Starter Motor whirring every third or fourth turn.

Have a friend with le Mans mk2, that he is resurrecting, he has it running now but every third or fourth press of the starter button results in the starter motor not engaging and a loud whirring noise, he has just fitted a new Ram clutch, new ring gear and has replaced the solenoid and fitted a reconditioned Bosch starter motor! has anybody had the same problem or know what it might be please.

Are you sure about flywheel teeth state. As our bikes tend to “die” on a particular compression stroke, it is often the engaging teeth of the starter motor hit the very same section of the flywheel crown, which over the years becomes worn off.

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What is the battery like? Try jumping it from a second battery if you’re not sure how good it is.

thanks for that, will get him to have a look at the flywheel teeth.

Battery is new 30AH and he also had it checked and all good.

But he says it’s a new ring gear and reconditioned starter - so presumably the pinion is good - which makes me think the pinion is not fully engaging with the ring gear, but only on the edge - it’s not going forward far enough?
That’s no good it will quickly knock the corners of the teeth off.

This has been a common big block Guzzi probelm from the late 70s to the end of the line with the 2012 GRiSO. :frowning:
The solenoid operates a lever which ‘flings’ the starter gear in to engage with the flywheel as the starter motor starts to spin. This ‘fling’ has to overcome the starter disengagement spring which is ready to force the gear back out of the flywheel as soon as the motor is running.

So if it starts with a ‘ZIP’ it flings in hard, But if it starts with a ‘meh’ the gear may not reach the flywheel - then the starter spins and spins doing nothing.

As the solenoid draws an immediate current of 30a dropping to 10a after the gear engages and the wires are as thin as capellini pasta - many times you just heat up the wires and the current at the solenoid rises too slowly.

It is worth putting in a “startus interruptus fix”

This uses fat Spaghettoni (or to be more technical “28/0.30”, 2.0mm², 17.5A multistrand or if you are very patient the thicker “44/0.30”, 3.0mm², 27.5A
(for yanks the thick one is American Wire Gauge 9 the thinner one is AWG 12)
to take 12v from the battery to a dedicated relay fired by the capellini wire original trigger then a short fat wire to the solenoid. If you take your 12v from the power post on the starter and mount the relay down there it is easy to use the trigger wire to fire the relay, 20a fused realays are cheap on Ebay.

A Startus Interruptus fix puts 12v 20a to the solenoid all at once and the solenoid says “Naturalmente signore” - all sorted


A classic case of coitus interruptus.

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Thats brilliant Johnny, thank you for all the replies lads! have forwarded them on to my mate and hopefully another Guzzi will hit the streets soon.

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@Guzzi-works before your mate does all the work he should take a 60cm length of the very thick wire and crimp a female spade connector on it. bare the other end. plug the connector onto the solenoid trigger terminal and flash the bare wire on the battery 12v.

If the starter still spins slow there is a chance that it has bad brushes and a dirty commutator or that the solenoid is weak.

But really Startus Interruptus is more likely and i would do it on any big block just to get rid of a known weak spot.

Btw never lubricate the solenoid centre body as it seals in an air cushion that will stopit completing its movement.

Thanks again Johnny, have passed that on to him, will come back and let you know how he got on with all this. Cheers.

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No 'bendix screw thread ’ on the starter, the pinion is engaged by the solenoid. This is a red herring!

Sorry yes, thank you for the correction, don’t know why i said Bendix? it’s just a straight lever fling on the Guzzi starter, that is why the solenoid has to be mounted piggy-back.

However that does not change the point that there is always a disengagement spring to chuck the starter gear back out of the flywheel once the engine is running.

If the solenoid is not forced in hard it fails to overcome that spring so, as I said the starter gear will not get to the flywheel.

Kiwi Roy on the Ghetto has traced the actual starter solenoid draw he found a very high momentary inrush current to the solenoid because there are two sets of windings the one flinging the gear in momentarily draws 20-30a then once it is in there is a holding current of 10a.

If the voltage to the solenoid is not high the solenoid moves slowly spending a long time in the 20+a zone drawing that current down the thin solenoid wire.

Yes thanks :+1: :slightly_smiling_face: – I would still want to know does the starter gear mesh correctly with the ring gear, because of new non-standard parts being fitted.

Its possible -
but as Startus Interrupus is the most common problem of this type on big-block engines and is also the easiest to test for (with a fat lead to the solenoid), I would start there.

Once that is ruled out the more exotic problems can be investigated.

Not wishing to keep labouring the point, but first post says “engaging and a loud whirring noise” so I have to conclude power is getting through…

Of course it’s always difficult getting third hand information, not being there to see it … :slightly_smiling_face:

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