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  #1  
Old 10-26-2019, 07:39 AM
roadrunner20's Avatar
roadrunner20 roadrunner20 is offline
 
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Location: Andrews, NC (KRHP)
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Default starter kickback on new Surefly installation

Need some suggestions on resolving my issue.

On keyed ignition startup... prop will begin start on prop rotation, then reverses slightly, starter re-engages with the grind. Stop
This happens on cold primed start about every second or third start

Here's my setup
left mag: replaced with Surefly, advance 25* timing set on dip switch, set on TDC
right mag; Slick impulse set on 25* BTC

Timing set on starter dot marking.
Engine Superior IO-360

Surefly suggested I look at the voltage at starter to insure > 10V
My starter voltage is 12.8/12.9 volts.

FWIW, I've checked & rechecked timing to above.
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  #2  
Old 10-26-2019, 08:10 AM
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bkervaski bkervaski is offline
 
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Can you describe your priming procedure?
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  #3  
Old 10-26-2019, 08:13 AM
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Quote:
Originally Posted by bkervaski View Post
Can you describe your priming procedure?
Half inch throttle. Full mixture. Prime 3-5 seconds. More like 5 secs if not flown regularly
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Old 10-26-2019, 08:17 AM
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bkervaski bkervaski is offline
 
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Are you pulling the mixture back out to start then feeding it in as needed but very slowly?

I’m asking because that kickback is what will happen with PMags if there is excessive leftover fuel in the cylinders on a failed start. The PMag continues to ignite both top and bottom plugs as the prop kicks back and if there is fuel it will try to keep going.

Feeding the mixture very slowly as it starts will resolve the condition I’m describing in the case of PMags.

You may be over-priming a bit as well, prime until you have positive fuel pressure vs a number of seconds.

Also, try 1/4 throttle instead of 1/2.
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Last edited by bkervaski : 10-26-2019 at 08:25 AM.
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  #5  
Old 10-26-2019, 08:35 AM
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Quote:
Originally Posted by bkervaski View Post
Are you pulling the mixture back out to start then feeding it in as needed but very slowly?
Mixture out on start. Moderate push to full on start. Most times, I'll get the kickback on just 1/2 prop turn

Quote:
I’m asking because that kickback is what will happen with PMags if there is excessive leftover fuel in the cylinders on a failed start. The PMag continues to ignite both top and bottom plugs as the prop kicks back and if there is fuel it will try to keep going.
That makes sense.

Quote:
Feeding the mixture very slowly as it starts will resolve the condition I’m describing in the case of PMags.

You may be over-priming a bit as well, prime until you have positive fuel pressure vs a number of seconds.
Thanks. I'm going to the airport now & will give that a try.

Otherwise, once running, it's very smooth & CHTs very stable
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  #6  
Old 10-26-2019, 08:40 AM
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Also, try 1/4 throttle instead of 1/2.

Surefly and PMag both have standard recommended start procedures but you may need to tweak a bit.
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  #7  
Old 10-26-2019, 12:04 PM
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Quote:
Originally Posted by bkervaski View Post
Also, try 1/4 throttle instead of 1/2.

Surefly and PMag both have standard recommended start procedures but you may need to tweak a bit.
Thank you Bill.
Looks like this has resolved the issue. I hope.
Apparently, you were correct in that I was way over primed.

I did 4 starts, following various down times and have had no kickbacks.

As you suggested, on my initial start:
1/4 throttle, prime until pressure. Stop.
On starting:
1/4 throttle, from idle cutoff, slowly enrich on engine start

FWIW, I've not been able to locate Surefly's start procedures in my paperwork or their website. Send me a url if you happen upon one.
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  #8  
Old 10-26-2019, 01:22 PM
Scott Hersha Scott Hersha is offline
 
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Another thing to consider is what prop you have. If you have a light weight prop, it might not have enough flywheel effect to carry it through the compression stroke. The newer versions of the Pmag software automatically retards the spark to 4* after top center when the start timing is set to TDC. This should prevent kick back. It sounds like you are fuel injected. If that?s the case, you shouldn?t need any prime at all to start the engine if it has been run in the last 2 hours or so. There?s plenty of fuel in the spider to get the the engine started. Leave the mixture in idle cutoff, crack the throttle, and hit the starter. When it fires, slowly bring the mixture out of idle cutoff. No boost pump needed. EI systems start the engine much leaner than mags. You can ?fool? the Surefly into starting at a few degrees after TDC and it shouldn?t affect the ?run? timing. After I installed two Pmags on my previous (RV8) airplane, we had two kick backs with a lightweight Whirlwind prop. The second one broke a few teeth off my starter ring gear. I reset the timing to an extra 2* after TDC. It started fine and I never had another kickback event.
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  #9  
Old 10-26-2019, 01:38 PM
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Quote:
you shouldn?t need any prime at all to start the engine if it has been run in the last 2 hours or so
Good point. On "hot" starts I don't prime at all. I just put my throttle at 1/4, mixture closed, start it and slowly feed in mixture.
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  #10  
Old 10-26-2019, 01:39 PM
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roadrunner20 roadrunner20 is offline
 
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Quote:
Originally Posted by Scott Hersha View Post
Another thing to consider is what prop you have. If you have a light weight prop, it might not have enough flywheel effect to carry it through the compression stroke. The newer versions of the Pmag software automatically retards the spark to 4* after top center when the start timing is set to TDC. This should prevent kick back. It sounds like you are fuel injected. If that?s the case, you shouldn?t need any prime at all to start the engine if it has been run in the last 2 hours or so. There?s plenty of fuel in the spider to get the the engine started. Leave the mixture in idle cutoff, crack the throttle, and hit the starter. When it fires, slowly bring the mixture out of idle cutoff. No boost pump needed. EI systems start the engine much leaner than mags. You can ?fool? the Surefly into starting at a few degrees after TDC and it shouldn?t affect the ?run? timing. After I installed two Pmags on my previous (RV8) airplane, we had two kick backs with a lightweight Whirlwind prop. The second one broke a few teeth off my starter ring gear. I reset the timing to an extra 2* after TDC. It started fine and I never had another kickback event.
Thank you Scott. Very Interesting.
I do only prime on cold starts.
And yes, I do have a light prop. A Catto 3-blade, 2006 model with no nickel leading edge.
I'll see how it goes & will consider the 2*.
I was beginning to be frustrated with the whole setup & considered going back with my Slick. This at least puts me on a path to some sort of resolution.
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