Powerplus Magneto Timing Help Needed

[1917PowerPlus]

I am not able to use the timing marks on my Bosch Mag-Dynamo and according to what I have read, the mag should be set so the points break at 9/32 BTDC on the rear cylinder (#1) in full advance. Does anyone know where it should be firing when it is in full retard? I currently have the timing control lever adjusted so when it is set to full retard, the points are breaking at TDC, is this correct? The motor is running nicely but the amount of adjustment I have available on the mechanical advance is minimal in this configuration.

Thanks,

Todd

[gharper]

First off, 9/32" seems like not much advance to me. I would be thinking more toward 3/8" or even 7/16", maybe someone with Powerplus experience has a better number. Yes, more than recommended in the day but we have much better fuels today which will allow more advance and still not knock, and give more power. We also tend to run these motors differently than back in the day. However, with more advance, the operator needs to practice Zen and the art of manual spark adjustment while riding. This requires the operator to become one with their engine and constantly adjusting the spark when the engine is at low RPM, especially when working hard, such as lugging around a corner in second gear or dragging a sidecar and then advancing as engine RPM increases. Think about it, this happens constantly in newer motors, it's just done automatically. It is imperative to good engine performance and long life.

As to where to set at full retard, not a big issue. The important thing is where it is set when advanced. Also the MOST important thing is to be absolutely sure the timing is set exactly the same on BOTH cylinders. Instructions from back in the day say to set timing to the rear cylinder and you're done. That asumes you have the correct mag for that motor and nothing has been altered, a rarity today! It may require some careful stoning of the leading edge of the points cam for one cylinder or the other to get them dialed in exactly the same. This can be a time consuming process but well worth the effort. Once that is done, let the fully retarded timing fall where it falls, it doesn't really matter.

If you are running a Bosch Mag-Dyno (DVAR I assume....) the points housing rotates to change advance and retard settings. There is a notch cut in the back of that ring that hits a pin in the case, this limits advance and retard. The size of the notch can be enlarged slightly if more advance or retard is needed (affecting both cylinders equally). Be careful, it's easy to enlarge, but not to make smaller!

Good Luck!

Gene

[1917PowerPlus]

Thanks Gene. I have my Bosch Mag-Dyno adjusted so full retard is TDC, is there any advantage to going beyond, past TDC? I think I will adjust my timing gear a tooth or two to provide more advance capability since I’m currently hitting the stop pin at 9/32 TDC when full advance.

Todd

[gharper]

Todd,

No advantage to retarding the spark past TDC other than making it backfire real loud when coming down a hill, or if you're trying to win the slowest idle competition! Actually, it probably won't even run much past TDC.

Gaining a bit more advance will make a big difference in performance and that's where I would spend my efforts. You can live with 7/16" advance if you save that for high RPM use and adjust accordingly as you ride. Again, I cannot stress enough how important it is to manually retard the spark as engine load increases at lower RPM. Otherwise, the engine is trying to compress an explosion, and it isn't good on the bottom end, or the cylinders! Lugging an engine with too much advance is very bad, but running at high RPM with lots of advance is good, but not too much.....

Having ridden old bikes with sidecars and 3 speed transmissions in the Rocky Mtns. all my life, it is second nature to be adjusting the timing every time I run through the gears. It's amazing how performance is affected by doing that. Just remember, the lower the RPM, the more retard is needed, as engine RPM picks up, ease the timing forward, you can feel the difference. For example, 3 speed gear splits are very wide, so accelerating up a hill loaded with sidecar and passenger is hard work. Rev the engine up as high as comfortable, then grab a gear as quickly as possible. Get back on the throttle and retard the spark about 1/2 way and adjust back and forth a bit to find the perfect spot, it will be very obvious. It will pull much better than leaving it fully advanced. Then as RPM increases, slowly advance the timing. Pulling long steep grades is a good example of how important perfect timing is under load. I will open the throttle until doing so does not make any difference in acceleration and hold it there, that may be only 3/4 open. Then gently retard and advance the timing until max power is developed and hold it there until RPM starts to pick up, then slowly advance. That's the place where everything is the happiest. Maybe envisioning a centrifugal advance would help, at low RPM, timing is retarded, as RPM increases weights move out and advance the timing, so it is constantly changing with RPM, automatically.

Remember Grasshopper, Zen and the art of manual spark adjustment must be practiced every day to be a master!

Gene

[1917PowerPlus]

Thanks again Gene, I appreciate your input. Yesterday, I made a single tooth adjustment with the timing gear and that put me spot on. Full retard is just past TDC and with a minor adjustment, I was able to set it to TDC and full advance is just under 1/2 BTDC. She seems to really like the change, idle is nice and good Power with no backfire, took her out for a late lunch today.
Todd
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[gharper]

Very good Todd!!

Now practice your Zen.........

[exeric]

My old buddy Marsh Lantz taught me to always retarded the spark on Indians, and Harleys when going around corners, idling, or just putting around. He gave the same advice Gene did, but not as diplomatically

[1917PowerPlus]

Thanks for the input guys, just waiting for the weather to break so I can get her out and practice my zen. Anyone have any leads on a 1917 VA. MC tag?

Todd