Lycoming O-360 kick back when cold

jd21476

jd21476

Line Up and Wait
Joined
Jan 17, 2018
Messages
701
Location
San Diego, CA
Display Name
Display name:
jd21476
I had this happen twice so far and I have only owned the plane for two months. When I crank the engine it seems to suddenly have a kick back and the starter disengages. I let it sit for a minute and the she starts and runs fine. It did it when I tried to start her when it was 27 degrees out when I bought her in Idaho and the. She did it tonight and its almost 55 degrees in Socal.

What causes this and is it harmful or fairly common?
 
which start method do you have? slickstart?
 
When it starts, does it normally fire off on release of key?
 
That happened to a friend of mine caused by (he thinks) a weak battery. In his situation, it took a chunk of his starter case off.
 
Starter disengaging? Sounds like it's kicking forward, not back.

If it's kicking in reverse, you might have a bad ignition switch. That switch will shut off the non-impulse mag during start so that it can't fire at the advanced position, something that would cause kickback.
 
retpd2001 said:
That happened to a friend of mine caused by (he thinks) a weak battery. In his situation, it took a chunk of his starter case off.
Click to expand...
Been there, done that. Kickback is not condusive to long starter life. @jd21476 get it figured out, as you've probably been lucky so far.
 
I am going to have my mechanic look at it. My assumption is that the starter is kicking off. Once it starts she runs just fine.
 
I've had this happen a couple of times with the Luscombe on colder days. Fortunately the starter was not damaged and all five fingers are intact.
 
Doug Reid said:
Best answer.
Click to expand...

Depends on the system. If it's an SOS, timing could be fine, but the advance points aren't being grounded either by the switch, broken p-lead or something else. The OP never told us what system he has.
 
If it's a timing thing you risk this. In this case the Skytec starter survived.

7068F695-B55F-4F4B-9987-A39AB436798B.jpeg
 
Chip Sylverne said:
Depends on the system. If it's an SOS, timing could be fine, but the advance points aren't being grounded either by the switch, broken p-lead or something else. The OP never told us what system he has.
Click to expand...

Still a timing issue....whether sos or impulse coupling...both should fire near TDC on startup.
 
Since it's intermittent and happened when it was cold my guess is the impulse coupler. Sometimes they get a bit gummed up and especially in cold weather with 100W oil the shoes stay in and don't catch the pawl (or whatever it's called) Result is the plugs fire at 25 deg advanced and you get the kick-back. Could be that the non-impulse mag is not getting grounded by the ignition switch as Dan said but I think then it would tend to happen all the time. You can check this when it's cold, before starting, with switch off turn prop by hand and listen for the 'click' of the impulse. Solution is to have your mechanic do a 500 hr on the mags and clean up the impulse coupler.

To answer your question: yes it's harmful. Get it fixed.
 
Silvaire said:
Since it's intermittent and happened when it was cold my guess is the impulse coupler. Sometimes they get a bit gummed up and especially in cold weather with 100W oil the shoes stay in and don't catch the pawl (or whatever it's called) Result is the plugs fire at 25 deg advanced and you get the kick-back. Could be that the non-impulse mag is not getting grounded by the ignition switch as Dan said but I think then it would tend to happen all the time. You can check this when it's cold, before starting, with switch off turn prop by hand and listen for the 'click' of the impulse. Solution is to have your mechanic do a 500 hr on the mags and clean up the impulse coupler.

To answer your question: yes it's harmful. Get it fixed.
Click to expand...
Slick Start,, doesn't have impulse couplings.
Even if they were used, that happening is very remote.
Next chance you get, snap a mag and see how strong that spring is..
 
jd21476 said:
Im not sure which system I have. Im fairly new to the plane.
Click to expand...

When you turn the key and the engine is cranking, do you hear a buzzing sound coming from under the panel?
 
My mechanic is going to look at it this Friday when I get back in to town.
 
jd21476 said:
Im not sure which system I have. Im fairly new to the plane.
Click to expand...

What kind of plane is it? I don't see where you've posted that information anywhere. The type of airplane isn't an absolute way to determine what type of starting system you have but it can sure help narrow things down.
 
Tom-D said:
...Next chance you get, snap a mag and see how strong that spring is..
Click to expand...

It's not the spring Tom, it's only gravity that causes the counterweights to extend and catch the pin. As soon as the mag begins to spin the counterweights retract and no longer make contact with it.

Anyway, I didn't see that he had a Slickstart so this is all irrelevant.
 
Silvaire said:
It's not the spring Tom, it's only gravity that causes the counterweights to extend and catch the pin. As soon as the mag begins to spin the counterweights retract and no longer make contact with it.

Anyway, I didn't see that he had a Slickstart so this is all irrelevant.
Click to expand...
if it isn't the spring, see if it works when the spring is broke.
 
It isn’t the spring that causes it to not catch the pin, it’s just a gummed up counterweight. If it doesn’t catch the pin when you crank it over it doesn’t work even if it has a perfectly good spring and the plug fires at the advance setting that the mag is timed to. That’s what causes the kickback.
 
Silvaire said:
It isn’t the spring that causes it to not catch the pin,
Click to expand...
What ? think you best review your basic theory of a impulse coupling.
If the spring is broken it doesn't catch the pin. it will not fire, simply because the rotor is way out if time, and does not have any energy stored in the mag.
remember if the coil is not energize until the spring is unloaded as the spring is released.
 
The spring has nothing to do with the flyweight catching the pin. It does that because of gravity. When the toe of the flyweight catches the pin it stops the rotor from turning. The outer body continues to turn, winding up the spring until it hits the trigger ramp at the heel of the weight which then pivots and releases from the stop pin. The spring tension then causes the rotor to snap back to it's normal position. The centrifugal force causes the flyweight to retract the toe so it doesn't catch the pin anymore. If the spring is broken the toe will still catch the stop pin and will still release but it won't snap back to the advanced position. It will be stuck at the retarded position or somewhere in between. It might start and idle okay but you won't get any power. I don't think it will cause it to kick back though, that happens if the toe doesn't catch the pin so the rotor never gets retarded and the plug fires at the advanced position.

Both of my planes have Bendix mags with impulse couplers. I've had them apart plenty of times and know exactly how they work.
 
I think I figured it out and its probably my own fault for not reading the PoH cover to cover when I bought it. I finally got around to reading the entire POH and it says under start up procedure to start the engine on the LEFT mag and then go to BOTH. After do some research as to why this is, it looks like it retards the timing on the LEFT and that prevents kckback.
 
jd21476 said:
I think I figured it out and its probably my own fault for not reading the PoH cover to cover when I bought it. I finally got around to reading the entire POH and it says under start up procedure to start the engine on the LEFT mag and then go to BOTH. After do some research as to why this is, it looks like it retards the timing on the LEFT and that prevents kckback.
Click to expand...
 
jd21476 said:
I think I figured it out and its probably my own fault for not reading the PoH cover to cover when I bought it. I finally got around to reading the entire POH and it says under start up procedure to start the engine on the LEFT mag and then go to BOTH. After do some research as to why this is, it looks like it retards the timing on the LEFT and that prevents kckback.
Click to expand...

It’s because the left mag has the impulse coupler. I think most of us were assuming you had a keyed ignition which automatically grounds the right mag when you go to start. You apparently have a separate mag switch (or switches)
 
I presume you have Key Start Ignition?

Normally in START the Right mag is killed by grounding

To do this a jumper is required on the Ignition Switch.

Without the jumper you will have a weak advanced spark.

Easy to check with a timing light
 
Some ( not ALL ) Bendix & Slick Mags actually have 3 Springs.

The large Spring fires the Impulse.

The 2 smaller ones ( if equipped) assist in Pawl Engagement.

Failure to engage the Pawl will give you a weak advanced Spark.

A magnetized Coupling will do the same.
 
jd21476 said:
I think I figured it out and its probably my own fault for not reading the PoH cover to cover when I bought it. I finally got around to reading the entire POH and it says under start up procedure to start the engine on the LEFT mag and then go to BOTH. After do some research as to why this is, it looks like it retards the timing on the LEFT and that prevents kckback.
Click to expand...

So you have a push button starter, not a keyed ignition switch?
 
You must log in or register to reply here.
Back
Top