything functioning on the engine I've never managed to bump start either of mine solo - the back wheel just locks up as soon as you drop the clutch. You need to add at least one other adult size person (or two kids!), get it moving in gear with the valve lifter in and then let go of that.

I once had a battery fail on me during a trip on a DL650. It could no longer hold the charge, so some mornings, when it was below 0 C, I had to push-start the thing. Was really easy to do so, though, as it always fired on first attempt. But the battery wasn´t completely flat, just partially discharged.

Ta for your experiences. I asked because I seem to recall reading somewhere that push starting an efi, even with a good battery, did not work - as if the engaging/spinning of the starter motor did something essential, electronically. But perhaps it's on certain models and I may have got it wrong.

Just remembered this old jump starting vid from the desert. Not an efi bike, just heavy.

Something in the back of my mind says not to push or tow start vehicles (well, cars at least) with catalytic converters - which applies to most, if not all, Efi vehicles in original form.

I am not sure where the thought came from or the reason, but maybe raw fuel going through, until it fires, is harmful to it.
Or maybe raw fuel confuses the sensors in the exhaust.

Maybe that's what I was thinking - it not advised - you're supposed to 'contact your authorised service centre'.

Perhaps raw fuel explodes in what might be a hot cat and scares the horses...

My BMW Brick outfit with 11.5 V in the battery can be bump started. On a simple system where the only thing lacking is the power to turn the starter it works. If you have a CAN network screaming "low battery call service" into the engine ECU it could be rather different and it will depend on the programming so probably different from bike to bike.

You should not JUMP start an electronic engine, some AA type starters are basically welding sets and not good for ECU's

Andy

I think someone touched on it above. In the majority of cases a flat battery is where there isn't enough current to turn the starter motor enough to start the engine (varies between bikes) BUT the battery isn't already damaged beyond use. If this is case, it is fine to bump-start an EFI bike. I did it to my WR250R the other day with no problem.

This is my understanding of it after doing breakdown work for a few years

The problem with push starting anything that has EFI is that if it has turned over until the battery is flat if it has been injecting fuel that hole time and not firing (damp HT and the ignition has been tracking ) when you come along and dry it out with WD40 or the like and push it or jump start it you then fire the engine up and all the unburnt fuel(and there will be a lot of it )l in the exhaust fires up and you get a bloody great bang and the exhaust box splits wide open
I know this because I’ve done it more than once
Bit Of a tip for both cars and bikes if you think it is flooded pull the fuse for the fuel pump then spin it over to try and dry out the cylinders
If there is lots of power in the battery and the only problem is the fact that the starter in not working then there wouldn’t be a problem with pushing it
But like has been said some of the operating systems for the engine management are getting far too clever for their own good and might stop the engine firing if the starter is not working
After all this I’m glad I still have carbs
Hope that’s all now as clear as Mud

Or Not

Consider the fundamentals; a “fuel injector” is a simple solenoid, a coil of wire surrounding a moving conductor. When a current is passed through the coil, the conductor moves opening the injector. Remove (or reversing) the current closes the injector. No current = no functioning injector.


The term “fuel injector” is a misnomer. It has no power to inject anything. The fuel pump picks up fuel from the tank and pumps it under pressure via the “injectors” which when open, allow fuel into the engine and in an open circuit schema, the excess is returned to the fuel tank. All the Efi bikes I know of use electric fuel pumps. No current = no fuel to the injectors.


Further, an Efi system consists of numerous sensors dotted around the bike such as water temp, MAP, throttle position and the lambda sensor etc., some of which draw current to function but all will require current to feed the signal back to the ECU which itself requires current to function.


However, all is not lost. With the exception of BMWs' GS boxers, all bikes use a simple “magnet excited” coil alternator which as long as it moves i.e. when the bike is “bump started” will produce some current. Depending on the model of your ECU and how it is programmed the loss of any or all sensors (i.e. due to loss of current to the sensor) will cause it to run in “default mode” which will allow the engine to function. Residual fuel pressure may remain in the circuit, especially on closed circuit fuel systems. Whether it is enough to start your bike depends on the design of the system, consult your service manual. KTMs' manuals are very informative and will tell you all you need to know.


With the car like GS boxer consult your manual which will tell you “consult your local BMW authorised service technician”.


To avoid you from sweating like a glass blowers arse bumping your 300kg RTW bike up a sand dune in high summer consider putting a LiFePO4 battery in your kit. It's about the size of a ciggy packet, will hold a full charge for several years and with jump leads will get you out of trouble (don't forget the jump leads!) or simply drop it in place of your dead battery.

Slightly off topic, but I saw a great tip over on advrider for bump starting a big heavy bike.

You need two bikes (one fine and obviously one with a flat battery!), parked back to back on centrestands so that that each rear wheels is off the ground and touching each other. Start the running bike and run to a good speed, which will spin the non running bike's wheel in a forward direction, change up a few gears and hold in the clutch. When enough speed is reached, drop the clutch and hey presto.

Sounds like a faff, but is actually really straightforward. There's a video on youtube showing two KTM adventures doing it, but I'm at work and can't access that site to provide a link.