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I have an aftermarket cdi on a 10590 M-Series, It runs ok for the most part. I do have an annoying ping that comes and goes. I originally thought that it was from a dirty idle and main jet. I have cleaned both numerous times, installed a in line filter and siliconed the air filter gasket as it was not sealing letting in air. My plug is black, no part is brown. To me its running very rich. I think the pinging I am getting is the plug taken a partial foul. I installed a new plug and mowed the lawn. After I was done running in the garage I started to get the same pinging signs again. Pulled the plug and its black as the ace of spades. I really do not believe the jetting is that rich I think its in the voltage coming from the cdi. Does anyone have a recommendation for a cdi supplier or should I try and find one used off another M-series. Thanks,

M's use the same coil as Duraforce, no problems with mine.

I have an OEM cdi coming hopefully that will take care of this issue.

I have installed an OEM Cdi from Jacks small engine that cost 60.00. After running for 15 minutes the plug color appeared to be getting better the black soot started to go away. I have been chasing this issue for a year. When you install a new plug you are conditioned that it should last for quite awhile. Not so with the aftermarket cdi, the plug would foul after one mowing. I would say partial foul as the mower would run ok on start up then develop a miss especially if I let mower sit for a bit before returning to mowing. I figured it had to be something in the carb. Any way I think I have finally fixed the issue with an OEM coil. Here is a video kind of explaining the process.

https://www.youtube.com/watch?v=BFAs6YU172U

Good to know. Will keep an eye out for my LB's that have aftermarket coil.
Don't know if you are on mytractorforum, but lots of LB users in the Outdoor Power Equipment subforum.

I think I have finally fixed the fouling plug issue. I do believe that the cdi was partially the cause for issue. However I was reading a repair manual and it gave a plugged exhaust port for causing plug to foul. I have never taken off the muffler so I figure something I should check. Sure enough there was some build up one side of the port. After all the mower is 25 years old and I have no idea how much it was used before I bought a year ago. I do think this contributed to fouling the plug. I did see a difference in plug color with just a cdi change. My guess is that with a clean exhaust port I would have not had the issue with the aftermarket cdi in that the parameters are very close to the oem cdi.

Thank you lewb,

I personally appreciate anyone who takes the time to return and post their findings and belief about their engine discrepancy and the corrective actions.

I can't tell you how many times I turn to forums to educate myself on a situation only to find someone who is/was having a similar frustration, and there was no confirmation on how it was fixed or what they believe the problem was in the first place.... How terribly inconsiderate those people are. Sometimes, they stop back and say thanks, but do not describe their findings.

I guess I feel that this open and FREE forum situation is just one of the most wonderful tools the internet has to offer.
I have saved thousands of dollars by learning how to fix stuff for myself, I have earned thousands of dollars by helping my friends fix stuff AND saved them quite a bit of money in the process.

I feel that anyone who comes here to gain something from this knowledge base, should try to give something back to it. Even if what you offer is not correct or great information, make a statement. At least someone will correct you for the benefit of everyone on forward, your statement may get the reader thinking along the right path, or you will express a process or test that did not work and thus save the next guy from making that same mistake or taking those step as a waste of time.

I guess I am just an idealist...

Have a great weekend everyone!

Ancient memories here..Back in the 1960's CDI's appeared and promised a better spark. They did for me running a carbureted auto, but the sooty description you describe seems more like a fuel feed problem to me. I am sure you have checked float buoyancy, needle point and seat, stroke of float (low and cut off) , and jammed needle (from crud) by now? Also main jet diameter, (not drill out). The CD I used was great on start up, blasting away at deposits, but unknown by most at the time the duration of the spark was short and not conducive to power production (not a concern here).

Yes, let us hope the good members of this forum continue with the generosity and patience typically shown .

motoman said:

Ancient memories here..Back in the 1960's CDI's appeared and promised a better spark. They did for me running a carbureted auto, but the sooty description you describe seems more like a fuel feed problem to me. I am sure you have checked float buoyancy, needle point and seat, stroke of float (low and cut off) , and jammed needle (from crud) by now? Also main jet diameter, (not drill out). The CD I used was great on start up, blasting away at deposits, but unknown by most at the time the duration of the spark was short and not conducive to power production (not a concern here).

Yes, let us hope the good members of this forum continue with the generosity and patience typically shown .

Click to expand...

When I bought the mower is was not running. So I have only seen the same plug color. My dura force with a drilled out main jet has a nice brown color. I have taken carb off and cleaned more than once. As far as I know the float, needle and seat are working correctly. I did have the float stick once when I re-assembled and installed it. I do have some mikuni jets from a round slide carb that I believe would thread in to this carb. I would like to go down one size to see if there is a difference. So far I have mowed my lawn 3 times with my original plug that I cleaned up with emery paper. I have not gotten a ping or miss since but the plug color is still pretty black. I am going to put a new plug in and see if that turns black as well.

Hi Lewb,

You may want to try an Autolite platinum plug. They used to be available from Miejer's but they don't stock them anymore. All I can say is I had an old Formal cub that missed using AC plugs, once I switched to Autolite plugs the miss went away.

Jeff

jp1961 said:

Hi Lewb,

You may want to try an Autolite platinum plug. They used to be available from Miejer's but they don't stock them anymore. All I can say is I had an old Formal cub that missed using AC plugs, once I switched to Autolite plugs the miss went away.

Jeff

Click to expand...

Thanks, I might have to try one.

Hi Lewb,

I re-reading through this thread, it wasn't mentioned, what is the color of the spark? Should be blue in color, yellow means it's weak. Have you checked the compression of the cylinder? I'm not sure if an engine with lower compression would cause your problem or not.

Jeff

jp1961 said:

Hi Lewb,

I re-reading through this thread, it wasn't mentioned, what is the color of the spark? Should be blue in color, yellow means it's weak. Have you checked the compression of the cylinder? I'm not sure if an engine with lower compression would cause your problem or not.

Jeff

Click to expand...

Plug color is dark black, 105 cold 100 warm, might be down some, not sure how that effects plug color. The dura force has 115 cold and the plug color is brown.

I think the compression should usually be higher when warm. Everything expands and tighter clearances.

Just a thought...

I have some OMC Engine Tune. It came in both aerosol and gallon jugs. It will (supposedly) break down carbon deposits and clean the rings/ring grooves in the piston.
It is for the outboard engines. You would pulse spray it in the intake bore of a warm, running engine without stalling out, then at the end you let it flow until stall. Let it sit for an hour, then fire it up and let it burn off.
I would also go in the spark hole and spray the bore with the little aerosol tube, too.

You can get a similar product at West Marine by their 2 cyc oil display by QuickSilver.

Black and sooty is fuel related.
Oil, oil mixture, fuel, fuel additives, and/or carbureation too rich.
And, as I'm sure we know, the spark plug looking like the color of cocoa powder is ideal. (so dad taught me)

I grew up hearing about a "hotter spark plug" when your old worn engine has a greasy oily black spark plug.
10 years ago, I attended a Champion seminar at an aviation show. Turns out the hotter plug has to do with, no, not a hotter spark...
... but, the spark plugs ability to remove heat from the cylinder. Huh?!?
Turns out that they make a longer porcelain insulator snout that is less inclined to transfer the heat to the surrounding cylinder head, thus making the cylinder run a little hotter.