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Elec. Advance versus Mech advance

Old 06-03-2006, 03:03 PM
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jw637362
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Default Elec. Advance versus Mech advance

I am interested in the difference between two terms Mech Advance and Elec. Advance.

1) What this means compared to coming from a Magneto application on a G-62 that I have now.

2) Does Getting a Mech Advance actually remove the Source coil and magneto or is that just on the Electronic.

3) Will I need a seperate battery for the ignition on a mechanical and what are the benefits of having either one.


Do you have a picture of a mechanical advance and electronic or diagram so I can way the differences, Pros & Cons

Thank you,
Jeff
Old 06-03-2006, 04:12 PM
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Antique
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Default RE: Elec. Advance versus Mech advance

Mechanical advance refers to the method of advance, both use an electronic circuit with a battery...The source coil and mag rotor are both removed either way....
Electronic advance reaches full advance at 4000 rpm, mechanical is linear with throttle movement to 28 degrees advance at wide open throttle..
Hard to tell the difference between the two...
There's a picture of the electronic advance on the Tom Pierce FW190 building thread in another forum here, or search for Tom Pierce....He's using a g62 lite electronic advance engine in his new FW190...
Old 06-03-2006, 05:27 PM
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Default RE: Elec. Advance versus Mech advance


ORIGINAL: RCIGN1

Electronic advance reaches full advance at 4000 rpm, mechanical is linear with throttle movement to 28 degrees advance at wide open throttle..
Hard to tell the difference between the two...
RCIGN1 - Well I think I asked the wrong question because you replied in Greek....[&o]

You have my engine there at your shop, I am debating the Mech advance conversion now that you have it, What will I gain from this conversion. Will I gain RPMS, torque, smoother running and starting. I am under the impression that you have smoother transistions with Electronic ignition, is this the case with mechanical conversion as well.

Pleae forgive my ignorance as I am only familier with the zenoah and magneto setup and can be hesitant on things at tiomes until I fully understand what is involved.
Jeff

Old 06-03-2006, 07:28 PM
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Default RE: Elec. Advance versus Mech advance

A magneto is an self powered electronic system.
What every body is calling an Electronic Ignition (EI) is a battery powered ignition system.
The magneto has fixed timing, the timing BTDC does not change with RPM. There are EI's that also have fixed timing.
For best performance the engine needs variable timing. less advance at lower rpm and maximum advance at full throttle. The maximum advance needed for max hp varies from engine to engine.
An engine does not care how the variable timing happens only about the amount. At idle and full throttle the mech adjustable timing and the automatic timing will be the same.
In the mid range they are a little different, not better or worse just different. Which one is for you depends on what plane your flying and how you are flying it.
90% of the fliers can't tell them apart.
Old 06-03-2006, 07:32 PM
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Default RE: Elec. Advance versus Mech advance

Jeff,
On an electronic ignition with either electronic or mechanical advance, you will see major improvements in ease of hand starting. Both will also idle lower & smother and transition better. There is NO difference in performance and very little difference in weight (a few grams max) between electronic & mechanical. Take your pick. Some like the electronic for less moving parts & some like the mechanical for the adjustability and linear advance.
Old 06-03-2006, 10:07 PM
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Antique
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Default RE: Elec. Advance versus Mech advance

Jeff...The crank has been straightened, a new carb rotator block installed..The bill so far is $60, it runs very well...Mechanical advance conversion is $150 total, electronic conversion is $175 total...
The electronic advance engines weighs 4 lbs 1 oz, the mechanical weighs 4 lbs 8 oz, hardly just a few grams...The difference is in the hub....
Let me know, I can finish it tomorrow and ship it Monday...
Old 06-03-2006, 10:16 PM
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jw637362
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Default RE: Elec. Advance versus Mech advance

Ok, Things are coming together now. Let me make an example and see if I am right.

Magneto and source coil are fixed timing,

If the source coil could be moved from left to right, this would mean adjustable timing.

So now that the timing makes sense, the difference is that the Electronic advance is the little sensor and pickup with little wire like one on the DA engine and the Mechanical is the White round thing like on a Brison.
An EI is more like the stationary Magneto and source coil, just on a smaller scale and the Mechanical actually moves with the throttle to a certain point to "Advance" the timing as the engine revs up and lowers the timing to compensate for the lowering of the rpms.
I hope this is correct because I feel good about it

Thanks a whole bunch!!!

Dang, just thought of something, On my airplane, I have to utilize the carburator rotate block so the throttle connection is on the bottom of the carb, by utilizing the mechanical advance, can this still be done or do I have to redesign the throttle servo hookup?


Jeff


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Old 06-03-2006, 11:07 PM
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Default RE: Elec. Advance versus Mech advance

Ignition systems 101...My carb rotator block is made from 3/8" epoxy board material...the carb is now closer to the cylinder...The throttle connection is at the end of the carb closest to the crank...The throttle servo connects directly to the new brass arm on the throttle shaft...It makes no difference which timing method is used, the connection remains the same...The mechanical advance has a 4/40 threaded rod link between the carb shaft and advance mechanism, a 6202 ball bearing on the back side of the prop hub...The hall sensor is mounted in a ring pressed on to the ball bearing...There is a magnet in the hub that triggers the advance when it passes the hall sensor...With mechanical advance the ring is rotated by opening the throttle..The spark timing is set for 28 degrees before top dead center for either method...The difference is that full advance is reached at 4000 rpm with electronic advance, and at Wide open throttle with mechanical advance..Contrary to popular opinion, I can find very little difference either way...I don't think the engine can tell the difference where the spark occurs after 4000 rpm, and very little if any before that..
To further complicate this, the electronic advance can be made to delay full advance until 6000 rpm..Again, no difference noticeable in performance..
The difference between my mechanical advance and the Brison pictured is the material on the Brison is Delrin or nylon with no ball bearing, and mine is aluminum with a 6202 sealed ball beaing..My hall sensor is epoxied into the aluminum, the C&H ignition setup on the Brison uses the exact same Sony DN6952 hall sensor in a removeable round piece held in by a setscrew...Since hall sensors rarely go bad I use epoxy...
The sensor on the DA is a small transformer using only 2 wires...The electronic advance on the DA works just like the electronic advance on all other engines...
The electronic advance chip on mine and C&H ignitions is the same part...
Static timing on mine and C&H electronic ignitions is set at 28 or 30 degrees BTDC...The first flip of the prop retards the ignition to 4 degrees BTDC, then follows the rpm of the crank.
Static timing on most other electronic advance ignitions is set at about 4 degrees BTDC and advances to 28 or 30 from there..
Hall sensor electronic ignitions with fire at 1 rpm, the other systems must be flipped a little faster for the transformer sensor to make enough voltage to fire the circuit....
Mechanical advance ignitions MUST be started with just a few clicks of throttle because the engine will kick back if the throttle is opened too far...Other systems always start retarded regardless of throttle position...
Spark timing can be changed on either system, by moving the sensor on the other systems or changing the length of the link on the mechanical...
Older engines with fixed EI can be changed to electronic advance by pluggin in a syncro spark module between the sensor and circuit board and locking the timing ring at 28 degrees BTDC..
Syncro spark modules are available from C&H...
Most engines with magneto and source coil ignition are set by the factory at 28 degrees BTDC....It can be changed by removing the mag rotor or flywheel and leaving the key out, then rotating the flywheel or rotor to whatever point is wanted..The key does nothin to keep the flywheel or rotor from slipping, it's only function it correctly place the rotor or flywheel on the shaft during assembly...The key on a tapered shaft crank is so soft it will shear if the retaining bolt comes loose....
Did I miss anything ?

Old 06-03-2006, 11:23 PM
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Default RE: Elec. Advance versus Mech advance

Well that pretty much explains it all, I now understand how it works........ I'll stick with making it back to stock and keep the magneto setup as It has always been reliable.
Thanks a lot Ralph but the conversion will have top happen later.

Jeff
Old 06-04-2006, 04:53 AM
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Default RE: Elec. Advance versus Mech advance

The electronic advance engines weighs 4 lbs 1 oz, the mechanical weighs 4 lbs 8 oz, hardly just a few grams...The difference is in the hub....
I'm not sure why you need the heaver hub? If I converted a Brison from mechanical to electronic, one of thredded rods would be eliminated, the ring would be fixed and a syncro module would be added. Little or No weight difference. In fact Brison reciently went from mechanical to electronic and there is no advertized weight difference. Are you leaving the original magnito hub with the large magnets in your mechanical set-up? Why do you need a different hub?
Old 06-04-2006, 05:08 AM
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Default RE: Elec. Advance versus Mech advance


ORIGINAL: tkg

A magneto is an self powered electronic system.
What every body is calling an Electronic Ignition (EI) is a battery powered ignition system.
The magneto has fixed timing, the timing BTDC does not change with RPM. There are EI's that also have fixed timing.
For best performance the engine needs variable timing. less advance at lower rpm and maximum advance at full throttle. The maximum advance needed for max hp varies from engine to engine.
An engine does not care how the variable timing happens only about the amount. At idle and full throttle the mech adjustable timing and the automatic timing will be the same.
In the mid range they are a little different, not better or worse just different. Which one is for you depends on what plane your flying and how you are flying it.
90% of the fliers can't tell them apart.

-----------------


A few decades ago, you could buy a chip sold by Stihl that could be added to a magneto ignition system and it would provide some spark advance. It has been a long time ago and I forget the exact amount of advance it provided. Folks used to buy them for their Quadra Q35 engines, which were hopelessly underpowered. I don't know if they are still around today or not.

Mechanical advance is smoother, as Ralph has implied, since the timing advances a little bit with each incremental advancement of the throttle. Most electronic advances are choppy. Some only have one advance which occurs at 4,000 rpm.

The downside to a mechanical advance is the danger of getting kick back when trying to handstart it simply by leaving the throttle open. Brison is famous for using mechanical advance. Mine worked flawlessly. Just don't forget to take the throttle back to idle or you will get slapped by the prop.
Old 06-04-2006, 10:31 AM
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Antique
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Default RE: Elec. Advance versus Mech advance

The reason for the weight difference between the two is the weight of the ball bearing I use and with EI a different hub is used that screws onto the threads on the end of the crank.The stock magneto rotor is not used either way..
The stock Zenoah prop hub is 2.80 inches in diameter..I make an aluminum hub to replace the stock mag rotor..I use 2 inch aluminum..I turn down the stock hub to 2 inches to match the hub and re locate the 2 bolts in the stock hub...
The EI hub has no ball bearing on the back and is turned down in the middle to 1.4 inches to save weight...I will make the next mechanical advance hub using the EI type parts and save an ounce or two, we'll see...
I use the ball bearing because when I started making ignitions everyone else copied A&M with their sometimes sloppy and sometimes tight rotating piece..They tried phenolic, aluminum, and Delrin, finally settling on Delrin and a somewhat loose fit...There is no play in a sealed ball bearing, and it will not get tight... My conversions use a G10 epoxy board carb rotator block and no bell crank, eliminating the extra link and possible point of failure....The throttle servo connects directly to the carb shaft...
Old 11-02-2014, 12:21 PM
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Geek1945
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I realize this is a very old thread yet, I'd be remiss if failing to point out a flaw in the discussion. Magneto ignitions of the static type, Walbro has introduces variable timing magneto modules which cost about the same as on board battery power CDI's, fail to follow a dynamic ignition curve and are set for maximum advance (earily) or design operating RPM. Another way is to mechanically rotate the magneto module via carburetor linkage so timing varies with throttle position. This is accomplished by mounting the module on a fixed plate with arc cutouts which follow the rotating flywheel as the throttle advances so does the module. The difficulty in this arrangement is maintaining the module lamination's to flywheel air gap also the module must be easily moveable so you don't smoke throttle servo. This is difficult to do without precision metal working equipment not to mention costs, so the on-board CDI has prevailed for the great majority of RC gas engines.

The pros and cons of magnetos are well known hot spark at high RPM's and weak spark starting whether a magneto advances or not is a function of original design. Magnetos aren't dead technology even being used in new piston aircraft since no external power is required. Mallory makes racing magnetos which have both mechanical and electronic advance. This racing magneto fit into the engine distributor mount and resemble old Delco electronic distributors

Another problem facing both (on-board & module) ignition types is SCR switching recovery dT/dR time this identical to point bounce when the timing between firings fails to maintain sync with engine RPM. There are electronic solutions like replacing the the SCR with MOSFET's or JFET's in fact your PC/Laptop SMPS-Switch Mode Power Supply likely is doing that as you read this at a frequency beyond your hearing range. But and big but at that, if an engine with enough cylinders can operate above 50KHz firings per/second even these hi-switching transistor might have difficulty. OK think P&W 'corncob' R4360's 56 plugs 28 firing each revolution for starters,

Now for some more useful stuff, I know you are all aware that single cylinder RC CDI's are at least overpriced by 200% so if your interested in switching to a better 12-15v CDI for $20, hey with LiPO's it's easy, it will provide higher plug voltage draw about the same or less wattage and have separate 2 & 4 stroke models just say so.

Ed doing FAA Radar/Computers/Microwave TDM/Telecom since 1965
Old 11-02-2014, 12:21 PM
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I realize this is a very old thread yet, I'd be remiss if failing to point out a flaw in the discussion. Magneto ignitions of the static type, Walbro has introduces variable timing magneto modules which cost about the same as on board battery power CDI's, fail to follow a dynamic ignition curve and are set for maximum advance (earily) or design operating RPM. Another way is to mechanically rotate the magneto module via carburetor linkage so timing varies with throttle position. This is accomplished by mounting the module on a fixed plate with arc cutouts which follow the rotating flywheel as the throttle advances so does the module. The difficulty in this arrangement is maintaining the module lamination's to flywheel air gap also the module must be easily moveable so you don't smoke throttle servo. This is difficult to do without precision metal working equipment not to mention costs, so the on-board CDI has prevailed for the great majority of RC gas engines.

The pros and cons of magnetos are well known hot spark at high RPM's and weak spark starting whether a magneto advances or not is a function of original design. Magnetos aren't dead technology even being used in new piston aircraft since no external power is required. Mallory makes racing magnetos which have both mechanical and electronic advance. This racing magneto fit into the engine distributor mount and resemble old Delco electronic distributors

Another problem facing both (on-board & module) ignition types is SCR switching recovery dT/dR time this identical to point bounce when the timing between firings fails to maintain sync with engine RPM. There are electronic solutions like replacing the the SCR with MOSFET's or JFET's in fact your PC/Laptop SMPS-Switch Mode Power Supply likely is doing that as you read this at a frequency beyond your hearing range. But and big but at that, if an engine with enough cylinders can operate above 50KHz firings per/second even these hi-switching transistor might have difficulty. OK think P&W 'corncob' R4360's 56 plugs 28 firing each revolution for starters,

Now for some more useful stuff, I know you are all aware that single cylinder RC CDI's are at least overpriced by 200% so if your interested in switching to a better 12-15v CDI for $20, hey with LiPO's it's easy, it will provide higher plug voltage draw about the same or less wattage and have separate 2 & 4 stroke models just say so.

Darn forgot links: http://www.walbro.com/media/39691/Ign5-8-13.pdf https://www.google.com/patents/US640...ed=0CB0Q6AEwAA


Ed doing FAA Radar/Computers/Microwave TDM/Telecom since 1965

Last edited by Geek1945; 11-02-2014 at 12:30 PM. Reason: add links
Old 11-02-2014, 09:04 PM
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bcchi
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Originally Posted by Antique
Ignition systems 101...My carb rotator block is made from 3/8" epoxy board material...the carb is now closer to the cylinder...The throttle connection is at the end of the carb closest to the crank...The throttle servo connects directly to the new brass arm on the throttle shaft...It makes no difference which timing method is used, the connection remains the same...The mechanical advance has a 4/40 threaded rod link between the carb shaft and advance mechanism, a 6202 ball bearing on the back side of the prop hub...The hall sensor is mounted in a ring pressed on to the ball bearing...There is a magnet in the hub that triggers the advance when it passes the hall sensor...With mechanical advance the ring is rotated by opening the throttle..The spark timing is set for 28 degrees before top dead center for either method...The difference is that full advance is reached at 4000 rpm with electronic advance, and at Wide open throttle with mechanical advance..Contrary to popular opinion, I can find very little difference either way...I don't think the engine can tell the difference where the spark occurs after 4000 rpm, and very little if any before that..
To further complicate this, the electronic advance can be made to delay full advance until 6000 rpm..Again, no difference noticeable in performance..
The difference between my mechanical advance and the Brison pictured is the material on the Brison is Delrin or nylon with no ball bearing, and mine is aluminum with a 6202 sealed ball beaing..My hall sensor is epoxied into the aluminum, the C&H ignition setup on the Brison uses the exact same Sony DN6952 hall sensor in a removeable round piece held in by a setscrew...Since hall sensors rarely go bad I use epoxy...
The sensor on the DA is a small transformer using only 2 wires...The electronic advance on the DA works just like the electronic advance on all other engines...
The electronic advance chip on mine and C&H ignitions is the same part...
Static timing on mine and C&H electronic ignitions is set at 28 or 30 degrees BTDC...The first flip of the prop retards the ignition to 4 degrees BTDC, then follows the rpm of the crank.
Static timing on most other electronic advance ignitions is set at about 4 degrees BTDC and advances to 28 or 30 from there..
Hall sensor electronic ignitions with fire at 1 rpm, the other systems must be flipped a little faster for the transformer sensor to make enough voltage to fire the circuit....
Mechanical advance ignitions MUST be started with just a few clicks of throttle because the engine will kick back if the throttle is opened too far...Other systems always start retarded regardless of throttle position...
Spark timing can be changed on either system, by moving the sensor on the other systems or changing the length of the link on the mechanical...
Older engines with fixed EI can be changed to electronic advance by pluggin in a syncro spark module between the sensor and circuit board and locking the timing ring at 28 degrees BTDC..
Syncro spark modules are available from C&H...
Most engines with magneto and source coil ignition are set by the factory at 28 degrees BTDC....It can be changed by removing the mag rotor or flywheel and leaving the key out, then rotating the flywheel or rotor to whatever point is wanted..The key does nothin to keep the flywheel or rotor from slipping, it's only function it correctly place the rotor or flywheel on the shaft during assembly...The key on a tapered shaft crank is so soft it will shear if the retaining bolt comes loose....
Did I miss anything ?
You and TKG have this one.Too complicated for this farm boy to understand.But I agree.
BCCHI
Old 11-03-2014, 10:11 AM
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Well I may as while add my 2 cents. I was reading about flywheel mag ignitions on various engines, like leaf blowers. I read where the ignition on my MB290 leaf blower has built in advance even though it had a flywheel mag. I hooked up a sears DC timing light and ran the engine at various RPM,s. Sure enough it did have spark advance. Took a photo even when running. That engine is at least 5 years old now and still rips. Also it will idle pretty slow. It did not want to start the other day. Took the carb apart & it was clean. But the pumping diaphragm was bad. Did not see it at first then took a real bright flashlight and shinned it on one side...and a bunch of tiny holes showed up on the other side. Very good way to check that way. Capt,n
Old 04-06-2016, 04:07 PM
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microdon2
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I have an older A&M \ Sachs 3.2 engine and it's kicked-back on me both times I've started it. Finally am doing some research (including this thread) and just learned that I need to pull the throttle all the way back to idle when starting, which now, in hind-sight, makes sense. (I was starting with WOT and choke closed). FYI - I soldered-closed the hole in the choke plate, so this engine pulls gas just fine. Today it fired on the fourth or fifth flip. Then kicked-back on me (good think I was wearing a heavy glove)).

(btw - then I used a high-torque starter to start this engine and it runs great. Sounds like a beast!!)

So a question - to start this engine - should I choke it and still leave the throttle down to idle? I've always done WOT \ choke, to draw fuel. Will this draw enough fuel with the throttle close to idle?

Thanks.
Old 04-06-2016, 05:30 PM
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You get a better pull on the fuel with the throttle full. In this case I would prime the engine ignition off. Then once the engine is primed, close the throttle to a fast idle and start This kind of start brings flooding into play for many. You can choose which thing you deal best with.

If I know I have flooded an engine and it will turn with a Hi torque starter, I run the starter at ignition off full throttle and let the engine clean and prime like that. Works great.

Oh, this is an ignition with mechanical advance right?
Old 04-06-2016, 05:39 PM
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microdon2
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Thanks for the quick reply. Yes, it's an old C&H Ignition and a mechanical advance. Pretty cool setup. I'll try what you suggest - maybe WOT \ Choke for three flips, then go to Ign on, no choke, low idle. I do have a high-torque starter, but prefer start gassers by hand.

Not sure I understand your comment on flooding. I've always thought that - once flooded - the spark plug needed to be pulled and dried-out. Can I get the same result just by using an electric starter and turning it at WOT? Does that "suck" the fuel away from the plug?
Old 04-06-2016, 08:00 PM
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With mechanical advance you don't want to be turning it over with anything at full throttle and the ignition "ON"
Old 04-07-2016, 02:58 PM
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CK1
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What I do on my mechanical advance side carb engines for the first start is , 1) Ignition off , choke closed , wide open throttle , flip till gas drips from carb.
2) Ignition off , choke open , WOT , flip 3 or 4 times to draw charge into cylinder . 3) Igntion on , choke open ,throttle 2 clicks above idle , flip till pops ,return to idle
.
On electronic advance 1) ignition on , choke closed, throttle half to full , flip till it pops . 2) Ignition on , choke open , throttle at 2 clicks above idle , flip till runs .
Been using these procedures on all side carb engines for many years an still have most of my knuckles and fingers.
On rear carb engines I refrain from the choke until it drips part , as it usally ends with pulling the sparkplug and drying the cylinder . For some reason the fuel charge saturates the cylinder faster on rear carb engines

Last edited by CK1; 04-07-2016 at 03:00 PM.
Old 04-07-2016, 03:15 PM
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microdon2
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CK1 - thanks for the detailed starting procedure. I will try your method for this mechanical advance Sachs 3.2.

btw - different question. Why do these mfg's keep selling carbs with holes in the choke plate for RC plane engines? Seems to counter the very point of a choke. And does everyone close those holes (as I do)?

Thanks.
Old 04-07-2016, 03:22 PM
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CK1
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I have never needed to close that hole on any
engine . I always believed it was there to allow enough airflow to carry the fuel into the engine , no airflow no fuel movement.
Old 04-07-2016, 04:53 PM
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Originally Posted by CK1
I have never needed to close that hole on any
engine . I always believed it was there to allow enough airflow to carry the fuel into the engine , no airflow no fuel movement.
+1 though I did close the hole on one engine that was especially reluctant to pull fuel. I later drilled a small hole in the solder used to close the hole as it was prone to over choking otherwise.

Last edited by Truckracer; 04-07-2016 at 04:56 PM.
Old 04-10-2016, 07:49 PM
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microdon2
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Today I started the Sachs 3.2 using the method described here - choke closed, WOT, Ign Off - for three flips, then throttle down to idle, choke open, Ign on, and the engine started easily! No kickback at all. I'm very happy with how this engine starts and runs. And today it flew a 96" Kangke Monocoupe with power to spare! And I don't need a starter. Thanks everyone for your help.

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