Try looking on YouTube, they have several good videos of how it is done. BSK garage has a informative video check both primary and secondary.
McCulloch Chain Saws
- Thread starter Bruce Hopf
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There are a couple different ways to check,one for primary,the other for secondary.Difficult for me to explain.I know how to check the coil if that's what you're trying to get at.
Ed
Ed
First check is to pull the plug and ground it to the cylinder (or a screwdriver or something else that will establish a ground to the engine) while connected to the coil. Remove the kill wire from the coil in case it happens to be shorted to ground somewhere -- effectively killing spark even if in the 'on' position. Pull the saw over briskly and check if there's any spark at the plug. May need to do it in dim conditions to see spark. If there's good spark, the coil is probably good. If there's no spark, use a multi meter in continuity mode to check the plug lead itself between the coil and the boot to make sure there isn't a break in the high tension conductor or the spring has maybe come loose from the lead. Most plug leads screw into the coil body and can simply be removed for the test. The desired result will be a reading of all zeros indicating a short. If there's no reading, the lead has a break in the conductor.
Testing a coil itself involves checking between the primary and secondary legs for resistance readings according to the coil maker's design. The primary and secondary impedance should be known for those tests to make sense.
Bear in mind that a cold coil that passes bench tests may not behave correctly under hot conditions. In those cases about the only easy test is to do a spark test when the saw is hot and the coil seems to fail or not restart. Good spark cold but no spark hot..., bad coil.
What specifically are you testing? (Sorry if you mentioned it already and I missed it.) Someone here most likely has the same coil to test (or the specs) to at least compare or provide test result numbers.
Here's the vid I believe Ed was referencing fwiw.
That's the video I was trying to upload.
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My bad. Was sorta hasty referencing it and thought Ed was the one who mentioned it.
No worries, I couldn't do it.
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Thank you that's exactly what I was looking for I wish I would have joined this group a long time ago thanks again guys for everyone's help
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For a YouTube vid, just copy the URL link to the video from the browser address bar then click on the media button in the composition toolbar and paste the link into the space provided. Click 'embed' and there ya go. This is if using a computer. Not sure about Tapatalk or other phone apps.
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For points type ignition coils an ohm meter is sufficient. The primary and secondary windings are both connected (common) to the ground terminal. From the primary lead or terminal resistance to ground will be quite low, generally between 1 and 2 ohms (Ω). Secondary resistance (spark plug lead to ground) will be between 5K and 10K ohms (5,000 to 10,000 ohms).
For electronic ignition coils you won't learn much with only an ohm meter, you really need to check both capacitance and inductance. The electronic ignition coils for the 600 Series saws (same coil is used on 10 Series electronic ignitions) will be around 5 to 5.5 H.
I have also checked some of the later electronic ignition coils such as those used on the plastic McCulloch saws, Mini Macs, and the like. They are quite different again with 0.56H and 0.57 µf (micro farads, the Farad is the basic unit for capacitance) and only 0.841 ohms (Ω).
Bottom line...you have to know what a good coil measures to be able to test a questionable one to make sure it is within specifications.
Mark
For electronic ignition coils you won't learn much with only an ohm meter, you really need to check both capacitance and inductance. The electronic ignition coils for the 600 Series saws (same coil is used on 10 Series electronic ignitions) will be around 5 to 5.5 H.
I have also checked some of the later electronic ignition coils such as those used on the plastic McCulloch saws, Mini Macs, and the like. They are quite different again with 0.56H and 0.57 µf (micro farads, the Farad is the basic unit for capacitance) and only 0.841 ohms (Ω).
Bottom line...you have to know what a good coil measures to be able to test a questionable one to make sure it is within specifications.
Mark
Thank you sometimes I just want to know how something works like the multimeter
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I probably could've explained it to you (or at least tried to),but not as good as Pogo or Mark H did.I don't know all the technical terms,but if I have the multi meter in my hand I know what to do with it.Thanks Pogo & Mark for explaining it way better than I could've.
Ed
I had a non-forum visitor this week who is quite familiar with 10 Series saws and we had another go at Kevin's recalcitrant 7-10...unfortunately the results were the same. It would start and run at full throttle but would not idle. Once again we swapped carburetors from his good running 4-10 and it acted exactly the same. He attributes the problems to the scoring evident when you look through the intake port with the carburetor off, says he had a couple of 7-10's with similar scoring that behaved the same way.
On to a more successful task, I replace the Briggs & Stratton engine on my log splitter, sad that the original only lasted through 26 years of my hard use but the muffler had rusted out, one of the muffler bolt had broken off in the head, and the 3/4" pipe/muffler I threaded in the port was just not up to the hours of running this unit puts in. This photo was from a few years ago before the original muffler and deflector went away working on a large maple tree in my driveway.
Just to keep with the theme of this thread, we used McCulloch saws on that project.
I had this 16 HP Duro Max, Chinese clone of a Honda on hand so I used it. It was necessary to modify the engine mount and move the engine ahead a few inches. Surprisingly the Duro Max had the same bolt circle pattern as the Briggs & Stratton so the pump mount bolted right up. I had to cut the shaft down about an inch as it was much longer than the Briggs but all in all it was a fairly painless swap. I decided to put the fender back on the engine side to help keep road debris, etc. out of the engine, I left the other side off since that is where the wood goes once it is split...better to bounce them off the tire than wreck a fender.
I am ready for action again, good thing since I have a couple of projects coming up this week weather permitting.
Mark
On to a more successful task, I replace the Briggs & Stratton engine on my log splitter, sad that the original only lasted through 26 years of my hard use but the muffler had rusted out, one of the muffler bolt had broken off in the head, and the 3/4" pipe/muffler I threaded in the port was just not up to the hours of running this unit puts in. This photo was from a few years ago before the original muffler and deflector went away working on a large maple tree in my driveway.
Just to keep with the theme of this thread, we used McCulloch saws on that project.
I had this 16 HP Duro Max, Chinese clone of a Honda on hand so I used it. It was necessary to modify the engine mount and move the engine ahead a few inches. Surprisingly the Duro Max had the same bolt circle pattern as the Briggs & Stratton so the pump mount bolted right up. I had to cut the shaft down about an inch as it was much longer than the Briggs but all in all it was a fairly painless swap. I decided to put the fender back on the engine side to help keep road debris, etc. out of the engine, I left the other side off since that is where the wood goes once it is split...better to bounce them off the tire than wreck a fender.
I am ready for action again, good thing since I have a couple of projects coming up this week weather permitting.
Mark
2broke2ride
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Mark, what scoring might you be referencing? Is there something visible on the piston or something in the cylinder? The piston, as you know, is new and I dont recall any scoring in the cylinder at all. I honed it very lightly with a ball hone when I initially rebuilt it.
I have a 7-10 with 2 or 3 deep grooves on the exhaust side and yeah it doesn't have quite the pull of my better 7-10 but it still runs very very well a really nice snappy saw
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That's what I'm wondering, I have a 10-10 that is pretty rough looking but still runs well enough.
Unless it's to do with sealing the ports. Perhaps if I put a new piston in the tired 7-10 it mite do the same thing
The thing to do would be take a runner and put the suspect cylinder on the with the runner crank but that's a few hours of faffing about
My money is still on a mismatch between the cylinder porting and the piston.
A comparison between the cylinders used for each type of piston would shed some light. I have one from a dismantled 10-10 that should represent the porting of the early 'port hole' style piston, but nothing for a later 70cc cylinder designed for the windowed pistons (unless I tore down a PM700 just for the exercise).
A comparison between the cylinders used for each type of piston would shed some light. I have one from a dismantled 10-10 that should represent the porting of the early 'port hole' style piston, but nothing for a later 70cc cylinder designed for the windowed pistons (unless I tore down a PM700 just for the exercise).
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