What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Check timing before first engine start?

jcarne

Well Known Member
Patron
Hello, I had an A&P tell me it might be a good idea to check the timing before starting the engine for the first time in a couple of days. This is a new engine from Lycoming that was run on a test stand for an hour. Is this necessary? Seems pointless to me. FYI it has standard slick mags. Thanks!
 
If you have a buzz-box, it takes 1 miute to check it, so why not. If you don't have a buzz-box, get one. It is hard to maintain your own engine without one.
 
Timing

Absolutely verify that’s it’s correct before first start. I got stories.

Don Broussard A&P-IA-ATP
RV9 Rebuild in Progress
57 Pacer
 
I checked mine on a factory-new O-360. I think the mags were installed so they looked pleasing to the eye. The way they were installed clearly had nothing to do with engine timing! Their timing was "pin the tail on the donkey" accurate!
 
Thanks for the replies guys, I figured 30k would buy a properly timed engine. I guess I should have questioned that when I realized 30k doesn't even buy you an overhaul manual, or parts manual, or almost any documentation. I think Lycoming realizes they have the market cornered in a large way... I digress. I have a mag timer/sync. on its way, should be here tomorrow so I can get things ready for first engine start this weekend.
 
Thanks for the replies guys, I figured 30k would buy a properly timed engine. I guess I should have questioned that when I realized 30k doesn't even buy you an overhaul manual, or parts manual, or almost any documentation. I think Lycoming realizes they have the market cornered in a large way... I digress. I have a mag timer/sync. on its way, should be here tomorrow so I can get things ready for first engine start this weekend.

Let us know how yours checked out when you done.
 
Thanks for the replies guys, I figured 30k would buy a properly timed engine. I guess I should have questioned that when I realized 30k doesn't even buy you an overhaul manual, or parts manual, or almost any documentation. I think Lycoming realizes they have the market cornered in a large way... I digress. I have a mag timer/sync. on its way, should be here tomorrow so I can get things ready for first engine start this weekend.

You going to need it anyway.

Don Broussard
RV9 Rebuild in Progress
57 Pacer
 
It's my understanding that they do the run-in with shop magnetos and install whatever ignition you selected before they bag the engine for shipment. Chances they'll be timed correctly are just that, chances.

Ed Holyoke
 
FWIW, I did a full check of the my factory new M1B timing prior to first start (sounded like a good idea, and I was curious to see!). Both sides were dead nuts on 25 deg, per the data plate. I was happy to see this, and happy to be able to verify this myself with my buzz box. The biggest challenge was to identify the "dot" on the SkyTec starter housing .. it was there, but looked like an imperfection on the plating until I squinted the right way. Cross checked with the case split line and all is good now.

Interesting to hear, though, that the factory test was done with factory mags, and mine were slapped on after. I'd be TOTALLY HAPPY if they ran the shipping mags for a hour-ish before putting it in the crate.
 
Last edited:
I'll certainly let everyone know how they are timed once I get the tool tomorrow.

FWIW, I did a full check of the my factory new M1B timing prior to first start (sounded like a good idea, and I was curious to see!). Both sides were dead nuts on 25 deg, per the data plate. I was happy to see this, and happy to be able to verify this myself with my buzz box. The biggest challenge was to identify the "dot" on the SkyTec starter housing .. it was there, but looked like an imperfection on the plating until I squinted the right way. Cross checked with the case split line and all is good now.

Interesting to hear, though, that the factory test was done with factory mags, and mine were slapped on after. I'd be TOTALLY HAPPY if they ran the shipping mags for a hour-ish before putting it in the crate.

Wow thanks for posting that. I had an A&P doing the tech visit and he couldn't find a mark on the starter, neither could I. I wasn't really looking that hard so I'll check it out again. It would certainly make life easier than trying to use the case split line.
 
Okay, here are the results.

First, I never found a timing mark on the starter. So I located TC using a long drill bit. You can see that it lines up pretty well with about the left side of that starter bolt/rod. If anyone can point out the timing mark on this starter I would love to hear it. I also verified these timing marks with the top of the engine using the split line (pics below). Although I have less faith in the top of the case timing marks due to the contraption I had to make which could very well have a little error/slop in it.

Here is TC.

20200917_190404 by Jereme Carne, on Flickr

Here was the left mag at approximately 28.5 degrees using 2.4 degrees per tooth on the ring gear.

20200917_191102 by Jereme Carne, on Flickr

Here is the right mag at approximately 25.5 degrees. (take into account the position of the camera is slightly changed from the last pic) Also verified on the top of the case.

20200917_191131 by Jereme Carne, on Flickr

Left mag on top of the case.

20200917_193540 by Jereme Carne, on Flickr

And right mag.

20200917_193624 by Jereme Carne, on Flickr

In the end I corrected the left mag to match the right one. Timing was easy as you all mentioned but it certainly took a fair amount of trial and error to get them mags synced.

Would love to hear any feedback if you all have any. Thanks for your help and I'm glad I asked you guys as that left mag was a fair bit off! (searching the forum will reveal these engines running okay in the 29 degree range but it certainly isn't right/ideal so I'm glad it's fixed)
 
Not to start a thread drift but in my case I'm running one Lightspeed and one mag. The Lightspeed timing displayed on my EFIS is in the low 30's BTDC and my mag is timed to 25 deg BTDC. Could I retime the mag to better match the LS timing?

My mag is just a standard one (no retard breaker or shower of sparks) and I use the LS for starting
 
Although I have less faith in the top of the case timing marks due to the contraption I had to make which could very well have a little error/slop in it.

I use a self leveling laser line projector to make using the engine case split line simple. I mount it above the engine and line up the laser with the case split and then can read directly to the back side of the starter ring. I make sure the laser plane is truly lined up with case split plane by checking that the laser also hits items on centerline that are not at the same height as the upper case split, like the centerline of the tach boss. Works great.
 
Not to start a thread drift but in my case I'm running one Lightspeed and one mag. The Lightspeed timing displayed on my EFIS is in the low 30's BTDC and my mag is timed to 25 deg BTDC. Could I retime the mag to better match the LS timing?

My mag is just a standard one (no retard breaker or shower of sparks) and I use the LS for starting

Have you checked the LSE timing with an automotive timing light (vacuum line connected/disconnected) per Klaus' instructions? When are you seeing 30*BTDC? idle, low MP, high MP, what RPM? You can also use the same timing light rig to check dynamic mag timing, just for kicks

I would not advise changing the mag timing from 25*

RmbgFX8.jpg
 
Last edited:
Do NOT change the mag timing to 30 as you will definitely overheat the engine, and perhaps cause some damage. The majority of electronic ignitions are timed at O DBTDC, and that is what makes the starting so much easier. After that, it is a function of M/P, fuel flow, and timing curves that define the actual ignition timing.

So, if you are seeing 30, you need to understand WHERE, as both in cruise at certain power settings and on the ground at idle, both times 30 could be OK.

Vic
 
Check engine timing

I bought a new YIO-360-M1B with my 7A kit. It came with the Slick mags installed. I checked the timing before engine start and it was set to 25 degrees as it should be. The engine ran great except that hot starts were a real challenge. Way worse than any other injected engine I have ran before.

After 400 hours I decided to do the 500 hour inspection on the magnetos and found that the E-gap was set wrong from the factory! I set E-gap according to the Slick manual and now my engine starts very easily hot or cold.

Obviously you can’t trust the factory experts to know what they are doing. I wish I had checked E-gap 400 hours ago.

Bill Wuorinen
RV-7A N237W
Osprey 2 N137W
 
Back
Top