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Author Topic: Points Gap Adjustment Screw Size?  (Read 204 times)

patentgeek

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Points Gap Adjustment Screw Size?
« on: June 10, 2019, 05:46:21 pm »
What are the specifications for the screw that is used to adjust the points gap?

Mine appears to be an M4 x 0.75 x 4L (diameter x pitch x length), but Greg Bender's site indicates it might be M3.5 x 0.6 x 4L.

http://www.thisoldtractor.com/moto_guzzi_loopframe_distributor_points_to_points-plate_hold-down_screw.html

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banquo

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Re: Points Gap Adjustment Screw Size?
« Reply #1 on: June 10, 2019, 08:47:03 pm »
I could remove mine to see, but as you've already done that I'd be inclined to go with your own measurements.
No reason why the loop screw should be the same as that for the NF really (or is there?).
No way the major diameter of a 3.5mm would be as large as 4mm, so M4 sounds right, but standard pitch is 0.7mm, not 0.75mm...

patentgeek

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Re: Points Gap Adjustment Screw Size?
« Reply #2 on: June 10, 2019, 09:32:04 pm »
The points plate adjustment screws are M4 x 0.7.  When I tried to install one of those in the points gap adjuster screw hole, it felt like the wrong thread size.  So I compared the points plate adjustment and points gap adjustment screws to a couple of dies, and the points plate adjustment screw matched up with M4 x 0.7 and the points gap adjustment screw matched up with M4 x 0.75.

Of course a previous owner could have substituted a non-stock points gap adjustment screw and effectively "re-cut" the threads.  So hard to say whether my setup is original or not.

banquo

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Re: Points Gap Adjustment Screw Size?
« Reply #3 on: June 10, 2019, 10:03:50 pm »
Yes, that's always a problem on old bikes, and especially in the US, where someone's likely to have tapped to suit a UNC size. I spent ages last week trying to source a bolt to hold a tie-down in a Ford Transit van, eventually deciding it must be an M11 non-standard fine thread, only to discover it's a seat belt mount, and seat belt mounts are 7/16" UNF for some bizarre and historical reason....
« Last Edit: June 11, 2019, 10:27:12 pm by banquo »

patentgeek

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Re: Points Gap Adjustment Screw Size?
« Reply #4 on: June 11, 2019, 12:28:11 am »
Ha!  I've run into the same seat-belt bolt issue in a late 80's Honda automobile.

Rear passenger pegs on some vintage Euro motorcycles are the same - - - the entire bike is metric except for the passenger peg mounts.  Very weird.
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monohorizontal

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Re: Points Gap Adjustment Screw Size?
« Reply #5 on: June 11, 2019, 09:34:32 pm »
hello i have a motor on the workbench i just watch the screws do M4x0,9 but the original screws are shorter

patentgeek

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Re: Points Gap Adjustment Screw Size?
« Reply #6 on: June 11, 2019, 09:49:55 pm »
Quote
hello i have a motor on the workbench i just watch the screws do M4x0,9 but the original screws are shorter

The question isn't directed to the length but rather pitch.

I double checked my factory parts manual and couldn't find the points gap adjusting screw listed anywhere.

banquo

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Re: Points Gap Adjustment Screw Size?
« Reply #7 on: June 11, 2019, 10:31:35 pm »
Well; M4 x 0.7 is the coarse and M4 x 0.5 is the fine, so unless it's been retapped, should be one of those, and almost certainly the coarse thread...