Weedeater coil airgap

[bjorn773]

Don't laugh. I'm working on a string trimmer I was given. It has no spark. I checked the stop switch for resistance to make sure it wasn't shorted. I figure either my airgap is off or my coil is shot. Anybody know what it should be?

 

[nmurph]

stick a business card in there and you should be good to go. well, you do need to pull the card back out after you tighten the coil down.

 

[bjorn773]

Thanks, it isn't making sense. It ran before my boss tore it down to reseal the crankcase. I put it back together, now no spark. I'll try cleaning the coil and flywheel, it's pretty oily in there.

 

[striperswaper]

does it have points?

 

[lawnmowertech37]

Don't laugh. I'm working on a string trimmer I was given. It has no spark. I checked the stop switch for resistance to make sure it wasn't shorted. I figure either my airgap is off or my coil is shot. Anybody know what it should be?

What brand is the trimmer and what model ?

 

[bjorn773]

I don't see any points. It's a Weedeater Featherlight SST. Reset the airgap and still no spark.

 

[spudulike]

Ive had similar on a couple of saws - all I do is to take a sheet of typical A4 printer paper, fold a piece in half, place it between the flywheel and coil and then rotate the flywheel until the magnets are in line with the coil, loosen the coil and let it pull itself on to the paper using the flywheel magnets and then do up the location screws.

This has always worked for me, some coils need a thumping good pull on the handle to spark, some need much less - my Jonsered 630 needs a good tug as does my newly required Makita 340 so pull it over pretty sharpish to see if it is ok - make sure the coil ignition cut off isnt earthed out.

Spud

 

[bjorn773]

I used a business card but still get nothing. The previous owner said it died on them. They found a ruptured fuel line, which I have since replaced. Maybe the fuel line was not the problem. It's looking like this coil/magneto is bad.

 

[maico490]

Try it with the earth wire disconnected from the coil.

 

[eyolf]

Weedeater hasn't had a trimmer with points for years and years; that featherlight dates back maybe into the '90's.

Clean and set coil gap, double check for insulation failures. Unlikely that good coil would fail just sitting around, but also check magnets. Time honored check is will flywheel hold a 3/4" 1/2" drive socket? You can usually feel the magnets grabbing the coil legs as it rotates by, too.

 

[bjorn773]

Try it with the earth wire disconnected from the coil.

I just did. I removed both wires from the kill switch, cranked it and got nothing.

I didn't try a socket, but the magnets sure grabbed the coil hard when I was setting the gap.

 

[nmurph]

lightly sand and clean the magnet. it may be rusted from sitting and not getting enough voltage across the gap.

 

[lawnmowertech37]

set the air gap to about .008 - .012 thousands with a feeler gauge and see what you get then ?
if nothing you need a new module assy
this does not use points it is electronic ignition system
on the unit you will see a id tag supply me with the #s off the id tag i can check availability on a replacement module for it who knows i may even have one around here

 

[a. palmer jr.]

Those modules are plentiful and cheap. Sometimes you can find weedeaters at yard sales and flea markets. I have a lawnmower shop near me that sells them for $5. When many people have trouble with them around here they throw them away and buy a new one so there's lots of used parts floating around. I think there's a part number on them, not sure.

 

[tallfarmboy]

For just about every solid state module I have ever worked on, I double up a piece of notebook paper and find that it works perfectly.
As stated though... those weedeaters are almost given away once they develop a fuel issue (usually carb related) I bet you could find a new module pretty cheap.
Also, get yourself an Ohm meter and check for continuity through the plug wire.

TFB

 

[tallfarmboy]

One other thing... what condition is your plug in? Have you tried to get spark with a different plug? I have seen plugs with an internal short that would NOT let the spark get through to the electrode.

TFB

 

[bjorn773]

I've tried with an adjustable gap spark tester and a couple spark plugs. What should my coil resistance be? It seems like these parts should be pretty plentiful used, they made a ton of these units.

 

[KRP]

lightly sand and clean the magnet. it may be rusted from sitting and not getting enough voltage across the gap.

Voltage does not cross the flywheel to coil gap, only at the spark plug gap to ground. Cleaning the magnets helps set the gap accurately and keeps your business card clean.

 

[a. palmer jr.]

I've tried with an adjustable gap spark tester and a couple spark plugs. What should my coil resistance be? It seems like these parts should be pretty plentiful used, they made a ton of these units.

On most units nowadays they use ignition modules which includes more than just the coil. On a points ignition the primary side of the coil measures usually less than ten ohms while the secondary side is many times that, depending on the voltage needed. I'm not sure you can reliably test the module with an ohmmeter. Use a good sparkplug, set the airgap at about .010, unhook the wire from the kill switch and give her a try. If you don't have spark, good chances the module is shot.

 

[bjorn773]

Thanks for the help. Sorry I'm delayed in responding. I abandoned mission on this one since I was given another unit over the weekend. One final question: are the shafts interchangeable on these featherlites? Could I take the straight shaft and head off mine and put it on my father's curved shaft? He'd prefer a straight shaft if possible.