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Starter Solenoid

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Loopian View Drop Down
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    Posted: 28 Jul 2020 at 19:00
The starter solenoid on my 1971 v7 Special has finally given up well that’s Italian electrics for you only 49 years old!  The starter is still good so I’m after a replacement solenoid it’s a magneti marelli anyone have any ideas as to a replacement. 
Thanks 
Ian

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Dave P. View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Dave P. Quote  Post ReplyReply Direct Link To This Post Posted: 29 Jul 2020 at 09:32
It might we worth contacting these people for advice.

[URL= ][/URL]https://www.ebay.co.uk/itm/183926479150
TO LIVE OUTSIDE THE LAW YOU MUST BE HONEST.

1971 V7 Special. 1972 850GT.
1970 T120 Bonnie. 2009 500 Bullet.
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Richard Hyatt View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Richard Hyatt Quote  Post ReplyReply Direct Link To This Post Posted: 29 Jul 2020 at 11:58
I'm not sure, but you may find an auto electrician near you , who rebuilds starters and alternators.
Might be worth exploring
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Loopian View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Loopian Quote  Post ReplyReply Direct Link To This Post Posted: 29 Jul 2020 at 13:04
Thank you both for your suggestions I've now got the starter on the bench, the solenoid works on its own, the starter works on its own but the solenoid will not throw the bendix when tested together.  That solenoid on eBay looks spot on (thanks Dave) but I cannot find any part numbers on mine so it could be a bit of a gamble.  So I guess I will have to reluctantly pass it on to an auto electrician who specialises in starter motors and will certainly know better than me.  I’ll get on google.
Cheers Ian
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Richard Hyatt View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Richard Hyatt Quote  Post ReplyReply Direct Link To This Post Posted: 29 Jul 2020 at 13:32
Just before you commit to an electrician,
The solenoid relies on some amps to give the electromagnet in the solenoid enough thump to drive the bendix along the shaft.
You've ascertained that the solenoid will actuate ok , so is the shaft sticky or something that is overcoming the mechanical force of the magnet.
Never lubricate the shaft along which it slides.
I had a car once where the amps provided through the ignition switch was not enough to kick the solenoid into action.
Worth a look at quality of ignition switch and starter button contacts.
Have you explored voltage drops ? From one end of the circuit to the other ?
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Amboman View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Amboman Quote  Post ReplyReply Direct Link To This Post Posted: 29 Jul 2020 at 14:17
It sounds like the electromagnetic part of the solenoid is working, it's just not feeding power to the starter. This would be due to the contacts inside being dirty or burned. It's easy enough to disassembled the solenoid and clean the contacts. The process is similar to the Bosch solenoid that Greg does in this link (scroll down to no. 36):
Charlie
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http://www.AntietamClassicCycle.com
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Richard Hyatt View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Richard Hyatt Quote  Post ReplyReply Direct Link To This Post Posted: 29 Jul 2020 at 19:58
Just re-reading this thread again.

you say the solenoid works on its own -- does this mean that if you have a battery hooked up to NEG to the body of the starter for example starter clamped in the vice.

and then flash a POS to the little exciter terminal that the solenoid CLUNKS in and part of this clunking , slams the one way clutch/pinion into the flywheel and the final few movement brings the big internal copper bar across the big heavy internal contacts to fire the (now engaged) starter up.

does the solenoid actually move all the way into mesh or only just struggles to slide the pinion along?

if this is what is happening on the bike(driven by all the bike's wiring) then try to provide a good separate POS to this exciter terminal - if your starter clunks in solidly , then you know there is a supply problem on your bike.

Yes - you can stick a POS lead straight onto the OUTPUT side of the solenoid and motor the motor (albeit not in mesh)
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Brian UK View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 29 Jul 2020 at 23:22
This could be another variation on the Click, no crank syndrome.

We do need to know exactly what you mean by "the solenoid will not throw the bendix when tested together".
And exactly what happened when you tested the solenoid by itself.
Brian.

Better 5 minutes late in this world than years early in the next.
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Jerry atric View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jerry atric Quote  Post ReplyReply Direct Link To This Post Posted: 30 Jul 2020 at 08:17
I have a new old stock Bosch one still in the box, in my garage. PM me, I'll send a photo. I'm sure its a loop era one.

Edited by Jerry atric - 30 Jul 2020 at 08:20
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Loopian View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Loopian Quote  Post ReplyReply Direct Link To This Post Posted: 30 Jul 2020 at 09:32
Wow, I’ve only just come back on to the forum this morning, thank you all for your input.  I did google for a auto electrician but couldn’t find any one that looked promising nearby.  So I went back to me work shop and decided to bring out the big soldering iron and took apart the solenoid.  The 2 big terminals on the back of the solenoid are 8mm threaded studs 1 goes to the pos batt and the other to the starter. They are shaped like a T with the 8mm thread being the leg and the top is a copper plated plate and here is where the problem lies. With both of the plates the copper was thin and deeply pitted probably only about 40% left intact.  I’m amazed it worked at all.  I nearly gave up but as it happens I did have a small sheet of 2mm copper.  So using self cleaning flux and solder I filled up the craters and built up a layer of solder on top of the plate and filed it all down to make it flat and square.  I cut out a slightly oversized piece of copper sheet and using flux placed it on top of the soldered up plate, got out my blow torch and gently heated it all up until the copper stuck, then filed the copper down to size.  I put the solenoid back together and tested it, a much more positive clack. With my confidence up I then decided to take the starter motor apart and with a can of electrical cleaner, toothbrush, tooth picks and an airline I cleaned up a very black and greasy starter motor, the brushes had plenty of meat on them, the bearings were still good and the insulation was all in very good order amazing for I suspect nearly 50 years old.  I put it all back together put it in the vice and tested, absolutely spot on out with the bendix and a whiz of the motor.  It’s now back on the bike and turns the engine better then I have ever known in the last 5 years of ownership. I had already serviced the ignition switch and put new pos and neg leads on as its never turned over as sharp as my other bikes.  I’m not sure if my copper soldered T’s will stand the test of time so I think a spare solenoid might be prudent.  I’m now out for a good long ride today.
Thanks for all your support.
Cheers Ian
















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Brian UK View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 30 Jul 2020 at 10:26
Amazing what you can do with a bot of thought, and a few bits of scrap copper.

What was the copper bridge piece on the end of the plunger like?

Though beware of building contacts up too much, you could reduce the throw of the bendix and thus not having it mesh properly on the flywheel.
Brian.

Better 5 minutes late in this world than years early in the next.
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red leader one View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote red leader one Quote  Post ReplyReply Direct Link To This Post Posted: 30 Jul 2020 at 16:58
Any pics?
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Richard Hyatt View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Richard Hyatt Quote  Post ReplyReply Direct Link To This Post Posted: 30 Jul 2020 at 18:02
Well done.
Saved a fortune and learnt a huge amount.
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Loopian View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Loopian Quote  Post ReplyReply Direct Link To This Post Posted: 30 Jul 2020 at 18:57
Brian the copper bridge piece on the end of the plunger just needed a scuff up and by the time the solder melted I don’t think I built the contacts up any more then from original so fingers crossed. 
RLO I’m afraid I haven’t got any pictures which is a shame but to be honest it wasn’t really on my radar as I was just making it up as I went along which to be honest probably took up all my brain power!
Richard I’ve certainly learnt a lot and I enjoyed myself at the same time and felt like I earned my evening beer.
Cheers Ian
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Richard Hyatt View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Richard Hyatt Quote  Post ReplyReply Direct Link To This Post Posted: 30 Jul 2020 at 18:59
Cheers
If you ever felt inclined , it is the voltage drop across these 2 big copper contacts, that can be measured. 
It gives you electrically what you saw visually ---- in other words a bad contact patch and thereby bad transmission of electricity.
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