R

rwarre

Well Known Member
So I sent my slick mags in for the 500 hour inspection, no problems getting them off. When I took them off, I rotated the prop until the 25 degree mark was at the split in the case. However, I used the mark on the outside(next to the spinner) of the starter ring and not the inside. My question is when I put the mags back on should I align the timing mark with the starter hole or leave the prop in the present position. I understand about using the slick pin to hold the gears in place, but I didn't want to screw anything internally on the engine. Thank Randy
 
rwarre said:
until the 25 degree mark was at the split in the case. However, I used the mark on the outside(next to the spinner) of the starter ring and not the inside.
Click to expand...

This mark lines up with a pin you insert into a hole in the starter, NOT the crankcase split.
 
Also, you cannot time close enough just by placing the prop at the mark and sticking the mags on. That's really just to get you on the correct tooth. You need to install the mags then use a timing light or else yo uh may wind up quite a few degrees off.
 
Slick Timing

Randy: You can use either set of timing marks to install your mags. I like to mark the front side of flywheel tooth that lines up with the 25 deg mark on the back side of the flywheel. This way you can stand in front of the engine and line up this tooth with the crankcase split. If you use a black sharpie your timing mark will likely be there next year. Using the 25 deg mark on the front side of flywheel and lining it up with the starter hole works fine and does the same thing. This will get you in the ballpark to install the mag and a timing light will allow you set it where it needs to be. DO NOT turn the prop with the timing pin in the mag. DO use the correct gaskets, lock washers and torque. Send me a pm if you need assistance.

Don B
RV 9 Engine Build in Progress
A&P, IA ect.
 
Last edited:
I saw a variety of answers on this thread that conflict. So for clarification, when installing the magneto should the engine be set to TDC or 20/25deg (per eng spec) using the timing marks aligned at the starter pin hole?
 
Bill.Peyton said:
The link is to an article on how to install a magneto.

http://www.aviationpros.com/article/10383985/magnetos-installation-tips
Click to expand...

I think this is one of those cases that the more you read, the more one gets confused.

The article on the second page indicates

"slowly continue to turn the prop until the timing mark listed on the engine data plate lines up exactly with the split line on the top of the crankcase for Lycoming engines or the split line on the bottom of the crankcase for Continental engines. "

Are most Lycomings timings are done based on the split line on the case and fewer are based on the small hole onthe starter?
 
Mag tiiming

Randy,
Check for compression on #1 cyl, line up the mark with the hole in the starter. Then mount the mag with the pin installed for the rough timing. For final timing I use a piston stop and a digital protractor mounted on the spinner. Then do the final timing with a buzz box. You are welcome to use my equipment. I'm at Platte Valley Airpark in Hudson, Colorado. I would also be glad to fly up and assist this weekend if the weather cooperates.

Brian Scollon
 
There are two sets of timing references. "front" or "back"...

If you want to do it from the front then the marks on the propeller side of the "flywheel" will allign with the pin in the starter. Conversely, you have the same set of timing values on the engine side of the "flywheel" that line up with the top splitline of the case. If you see 25 degrees at the starter pin with the front marks, then you will also see 25 degrees at the top splitline with the rear marks.

One of my engines does not have an aircraft starter, so there is no reference from the front side. In that case, I use a laser level that projects a straight line and mount it to the boot cowl so it lines up with the engine case split. Of course, it will also cast a line on the flyweel making it easy to set.
 
Last edited:
You must log in or register to reply here.