Cranking speed

[homer]

Does anyone have good ideas how to improve cranking. I am having problems with trigger signal when the battery is not fully charged. One long cranking drops the voltage and after that trigger signal is too messy to filter. Engine wont spin fast enough and every power stroke slows its speed.

Starter motor is 5 years old. Should I go up with wire diameter? Starter motor overhaul?Ecu turns off all but fuel pump when cranking. Straight feed to the starter relay from the battery. Lighs off, new lithium battery with 240CCA...

[no class]

The big twins use compression release valves on the heads to get cranking up to speed .... or perhaps you may need a second switchable battery to help out ?

[homer]

Second battery is a solution but I am not sure how to do it.

[Fjbj40]

Get a smaller lithium battery and install it in parallel with existing battery, that will get you 12 volts with the increased CCA you need. It would add maybe 2.5 lbs to the bike.

So from one battery to another you go, negative to negative, positive to positive. Ground one battery, or both if you wish and then from either positive post feed the start relay as per normal.

[Gixer1460]

16 minutes ago, homer said:

Second battery is a solution but I am not sure how to do it.

Two alternatives - 2 batteries parallel connected for 12v - may not improve the cranking, just allow you to do it for longer OR series connected for 24v starting which will really spin it over! If the latter is chosen, then connect all the bike electrics up to the first battery inc. the starter motor thick cable, but run that to the second battery negative post, then run another thick cable from the + to the starter soli and then soli to starter motor. This way the 2nd battery is only included in the circuit when starter is engaged and is isolated from everything else........ it won't be charged but it only gets used for a few seconds so a plug in charge every few weeks ain't a big drama! 

[homer]

7 minutes ago, Gixer1460 said:

Two alternatives - 2 batteries parallel connected for 12v - may not improve the cranking, just allow you to do it for longer OR series connected for 24v starting which will really spin it over! If the latter is chosen, then connect all the bike electrics up to the first battery inc. the starter motor thick cable, but run that to the second battery negative post, then run another thick cable from the + to the starter soli and then soli to starter motor. This way the 2nd battery is only included in the circuit when starter is engaged and is isolated from everything else........ it won't be charged but it only gets used for a few seconds so a plug in charge every few weeks ain't a big drama! 

Thanks. I was thinking about 24V system but was not sure how to do it. I will try it

[no class]

[homer]

But as Gixer1460 said paraller wont help cranking speed. Engine needs to turn faster to get better signal. I was wondering is it so bad because stock generator flywheel is deleted. It might balance the crank rotation.

I have a small battery to connect in series so I can test will it help. 

[Arttu]

Lack of flywheel will definitely make it more difficult to get proper crank signal.

Choice between parallel and series connection of the batteries isn't that simple. To get more power from the starter you need both voltage and current. If voltage drops low then the starter won't take current. And if the battery can't give enough current the voltage will drop.

Connecting batteries in parallel improves current output so voltage will drop less while cranking. So if single battery can't give enough current then parallel connection will help.

Series connection will double the voltage and then the starter tries to take also double amount of current. But to get benefit of increased voltage both batteries must be capable of deliver enough current. So if you use something really small as second battery then it's voltage will drop close to zero and benefit will be negligible or even negative.

If you are experimenting with dual batteries I would try first parallel connection as it is simpler and less risky.

[Screwriverracing]

Going for the 24 volt for starting works well, my 13 to 1 bike starts really well on this and spins over really easily. This is also running total loss ignition, and lasts a day of racing. I would try this first.

Cheers SRR

[Reinhoud]

The starter motor can handle 24 Volts?

[markfoggy]

Take all the pugs out so that it turns over easier/less compression.

Then put them back in once it's running.