Help: Lawn-Boy 21" SilverPro Series, 10247, DuraForce (2-cycle) behaving badly

[dewguy1999]

Re: Help: Lawn-Boy 21" SilverPro Series, 10247, DuraForce (2-cycle) behaving badly

No sir. Running it out of gas is fine. When it stops you are done. I typically throttle the mower back to low speed when I'm done cutting (mowers cool better when they are run on low speed for a while before shutting off) and let it run parked in front of the garage, cut the fuel and let it wind down on its own. Then I park it until next time. Turn on the fuel, wait a few minutes for the bowl to fill, and pull the starter. :thumbsup:

I'll be looking forward to your response!

After watching a bunch of YouTube videos for engines misfiring, knocking and backfiring, I think the way it was behaving when set to fast best fits backfiring, would that change your diagnosis?

 

[bt3]

Re: Help: Lawn-Boy 21" SilverPro Series, 10247, DuraForce (2-cycle) behaving badly

If you think it is a Backfiring issue, this is typically one of the following problem sources;

-Exhaust Ports or Muffler Clogged
-Reed valve or Valve Bed bad, stuck, or clogged
-Crankcase seals that are out of position or leaking
-Crankcase leaking pressure/vacuum from a bad reassembly or a sealing issue

A "Reed Valve" issue is easy to check by pulling the carb and looking at the valves with a flashlight. See if they are working by slowly turning the crank and looking and listening for them operating. Reeds are what 2 cycle engines use in place of valves. However, Reeds don't usually make a backfiring issue at only one speed. Usually this is linear. Meaning, you get it across the power band and not just at high RPM, however, it is possible that a bad reed will contribute more at high RPM than low. Reed failure or a stuck Reed valve (sticking can be because of a piece of debris in the reed from carbon to a few grass blades or a leaf twig) will usually make it difficult to start, and you don't have that problem.

Again, let's try the fresh fuel. from that point we can move forward it it does not solve the problem outright. It just might. If that does not cure the issue, then we look at Carb and other potential issues.

 

[dewguy1999]

Re: Help: Lawn-Boy 21" SilverPro Series, 10247, DuraForce (2-cycle) behaving badly

If you think it is a Backfiring issue, this is typically one of the following problem sources;

-Exhaust Ports or Muffler Clogged
-Reed valve or Valve Bed bad, stuck, or clogged
-Crankcase seals that are out of position or leaking
-Crankcase leaking pressure/vacuum from a bad reassembly or a sealing issue

A "Reed Valve" issue is easy to check by pulling the carb and looking at the valves with a flashlight. See if they are working by slowly turning the crank and looking and listening for them operating. Reeds are what 2 cycle engines use in place of valves. However, Reeds don't usually make a backfiring issue at only one speed. Usually this is linear. Meaning, you get it across the power band and not just at high RPM, however, it is possible that a bad reed will contribute more at high RPM than low. Reed failure or a stuck Reed valve (sticking can be because of a piece of debris in the reed from carbon to a few grass blades or a leaf twig) will usually make it difficult to start, and you don't have that problem.

Again, let's try the fresh fuel. from that point we can move forward it it does not solve the problem outright. It just might. If that does not cure the issue, then we look at Carb and other potential issues.

I hope it is the gas, because the alternatives don't sound like anything I want to tackle. I'll post again when I have something new to report.

 

[bt3]

Re: Help: Lawn-Boy 21" SilverPro Series, 10247, DuraForce (2-cycle) behaving badly

I hope it is the gas, because the alternatives don't sound like anything I want to tackle. I'll post again when I have something new to report.

No problem. Those I listed are highly suspect. But if the gas does not work, then there are other much simpler things we can try before you tackle the most suspect. One step at a time.

 

[dewguy1999]

Re: Help: Lawn-Boy 21" SilverPro Series, 10247, DuraForce (2-cycle) behaving badly

No problem. Those I listed are highly suspect. But if the gas does not work, then there are other much simpler things we can try before you tackle the most suspect. One step at a time.

I haven't purchased new gas yet, but I did go out and cut the grass again (the neighbors must think I'm nuts). It started after the second prime and pull and pretty much ran the same as it did on Wednesday. I was trying to use up the old gas (as I don't have any way to get rid of it) but there's still a few ounces left in the tank. Do you think adding the new gas (when I get it) to the old would be okay?

I made a movie of the sound it's making, Lawn-Boy 10247 missing, hope that works.

Here's a pic of the largest section of my front lawn showing my Lawn-Boy's handiwork.

 

[lawnboywillneverdie]

check for spark.if you have spark spray some starting fluid or carb cleaner in the plug hole and replace the plug if it pops but dies you got carb issues such as a clogged main jet.dont give up its worth the trouble new mowers are not like a duraforce.once you get in your groove
its a snap to work on one

Question the air inlet tunnel is missing on my duraforce. Will that have a profound effect on how it starts and runs?

 

[dewguy1999]

Re: Help: Lawn-Boy 21" SilverPro Series, 10247, DuraForce (2-cycle) behaving badly

Question the air inlet tunnel is missing on my duraforce. Will that have a profound effect on how it starts and runs?

You might get a better response to your questions if you start a new topic. :smile:

 

[bt3]

Re: Help: Lawn-Boy 21" SilverPro Series, 10247, DuraForce (2-cycle) behaving badly

I haven't purchased new gas yet, but I did go out and cut the grass again (the neighbors must think I'm nuts). It started after the second prime and pull and pretty much ran the same as it did on Wednesday. I was trying to use up the old gas (as I don't have any way to get rid of it) but there's still a few ounces left in the tank. Do you think adding the new gas (when I get it) to the old would be okay?

I made a movie of the sound it's making, Lawn-Boy 10247 missing, hope that works.

Here's a pic of the largest section of my front lawn showing my Lawn-Boy's handiwork.
View attachment 23207

Lawn looks superb. Very nice indeed.

OK, from what I can tell in that video (nice job by the way!) YOU ARE NOT backfiring. It's missing, skipping and surging. First take is that the surge is from the missing and hitting cycle that develops into a perceived surge but it's the skipping that begins the cycle onset.

Should be a simple fix as compared to a backfire.

First: FRESH FUEL!

Second: NEW SPARK PLUG. Check that plug! Is it new? I can't remember. For a few bucks, replace it if it is not new.

Third: MAGNETO AND FLYWHEEL. Is there RUST on the flywheel magnets? Sand it off. I'm helping a few guys here so forgive me if I got you mixed up, but didn't you just replace the magneto with an aftermarket CDI? Try your old CDI (if that was still working - can't remember) and see if the problem clears. These LawnBoy CDI modules are notorious for failure, sometimes out of the box. Especially aftermarket. That's why I go with the cheap 19 buck new style CDI at Amazon. If it fails in a few months, I'm ok with it. However, most will last for years. May not be your problem but if it started when you put the new CDI on, then this is highly suspect!

Forth: CARB ISSUE. Bad adjustment or poor venturi flow through a jet, bad float or needle valve. I think you just cleaned the carb? Did you replace the float and needle? Did you change the carb adjustment screw setting? There is an external screw with a spring that adjusts the carb setting.

90 percent it's one of the above. I personally would work them in the order that I typed them. Keep us posted please!

 

[dewguy1999]

Re: Help: Lawn-Boy 21" SilverPro Series, 10247, DuraForce (2-cycle) behaving badly

Lawn looks superb. Very nice indeed.

OK, from what I can tell in that video (nice job by the way!) YOU ARE NOT backfiring. It's missing, skipping and surging. First take is that the surge is from the missing and hitting cycle that develops into a perceived surge but it's the skipping that begins the cycle onset.

Should be a simple fix as compared to a backfire.

First: FRESH FUEL!

Second: NEW SPARK PLUG. Check that plug! Is it new? I can't remember. For a few bucks, replace it if it is not new.

Third: MAGNETO AND FLYWHEEL. Is there RUST on the flywheel magnets? Sand it off. I'm helping a few guys here so forgive me if I got you mixed up, but didn't you just replace the magneto with an aftermarket CDI? Try your old CDI (if that was still working - can't remember) and see if the problem clears. These LawnBoy CDI modules are notorious for failure, sometimes out of the box. Especially aftermarket. That's why I go with the cheap 19 buck new style CDI at Amazon. If it fails in a few months, I'm ok with it. However, most will last for years. May not be your problem but if it started when you put the new CDI on, then this is highly suspect!

Forth: CARB ISSUE. Bad adjustment or poor venturi flow through a jet, bad float or needle valve. I think you just cleaned the carb? Did you replace the float and needle? Did you change the carb adjustment screw setting? There is an external screw with a spring that adjusts the carb setting.

90 percent it's one of the above. I personally would work them in the order that I typed them. Keep us posted please!

Thanks for checking out the video and making sense of what I was hearing.

Before I can mow again, next week, I have to get fresh gas. Will it be okay to mix the new with the little that's currently in the tank when I fill it up?

Spark plug was new in May and I've had it out and cleaned it/checked the gap a few times since then, but I'll get a new one if if the fresh gas doesn't do the trick. I replaced the CDI on Wednesday with a aftermarket one, but it ran fine at first. I still have the old CDI but because of the problem starting I was suspecting it of failing, but it's there if I need it. I don't recall seeing any rust on the flywheel magnets, but if I open it up I'll check for it.

I haven't done anything to the carb, but because it was leaking fuel I installed the shut-off valve as a immediate fix, but it probably needs to be cleaned and maybe even rebuilt.

 

[bt3]

Re: Help: Lawn-Boy 21" SilverPro Series, 10247, DuraForce (2-cycle) behaving badly

OK, I'm up to date with you again. Thanks for the recap.

Did the skipping issue start AFTER you installed the shutoff valve? Just a hunch that perhaps the valve is not flowing well and you are leaning the fuel flow somehow with it. That's a longshot. I'm just speculating outside the normal issues box.

Drain ALL of the old gas before you put new in. You want fresh gas from the getgo to diagnose if the gas is curing the problem. It is even possible there was a little moisture (water) in the old gas. I always run a few cap fulls of HEET Isopropyl (in the RED BOTTLE - NEVER the Ethyl in the YELLOW Bottle in a 2 stroke) to take water out of the gas. Heet also has a mild cleaner in it to help with carb cleaning on-going. I'm just going overboard here to help you diagnose ALL issues.

The Carb may be dirty, the float may be stuck and/or the needle valve may not be working properly. However, if these issues JUST started, the carb is the last thing I'd go to for issue. Servicing a carb on a LawnBoy 2 stroke is a walk in the park with a Cocker Spaniel! Really fairly easy. Lots of Youtube videos to help you out. But let's not go there yet.

Did anything happen to the air filter? Is the filter clean and lightly oiled?

Replace that plug. They are cheap as you know. I've heard issues lately with plugs failing quickly or right out of the box. For what it costs, even if it's not the plug, you can always use a spare hanging around. I've got a few. Why not.

In my motor, there is a small insert screen in the fuel line right where the fuel line connects to the carb. If your Duraforce has one, take it out and clean it with carb spray. I'd take that opportunity to carb cleaner spray the fuel inlet port. I'd spray a little in the air intake port. Can't hurt. Just don't overdo it.

That's about it. You've got some homework there and that should keep you busy over the weekend. I'll be on here all weekend if something crops up!