Starter motor brushes, 2 or 4

[Steve M]

I think I've seen discussion on this topic before but can't find it. I am working on a Z1100 shaft with a lazy starter. It has 2 brushes and 4 magnets. Could I replace the 2 brush plate with the later 4 brush version or are the windings different for the two types? many thanks for any advice.

[Al]

I would be surprised if any parts are interchangeable between 4 and 2 brush set-ups but you never know.
Perhaps the easiest thing would be to source a good 4 brush motor and re-furb it or yours because the standard system doesnt struggle therefore something must be amiss.
A really good clean up in the hands of someone who does that sort of thing should sort it all out but after 40 years plus, the supporting ancilliaries may be the issue.
I would replace the battery cables and the lead from the solenoid to starter and from engine earth back to the battery with new stuff.

This works best as it has better density per unit of cross sectional area..
https://www.vehiclewiringproducts.co.uk ... rter-cable
They do black and red and some pre-made to lengt options too with terminals readily done.

New brush kits may be available for what you have now like one of these perhaps.
https://www.electrexworld.co.uk/acatalo ... s_720.html
The 4 brush plate is a drop in, dont know about the two brush item.

Solenoid may be gone high resistance so one of these will do as a replacement.
https://www.electrexworld.co.uk/acatalo ... ml#SID=726
Its not the only option but i have had one of these for eight years trouble free and the standard one was about £90 or something stupid like that.

Finally the battery CCA may be holding it back.
I assume its in good order but if it isnt then a new one with better Cold Cranking Amps may help.

AL

[Steve M]

Thanks Al, that's really useful info.

[Al]

Forgot to mention; one 'constant' (see 'constant pain in the f&*^i&g a&*e') is the point where the earth return runs from a tapped hole on the back of the crankcases to the battery. Where the ring terminal bolts on there, it builds up a layer of aluminium oxide and annually i have to scrape it off or it wont run the starter motor properly. I have a sharp, broad bladed flat screwdriver which i use like a wood chisel to gently plane off about a few thou of crust. Its like kettle scale and it gets on there like nobodys' business.

AL

[gray]

if you used a little dialectic grease there( ie electricity- conducting) after doing your yearly scrape then that might slow up the oxide reforming between the crankcase and the ring terminal

[Al]

Thanks gray, its on my list.
AL

[zed9]

After checking cables and brushes as stated above also check the commutator that brushes connect onto by looking at them once brushes are removed. You may find they are tarnished and have burn/arching marks due to hight currect passing though them.

After years of sevice carbon from brushes will build up between plates on commutator which could cause shorts or low resistance between them. If they are marked you should be able to clean them withought taking it apart using a fibreglass pencil though have not personally tried it on a zed yet but have on many other things.

You can use a fibreglass pencil which is only a few quid on scum bay. Extend the fibreglass a couple of mm and press on cummutator while spinning motor. Also give it a good spray clean with brake cleaner to flush out the carbon dust and bits. If commutator is quite bad take motor apart and clean it gently with fine wet/dry about 600 grade then 1,000 so copper surface is smooth. If do do take it apart remove carbon from between the copper plates.

Fibre glass pencils are good at cleaning up gold and copper contacts without damaging surface.

[Steve M]

Thanks for that