From:Gene Harper
Subject:RE: Ignition timing SPECS.... Date:Mon Feb 21 00:27:01 2011
Response to:3322

I don't have a Henderson, so I don't know the details on them but do have early Vtwins. Just started up my 1919 Excelsior after 14 years of accumulating the right parts, including the correct Midco generator/ignition unit. It starts up incredibly easily, runs very strong, but havn't heard a single ping or stumble and it will idle down slower and smoother than a 45 degree V twin ought to. The secret is to set the timing as far advanced as possible, without creating any pinging and set the timing on each cylinder. You will find that there is always a difference from one cylinder to the next, either because the points cam is worn in some place, or they were not cut accurately from the beginning. Set the timing on one cylinder, then check the next. It takes lots of time, but hand dress the leading edge of the cam that is firing late until it matches the early (correct)cam. Max Bubeck told me to do that on my 24 chief and I thought he was full of hot air, but he was right! It makes all the difference in the world!

The X book says to set the timing at 3/8" BTDC and the Midco book said 5/16" BTDC. I've found that for my altitude in Denver (mile high and above) and the type of riding I do, that is not enough advance. I was shooting for 7/16" BTDC when I set it up. When all was said and done, it wound up being .410" BTDC on the front and .408" BTDC on the rear, with the control fully advanced. The advantage of a manually controlled spark advance is that you can adjust it as you ride to suit road conditions and is essential if dragging a sidecar and passenger along in hilly country. Remember that the higher the RPM, the more advance it needs, up to a point of course. So, set the timing with the mag fully advanced and go a bit beyond the book specification. This will allow plenty of spark advance potential and can be dialed in as you ride. Use sound and feel to dial it in.

Not a specific answer to your specific question, but hope it is useful information.

Gene Harper

Just wondering if anyone out there actually figured out the ignition timing "specs" like best idle timing in degrees (B?)TDC and full advance in Degrees BTDC rather than setting up using the age old static (and oh so accurate....) method decribed? I am guessing something like 5 BTDC to 20-25 BTDC (whatever the particular mag used adjusts)

Thanks in advance, Dave