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Post by MCS on Oct 19, 2008 22:05:16 GMT -5
First, make sure you read the Magneto Ignition System I put out on Tutorials. When you look at these point replacement modules you will see only two leads. One will be connected to "ground" just like the points and the other lead will connect to the wire that used to connect to the points and condenser and that goes to the coil. The points and condenser are completely eliminated from the primary side of the coil, so this module has to handle what used to be done by the points and condenser since the old coil and flywheel are reused with no changes. With point operation, the spark plug fires when the points open. The crankshaft has a cam ground into it that is fixed in relationship to the piston and TDC. In the solid state module configuration we do not have this function. The points were eliminated and there is no mechanical connection to the engine, so how is spark timing controlled with these devices? In the point system, the closing of the points isn't critical but we do need them closed when the magnets pass the coil so the same is true for our solid state module. I do not know the insides of one of these module but from my years of electronics, I'd say there is some type of circuit that provides a current path so when the magnets start pass the coil there is current flow in the module. The current flow will developer a trigger voltage that will turn on some type of solid state device that will allow full primary current to flow as the magnets continue to move past the coil just like the closed points. Once the coil is "charged" the current flow through the primary has to be interrupted for the field to collapse and create the high voltage to fire the spark plug. To create the interruption, the solid state device has to be turned off just like the points open. How this is done isn't important for this discussion, but realizing that the turning off of our solid state points is not precisely timed to piston position and TDC as are mechanical points. The relationship between the flywheel magnets and the coil core is the only relationship that exists and the flywheel is keyed to the crankshaft. This is our timing but it isn't as precise as mechanical points and this explains why some saws do not respond well to this conversion where others work great.
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Post by MCS on Jul 1, 2009 19:06:44 GMT -5
A successful conversion Thought I add an update to this tutorial. This saw had a blue solid state ignition module so I had to mount a different point box and coil. Some notes: - You can leave the points and condenser in the saw but you will have to cut the wire from the coil primary to the points. What ever you choose to do, make sure the wire is clear of the underside of the flywheel. If you want to leave the wire in tack, disconnect from the coil and zip tie it. Crimp a slip on connector to the wire from the module to the coil.
- Mounting the chip may be a problem on some ignitions. I've had some where the core is riveted to the point box.
- I think on this saw, the spark is slightly advanced from a point configuration. When I first pulled it over, it popped and pulled the rope out of my hand. A good grip and firm pull is needed on this saw.
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Post by billg on Jul 2, 2009 1:44:45 GMT -5
You mentioned the spark being advanced. I believe you are correct as that is what I have found with mine. I have a Mac 125 with one that is just to da;; tough to start.
Bill
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Post by RBW on Jul 2, 2009 20:10:39 GMT -5
Do you guys feel there are any power gains to be seen with these on a saw?
I run these in my tractors and they seem to not only start easier in bad weather but also run better at all RPM.
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Post by MCS on Jul 2, 2009 22:55:15 GMT -5
I don't know if there is a power increase but the spark is definitely advanced so it wouldn't surprise me if the RPMs were up a little. I pulled the flywheel and rotated the point box as much as it would go and drilled a new hole in the upper mounting plate. I took some measurements but I think all I gained was 3 degrees. It still kicks back. I'll have to get a nice sharp chain on it and stick it in a piece of oak and see if it will keep up with the 750 ;D I've never gone looking for one but is there a tachometer that will work on these one lung engines? RBW - you use these on a farm tractor? Do you need one for each cylinder?
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Post by RBW on Feb 14, 2010 15:02:26 GMT -5
Wow, I been out of the loop on this one for a while, Sorry.
No, I have several Old School Compact tractors, most with the huge old Briggs engines in them. Their usually mounted in either backwards or are so friggin buried that getting to the mag/points if need be is a 4 hour job. These lil chips eliminate all that hassle.
Mine all run wet/dry/iced over/hot/covered in mud.
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Post by 925fetish on Feb 21, 2010 19:07:04 GMT -5
That there is a good one of them
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Post by storres44 on Mar 18, 2011 15:37:29 GMT -5
ew guy that just got into the hobby of Chainsaw tinkering...I picked up a Homelite SXLAO (UT-10045C) at the local scrap yard. This saw had a wicked bow bar on it (something I have never seen), so I had to have it. So for $5 I picked up fixer-upper that I originally planned on fixing and selling. But since then, have decided that I want to keep this machine after I read all the positive reviews about it, and how dependable it is. Plus, this would be the biggest hp chainsaw in me and my dad's fleet. So, I want to throw a 20" bar on it and get it going. So, I've torn into it and I discovered that it is not getting any spark to the cylinder. (I remove the spark plug from the cylinder and shorted it to the chassis and no spark). So I removed the coil/module (A94605S) and measured the following: 4.8k ohms across the secondary winding and ground. (Chassis Gnd. connection to spark plug wire connection.) 4.8k ohms across the kill switch terminal and the spark plug wire connection. 3.3 ohms across the kill switch terminal and the chassis ground connection. (A short circuit)...Does this need to be open for the coil to operate? Is this (A94605S) coil not working based on what I measured? What resistance values should I have across the terminals?
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Post by tribulation138 on Mar 18, 2011 16:43:55 GMT -5
does anyone know if the chip works on solid state modules?
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Post by MCS on Mar 18, 2011 17:49:02 GMT -5
The blue solid state ignition modules have a small circuit board with a few transistors and stuff on it. Since this is all molded into the module you cannot tell what has gone bad and whether there is a clean connection to the coil primary without any parallel circuits. As a result, I really doubt you would have any luck getting a "chip" to drive this. The other part would be magnet placement in the flywheel. Without points, timing is strictly a function of the magnet passing the core.
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Post by storres44 on Mar 19, 2011 12:55:48 GMT -5
So it sounds like I have two options 1.)buy a new SS module the direct repalcement (A94605S) $55.00 or 2.) convert to point system, like MCS did on his saw. What are the advantages and disadvantages of these options?
Is option 1.) more expensive? Is option 2.) more reliable and easier to work on? It sound that the SS module is the achilles heal of the SXLAO? Does that sound about right.
I guess I am asking what would the Homelite experts recommend me to do.
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Post by tribulation138 on Mar 19, 2011 13:14:27 GMT -5
Points are ok and easy to deal with. but they do eventually wear out. I had some points just die on me recently. I had a extra pair lying around and she is good as new.
If I were you I would make the saw a point set up (crank shaft, flywheel, coil, etc) but without the condenser and points. Buy a ignition chip for 16-17 bucks and have fun with a awesome spark!
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Post by storres44 on Mar 20, 2011 21:00:43 GMT -5
What would the parts list to complete this conversion look like? I am assuming, coil, two legged core, crankshaft, fly wheel, and the chip. What is the part number for the chip? What other parts do I need? My flywheel will not work???
Thanks
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Post by tribulation138 on Mar 21, 2011 5:18:28 GMT -5
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Post by MCS on Mar 21, 2011 6:45:15 GMT -5
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Post by storres44 on Mar 21, 2011 12:10:42 GMT -5
Thanks Tribulation and MCS!! MCS when you did the conversion did you have to convert to a different fly wheel, and crankshaft? or will my original flywheel and crankshaft work (phelon). Also, I noticed when you did the conversion, your coil was a two legged core, and the part frmon mfgsupply was a one legged core (94711Cs). Do you think this will make a difference? Do you think this attributed to the spark being advanced in your saw?
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jbsaws
Saw Builder
October 1964: Homelite receives Popular Science Award for development of XL-12
Posts: 242
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Post by jbsaws on Dec 3, 2011 9:41:27 GMT -5
I read this thread to learn more about the topic, then googled it. I found a thread from a different forum in which a guy reported that he burned up three of these modules in a Mac before he realized he was mounting it too close to the coil pack. He reported that he moved it farther away and had no more problems.
Since I have a little less than a thimble's full of knowledge about this, I don't know if the same issue applies to Homelites, but I decided to add this to the thread just in case.
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Post by MCS on Dec 5, 2011 15:07:39 GMT -5
Heat is the number one enemy of solid state (transistor) devices. The module case dissipates heat through what ever it is mounted to so finding a spot that does not create heat, i.e. cylinder, is key. I only have two in use but the SXL and XL-9xx have lots of room for mounting.
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Post by xl12rocks on Jun 22, 2012 12:07:10 GMT -5
I pulled the flywheel and rotated the point box as much as it would go and drilled a new hole in the upper mounting plate. I took some measurements but I think all I gained was 3 degrees. It still kicks back. I was wondering if anyone had tried this. If the chips have the timing off then doesn't it stand to reason that repositioning the coil would correct the problem. I noticed on my XL-12's that the two mounting holes in the point assembly under the flywheel were slotted so there was some play for adjustment, but the single bolt behind the coil fixed the position. Would it not work to change the single hole through the assembly to a slot so that the coil position can be adjusted? If someone is really creative, I bet you could build in an accessible adjustment to change the coil position while the saw is running to get it perfect. I noticed that some chips claim to be adjustable themselves. The other thing I am wondering about is that some of these chips say that they don't work with multiple magnets. What exactly do they mean? There are two magnets beside each other on the flywheel. Are they referring to that, or do they mean flywheels that make two charges(sparks) each rotation?
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Post by tribulation138 on Jun 22, 2012 12:14:28 GMT -5
I pulled the flywheel and rotated the point box as much as it would go and drilled a new hole in the upper mounting plate. I took some measurements but I think all I gained was 3 degrees. It still kicks back. I was wondering if anyone had tried this. If the chips have the timing off then doesn't it stand to reason that repositioning the coil would correct the problem. I noticed on my XL-12's that the two mounting holes in the point assembly under the flywheel were slotted so there was some play for adjustment, but the single bolt behind the coil fixed the position. Would it not work to change the single hole through the assembly to a slot so that the coil position can be adjusted? If someone is really creative, I bet you could build in an accessible adjustment to change the coil position while the saw is running to get it perfect. I noticed that some chips claim to be adjustable themselves. The other thing I am wondering about is that some of these chips say that they don't work with multiple magnets. What exactly do they mean? There are two magnets beside each other on the flywheel. Are they referring to that, or do they mean flywheels that make two charges(sparks) each rotation? i have elongated the stator mount holes to mess around with the timing of spark b4
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