Author Topic: BB points timing  (Read 577 times)

Online Scout63

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BB points timing
« on: September 21, 2021, 10:32:41 PM »
I can’t get the left side points plate far enough advanced to open the points before I run out of adjustment. New points on a rebuilt engine.  I think I installed the distributor right and the right side points adjust fine. I could file the mounting holes a bit.  Is this common?  Thanks. Ben
Ben Zehnder - Orleans, MA USA

Online Scout63

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Re: BB points timing
« Reply #1 on: September 21, 2021, 10:33:58 PM »
More info - 1979 G5 with original Marelli distributor and cam.
Ben Zehnder - Orleans, MA USA

Offline nc43bsa

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Re: BB points timing
« Reply #2 on: September 21, 2021, 10:45:59 PM »
You can't get both cylinders to time correctly with the correct points gap without modifying the points plate.  This Old Tractor has a tutorial on this modification, but it's also OK to set the timing by changing the points from the specified gaps.
1990 MilleGT

Offline Rich A

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Re: BB points timing
« Reply #3 on: September 21, 2021, 10:47:47 PM »
As noted, it's a "feature" of the BBs. See: https://www.thisoldtractor.com/moto_guzzi_tonti_distributor_dual_points_plate_modification_so_you_can_time_both_cylinders_properly.html

I recently switched to a Dyna ignition, and it has been great so far (fingers crossed).

Rich A

Wildguzzi.com

Re: BB points timing
« Reply #3 on: September 21, 2021, 10:47:47 PM »

Offline mtiberio

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Re: BB points timing
« Reply #4 on: September 22, 2021, 06:01:37 AM »
An alternative to modifying your points plate. Adjust the points gap to slightly out of spec. IIRC, you adjust the upper points (right cylinder or red wire) to a gap of .019" (3 over stock) and the lower points (left cylinder or green wire) to .013" (3 under stock). Then you time the right side by rotating the dizzy, and then you will be able to slide the mezzanine plate sufficiently clockwise to advance the left side enough to get the timing right on both sides. Dwell will be a bit messed up which you can get back with an ignition amplifier if it matters that much to you. Since this isn't a V-8, dwell isn't that important. I actually find it easier to make small adjustments in the timing via changes in the gap vs sliding the mezzanine plate. I also replace all the flat head screws under my distributor cap with tiny allen bolts (and washers if necessary). This way loosening, adjusting and re-tightening becomes much more deterministic.
« Last Edit: September 22, 2021, 07:20:06 AM by mtiberio »
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Online Scout63

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Re: BB points timing
« Reply #5 on: September 22, 2021, 07:09:54 AM »
Thanks everyone.  I thought I was going crazy. I even tried rotating the distributor shaft on the cam over a tooth and that didn’t work. Wonderful replies. Ben
Ben Zehnder - Orleans, MA USA

Online Scout63

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Re: BB points timing
« Reply #6 on: September 22, 2021, 12:46:13 PM »
I just spent an hour filing the points plate and still off by a little.  I ordered a Dyna III, which is what I should have done a year ago. Maybe I’ll sort the points later and keep disconnected as a roadside backup. Maybe I won’t.
Ben Zehnder - Orleans, MA USA

Offline guzzisteve

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Re: BB points timing
« Reply #7 on: September 22, 2021, 01:15:42 PM »
Once upon a time we had Marelli points and it was a beautiful world. Then aftermarket came and I did what Mike does. Mine were usually .017" & .013.  Bigger is better than smaller.
I just did a set last week that came out 17 & 17 and have no idea what had been done before I looked at it.
Not all points are the same, look in the 1st Tips book if you can even get that stuff these days
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