I have a 2-cycle trimmer that was working just fine. Then during it's last use the speed began declining while in full throttle mode until it finally died. I changed the spark plug and now it only runs with the choke closed. If I try to open the choke or let off the throttle the engine dies. Any suggestions?

On Fri, 3 Jul 2015 15:57:42 -0700 (PDT), wrote:

I have a 2-cycle trimmer that was working just fine. Then during it's last use the speed began declining while in full throttle mode until it finally died. I changed the spark plug and now it only runs with the choke closed. If I try to open the choke or let off the throttle the engine dies. Any suggestions?

Just guessing, dirt in a carburetor port.

Closing the choike limits the air and increases the ratio of gasolne to
air. If there is very little gas going into the gas-air mixture in the
first place, that could be making it rch enough to run.

Does it put out black smoke when it's running with the choke closed? If
it usually does and now it doesn't that supports my view.

What to do? What's that spray int he black and white can meant to
clean carburetors. I'd try that, all over, before rebuilding the carb.
Gum out. And maybe mix some gum-out that's designed to be mixed with
the gas with the gas,

If you decide to clean the carb better than this, post back.

On 7/3/15 6:57 PM, wrote:
I have a 2-cycle trimmer that was working just fine. Then during it's
last use the speed began declining while in full throttle mode until
it finally died. I changed the spark plug and now it only runs with
the choke closed. If I try to open the choke or let off the throttle
the engine dies. Any suggestions?


Mine is nearly 35 years old, but I guess they are the same in many ways.

I have a Walbro carb. On the side with the fuel inlet is a plate held
by a center screw. That's the pump compartment. With the choke on and
the throttle open, the pump gets bigger air pulses to pump harder. For
me, the problem has usually been that moisture in the fuel has caused
the outlet screen of the pump to clog. A q-tip and a little cleaning
solvent will fix it.

The last time, gas deposits on the face of the body against which the
pump gasket seated, showed that I had an air leak, which kept the pump
from working right. Removing the deposits fixed it.

On Fri, 03 Jul 2015 21:11:30 -0400, J Burns wrote:

On 7/3/15 6:57 PM, wrote:
I have a 2-cycle trimmer that was working just fine. Then during it's
last use the speed began declining while in full throttle mode until
it finally died. I changed the spark plug and now it only runs with
the choke closed. If I try to open the choke or let off the throttle
the engine dies. Any suggestions?


Mine is nearly 35 years old, but I guess they are the same in many ways.

I have a Walbro carb. On the side with the fuel inlet is a plate held
by a center screw. That's the pump compartment. With the choke on and
the throttle open, the pump gets bigger air pulses to pump harder. For
me, the problem has usually been that moisture in the fuel has caused
the outlet screen of the pump to clog. A q-tip and a little cleaning
solvent will fix it.

The last time, gas deposits on the face of the body against which the
pump gasket seated, showed that I had an air leak, which kept the pump
from working right. Removing the deposits fixed it.

I'd go with what J B said. (After all, he invented welding.)

wrote:
I have a 2-cycle trimmer that was working just fine. Then during it's last use the speed began declining while in full throttle mode until it finally died. I changed the spark plug and now it only runs with the choke closed. If I try to open the choke or let off the throttle the engine dies. Any suggestions?

I don't know how old it is but exhaust port maybe plugged up with
carbon/dirt.
Just remove muffler and look, see.

On Fri, 03 Jul 2015 20:07:42 -0600, Tony Hwang
wrote:

wrote:
I have a 2-cycle trimmer that was working just fine. Then during it's last use the speed began declining while in full throttle mode until it finally died. I changed the spark plug and now it only runs with the choke closed. If I try to open the choke or let off the throttle the engine dies. Any suggestions?

I don't know how old it is but exhaust port maybe plugged up with
carbon/dirt.
Just remove muffler and look, see.
Carburetor deposits and vacuum leaks are much more likely on today's
2 strokes since most run on a weak oil mixture, using low ash
clean-burning (relatively) oil - and ethanol gasoline. This adds up to
low exhaust deposits, and all kinds of sneaky stuff clogging up fuel
systems and deteriorating gaskets etc.

On Friday, July 3, 2015 at 9:42:18 PM UTC-5, wrote:
On Fri, 03 Jul 2015 20:07:42 -0600, Tony Hwang
wrote:

wrote:
I have a 2-cycle trimmer that was working just fine. Then during it's last use the speed began declining while in full throttle mode until it finally died. I changed the spark plug and now it only runs with the choke closed. If I try to open the choke or let off the throttle the engine dies. Any suggestions?

I don't know how old it is but exhaust port maybe plugged up with
carbon/dirt.
Just remove muffler and look, see.
Carburetor deposits and vacuum leaks are much more likely on today's
2 strokes since most run on a weak oil mixture, using low ash
clean-burning (relatively) oil - and ethanol gasoline. This adds up to
low exhaust deposits, and all kinds of sneaky stuff clogging up fuel
systems and deteriorating gaskets etc.

Someone gave me a WeedEater leaf blower recently that had the problem that Tony describes...nearly closed-off exhaust port.

On Fri, 3 Jul 2015 20:23:06 -0700 (PDT), bob_villa
wrote:

On Friday, July 3, 2015 at 9:42:18 PM UTC-5, wrote:
On Fri, 03 Jul 2015 20:07:42 -0600, Tony Hwang
wrote:

wrote:
I have a 2-cycle trimmer that was working just fine. Then during it's last use the speed began declining while in full throttle mode until it finally died. I changed the spark plug and now it only runs with the choke closed. If I try to open the choke or let off the throttle the engine dies. Any suggestions?

I don't know how old it is but exhaust port maybe plugged up with
carbon/dirt.
Just remove muffler and look, see.
Carburetor deposits and vacuum leaks are much more likely on today's
2 strokes since most run on a weak oil mixture, using low ash
clean-burning (relatively) oil - and ethanol gasoline. This adds up to
low exhaust deposits, and all kinds of sneaky stuff clogging up fuel
systems and deteriorating gaskets etc.

Someone gave me a WeedEater leaf blower recently that had the problem that Tony describes...nearly closed-off exhaust port.
Not saying that can't happen, but it is a LOT less common than in the
18:1 mix days using #30 engine oil

On 7/4/15 12:24 PM, wrote:
On Fri, 3 Jul 2015 20:23:06 -0700 (PDT), bob_villa
wrote:

On Friday, July 3, 2015 at 9:42:18 PM UTC-5,
wrote:
On Fri, 03 Jul 2015 20:07:42 -0600, Tony Hwang
wrote:

wrote:
I have a 2-cycle trimmer that was working just fine. Then
during it's last use the speed began declining while in full
throttle mode until it finally died. I changed the spark plug
and now it only runs with the choke closed. If I try to open
the choke or let off the throttle the engine dies. Any
suggestions?

I don't know how old it is but exhaust port maybe plugged up
with carbon/dirt. Just remove muffler and look, see.
Carburetor deposits and vacuum leaks are much more likely on
today's 2 strokes since most run on a weak oil mixture, using low
ash clean-burning (relatively) oil - and ethanol gasoline. This
adds up to low exhaust deposits, and all kinds of sneaky stuff
clogging up fuel systems and deteriorating gaskets etc.

Someone gave me a WeedEater leaf blower recently that had the
problem that Tony describes...nearly closed-off exhaust port.
Not saying that can't happen, but it is a LOT less common than in
the 18:1 mix days using #30 engine oil


I believe port blockage is a gradual process that reduces noise and
power, but the motor still starts normally. I've cleaned carbon from
ports and sometimes mufflers, but I've never had enough to notice a loss
of power.

On Sunday, July 5, 2015 at 4:11:46 PM UTC-5, J Burns wrote:

I believe port blockage is a gradual process that reduces noise and
power, but the motor still starts normally. I've cleaned carbon from
ports and sometimes mufflers, but I've never had enough to notice a loss
of power.

Then this one should be written into the books...it would barely start and stay at low speed. Nearly 100% blocked. I don't know what they used for gas/oil mix?

On 7/5/15 6:17 PM, bob_villa wrote:
On Sunday, July 5, 2015 at 4:11:46 PM UTC-5, J Burns wrote:

I believe port blockage is a gradual process that reduces noise
and power, but the motor still starts normally. I've cleaned carbon
from ports and sometimes mufflers, but I've never had enough to
notice a loss of power.

Then this one should be written into the books...it would barely
start and stay at low speed. Nearly 100% blocked. I don't know what
they used for gas/oil mix?


.... or the gas/air mix. Mine can easily be set too rich, and it might
seem satisfactory. I set it as lean as it will still respond to the
throttle.

The OP said his problem happened suddenly. Mine has usually happened
because the screen got gummed by a material caused by getting moisture
in the fuel. It's hard to see because it's colorless and translucent.
It hasn't happened so much since I started mixing fuel 500ml at a time
in a 600ml soda bottle, so it's sealed against air and used pretty
quickly. I discovered that epoxy cement could seal the hole where the
fuel line exits the tank. That helped, too.

The second cause in my experience has been air leaks around a carburetor
gasket.

I found a third cause at my neighbor's this year. His fairly new trimmer
suddenly wouldn't run without the choke. He'd refilled it with fuel that
had been sitting in a milk jug a couple of years. When I finally
figured it out, I dumped the tank back into the bottle and filed it with
fresh fuel from my bottle. After it burned the fuel in the line and
carburetor, it ran like new.

On Fri, 03 Jul 2015 20:07:42 -0600, Tony Hwang
wrote:

wrote:
I have a 2-cycle trimmer that was working just fine. Then during it's last use the speed began declining while in full throttle mode until it finally died. I changed the spark plug and now it only runs with the choke closed. If I try to open the choke or let off the throttle the engine dies. Any suggestions?

I don't know how old it is but exhaust port maybe plugged up with
carbon/dirt.
Just remove muffler and look, see.

Second this. Esp, if you run it part throttle. A factory service guy
told me these engines are designed for either idle or WOT. Ours gets
plugged every couple of years, . (I do run part throttle.)

Anyway, there's a 'spark suppressor' screen in the exhaust port. I
hit it with a propane torch. That ignites the wet stuff. After that
burns off, just brush the residue out, and good to go.

On Monday, July 6, 2015 at 6:04:56 AM UTC-5, wrote:

Anyway, there's a 'spark suppressor' screen in the exhaust port. I
hit it with a propane torch. That ignites the wet stuff. After that
burns off, just brush the residue out, and good to go.

I would caution doing this...with fumes and mix in the crankcase? Not a good idea! *L*

On Mon, 6 Jul 2015 04:13:08 -0700 (PDT), bob_villa
wrote:

On Monday, July 6, 2015 at 6:04:56 AM UTC-5, wrote:

Anyway, there's a 'spark suppressor' screen in the exhaust port. I
hit it with a propane torch. That ignites the wet stuff. After that
burns off, just brush the residue out, and good to go.

I would caution doing this...with fumes and mix in the crankcase? Not a good idea! *L*

Do I need to say, "after taking it out"? OK: AFTER TAKING IT OUT.

On Monday, July 6, 2015 at 8:31:28 AM UTC-5, wrote:
On Mon, 6 Jul 2015 04:13:08 -0700 (PDT), bob_villa
wrote:

On Monday, July 6, 2015 at 6:04:56 AM UTC-5, wrote:

Anyway, there's a 'spark suppressor' screen in the exhaust port. I
hit it with a propane torch. That ignites the wet stuff. After that
burns off, just brush the residue out, and good to go.

I would caution doing this...with fumes and mix in the crankcase? Not a good idea! *L*

Do I need to say, "after taking it out"? OK: AFTER TAKING IT OUT.

Yes, and you would need to say, "take the screen out first..." because someone might think you meant take the fuel out...which would leave fumes to explode. Sorry you took a caution as a criticism.

On Mon, 6 Jul 2015 06:43:16 -0700 (PDT), bob_villa
wrote:

On Monday, July 6, 2015 at 8:31:28 AM UTC-5, wrote:
On Mon, 6 Jul 2015 04:13:08 -0700 (PDT), bob_villa
wrote:

On Monday, July 6, 2015 at 6:04:56 AM UTC-5, wrote:

Anyway, there's a 'spark suppressor' screen in the exhaust port. I
hit it with a propane torch. That ignites the wet stuff. After that
burns off, just brush the residue out, and good to go.

I would caution doing this...with fumes and mix in the crankcase? Not a good idea! *L*

Do I need to say, "after taking it out"? OK: AFTER TAKING IT OUT.

Yes, and you would need to say, "take the screen out first..." because someone might think you meant take the fuel out...which would leave fumes to explode. Sorry you took a caution as a criticism.

A momentary overreaction.