LiS 150 stator slots not long enough (points)

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johnny650
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Wed May 16, 2018 8:46 pm

I have done a search of the forum and elsewhere but not really found a clear answer or solution to this problem although it seems to crop up fairly frequently it seems but usually with BGM stators.

I have a series 3 crankcase fitted with an old spare Ducati points Stator that I have refurbished .
I have adjusted the stator fully clockwise as far as the slots will allow and still can only achieve 24 degrees points opening .

As the crank, stator and flywheel are all original Lambretta equipment I cannot figure out why I cannot adjust the stator sufficiently to achieve a 19 degree advance setting ?

I do not think the slots would enlarge sufficiently without breaking so that isn't a solution .
I do have a couple of other flywheels I could try tomorrow but is there anything else I could try ?
Is it practicable to adjust the points cam or the points gap setting to reduce the advance sufficiently ?

firekdp
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Wed May 16, 2018 9:02 pm

What make of points are you using? Are you sure that they have the correct cam profile?

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rosscla
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Wed May 16, 2018 10:19 pm

That's a good point there's often Vespa points sold as Lanbretta ones and the heel cam is definitely different.

Motoplat ones are also different I think.
"Our dilemma is that we hate change and love it at the same time; what we really want is for things to remain the same but get better."

Adam_Winstone
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Wed May 16, 2018 10:36 pm

Points cam could well not be original spec/length.

You can elongate the slots considerably without weakening the base too much... and every little helps. I do this all the time on stators of all kinds.

Change the points gap, you'll be amazed how much this alters the firing point.

Good luck.

johnny650
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Wed May 16, 2018 11:03 pm

firekdp wrote:
Wed May 16, 2018 9:02 pm
What make of points are you using? Are you sure that they have the correct cam profile?
thats a very good question !... I have no idea . they are just a set of points I ordered from a well known WSM dealer .
I assumed that the points were pretty universal through the 6x coil stator range :?

johnny650
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Wed May 16, 2018 11:08 pm

Adam_Winstone wrote:
Wed May 16, 2018 10:36 pm
Points cam could well not be original spec/length.

You can elongate the slots considerably without weakening the base too much... and every little helps. I do this all the time on stators of all kinds.

Change the points gap, you'll be amazed how much this alters the firing point.

Good luck.
I cannot elongate the slots in this stator enough or the tabs would simply break off . theres scarcely 5mm at either end and I reckon I'd need about 3-4mm to achieve a 19 degree advance.

I had tried filing the points cam heel down a couple of mm but it didn't seem to make a lot of difference. I also narrowed the points gap to 0.3mm but that didn't make a lot of difference either

firekdp
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Wed May 16, 2018 11:41 pm

With all parts correct the stator shouldn't be far off the middle of the slots.
Although the points gap will alter the timing, it shouldn't be used for that. The points gap setting is to ensure that the points open when the alignment of the magnet over the coil produces the strongest flux in that coil. The wrong points will obviously throw this out.

johnny650
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Thu May 17, 2018 10:30 am

yes I have suspected that the points might have been the problem as all the other components are standard Italian oem stuff ie crank stator and flywheel although these particular parts have never been used together before .

I'll wire up another stator today and fit a different set of points and see where that gets me and report back.
Thanks everyone for the advice

johnny650
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Thu May 17, 2018 11:39 am

When you look at how dismally poor the manufacturing precision and quality control is on these components,... its little wonder that they often fail to fit or work is it ! its hard to buy anything from Asia these days that doesn't require finishing off or 'adjusting' in order for it to work properly.

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Adam_Winstone
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Thu May 17, 2018 9:01 pm

johnny650 wrote:
Wed May 16, 2018 11:08 pm
Adam_Winstone wrote:
Wed May 16, 2018 10:36 pm
Points cam could well not be original spec/length.

You can elongate the slots considerably without weakening the base too much... and every little helps. I do this all the time on stators of all kinds.

Change the points gap, you'll be amazed how much this alters the firing point.

Good luck.
I cannot elongate the slots in this stator enough or the tabs would simply break off . theres scarcely 5mm at either end and I reckon I'd need about 3-4mm to achieve a 19 degree advance.

I had tried filing the points cam heel down a couple of mm but it didn't seem to make a lot of difference. I also narrowed the points gap to 0.3mm but that didn't make a lot of difference either
I wasn't suggesting that you elongated to reach the desired firing point, rather suggesting that elongating them somewhat would gain you some more adjustment and that adjusting gap could also gain you some also, however, points cam is still an issue that would be best reviewed too.

I hope you get it sorted.

Adam

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