URGENT again! bike wont start now...??

[CMSMJ1]

you can use jump leads but be careful and try not to run it for more than 15-20 seconds at a time. The leads adn the wiring can get hot.

Plugs might still be dead so it might not start. no throttle..choke...let it catch before you start giving any throttle.

good luck

[magg]

Jump starting from a car battery with or without car engine running might prove detrimental to your bike battery. Car batteries and alternators have a charge current capability that greatly exceeds your bike batteries requirement. Would be better to use a charger that had current limiting to suit bike batteries if you cannot bump start it.

[xivlia]

hmm okay, i cant really bump start as the bike is on a rear paddock stand and tyres are flat.. so thats not an option. il see what i can do. i checked the plugs and they seem to be sparking.

[Neosophist]

Jump starting from a car battery with or without car engine running might prove detrimental to your bike battery. Car batteries and alternators have a charge current capability that greatly exceeds your bike batteries requirement. Would be better to use a charger that had current limiting to suit bike batteries if you cannot bump start it.

Hook up just the car battery with appropriatly thick jump leads, this will not cause you any problems providing your bike is in good working order.

Both batteries are 12 volts. While the car battery has a greater reserve charge it will only supply the amount of power demanded by the bike.

This will let you crank your bike over much longer, which is where damage can occur by overheating and burning out the starter motor...

5 seconds bursts with a 2 minute rest-cycle.

Using inadequate jump leads can also be a problem as these will get hot and burn.

Your bike also has it's own fuses designed to blow at specific ampages so battery capacity aside these will blow if you have a problem.

Your issue is probably dry carbs and soaking plugs.. no idea why you did this but follow arsey30's advice.. drive them out on a gas stove / blow lamp and clean them up.

Crack the drain-screw on the bottom of the carb and make sure you get fuel comming out to show you have fuel being supplied.

A good charged battery is a must (or if you are using a helping car-battery you'll have enough power)

You'll only get a spark if you hold the threads of the plug to a metal part of the engine.

You need full choke and not throttle at all..

crank for 5 seconds, wait 2 minutes and repeat.. providing carbs are set right and not leaking it'll catch and fire if you havn't fubard your plugs.

People worry about battery capacity but think about your home plug sockets.. most UK sockets are on a ring-main that has a 30 amp fuse.. meaning all plug sockets in the home can supply upto 30 amps of current before they blow.

However many appliances are fitted with a 3 amp fuse (meaning they draw less than 3 amps of current) but connecting them to a supply that has a potential to supply 10 times their blow rate doesn't do any harm as it is the device itself that determines the amount of current draw, so long as it's a 240v device there wont' be a problem.

The internal fuse (i.e 3 amp in the plug) is there to ensure that it blows and cuts power when the device draws more than 3 amps.. a lot less than the total power available.

The same is true with the motorbike and using a bigger battery... just beware a startermotor can overheat a burn out.. a motorcycle battery will become flat before a car battery as there is less 'reserve' in it, so chances of burning it out are less likely.

Just do the 5 seconds crank / 2 mins rest and you'll be fine.

[xivlia]

hmm okay thanks for the advice. the carbs are getting fuel ive checked the drain valves. my plugs are sparking ive checked that too. il just chgarge battery with my dads car battery.

[xivlia]

good news. bike is working again! :D thanks everyone who gave advise!! :D

[magg]

A couple of further comments.

There is no fuse when jump starting. The battery charge current is the voltage difference between the source, 13-14.5 volts depending on whether the car engine is running, divided by the bike battery resistance in the discharged state, which will be low. A lot of energy could be injected into the bike battery that may affect the battery's physical structure, particularly if this exercise is repeated a number of times.

Bump starting will only result in a charge rate limited by the output capability of the bike alternator, once the engine is running, and should not be seriously detrimental to the battery's life.

I do agree that the inexhaustible reserves of a car battery need to be remembered, so as not to over-use the bike starter motor, perhaps another reason not to to use a car battery, if unsure.

Just concerned that people do not take up the jump start method without some consideration of the potential adverse affects.

[Neosophist]

A couple of further comments.

There is no fuse when jump starting. The battery charge current is the voltage difference between the source, 13-14.5 volts depending on whether the car engine is running, divided by the bike battery resistance in the discharged state, which will be low. A lot of energy could be injected into the bike battery that may affect the battery's physical structure, particularly if this exercise is repeated a number of times.

Bump starting will only result in a charge rate limited by the output capability of the bike alternator, once the engine is running, and should not be seriously detrimental to the battery's life.

I do agree that the inexhaustible reserves of a car battery need to be remembered, so as not to over-use the bike starter motor, perhaps another reason not to to use a car battery, if unsure.

Just concerned that people do not take up the jump start method without some consideration of the potential adverse affects.

Of course there is a fuse when jump starting. Your 30 amp main fuse and all the other fuses on the bikes electrical systems.

Pull this from the bike and see what happens when you try to jump start.

The good battery does not recharge the dead battery, it replaces it. The dead battery will have a lower potential than the good battery so some current will flow through the dead battery and give it some charge, but this will be minor and only in principle as the car battery is still only a 12v battery, you need a higher voltage terminal volrage to charge, i.e. 14v.

Perhaps a REAL issue that has been overlooked here is that the only negative side to jumping the bike is the extra load on the bikes own charging system.

If you have a flat battery and have time, charge it yourself with a battery charger. The charging system on the bike is designed to run the bike and keep the battery at optimum charge.

Trying to recharge a deeply discharged battery with the bikes system will place a considerable load on an already taxed system, especially when running lights et al. I've seen many a brown and burned altenator from having a dead battery too long.

Jumpings ok for a get you home or in an emergency but always recharge the battery as soon as you can with a suitable charger.

An optimate does wonders for keping your battery and chargign system in good condition too.

If your bike suddenly goes flat and it's not been from trying to start the bike then always investigate the cause too.

[magg]

When you jumper batteries you usually connect a fully charger battery across a discharged battery.

Current will flow from the fully charged battery into the bike battery and also through the bike fuse system to other circuits which will enable you to start the bike. There is no fuse between the fully charged battery and the discharged bike battery, unless someone adds one or it is included in the jumper leads which would be unusual.

Yes the discharged battery will be at a lower potential and that is what causes a current to flow into it. The only limit to the current flow into the discharged battery is the internal resistance of the discharged battery, which will be very low, and that of the leads connecting to two batteries together.

The large in-rush current that the fully charged battery can supply, and here we are talking about a car battery, is something a discharged bike battery would not normally be expected to absorb. Thus the bike battery structure could be stressed, particularly if the jump start process needs to be repeated a number of times.

This is why battery chargers for smaller capacity batteries, like bikes, have a lower current capability when compared to the type used to charge car or truck batteries.

There is no load on the bike charging system, the battery used to jump start the car/bike whatever is supply all the power to the electrical system.

[Neosophist]

There is no load on the bike charging system, the battery used to jump start the car/bike whatever is supply all the power to the electrical system.

The battery supplies the power to the starter motor. Once the engine starts, the altenator is providing almost all of the power to the bike and re-charging the battery.

When you remove the charged battery the bike still carries on running even with the dead battery, this is becuase the altenator is providing power to the bikes electricals and also recharging the battery.

If you've jumped a very discharged battery then the altenator will be working hard to charge this battery, combind with lights you can over-stretch a small bikes charging system, which is why you may over-load the altenator.

Of course jump leads don't have fuses, there not needed there. Even a motorcycle starter draws high amps when cranking, look how thick the cable is to the starter-motor.

The NC24 motorcycle battery has 80cca capacity.

The large in-rush current that the fully charged battery can supply, and here we are talking about a car battery, is something a discharged bike battery would not normally be expected to absorb.

The bike battery isn't absorbing anything but a neglible amount, the good battery voltage isn't high enough compared to the existing battery, unless there is something serioulsy wrong with it. A 'dead' battery will in most cases have a terminal voltage of at least 12v.

The current flows to the motorcycle starter motor and electrics.

Unless something is seriously wrong with your battery, akin to a dead-short then there won't be a problem. If you've just run it down from cranking or it's gone flat from a week or two of neglect then a jump will be fine.

Just becuase your car battery has a 1000cca of power doesn't mean all that power is used. When connected to your motorcycle the bike will only draw the current that is required to turn the starter motor and run the neutral light and anything else you might have switched on.

Internal resistance is going to be very similar for both batteries.

I think you are confusing actual resistance with equivalent resistance too.

The internal resistance of a battery actually drops slightly as the terminal voltage increases. This is why when using a constanct voltage charger (like a typical home automotive charger, which is current limited to say 1amp or 4amp and charges at 13.2v or similar) the current rate goes down as the battery charge increases, you see the ammeter drop.

If the resistance of the battery increased then the charge rate would go up...