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Tecumseh TC300 2-stroke has weak spark


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09-18-07, 05:59 PM   #1  
Tecumseh TC300 2-stroke has weak spark

Tecumseh TC300 2-stroke engine has very weak spark. You can barly see or hear the spark even in dim light. The spark is also intermittent, where majority of time it is sparking but weak. Sometimes, there appears to be no spark at all. Once in a great while (after 50 pulls of stater cord) you may see one bright strong spark. I would expect a strong spark with an easily seen and audible snap, snap, snap. The entire ignition system consists of the flywheel magnets, solid state ignition module and sparkplug. The ignition module has been replaced and several spark plugs tried, with no change in the spark. The magnets appear to be strong. Spark appears strangly intermittent. The engine is very difficult to start, if it starts at all. Thanks for any advice.

 
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09-18-07, 06:13 PM   #2  
I'm not famillar with this engine, but it sounds like you've got the bases covered, but just for a last try, disconnect the kill wire & try it again. I wonder if you have some problem with the kill circuit?? Hang on, the pros will be here soon with more experience on 2-stroke tecumseh!! Good luck, Roger

 
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09-18-07, 06:19 PM   #3  
One last thought, Is it possible the ign coil could be installed backward?? I ran into this with a Kohler & had weak, intermitant spark. I posted that one here & someone had it pegged in an hour. Let us know how you make out, Roger

 
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09-18-07, 06:27 PM   #4  
Tecumseh TC300 2-stroke has weak spark

You may be onto to something hopkinsr2 about the kill switch. I had checked the kill switch with a ohm meter and it measured good (zero and infinite resistances). However, this was tested in perfect conditions with the toggle switch fully on and off. Perhaps when the engine is being vibrated during the starting process the switch could be intermittent. That would seem a most likely reason for an intermittent spark. I will have to try disconnecting it entirely. As for the ignition module, it can only be installed one way. Thanks for the replies.

 
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09-18-07, 06:44 PM   #5  
tecumsek TC300 2-stroke has weak spark

Oh yeah! The TC300 is a small 50cc (3.0 cubic inch) engine used in some portable power equipment. In this case it is for powering a bicycle with a roller on the rear tire. A friend asked me to troubleshoot why it was so hard to start and would then soon die. He thought it was the carb. I thought the symptoms sounded like ignition problems. I am used to wrenching on motorcycles and dirt bikes, that have very strong sparks with a very audible snap. With a weak spark you could barely see, I felt I was onto something.

 
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09-18-07, 11:12 PM   #6  
Is the armature air-gap set correctly? Do you get better results if you spin the engine faster? Is the spark blue, or orange?


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09-19-07, 05:12 AM   #7  
Tecumsek 2-stroke has weak spark

The air gap has been set correctly. The spark is always light yellow. Spinning engine faster appears to increase the spark slightly, but it is still light yellow. It is never blue or orange.

 
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09-19-07, 05:25 PM   #8  
Tecumseh TC300 2-stroke has weak spark

I disconnected the kill switch. Also rechecked the air gap between the ignition module and the flywheel magnets. There is a blue spark but it still seems very weak. It is a little stronger if you spin the flywheel faster. In order to see the blue spark, you must check it in a darkened room. Also, on the ignition module, there are two areas of laminations (separated by and inch or so) that ride above the flywheel magnets. I set the air gap as per the service manual. However. the manual does not specifically mention the required gap for the 2nd set of laminations. Should this be set for the same gap width?

 
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09-19-07, 07:30 PM   #9  
The gap shoud be the same for both legs of the armature. If you have a new armature set correctly, and the kill switch is disconnected and the spark is blue and consistent, I would think the ignition system is fine. The fact that it's a thin spark can be ok, as long as it's blue. You might change the width of the spark with a different type plug.


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09-20-07, 12:10 PM   #10  
For what it's worth and for confirmation, the TC-series Tecumsehs are the only Tecumsehs that require a .030" coil airgap. All other solid state ignitioned Tecumseh's are set at .0125". What spark plug do you have installed and at what gap? The correct Champion plug is a RCJ8Y set at .030". Is the kill switch set into the flywheel shroud on yours? If so, I've seen these switches fail frequently and if you replace it, it should be Tecumseh part number 610650B.

 
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09-21-07, 08:12 PM   #11  
Tecumseh TC300 2-stroke has weak spark

I am using both new and old Champion RCJ8Y plugs with gap set to .030". Both plugs were sent from factory at .025". I've set the air gap of both armature legs to .030". I have previously tried an air gap of 0125". The kill switch is mounted on the flywheel shroud. Previously I had an intermittent spark yellow in color. After alot of fiddling I now seem to have a consistent blue spark, although it is very thin. Since the engine is not mounted on the bicycle, trying to start it is not an easy task. I'll try it tomorrow. Many thanks for the replies.

 
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