Starter Schematics

[Kiwi_Roy]

Hi,

I recently pulled apart one of the Bosch starters to compare it with a Valeo.

The Bosch has a series wound motor with a direct drive (no gearbox). A series motor can generate very high torque.

 

The Valeo has a motor with permanent magnet fields and a planetary gearbox to increase the available torque.

 

The solenoids on both starters are similar, they both have dual coils and require a really good circuit from the battery to pull in.

The bike wiring schematics do not show the dual coil arrangement, it's more like a black box.

The solenoid draws a very heavy current for a fraction of a second, If there is too much resistance in the circuit the it will not be

able to pull in and close the main contacts.

 

The battery - fuse - relay - solenoid circuit I have shown is about as simple as it gets. For those of you that have the solenoid

powered through the ignition switch I strongly suggest you consider re-wiring to bypass the switch. Running the start relay coil

through ignition switch is OK, it only draws a fraction of an Amp

You will notice I show a 15 Amp fuse in a circuit drawing up to 50 Amp, the fuse won't blow because the peak current only

flows for about 1/10 of a second, just until the main contact closes.

 

Bosch Starter.pdf

Valeo Starter.pdf

 

I hope this helps

Roy

[Chuck]

More good stuff.. Thanks!

[dark_bike]

Hi Roy,

 

seems I have to add further wires then.

<_>

 

what are the respective advantages of these starters? Is the valeo easier on the battery? the bosch better at bringing unwilling engines to life?

 

tom

[Kiwi_Roy]

Hi Roy,

 

seems I have to add further wires then.

<_>

 

what are the respective advantages of these starters? Is the valeo easier on the battery? the bosch better at bringing unwilling engines to life?

 

tom

 

I don't know which is best, I think the Bosch should spin the engine faster, it looks like it will draw a lot more current.

Series motors used to be used for traction applications such as electric locomotives, they have a wide speed range whereas a shunt motor (read Valeo)

quickly runs out of torque at speed.

The Bosch certainly looks a lot beefier.

 

I know some owners have switched from Valeo to Bosch and probably the other way. I have also heard the Chinese Valeo have some issues but I haven't any

experience with those.

 

I suspect others have switched instead of fixing the root cause, bad solenoid circuit wiring (see note 1 on my sketches).

 

These days series motors have been replaced by 3 phase AC motors with Variable Frequency Drives for traction, perhaps one day we will see this

type in a Guzzi starter, I was really surprised to see a permanent magnet Valeo. Perhaps Guzzi will come out with an electric drive train, who knows?