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Post by mmills79 on Aug 31, 2020 11:52:30 GMT -5
I have a couple of questions about this coil
!) Does does anyone know the specs for this coil? In particular, I am looking for the table that shares the resistance readings one would find using an ohm meter to check if the coil is good or not.
There should be a table somewhere that shows the primary resistance (the magneto side) or the resistance between ground and the lead that goes to the points AND what the resistance is for the secondary (high voltage side) of the coil - from ground to the spark plug wire. Please share.
2) Does anyone know of a compatible replacement for this coil? This is a three terminal device with a) ground lead b) terminal for points lead wire plus kill lead wire and c) the spark plug pin terminal. I believe you should be able to buy the coil by itself (and use a new or re-use an old iron core) or purchase the complete coil with the iron core.
3) Any other important/useful information about this coil you would like to share?
3a) follow up questions: the spark plug wire plugs into a PIN located in a small tube on the coil. Anybody clean this PIN before and if yes, what did you find was the best way to do it?
3b) Any good way to ensure that you have a good connection between the spark plug PIN on the coil and the spark plug wire itself?
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Post by undee70ss on Aug 31, 2020 15:47:30 GMT -5
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Post by Clasec on Aug 31, 2020 19:17:28 GMT -5
I have a couple of questions about this coil !) Does does anyone know the specs for this coil? In particular, I am looking for the table that shares the resistance readings one would find using an ohm meter to check if the coil is good or not. There should be a table somewhere that shows the primary resistance (the magneto side) or the resistance between ground and the lead that goes to the points AND what the resistance is for the secondary (high voltage side) of the coil - from ground to the spark plug wire. Please share. 2) Does anyone know of a compatible replacement for this coil? This is a three terminal device with a) ground lead b) terminal for points lead wire plus kill lead wire and c) the spark plug pin terminal. I believe you should be able to buy the coil by itself (and use a new or re-use an old iron core) or purchase the complete coil with the iron core. 3) Any other important/useful information about this coil you would like to share? 3a) follow up questions: the spark plug wire plugs into a PIN located in a small tube on the coil. Anybody clean this PIN before and if yes, what did you find was the best way to do it? 3b) Any good way to ensure that you have a good connection between the spark plug PIN on the coil and the spark plug wire itself? Here is a way to test the coil. Hope this helps.  Magneto test-1 by Clasec, on Flickr  Magneto test-2 by Clasec, on Flickr |
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Post by onlyhomelites on Sept 1, 2020 7:41:33 GMT -5
You've already gotten some great info...in terms of the wire to coil connection, it'll come naturally as long as you use the proper size wire. It will center up and thread right on the post. I don't recommend spraying any cleaner down in there though.
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Post by mmills79 on Sept 1, 2020 10:06:29 GMT -5
@ onlyhomelites (admin): I should preface this with I am an electrical engineer and my preference for a good electrical connection is to solder it. A good mechanical connection can also be made when twisting wire together and securing it with a device like a wire nut (and using other similar connection devices). This "PIN" mechanical connection however, seems iffy to me. For one, there is no real way to secure the connection that I see. It's just a press in/snug/friction fit that you are relying on. The spark plug wire I'm using is 7mm with a "wire" lead (the correct size). I have seen the center connection to the PIN get compromised from vibration, dirt, arcing, etc over time. If you have any recommendations on how to keep the connection free from compromise (like added resistance), I would be very interested to know your thoughts. Like.... is there some kind of electrical contact grease I should be using? Good to know you don't think it wise to use contact cleaner on the PIN. That is what I was wondering. Would it be safe to use a finger nail file to lightly clean up the PIN? ....or do you have any other cleaning recommendation? I re-read your reply and my eye caught that you used the word "rethread". ...are you saying that when you push the wire onto the pin you have to rotate the spark plug wire to thread it onto the PIN? I thought the PIN was just a "spike" or a like a needle..... |
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Post by mmills79 on Sept 1, 2020 10:12:32 GMT -5
undee70ss - Thank you for answering Q2 and sharing one place to get a replacement.....
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Post by mmills79 on Sept 1, 2020 10:40:53 GMT -5
@ Clasec
This is a chainsaw so there is no direct battery connection. I could use some clarification, I'm not sure I understand the procedure to energize the system and where you make the battery connection?
Do you make some temporary connection to the primary of the coil, placing the battery negative to ground and the positive on the coil lead that goes to the points? ...and is the procedure to test for spark: that you repeatedly make and break the connection to the battery and look for spark across the plug gap?
...and lastly, the article was somehow truncated where it tried to explain how you check the condenser and the device to use. Can you post that last section, please?
again, Thank You!
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Post by mmills79 on Sept 1, 2020 10:43:06 GMT -5
I have a couple of questions about this coil Q1) Does does anyone know the specs for this coil? In particular, I am looking for the table that shares the resistance readings one would find using an ohm meter to check if the coil is good or not. There should be a table somewhere that shows the primary resistance (the magneto side) or the resistance between ground and the lead that goes to the points AND what the resistance is for the secondary (high voltage side) of the coil - from ground to the spark plug wire. Please share. Q2) Does anyone know of a compatible replacement for this coil? This is a three terminal device with a) ground lead b) terminal for points lead wire plus kill lead wire and c) the spark plug pin terminal. I believe you should be able to buy the coil by itself (and use a new or re-use an old iron core) or purchase the complete coil with the iron core. Q3) Any other important/useful information about this coil you would like to share? Q3a) follow up questions: the spark plug wire plugs into a PIN located in a small tube on the coil. Anybody clean this PIN before and if yes, what did you find was the best way to do it? Q3b) Any good way to ensure that you have a good connection between the spark plug PIN on the coil and the spark plug wire itself? Lastly to ALL; Still looking for any answer to Q1.... |
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Post by sweepleader on Sept 1, 2020 18:02:55 GMT -5
@ Clasec This is a chainsaw so there is no direct battery connection. I could use some clarification, I'm not sure I understand the procedure to energize the system and where you make the battery connection? Do you make some temporary connection to the primary of the coil, placing the battery negative to ground and the positive on the coil lead that goes to the points? ...and is the procedure to test for spark: that you repeatedly make and break the connection to the battery and look for spark across the plug gap? ...and lastly, the article was somehow truncated where it tried to explain how you check the condenser and the device to use. Can you post that last section, please? again, Thank You! No battery, except when you use the procedure to test. The battery is a flashlight D cell or two with jury rigged wiring. The coil needs to remain fastened to the saw with the condenser in place and the points open so that the condenser is still in the circuit, or the condenser needs to be removed with the coil and the two grounded together with the battery. If there is good spark, the condenser is good. If there is no spark the condenser or the coil or both could be bad. Testing the condenser requires a commercial tester or a homemade one. Homelite published a schematic on building one, it is featured in another thread. |
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Post by sweepleader on Sept 1, 2020 18:08:10 GMT -5
I have a couple of questions about this coil Q1) Does does anyone know the specs for this coil? In particular, I am looking for the table that shares the resistance readings one would find using an ohm meter to check if the coil is good or not. There should be a table somewhere that shows the primary resistance (the magneto side) or the resistance between ground and the lead that goes to the points AND what the resistance is for the secondary (high voltage side) of the coil - from ground to the spark plug wire. Please share. Lastly to ALL; Still looking for any answer to Q1.... Never seen real specs for the coil. I use an ohm meter to test for continuity from the plug wire to ground and from the points wire to ground. If either is open, check the connection between the coil and the laminations were the coil is mounted. Most small engines use a wire there or a friction fit of the coil to the laminations with a metal tab that is normally fairly hard to see. The coil can be bad in the high voltage mode and still show continuity and resistance thus the live test is best. It can check good for resistance and still no spark. |
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Post by sweepleader on Sept 1, 2020 18:13:14 GMT -5
The coil wire is indeed threaded to the "pin". If the area is free of old rubber insulation and crud, I thread on the new wire and smear a little RTV around the joint to seal it. No anti corrosion anything is needed. Not much need to clean/scrape the pin, high voltage will jump any crud with ease if it can jump the spark gap. If the coil is in good shape, it will actually generate the higher voltage needed to clear that area as it dissipates the energy built up during charging of the coil.
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Post by mmills79 on Sept 1, 2020 20:15:35 GMT -5
@ Clasec - Thanks for the follow up. I think I understand. I'll give it a try tomorrow. I'm always interested in the big picture and I wanted to better understand the circuit so, I found this youtube video which I think does a really good job explaining the magneto theory. I hope this group finds it interesting and informative: www.youtube.com/watch?v=julmHkDTQWA |
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Post by mmills79 on Sept 1, 2020 20:25:52 GMT -5
@ sweepleader - I have been pushing the wire onto the coil PIN to date. If I heard you correctly, you are confirming, I am installing the wire incorrectly onto the coil pin. I should in fact twist the wire onto the PIN (which I guess has a small thread?) until it seats. I'm guessing that if I were to file the PIN with a nail file to clean it, I would then possibly destroy the thread on the pin. Do I have this all correct?
Anything else (other than the RTV) that I should be aware of?
Thank you.
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Post by mmills79 on Sept 1, 2020 20:28:14 GMT -5
All, Magneto Theory - I'm always interested in the big picture and I wanted to better understand the circuit so, I found this youtube video which I think does a really good job explaining the magneto theory. I hope this group finds it interesting and informative: www.youtube.com/watch?v=julmHkDTQWA |
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Post by 5terrysupersaws on Sept 1, 2020 22:32:20 GMT -5
Resistance measurements from an ignition coil on a similar saw in the same family ;
PRIMARY - 0.7 Ohms SECONDARY - 7.91 K Ohms ( High Tension Lead and Spark-Plug Terminal included )
Dielectric Grease is my preference .
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Post by mmills79 on Sept 2, 2020 10:54:40 GMT -5
5terrysupersaws - I have two coils. I got about 7.5K ohms on coil one (similar to yours) but 6.0K ohms on coil #2. The primary for me on both was a virtual short, not even 0.7 ohms. Maybe it's the cheap Harbor Freight ohm meter I was using... So, out of curiosity, would the range on these coils be +-10%? ......or something else. The range is also kinda important. Coil 2 was 1.5K ohms different than coil 1.
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Post by sweepleader on Sept 2, 2020 22:05:20 GMT -5
I think you have it correct. The video is pretty good.
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Post by mmills79 on Sept 4, 2020 10:59:58 GMT -5
@ sweepleader
Above you commented that "I think you have it correct."
Were you referring to my +-10% value range?
...sorry if I am just dense - want to be sure of the value range.
...and if that is what you were talking about would you then say that the second coil is out of spec & likely bad since it is more than 10% difference measured at 6.0K ohm?
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