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Magneto slip ring contamination

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Hi all,having done 75 miles on my 56, 88 after a ground up resto, i have encountered a problem with the pick up brushes.I have put new pick ups in and after a run of about 15 miles it starts to misfire and wont tick over slowly. After a couple of outings where i cleaned every thing,plugs carb ect i have narrowed it down to carbon on the slip ring. I clean it off and its fine for another 10 miles then starts to play up.How do you check the hardness of the brushes as i suspect they are to soft. The only other thing i thought of doing was to keep running it and see if it gets better. Anyone had this issue. thanks,colin.

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It is essential you fit brushes of the correct hardness from a reputable magneto parts supplier. There have been cases of damage to windings apparently caused by stray tracking from slip rings contaminated by carbon from soft brushes.

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I have read on another forum of bikes having misfires caused by sub standard brushes which are being sold at auto jumbles..

I think as Gordon says, it is best to get them from reputable suppliers.

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Yes,got that thanks guys,i cant remember where i got the pick ups from but i will give one of the experts a bell tommorrow. Thanks to all.

Previously Gordon Johnston wrote:

It is essential you fit brushes of the correct hardness from a reputable magneto parts supplier. There have been cases of damage to windings apparently caused by stray tracking from slip rings contaminated by carbon from soft brushes.

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Hi Colin

I overhaul Magnetos for a living and have come acrossthis problem plenty of times. We donât supply spare parts so have no hesitation in recommending Dave Lindsley ( www.davelindsley.co.uk ) as a source of the correct type. If you ask him for K2F twin brushes youâll get the right ones. They have a groove up the side. So far we are yet to find a suitable brush without the groove, or an unsuitable brush with a groove. Hardly scientific so I wouldnât want to say it is a definitive way of telling how hard the brush is, but it seems to work as a rule of thumb. The groove has no impact on the performance of the brush; it just seems that whoever is making them with a groove is using the right material.

Itâs also worth pointing out that you can go too far the other way; a brush that is too hard will wear a groove in the slip ring and begin to cause problems this way. There are a couple of pictures and some information on this on our website: http://www.themagnetoguys.co.uk/Slip_Rings.php

In the absence of proper laboratory test equipment, an easy test is to use the brush to draw on a piece of paper. If, after the first stroke, there is no mark on the paper it is almost certainly too hard. If, after half a dozen or so strokes, you are still getting a carbon streak on the paper, it is probably too soft.

Softer brushes will work fine in singles though they may wear more quickly. They will leave a carbon track but, being a single it doesnât matter, the slip ring has a continuous brass band anyway. Even with the softer brushes, you should get thousands of miles out of a single before needing to clean the slip ring.

Hope this is of some help

Andy

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Thats useful gen thanks .I will have a look tom and check the carbon brushes. Thaks again.

Previously andy_marks wrote:

Hi Colin

I overhaul Magnetos for a living and have come acrossthis problem plenty of times. We donât supply spare parts so have no hesitation in recommending Dave Lindsley ( www.davelindsley.co.uk ) as a source of the correct type. If you ask him for K2F twin brushes youâll get the right ones. They have a groove up the side. So far we are yet to find a suitable brush without the groove, or an unsuitable brush with a groove. Hardly scientific so I wouldnât want to say it is a definitive way of telling how hard the brush is, but it seems to work as a rule of thumb. The groove has no impact on the performance of the brush; it just seems that whoever is making them with a groove is using the right material.

Itâs also worth pointing out that you can go too far the other way; a brush that is too hard will wear a groove in the slip ring and begin to cause problems this way. There are a couple of pictures and some information on this on our website: http://www.themagnetoguys.co.uk/Slip_Rings.php

In the absence of proper laboratory test equipment, an easy test is to use the brush to draw on a piece of paper. If, after the first stroke, there is no mark on the paper it is almost certainly too hard. If, after half a dozen or so strokes, you are still getting a carbon streak on the paper, it is probably too soft.

Softer brushes will work fine in singles though they may wear more quickly. They will leave a carbon track but, being a single it doesnât matter, the slip ring has a continuous brass band anyway. Even with the softer brushes, you should get thousands of miles out of a single before needing to clean the slip ring.

Hope this is of some help

Andy

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Hi again,just realised that i looked at your website yesterday. Guess if i cant sort it i should send it to you for a diagnostic. Cheers,colin.

Previously andy_marks wrote:

Hi Colin

I overhaul Magnetos for a living and have come acrossthis problem plenty of times. We donât supply spare parts so have no hesitation in recommending Dave Lindsley ( www.davelindsley.co.uk ) as a source of the correct type. If you ask him for K2F twin brushes youâll get the right ones. They have a groove up the side. So far we are yet to find a suitable brush without the groove, or an unsuitable brush with a groove. Hardly scientific so I wouldnât want to say it is a definitive way of telling how hard the brush is, but it seems to work as a rule of thumb. The groove has no impact on the performance of the brush; it just seems that whoever is making them with a groove is using the right material.

Itâs also worth pointing out that you can go too far the other way; a brush that is too hard will wear a groove in the slip ring and begin to cause problems this way. There are a couple of pictures and some information on this on our website: http://www.themagnetoguys.co.uk/Slip_Rings.php

In the absence of proper laboratory test equipment, an easy test is to use the brush to draw on a piece of paper. If, after the first stroke, there is no mark on the paper it is almost certainly too hard. If, after half a dozen or so strokes, you are still getting a carbon streak on the paper, it is probably too soft.

Softer brushes will work fine in singles though they may wear more quickly. They will leave a carbon track but, being a single it doesnât matter, the slip ring has a continuous brass band anyway. Even with the softer brushes, you should get thousands of miles out of a single before needing to clean the slip ring.

Hope this is of some help

Andy

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Hi Colin

Give us a ring before you send anything. We are very busy at the moment but will do our best to help out if we can.

Andy

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Ok,thanks again.colin.

Previously andy_marks wrote:

Hi Colin

Give us a ring before you send anything. We are very busy at the moment but will do our best to help out if we can.

Andy

 



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