Someone please help

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Agreen

Agreen

Member
Feb 10, 2013
792
11
18
Southeastern GA
Before I throw this weedeater leaf blower is hard as I can in to a lake. With bricks tied to it.


A little history:

-I found it sitting in a pile of crap by a trash can.
-It has good compression.
-I rebuilt the carburetor, and it's definitely working (fuel sprays out soooo nicely without the spark plug in)
-I have resealed the crankcase
-I seem to have intermittent spark.

If I pull the spark plug and put a finger over the hole, it pushes my finger away and shoots fuel mist, every revolution. It has NOT ONCE even coughed or chugged. I pulled the carb (zama/walbro diaphragm carb) and cleaned it. And I do mean CLEANED it right! I completely disassembled it, soaked the metal parts in carb dip over night, and i even pulled the high and low needles out and shot carb cleaner through them to see that the main jet and idle orifices weren't blocked. The crank case leaked, and I fixed the leak. The primer works great, it has a new filter stone and fuel lines. Now it's carburetting, but not firing at all!

I tested spark with a tester, and got good spark. Later I did the same test and got no spark. I fooled with the settings some more, nothing. I tested spark by grounding the plug and got good blue sparks. Did some more work, then I get a few random sparks every few rotations. I have other (similar) 2 strrokes sitting in my garage, so I tried replacing the CDI with another one. Same spark story, and still no start. The magnets... well, I don't think the magnets can lose their magnetism. The flywheel can not be keyed any other way (there's a flat side, and the fins go out). I also set the air gap for the magneto with 3 sheets of notebook paper as recommended. Nothing. It's a good plug, I've tried 3 different plugs, another CDI, and the carb works, and it has compression (and crankcase pulse to the carb's diaphragm, which would keep it running, not prevent it from starting)

Should i drop the $30 on a new CDI for a gamble? I don't want to keep pouring money in to something that's not worth it. I have an electric leaf blower, i just thought a gas one would be nice to not have to drag my extension cord around.

Thoughts?
 
YesImLDS

YesImLDS

Member
Jun 29, 2013
960
12
18
Columbia, Missouri
Is there anyway to set timing? Could be you have everything properly, but the timing is off. I don't know much about any other 2-strokes than china girls, but if you have compression, fuel and spark that's all you technically need to start a motor, but if it's not timed to spark at the right moment it won't run.
 
xseler

xseler

Well-Known Member
Apr 14, 2013
2,886
151
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OKC, OK
If this is an actual "Weedeater" brand, they were notorious for their cylinder heads becoming just loose enough to suck air past the base gasket. It caused some weird-assed problems. Would start and run normally one time. Not start the next. Or would start and then immediately redline and die. Might be worth a check.

Good luck!
 
Agreen

Agreen

Member
Feb 10, 2013
792
11
18
Southeastern GA
Nope, the flywheel contains the magnets for the cdi, and it can only go on one way. There's a set of pawls that go towards the outside for the pull start. If it were on backwards, I wouldn't be able to pull start it.

Sounds weird, huh? I can get an engine tuned if it at least gives me something to work with. But not even a cough!

I'm thinking weak or dying CDI module, but 2 in a row? Well, I will say that I never really did get the chainsaw working that I pulled that other CDI from. So I could just be changing out parts with bad parts!!
 
2door

2door

Moderator
Staff member
Sep 15, 2008
16,302
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Littleton, Colorado
Terrence,
If fuel is "spraying out" of the spark plug hole when you spin it over it sounds to me as if you have an excess of fuel and a too rich mix to start. You shouldn't see that much fuel coming into the cylinder. My first guess is there's something wrong in the carburation circuit based on your description of what you're seeing. Too much fuel and drowning the plug is my suggestion.

Try pinching off the fuel supply and start with a dry plug and a little fuel dribbled into the carb inlet and see if it fires.

Tom
 
Agreen

Agreen

Member
Feb 10, 2013
792
11
18
Southeastern GA
xseler said:
If this is an actual "Weedeater" brand, they were notorious for their cylinder heads becoming just loose enough to suck air past the base gasket. It caused some weird-assed problems. Would start and run normally one time. Not start the next. Or would start and then immediately redline and die. Might be worth a check.

Good luck!
Click to expand...
Yes, weedeater brand. And you're right! The crankcase leak I fixed was the cylinder jug bolts were loose and stripped! So I pulled it all apart, cleaned it thoroughly, drilled the damaged threads out of the base, tapped them, inserted a helicoil thread repair (1/4x20) and used red loctite on the thread insert and bolt. The spaghetti seal was still good, but I played a thin layer of fuel-resistant sealant around it anyways.
 
Mike B

Mike B

New Member
Mar 23, 2011
2,256
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Central CA
Put it back in the trash can where you found it, that's where it belongs.

Junk is junk. Take out the trash!
 
Agreen

Agreen

Member
Feb 10, 2013
792
11
18
Southeastern GA
2door said:
Terrence,
If fuel is "spraying out" of the spark plug hole when you spin it over it sounds to me as if you have an excess of fuel and a too rich mix to start. You shouldn't see that much fuel coming into the cylinder. My first guess is there's something wrong in the carburation circuit based on your description of what you're seeing. Too much fuel and drowning the plug is my suggestion.

Try pinching off the fuel supply and start with a dry plug and a little fuel dribbled into the carb inlet and see if it fires.

Tom
Click to expand...
Ha-ha, that was before I turned the high and low needles in. I actually had it assembled for a bit with the needles only in by about 1/2 a turn each.

I fixed it by turning the needles in all the way and pumped the remainder of the fuel in the transfer area out without the plug in, dried the spark plug off, then another attempt.

Here's where I got creative. I used a corded power drill and cranked it with that while fiddling with the mixture settings.

Still, nothing.
 
Ludwig II

Ludwig II

Well-Known Member
Jul 17, 2012
5,071
783
113
UK
Perhaps it's female and just doesn't like you. 2 strokes are like that. Divorce it.
 
MEASURE TWICE

MEASURE TWICE

Well-Known Member
Jul 13, 2010
2,775
1,274
113
CA
Below I mention about a gas generator, but note the electricity generated from the generator is not what I am pertaining to on how I fixed the generator. I am taking about the engine part of the gen-set and getting the engine to run.

I have a old Coleman Generator that was really hard to start I got for free from a guy that got a newer generator. I found the spark intermittent and eventually then nothing, so I got a new magneto. The magneto with these include in the epoxyed area next to the coil laminations some active device, some kind transistorized thingy to make the spark. No separate points and condenser like on the old non-electronic Briggs & Stratton Engines I have always known inside an out. The Briggs also have an updated version of their magneto and you disconnect the movable points parts making it solid state ignition, the magnet on the flywheel moving past the magneto laminations and the distance of the magnet to the lamentations along with the stuff you can't see electronic do the rest.

Ok, then I got the spark and have it running.

So you say you changed the CDI by swapping from another of the same (hopefully other known good running engine).

You could also still have a weak spark that under compression will not fire. With spark plug out in ambient air pressure you could be getting fooled that it is also sparking inside the cylinder.

I don't know if hooking a inductive coupled clip on timing light to the spark plug high tension wire as you pull the recoil and look for a flash actually tells you something. Does anyone know if the strobe light on the timing light would flash but no spark simultaneously inside the cylinder under compression the spark plug would not actually fire?

Just throwing this around to see if maybe it is something that could be done.

You can actually have magnets get weaker. Heat is a killer of the magnet flux. There are some ways to use another magnet and try to get the one on the flywheel recharged. Something was said somewhere about magnetos losing magnetism, but I thought they only utilize the magnetism from the flywheel magnet., but I guess some old engine do have magnets built into the magneto on them.

What if it is not too much trouble swap the flywheel also along with the CDI, and see. If the magneto is something separate from the CDI, that too. Shot gunning trouble shooting is not what this is too much of as long as you have the time and since you have free parts, I myself am interested to see what happens.

On magneto recharging of old engines
http://www.gasenginemagazine.com/gas-engines/magneto-recharging.aspx
 
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