3W QS106 Kicking Back

[bob_nj]

I bought this QS new in April of 2003.
Broke it in on ashless for about 6 gallons and then went to synthetic.
Using 50:1, ignition on 6v.

I don't fly this engine much as it is on a backup 35% plane.

Last summer the engine starting kicking back while starting.
I mean it was kicking back hard.
I posted a thread, Garrett got involved and I sent the engine away to
be looked at. Before I sent it out, I tried a brand new ignition with
the same resutls. It still kicked hard.

Long story short, I got the engine back and it ran fine until
yesterday at the field.
I've been away in Iraq and have not flown the engine for about a year.
The engine was broken in again after getting it back last year and has not
been flown since then.
I was using a 28x10 Biela with good results after break in.

This weekend I wanted a little more zip and switched to a wood 26x10
Menz thin. It was neat because it gave me some instant throttle and alot
of slip where the 28x10 was grabbing. It was windy and I thought the shorter
diameter would be fun to try.
I flew the prop once and it seemed OK.
I leaned the low end a little for the next flight, and right after choking the
engine kicked back on my buddy and broke the Menz thin prop.

Had to switch back to the 28x10 Biela.
Since no one wanted to start for me, I started for the next 3 flights.
I decided to choke with the ignition off, flip four times, turn the ignition on and
then start. The next three flights I started the engine and it didn't kick.

At my wits end and a little paranoid at this point.
Anyone else had this happen to them?

I also run a 3W 140, and QS150 and like them alot.

Thanks for any input_bob

[3dubya]

Check the ignition timing mate, the prop boss key might of sheared and your timing is now out, and is always gonna be out cause boss is slipping under load. There is a little marker on boss you use when piston is on on top dead center which lines up with marker on case.

[bob_nj]

OK, so when the piston is TDC, there are some marks that should line up?

[3dubya]

Yer its best to have the header off so you can see piston. One magnet is for ignition the other is for ignition taco. The first magnet that goes under sensor is ignition, if its under magnet just past TDC its in the right spot, in this spot check for these other specific marks to line up. The boss might of only slipped a tiny bit. If you cant see any probs, id still pull the boss off, which Ive never done it myself yet. Its the first thing id look at for piece of mind on misfires.

[bob_nj]

Sounds like alot of stuff I don't want to deal with.

It it's that deep, it's time to take it out in the driveway and run over it...

[3dubya]

Anything mechanical can fail dude what ever the brand in R/C, LOL take up knitting maybe...

[bob_nj]

You are definitely right. I've been in this for over 30 years and have paid some dues.

This just makes me crazy though.
Don't get me wrong, I've done my share of tinkering in all aspects of the hobby.

I will mess with the things I know, and not mess with the rest.
From pop off pressures to making my own 40% wiring harnesses, It's been an
adventure.

This, this though makes me koo koo...

[Dan767]

If you have the low end on the rich side, or it's dripping wet when you choke it, it will kick back. I have the same engine, had the same problem. I have the scar to prove it. Leaned out the low end, and I don't start it flooded. If it is flooded, be sure the ignition is off, throttle full open, choke off. Flip 4 or 5 times to clear it. Throttle closed, no choke and you should be off and running.

[plane]

Bob, it's your new style ignition unit doing it. My buddy has two QS106's bought around 2003 and they both kick back hard. I'm guessing this problem has been resolved once and for all and the newest IIS ignitions are working properly.

[high alpha]

Send it back to AI and have the boys look at it,they are in NJ as well.

[bob_nj]

Plane, did your buddy send his ignition back?

If so, what was the result?

Thanks_bob

[plane]

He sent one of them back and Gerhard said it was ok. We remounted it and guess what? It still kicks back. I suggested to him that he deal with Bobby at Cactus but he hasn't done that yet.

I checked his motor thoroughly and the timing is correct.