Motor gurus?

[Gregor 4,846]

For you motor experts out there, I have a puzzling problem. A guy asked me to look at his Troy Bilt Tiller. It has a Kohler K-161T motor on it. If I put my spark tester on it, between the high tension lead and ground, I have good spark. If I go between the high tension lead and spark plug, I have nothing. I have tried 4 NIB spark plugs. Same result with all of them. I have a K-161T exactly like this motor. Mine runs fine. I took the coil, condenser, and points from my motor, and installed them on this motor. Spun it over, and it ran for about 1/2 second and died. Now I have no spark again. I am at a loss. Any ideas?

 

Thanks  Greg

[Pullstart 62,905]

Did you use the spark plug from your 161?  I would suspect if you have a good one, you could try that.

[953 nut 55,281]

Could be a bad condenser. Remove the wire from the condenser and see if spark returns. The condenser is intended to extend the life of the ignition points. The engine can run without a condenser though not for an extended period.

[squonk 41,137]

He swapped the condenser already. I'm assuming this is a rope start magneto engine? If it is check your kill wire for chafing causing the coil to get partially grounded out

Edited February 12, 2023 by squonk

[wallfish 17,004]

Once had a K91 acting like that. Spark was OK with the plug out laying on the head but it would always loose spark with the plug installed. Drove me nuts!

Adjusting the points at very small intervals solved the problem somehow. It ended up pretty far off of .020

Guessing it was because of a weak spark (Coil maybe?) because it was always a soft orange, never got near that nice sharp snapping blue spark.

[Gregor 4,846]

I had already taken the wire off of the condenser, and got the same result. There is actually spark, but it's very weak, and very intermittent. 

 

There is no kill wire, just that little button on the points cover housing.

 

It is this type of coil. This one is from my motor, and it ran fine.

[squonk 41,137]

53 minutes ago, wallfish said:

Once had a K91 acting like that. Spark was OK with the plug out laying on the head but it would always loose spark with the plug installed. Drove me nuts!

Adjusting the points at very small intervals solved the problem somehow. It ended up pretty far off of .020

Guessing it was because of a weak spark (Coil maybe?) because it was always a soft orange, never got near that nice sharp snapping blue spark.

Yup. Play with the points gap. Mags are more fussy when it comes to the primary circuit build up time. How about the flywheel magnets? Did you try swapping flywheels? 

[Gregor 4,846]

6 minutes ago, squonk said:

Yup. Play with the points gap. Mags are more fussy when it comes to the primary circuit build up time. How about the flywheel magnets? Did you try swapping flywheels? 

There is only one large magnet. It is secure and seems to be quite strong, but I will try that.

[Gregor 4,846]

Same result. I will try playing with the points some.

[Gregor 4,846]

After playing with the points, and finally setting them at a loose .010", I was getting spark again. So I put the whole thing back together, spun her over, and she fired right up.   It will only run on about half choke, so I am going to clean and rebuild the carb. Thanks everyone for your help. I think this old guy really needs this tiller. I thing tilling gardens and doing yard work is pretty much how he supports himself

 

Thanks again.  Greg

[oliver2-44 9,756]

2 hours ago, Gregor said:

 I think this old guy really needs this tiller. I thing tilling gardens and doing yard work is pretty much how he supports himself

 

Thanks again.  Greg

 for helping this guy out. 

Its people like you that make Red Square the great forumn that it is.

[953 nut 55,281]

You may want to take a look at what condenser you are using. Here is a bit of information about them.

The Kohler 230722 Condenser fits all battery ignition single cylinder and twin cylinder from the K-90 to the K-582.  The 235786 condensers are for the magneto equipped Kohler engines only K-161 to K-301

The unit of measure for a condenser is the Farad. Many electronic components like radios and TVs use capacitors that are in the microfarad range (ten to the minus six power Farads) and our small engines use a condenser that is in the nanofarad range (ten to the minus ninth power Farads) which is based on the voltage range they work in. A magneto ignition system uses a 100 to 250 nF condenser and a battery ignition system uses a 200 to 500 nF condenser. A good multi-meter will have a capacitor testing function.

Armed with this information you can walk into your auto parts store and get a very confused look on the face of the person on the other side of the counter. The capacitance is not listed on the package and probably not in any of the on-line data they have for the condensers they stock. You just have to go by the application chart and be sure that the condenser you are buying is for the type ignition system your engine has, not just the horsepower or engine size.

If an engine idles well, but runs erratically when revved up, like it hits and misses, pops and backfires, then chances are, it needs a new condenser/capacitor. And always install a condenser/capacitor with the wire facing downward so rain water and/or when washing off engine, water will not enter inside condenser/capacitor, ruining it. With water inside the condenser, this will also allow it to idle well, but cause it to run erratically when revved up.

What is a farad (F)? A farad (F) is the standard unit of capacitance (C) in the International System of Units (SI). It indicates the ability of a substance to hold an electric charge. The value of most electrical capacitors is expressed in farads, microfarads (µF) or nanofarads (nF)