# Craftsman 25cc two-cycle engine spark problem.



## jmann7 (Oct 14, 2017)

I am trying to fix a neighbor's Craftsman weed wacker. It will not run because there is no spark. I have always fixed my cars, mowers, etc. and figured it needed a new coil. I purchased a new coil and even bought a spark tester which is used to replace the spark plug so that you can easily see the spark. I have not been able to get a spark. I have removed the engine block from the gas tank, throttle lever, etc. so that I only have the engine block with the new coil and spark tester on my workbench. This engine has one of those crank devices where you can buy a device for your drill, insert the device into the engine crank, and use your drill to start the engine. 

I still cannot get a spark. I have my drill rotating the flywheel and crankshaft, the new coil installed, the spark tester in place of the spark plug, and no other wires such as the kill switch attached but still no spark. The flywheel magnets have good magnetism and the coil gap is properly set.
Is there something unique about these little 25cc two-cycle motor which is causing my problem.

I am completely stumped. Any help would be appreciated.


----------



## AVB (Nov 28, 2014)

Without the model number it is a guess. 

Four things to check for.


That the flywheel magnets are strong.
That you are spinning the engine in the correct direction, a few run CCW. Your recoil will tell the correct direction.
That coil laminates are ground to cylinder. Several chainsaws I work on need a separate grounding strap due to coil being mounted on plastic.
That you didn't install the coil upside down. Some are easily done, other are nearly impossible to do.


----------



## jmann7 (Oct 14, 2017)

I do not understand the situation when dealing with the coil not being grounded to the cylinder and how a grounding strap is used. Please explain.

The model number is one of the following 3167110(20,21,22 or 23). I could not get the complete model number because part of it was destroyed.


----------



## AVB (Nov 28, 2014)

jmann7 said:


> I do not understand the situation when dealing with the coil not being grounded to the cylinder and how a grounding strap is used. Please explain.
> 
> The model number is one of the following 3167110(20,21,22 or 23). I could not get the complete model number because part of it was destroyed.


Look at the engine design on this one and a grounding is not necessary due the all metal contact between the coil laminates and the cylinder.

A grounding strap is use on engines that have plastic crankcases. It is basically a piece of conductive metal from the coil laminates to the metal cylinder. On this particular machine it not necessary.

From your previous posts it sounds like you have defective coil on your hands.


----------



## jmann7 (Oct 14, 2017)

This is the second coil that I have tried. The first one was used from ebay, the second one which is currently on the engine is a new one. If it is not the coil then I guess it must be the flywheel which has the magnets. If I can find one from Amazon I am going to order it because if it does not solve the problem then I can return it. I think this is why Amazon is killing everybody else. My daughter, who lives with me and works for Amazon from our home, says I can return stuff if it has not been used for a refund minus the return shipping cost.


----------



## jmann7 (Oct 14, 2017)

Problem solved. I decided to quit messing around with the coil tester and put the weed trimmer back together to find out if it would run because it did have a new coil. I was able to start it with no problems. I took a closer look at the spark tester and found the 2 adjustable contacts were actually in contact with each other which meant there would be no spark when the flywheel passed by the coil. The spark tester was a cheap one with the contacts being in a plastic cylinder which made it hard to clearly see the contact points due to the reflection caused by the curvature of the cylinder. I am 76 years old and wear glasses which made it hard to set the adjustable contacts because of the curvature of my glasses and the plastic cylinder. This goes to show that I should have spent a few more dollars and purchased a better quality spark tester which I am going to do.

Anyway, I am now a happy Mann.


----------



## AVB (Nov 28, 2014)

Glad you got it fixed...I would not never thought of the spark tester problem but of course I have never used one either.

I too wear glasses. SO nearsighted that I need my regular glasses and a pair of reading glasses to see my computer screen. I am constantly mis-placing the glasses as I look at things up close where neither glasses helps.


----------

