Problem with starter motor ( HELP !!! )

[flywheel1935]

So, I go out to the garage to check out an issue thats been bugging me for days, bought a new battery 6V, cleaned up the contacts on the starter motor 'switch' tried the starter and nothing !!!! anyway stripped starter motor, fitted new brushes, cleaned armature etc, put back, and tried starting via switch, all seamed good ? anyway at present the dynamo is not wired in, so after a while battery died, recharged battery , tried starting again, clonk, s/motor hardly moves, so thought switch may be problem ?? removed switch and place starter cable directly to motor contact, bit of life in the s/motor, BUT, as the garage was quite drank, I noticed a 'glow' between the starting handle casting and the rad surround (1935 Ruby), tried starting via direct contact to s/motor and glow  showed again ???? so simple question, do you think I need to have a direct earth lead going back to the battery, as guessing glow is engine trying the earth via body shell, over to the the experts.

[Chris KC]

There's a bit much to follow there flywheel and when it comes to electrics I'm no expert - but - for definite you want a big chunky cable (e.g. battery  lead) from one of the starter mounting bolts to an earth on the chassis frame (acceptable) or directly back to the battery (preferred).

By the way, when you say you bought a 6V battery, what kind of 6V battery did you buy? A proper one should crank the engine for quite a while in new condition and fully charged...

[flywheel1935]

Hi, battery came from supplier recommended by 7 Workshop, can't remember co ??? when arrived was fully charged, and did crank for ages, issue stemmed after re-charge??
But engine just re-built, so still 'tight', BUT sure issue is Cable/Earth ? so will go with earthing back to Battery.

[bob46320]

Yes, do not hesitate with a good earth, If you don't, its possible for the earth to return via the gearbox, through the bearings and all sorts. I have seen a bearing eaten away as it was "part of the earth return" on an old Riley.

[Jeff Taylor]

I agree it could be an earthing problem or incorrect thickness of battery / starter cable. Cable bought from a motor factors for a 12 volt system is not suitable for a 6 volt system – the cable should to be to the size specification shown below:

The correct specification battery / starter cable to buy for a 6v system.

Battery / Starter Cable – 315/0.40, 40mm², 13mm OD, 300A

AES stock it in cotton braid black or red – their Ref. No. 020203 @ £8.97p per metre:

https://www.autoelectricsupplies.co.uk/p...#flash-msg

The Green Spark Plug Company stock it in PVC black or red – their Ref. No. 0-982-10 @ £11.81p per metre:

http://www.gsparkplug.com/1x-meter-durit...982-10.htm

[Dave Wortley]

I put an earth from engine to chassis when sparks were generated between oil gauge and dashboard. The oil pipe was the earth.

[Colin Reed]

This is the main reason why on Marine installations every thing is earthed back to the battery and twin cables for every thing that has an electrical connection , nothing is earth through the engine for obvious reasons.

Regards all
Colin
NZ

[Ian McGowan]

I put an earth from engine to chassis when sparks were generated between oil gauge and dashboard. The oil pipe was the earth.

As Dave did, I ran an earth cable directly from the battery/body connection to one of the gearbox top securing bolts and all was well for years. Then one day the bacon slicer starter wouldn't turn above a grudging 4 or 5 rpm - certainly too slow to start the engine. Believing the 6v battery to be on its way out I purchased a new one; same situation with new battery - so I investigated properly, as I should have done in the first place! The problem was that the two starter motor securing bolts had come very slightly loose, sufficiently so as to restrict the heavy current flow needed to correctly operate the starter motor. I now have 2 perfectly good 6v 80Ah batteries - a spare is never a bad idea!!

[Reckless Rat]

I have a "belt and braces" approach. There is a braided earth strap between the timing case and the n/s cow horn fixing and a second earth cable from a cylinder head bolt to the battery. With an Exide 80A/H 6v battery the starter spins fine.

[flywheel1935]

Hi Guys, thanks for all the info, I will be running a direct earth from the s/motor to the battery, + engine to body via strap, + second battery in tool box , in parallel.
Happy Cranking !!!!!