Timing different from side to side

[chasbmw]

Mellville is a bicycle mechanic among other skills. He won't break his cam nose.

If one did manage to break the teensy fine threaded end of the cam, would a crank fired ignition be a workable fix?

As for the gloves, I have developed a taste for Held gloves and now buy them used. Thing is, evidently, I have longer than normal thumbs and most brands absolutely KILL my right thumb after a ride of any length. Held gloves work in that regard. Plus, all those nail head looking rivets look medieval.

Chuey

A crank fired ignition would be a very workable fix, no timing fluctuations due to either bends in the crank tip or a worn timing chain.

[barryh]

Motorworks don't sell to the US, they cite insurance liability costs.

However Motobins will sell to the US, and provide by all accounts a fast postal service, get a quote including postage.

http://WWW.motobins.co.uk

According to the website Motorworks changed their policy in January and do now ship new parts to North America but not 2nd hand or reconditioned parts.

http://www.motorworks.co.uk/vlive/AboutUs/index.php

[melville]

So I didn't get to it that weekend, but another solution was in the works (Thanks Blitz!!).

First, how about that cam nose? DI all set up:



Sorry about the glare:



Running it around several times got me to a deviation on the order of .005". As point gap is barely 3X that, I think that would explain a lot of my problem. Meanwhile, I've come into a Dyna ignition at a spouse approved price (again, thanks Blitz!). Looking at it and the Dyna instructions, I come to realize that it's extra special, as it's a D35-2 for dual plug. I'm not dual plugged presently, but if the heads need work someday, it's on the list. Meanwhile, how to accommodate the wiring? From the directions, it appears that rather than two 6 volt coils in series, it instead wants two 12 volt coils in parallel. I have some of those, genuine German Bosch:



And they fit the OG coil brackets! So I spent an afternoon doing the install and fussing over the static timing, then reinstalled the tank and fired it up. Timing is now the same on both sides per the strobe, at idle and at "F." The ride test to come on Moto Wednesday.

Heeding all the warnings, I am packing the old points ignition and wiring to make it work with the parallel 12V coil setup into my toolkit. I did the same thing for my Kombi when I converted it to a Pertronix setup 10 years ago. It really sets the tone, and makes the new ignition straighten up and fly right, knowing it can be replaced at any time.

[melville]

Moto Wednesday was called due to weather and replaced with Moto Thursday this week. I'm happy to report that the Dyna slices, dices, and fillets like nothing else. Fired right up, idles smoothly, no ping going up a 6% grade at an indicated 75 (had to back off as I was catching up to CHP) in 5th, and a vibe that ran through the handlebar at ~3200rpm (round town in 3rd gear) with the points is now conspicuously absent.

Again, many thanks to Blitz!

[mattcfish]

Great news. Did you straighten the nose, or compensate for the error by adjusting the two pick-ups on the Dyna?
Not sure about using two 12 volt coils. I think the Dyna Dual brown coils (used with the dual plug system) were 6 volt each with a 1.5 ohm impedance.

[Ken in Oklahoma]

I posted about this some time ago. As far as I know the idea is untested. Here goes:

I see nothing wrong in principle with wiring two coils in parallel, each coil firing one plug. The objection that I've heard is the concern that coils are going to be electrically mismatched. And that one will rob the other of current. Certainly, for simple resistors, there is a way to calculate just how much current will pass through each unequal resistor. Similarly one would never wire two solid state (semiconductor) diodes in parallel, expecting to double the current carrying capacity. The diodes will be just enough mismatched that the current distribution will be unequal. (The exception would be certain high current diodes which use diodes taken from the same "mother" wafer, in which case the manufacturing environment is virtually identical and so the performance is virtually identical).

So here's my thought experiment about wiring two coils in parallel. The premise here is that both coils are operating to specification. The positive sides of the two coil primaries are tied to the same 12V supply. And the negative sides of the coil primaries are tied to the same (high side) of the points. So, while the points are closed both coils "see" the same negative battery post. Thus the voltage across both coil primaries is identical.

Now open the points. Suddenly the voltage across the coil primaries drops to zero. The magnetic field in each of the two coils starts collapsing, and in the process the collapsing magnetic field induces a voltage in each of the coil secondary windings. That voltage rises until there is enough voltage to arc across the two sparkplug electrodes, firing whichever cylinder is coming up on compression.

But there is another element to the ignition process and that is the capacitor (condenser) across the points. That capacitor does a couple things, first "aborbing" the charge which appears across the points as they are opened, and secondly feeding that charge into to the coil secondaries which wil modify the characteristics of the voltage rise in the coil secondaries. My thoughts to that is that there is a wide latitude to the size of the capacitor required. Probably not an issue. And if it were an issue it could be addressed by paralleling two capacitors together.

So there you go. My thoughts. I could be wrong, and if so showing me where will make me smarter than I was when I wrote this piece.

Ken

[melville]

Great news. Did you straighten the nose, or compensate for the error by adjusting the two pick-ups on the Dyna?
Not sure about using two 12 volt coils. I think the Dyna Dual brown coils (used with the dual plug system) were 6 volt each with a 1.5 ohm impedance.

I did not lay hammer to the cam nose but instead worked the Dyna bits about. There are three spots to change timing with the Dyna--one is the position of the magnet on the advance mechanism--it has 360 deg adjustment, as you might expect. Next is the plate, which has about 15 deg to work with, and last are the pickups which have 10ish deg each.

12V 3 ohm was per Dyna (see the lower setup):

http://www.dynaonline.com/skins/downloa ... /D35-2.pdf

The difference in my application is that I was using Bosch single output coils.

[mattcfish]

http://www.dynaonline.com/skins/downloa ... /D35-2.pdf

Yeah, you are correct. looks like the D35-2 is designed to work with the Dyna "Green" dual output coils. They are 12 volt and 3ohms each. You should be golden then.
Since you can wire a D35-1 to do dual plugs using the brown coils...I wonder what the advantage of the -2 is?