So I just picked up a mac 10-10 for 60 bucks that ran when I got it, but of course that wasn't good enough for me and I tore it down to replace the crank seals and clean out 40 plus years of sawdust. Once I got it all back together I tried to start it, realized it wasn't sparking and figured I missed something when putting the ignition system back together. I cleaned the points and set the gap to .018, bolted the flywheel in place, and put on a coil I had from another 10-10 that was cleaned already and set the gap to .008, put on a new spark plug and no spark. Unplugged the kill wire and still no spark. Put the old coil back on after wire brushing the posts and nothing. I'm thinking I might have messed up the spark timing somehow but set everything based off the service manual. Any ideas on what I broke?
10-10A No Spark
- Thread starter tbupnorth
- Start date
Help Support Arborist Forum:
Do you have a spare capacitor to try? Check all the wiring between the points and the coil in case something is shorted to ground and verify contact resistance of the points surface.
Just tried the other capacitor with no luck. Wiring seems fine. Can't seem to find a multimeter, one that works anyway so I'll have to pick one up tomorrow to check resistance and perhaps a timing light.
No timing light is needed. Verify that the point gap is 0.018-0.020", the coil to flywheel clearance 0.008-0.010", and make sure you did not reverse the ground and points connections at the coil as that would reverse the polarity at the spark plug.
ALso make sure the points are very clean and making electrical contact when closed. Make sure none of the connections are accidentally grounded.
Mark
ALso make sure the points are very clean and making electrical contact when closed. Make sure none of the connections are accidentally grounded.
Mark
Keep in mind that the spark occur when the points open, not when they close.
Mark
Mark
So I found that the points opened just a tad late, trying to spark just after the flywheel passes the coil. Once I set it dead on at TDC l I got a nice strong spark again. I'll run it tomorrow to make sure everything is set and if it holds up it'll go to work with my freshly rebuilt 272xp. Thanks for the help
How are you setting the points? As mentioned, the spark occurs when the points open but they are not fully open at this point, you have to turn the engine until the points are at their maximum opening and adjust at that point. You do not want the spark to occur at TDC, that is too retarded, those saws with fixed advance are usually set to spark at least 20 to 25 degrees before TDC.
I'm sure it's fine as it reliably starts one pull and idles beautifully. I set the piston to top dead and wiggled it back and fourth until the gap was at its largest then set the points down on the feeler, tightened and then just eyeballed roughly where it would fire between the points and where the flywheel hit the coil to make sure I was in the ballpark then gave it a test fire and it just immediately ran perfect and has been since. I'm not really the best at explaining my whole process but I do understand how it works just had a hard time getting it dead on. First couple tries were a bit too advanced I believe
As long as you have the gap set right and often the correct setting is stamped on the points box cover, which is better than a spec in a manual, the timing should be fine. Some manuals will also give another dimension called the "edge gap" and it is a dimension for the FW magnets relative to the coil legs when the points open and is a good way to get the timing to exactly what the manufacturer wants. You can't really tell much about the correctness of the timing by how the saw idles as quite a range of timing will allow this, what is important is to get the right amount of advance or the high speed performance could be off and the only accurate way to check it is with a timing light. Changing the points gap within a small range will change the timing by a few degrees, but it has to be kept close to the right spec or the spark strength will suffer.
