Faulty coil/ignition problem tip.

[TownsendsFJR1300]

Just wanting to share a tip I recently used to diagnose a faulty coil.

The machine is a 2 stroke, "Weedeater" hedge trimmer, which I've owned 6-8 years (GHT225). Short of fuel lines its always ran flawlessly.

I was using the machine fairly hard the other day, it was very warm outside as I'm trimming away. Out of nowhere, it just starts to misfire and dies. Pull and pull, no start. 2-3 minutes later, starts like normal... Several times within an hour, does it again and again. Sounds like ignition failing. BTW, there are no #'s to test the coil..

Pull out my old timing light (clamps onto a 12 volt battery for power), the other wire of the tool clamps around the spark plug wire (between the plastic housing and the spark plug cap). Of course the motors cooled some and fires up. Turn off all the fan's in the garage and pull the trigger on the timing light, which of course lights up. Idles great, high speed is fine, light firing as expected.

After several minutes of running, getting it to that "certain" temp point (mine was at about mid throttle), it starts misfiring, the timing light firing intermediatly with the misfire. Light goes out, engine dies... Pull, no light.. Give it a couple of minutes, fire it up, timing light of course fires up...

Install a new coil (old one looked fine, flywheel to coil gap was correct).


The point,

While this isn't a MC engine, the diagnoses can be applied to any engine (including the FZ) if the ignition is in doubt/misfiring. Your able to isolate a single coil that could pass a "cold", meter test, but later act up when warm/hot or at a certain RPM.

Just an FYI to help when doing some trouble shooting for a misfire (intermediate or come and go). :thumbup:

 

[trepetti]

Thanks. That is great advice and really shows the 'McGyver' in you. Now.... Where did I put my old timing light?

 

[TownsendsFJR1300]

My original Sears light died years ago, this was a very cheap unit my neighbor gave me, but it worked!!!:thumbup:

 

[Motogiro]

Thanks. That is great advice and really shows the 'McGyver' in you.

Next week Scott will show us how to carve a db killer out of a pertater! :BLAA:

Good idea Scott! I seem to also remember an old type spark tester that used a little neon bulb that worked off induction around the spark wire. One end grounded and the other end just touched the outside jacket of the wire and you could see the same thing. Wonder if they're still around... somrthing like this. http://compare.ebay.com/like/251227888842?_lwgsi=y&ltyp=AllFixedPriceItemTypes&var=sbar

I miss the hum of my old timing light!

 

[TownsendsFJR1300]

Gaining access to the pretty short plug wires would be the hardest part.

The inline testers are great but with as deep as our plugs sit in the head, it'd likely be an issue just getting to them. If you can see the plug wire, you can slip the timing light end over it, no jerking on the cap ends (as fragile as they can be).

In my Weedeater issue I used a spare 12 volt battery to power the timing light up.

You could do the same for the FZ so you don't lift the tank.

You really don't want the tank lifted, as if heat is indeed causing the breakdown of the coil, you want to keep that operating heat there
(not vented and cooling down with the tank up). :thumbup:


I'll have to look into the "pertater" DB killers but suspect it'll likely turn into french fries!

 

[Motogiro]

I'll have to look into the "pertater" DB killers but suspect it'll likely turn into french fries!

The type tester I was thinking about had a ground clip and if you just touched the high tension plug wire jacket it would light.
Lol! I do the same with the pertators but usually home fries fer breakfast!


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