Ignition timing

[doghead]

I'd like to use my timing light to set the timing (fine tune)on my mule(2 cyl).

I just did a points inspection(set at .015") and timing inspection(after recently reading the "black magic" posts), and wondering if my "V's" were aligned or not. They were and it clicked at about 28 degrees!

I've read the"you want to hear it snap between 28-18 degrees". That required mine, to set the mag gear "V" one tooth to the "right" of the cam gear(opposite of what I've read else where).

If I use a timing light, where do you set the timing(degrees) and at what rpm? Is timing it by "snap or light" between the 28 and 18 marks all this is needed? Should I just ignore the gear mark settings?(it kinda bugs me)

I've read Charlie/ChuckW, Bill Watson and NickD's info on the web. I did not see anyone say they set the timing with a light at a certain RPM(the TM for the generator 2AO42 says Max RPM, but it has different timing marks).

 

[doghead]

Here's a crude visual of what I ended up with, to get it to snap between 28-18 degrees.

 

[Charlie]

I've had a few engines that I had to play around with the gear timing, only one that required the offset to the right.
You want both the "click" and the timing light to show you a mark between the 28 & 18 deg mark.
I use a timing light at idle. There's no advance in the magneto, so it does not matter what RPM you use. I made the adapter shown below for my light, and I use an induction pickup.
The real question is, how does your mule run? Some engines need the one-tooth-ofset in order to get the mag to fire between the 28 & 18 deg mark, some must be set mark-to-mark. I use the "click" method to determine which way to set the gear timing, and then use my timing light to "fine-tune" the mag setting.
I've been surprised at how much better most mule engines run with the one-tooth-ofset magneto timing, but there have been a few that just did not like it at all!

 

[Squirt-Truck]

DH, We always used a test light to set the timing on mags with impulse couplings.
Power the light, and when the points open the light goes off, that is the timing point and where the coil fires. The impulse snap is very close to that point but not exact. The impulse has to start before the points open and continue through the spark sequence.

 

[doghead]

Thanks for the replies. I will try to adjust the timing with a light, and see how much I can adjust it(either way).

I think it runs a bit less responsive and seems to have less top end power. I may need to re time the mag and set the marks aligned.

Before I disassembled it, it definitely ran well (power wise) and the click occurred just above the 28 degree mark. As it is now, It is snapping between the 28 and 18 and seems a bit sluggish, compared to how it was.


One of the issues I've had that led me to this timing/points inspections was, I could hear a very slight "popping" coming from the intake mushroom. It's an echoed sound coming up out of the frame tube, like it may have had a valve leaking. It has sounded this way about a year before when I had a carbon fouled sparkplug, and it lost power.

After all the timing stuff, it did not change any of that. Then as I went to drive it a bit, it suddenly smoothed out and the tiny/quiet/occasional popping sound went away.

I think I had a lifter or valve sticking possibly. I had replaced the oil filter housing last year, so I could use a screw on filter. At that time, I changed the oil and added a small amount of MMO.

I'll test with a light, and drive it some more and decide if it needs to be set before 28 degrees.

 

[doghead]

Just to be clear, the pic Charlie posted above, is the opposite side(offset), from where I set the timing mark to get it to snap between 28 and 18 degrees.

 

[Charlie]

Out of all the mules I have fooled with, I had one that drove me crazy. I finally set it one tooth to the right to get it to "click" between the 28 & 18 marks just like you did. The mule ran like crap, so I set it back mark-to-mark and it ran much better...never did figure that one out, but the owner has never complained of low power or anything....I think some AO42's just have Gremlins in them! Sometimes you have to beat them gremlins out with a BFH!

 

[doghead]

Today, I reset the magneto mark(V), to align with the cam mark(V). This is where it was to begin with.

I took a picture to show where it "snaps".

The short red mark is where I was when I made the adjustment, based on what I had read elsewhere.

It definitely runs better as it is in this picture(where it was to begin with). Much more crisp and responsive.


Thanks for your help.

 

[crorlo]

Can the magneto be installed in a 2 cylinder engine without removing the governor, as long as the impulse coupling clicks between the 18 and 28 marks after installing?

 

[doghead]

I already answered this in the other thread. We do not allow cross-posting, so please read and reply there.

 

[crorlo]

My engine is only running on cylinder #1. The other one is cold to the touch when the engine runs. Have replaced the mag, wires, spark plugs with all new hardware. Timed the ignition as per the above instructions, but still running on one cylinder. Then replaced the carburetor and fuel filter thinking it could be fuel. No avail. Any thoughts? Thanks.

 

[doghead]

Did you do a compression test on the bad cyl?

Both cyls share spark and and fuel. You have a problem with the bad cyl. Maybe a bad valve or rings or headgasket or stuck lifter.

Please ad your state to your info. It's a site requirement.

 

[crorlo]

Yes. Removed rocker arm covers. All valves opening and closing fully when turning by hand. Performed compression tests. All good and strong.

Engine is new, with 60 hrs. Only replaced old mag b/c is was hard to start, however, it ran well once its started. Started running bad after installing new mag.

On the new mag installation, I installed the mag gear to the left of the driving gear as posted here. The impulse coupling clicks between 18 and 28. I do not have a timing strobe light, but timed it with an magneto timing box (for aircraft, see picture). Points also opening at around 20, so I'm thinking timing is not the issue.

Noticed yesterday that cylinder is only cold at idle. It does fire some at higher RPM's, but erratic. Still much colder that the other cylinder, though.

Updated my info. Thanks.

 

[doghead]

Well, both wires spark at the same time. So it must be the wire on that side or the plug.

Are you sure the intake manifold is not plugged with something? Or is the exhaust plugged?

 

[crorlo]

Boroscoped the intakes. They are open and clean. Also tested the wires with a high voltage cable tester. Both checked good. Will check exhausts. Thanks.

 

[Charlie]

What plugs are you running? May need to go to a hotter plug, like an Autolite 2226 or Champion XMD21.

 

[crorlo]

Autolie 2223. Have ordered 2226's, and should have today. Thanks.

C

 

[Squirt-Truck]

Have you confirmed spark at the plug? Sounds like the insulator cap in the mag may have a crack on that connector. Like DH said, both cyl fire together there is no distribution.

 

[crorlo]

Yes. There is spark. The mag is new. Thanks.

 

[crorlo]

Problem solved: NOS magneto that has been sitting inside a box for 30+ years, does not mean that you should install right out of the box...

Opened up the NOS magneto, and cleaned points, and all electrical and ground contacts. Although sparking at ambient pressure, corroded points and contacts created too much impedance in the system to spark in the compression cycle for the #2 cylinder.

Also, hotter spark plug (as recommended here) seem to work better with this mule.

Thanks, All