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

dont waste your time with iso propyl or sea foam.It wont do anything.you need to remove the carb and clean the jets at which time you should drill out the jets with a micro drill bit set there are a few posts on this forum referring to the procedure.its worth the time to do it.you will see a great improvement in you mowers performance.your air induction tube is a necessary part as they would not have put it there if it was not needed.the induction tube works like a ram air scoop on a car scavenging forced air from the flywheel.if you take the carb off remove it as a unit not in two pieces as the govenor spring is hooked to the carb body.yes its a PIA but if you pay attention to detail its not that hard.

I've read where drilling out the jets is a sometimes fix for surging, but I don't think I'm ready to try rebuilding the carb just yet, plus, I never had surging before last Wednesday. I'm hoping that it's the stale gas and when I get fresh it will behave itself. I don't know what the air induction tube is, is that part #95?578 that Lawn-Boy calls a "Tunnel E"?

 

[bt3]

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

dont waste your time with iso propyl or sea foam.It wont do anything.you need to remove the carb and clean the jets at which time you should drill out the jets with a micro drill bit set there are a few posts on this forum referring to the procedure.its worth the time to do it.you will see a great improvement in you mowers performance.your air induction tube is a necessary part as they would not have put it there if it was not needed.the induction tube works like a ram air scoop on a car scavenging forced air from the flywheel.if you take the carb off remove it as a unit not in two pieces as the govenor spring is hooked to the carb body.yes its a PIA but if you pay attention to detail its not that hard.

Respectfully, I have to disagree. I'm sure you have a lot of experience with small motor repair, but so do I, and I can say that both products have extensively helped me with my mower repairs over the years, especially SeaFoam.

The carb on a L21ZSM is not easy to work on the jets, and they do clog. Originally took the carb off and soaked it in a bowl of SeaFoam overnight with SPECTACULAR results. Over the years, just putting SeaFoam in the tank (up to 2 oz per gallon as per SeaFoam recommendation for 2 stroke) also clears my carb issues.

Will it ALWAYS work? Of course not. Has it worked very well for me? Yes. It's been miraculous, actually. So, if you are uncomfortable with taking off the carb, there is nothing wrong with TRYING to run some SeaFoam through your carb via gas tank mix.

SeaFoam also adds stability to gas, so now I put in 3 oz per 2 gallons in my mixed gas can and have not had a carb issue since.

It's so easy to get tiny pieces of whatever into your fuel tank in a walk behind mower, at least some additives give you a chance to keep things clear.

YMMV. I have no connection with SeaFoam or Heet. Just a happy user.

 

[dewguy1999]

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

Well, I removed the old stale fuel mix from the fuel tank, got some fresh gas, mixed it up, filled the tank...and it's still running badly at the faster speeds. :frown: I don't know what I'll try next (but thanks to you guys I've got plenty of options) or when I'll try it but when I do I'll report back and let everyone know if I've made any progress.

 

[dewguy1999]

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

Well, I pulled the fuel line off the carb today to check the fuel flow. The shut-off valve was turned to off, so I wasn't expecting any fuel to come out of the fuel line but it did before I could get a container under it, just a little on to the deck and it was brown colored. Putting a container under the end of the hose and turning on the shut-off valve the fuel began to flow quickly, brownish at first but quickly turning clear (no longer brown). I'd say the flow is unobstructed as it was coming at maybe an ounce a second (give or take). Was the initial fuel that spilled out of the hose brown because it had discolored from sitting in the hose or something else? Should I be concerned about this?

Next I replaced the Champion RCJ8Y (non-resistor plug) that I'd been using since May with a new NGK BPMR4A (resistor plug). After priming it started up on the first pull...however, it's still running badly at higher speeds. :frown: I don't use it at more than half throttle normally so I'm not really sure how much more effort I'm going to expend on this. The only other thing that's been recommended to me (other than the carb cleaning/rebuilding) is to take off the new CDI and put the old one back on to see if it makes a difference. Since I think the old CDI was on it's way out I'm not sure I want to expend the effort on it, but if I do I'll be sure to let everyone know how it turns out.

Right now it's not leaking fuel from the carb with it's newly installed fuel line and shut-off valve, it starts on the first pull with it's newly installed CDI and spark plug and is cleaner than it's been in a long time so I think I've come out ahead. Oh yeah, I still have a Lawn-Boy. :smile:

 

[dewguy1999]

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

Well the weather was finally cooperating so I removed the new CDI, cleaned the rust off the old CDI and installed it. I made 4 attempts to start it, each attempt involving priming (3 presses) and pulling the cord 3-4 times to a great big nothing. It didn't even try to start, so, I guess that confirms that the old CDI is dead. I put the new one back on and on the 1st pull without priming it started. Only took me half the time to take the old CDI off and put the new one back on as it did to take the new off and put the old one back on. I guess I'm getting better at being a mechanic. :smile:

I also made a discovery while cutting the grass today. If I moved the speed lever all the way to the choke position and then pulled it back to the fast position (like you would do when start it) it would run badly. However, if I moved the speed lever all the way to the choke position and then pulled it back to the slow position and then pushed it back up to fast it would run like I remember it running, any ideas why this would make a difference?

Changing out the CDI was the last of my trouble shooting attempts. I know the carb needs a cleaning and a rebuilding, but since the weather here has taken a turn for the worse and doesn't seem to be going to get any better in the near future I'm probably going to wait on that 'til next spring when the weather will hopefully be better.

Thanks to everyone who has offered up help as I've learned a lot and become a better mechanic because of it.

 

[bt3]

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

Hey Dew, sounds like my machine regarding the throttle manipulation.

You definitely need to clean that carb and rebuild it. It's not a big deal really, something you can putter around with over the winter. Get a rebuild kit and soak that WHOLE CARB in a bowl of cleaner. As previously posted, I prefer Seafoam, but other cleaners would work. It sounds like you have a float/needle/jet issue, and possibly a mixture ratio issue. If I was there, I'd be able to diagnose and fix it in a day for you, but you'll get it, I'm sure. That mower is worth the work.

My machine was doing the same thing as I stated regarding throttle manipulation. On my carb, you can't get at all the internal jets, so I soaked it overnight in a bowl of cleaner and the next day blew it out with compressed air. Voila! Ran like a top. Some guys would suspect that your CDI HIGH SPEED side mag is bad *the CDI has a start side and a high speed side mag), but I suspect fuel issues first and foremost. These machines are finickey and yes, you can have a leaking reed valve or crank seal that will cause similar issues, but in your case, I suspect carb. It would not hurt to start adding 4 oz of a cleaner like SeaFoam to every 2 gallons of fuel mix. Works wonders for me. It's an excellent fuel stabilizer, so if nothing else, it will help keep your fuel fresh. At best, it will clean out any debris you have in your carb.

In case someone is reading this thread and has similar issues, again I'll list what I'd do and have seen on Lawnboy with regard to starting and poor running - loss of power issues;

1.) CDI Magneto bad, poorly gaped or a failing start or high speed side or both on the Mag, Spark plug dirty/gaped poorly or inoperative
2.) Exhaust ports/muffler clogged (2 stroke lawnboys do NOT tolerate clogged exhaust well)
3.) Carb issues. Clogged jets, mixture set improperly, float or needle valve issues. Make sure throttle is working, choke is closing and governor spring is relaxing on full throttle
4.) Reed Valves sticking or broken - take off carb and inspect them
5.) Crank seals leaking or worn out completely - gas/oil seeping out of the bottom crank is a sure sign
6.) Governor not set properly or not operating well. Set RPM around 3,200 RPM at high speed (F Engines). Make sure Governor Vane is swiveling well and freely and that the adjustment is working. Keep the swivel area clean and lightly oiled
7.) Poor compression issues that can come from some items listed above or from worn Piston rings
8.) Stale or bad gas, bad Gas/Oil mixture ratio, water in gas, contaminants in gas
9.) Clogged or dirty air filter - clean thoroughly and lightly oil
10.) Clogged Vent cap on gas tank filler cap, clogged fuel line, or fuel line shutoff valve

These are my top 10 issues that I suspect on my Lawnboy F-Engine. Of course there can be other deeper issues, but home mechanics can check these and make sure they are all up to snuff. Then if there is STILL issues, you call out the big guns or have a shop look at it.

 

[dewguy1999]

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

Hey Dew, sounds like my machine regarding the throttle manipulation.

You definitely need to clean that carb and rebuild it. It's not a big deal really, something you can putter around with over the winter. Get a rebuild kit and soak that WHOLE CARB in a bowl of cleaner. As previously posted, I prefer Seafoam, but other cleaners would work. It sounds like you have a float/needle/jet issue, and possibly a mixture ratio issue. If I was there, I'd be able to diagnose and fix it in a day for you, but you'll get it, I'm sure. That mower is worth the work.

My machine was doing the same thing as I stated regarding throttle manipulation. On my carb, you can't get at all the internal jets, so I soaked it overnight in a bowl of cleaner and the next day blew it out with compressed air. Voila! Ran like a top. Some guys would suspect that your CDI HIGH SPEED side mag is bad *the CDI has a start side and a high speed side mag), but I suspect fuel issues first and foremost. These machines are finickey and yes, you can have a leaking reed valve or crank seal that will cause similar issues, but in your case, I suspect carb. It would not hurt to start adding 4 oz of a cleaner like SeaFoam to every 2 gallons of fuel mix. Works wonders for me. It's an excellent fuel stabilizer, so if nothing else, it will help keep your fuel fresh. At best, it will clean out any debris you have in your carb.

In case someone is reading this thread and has similar issues, again I'll list what I'd do and have seen on Lawnboy with regard to starting and poor running - loss of power issues;

1.) CDI Magneto bad, poorly gaped or a failing start or high speed side or both on the Mag, Spark plug dirty/gaped poorly or inoperative
2.) Exhaust ports/muffler clogged (2 stroke lawnboys do NOT tolerate clogged exhaust well)
3.) Carb issues. Clogged jets, mixture set improperly, float or needle valve issues. Make sure throttle is working, choke is closing and governor spring is relaxing on full throttle
4.) Reed Valves sticking or broken - take off carb and inspect them
5.) Crank seals leaking or worn out completely - gas/oil seeping out of the bottom crank is a sure sign
6.) Governor not set properly or not operating well. Set RPM around 3,200 RPM at high speed (F Engines). Make sure Governor Vane is swiveling well and freely and that the adjustment is working. Keep the swivel area clean and lightly oiled
7.) Poor compression issues that can come from some items listed above or from worn Piston rings
8.) Stale or bad gas, bad Gas/Oil mixture ratio, water in gas, contaminants in gas
9.) Clogged or dirty air filter - clean thoroughly and lightly oil
10.) Clogged Vent cap on gas tank filler cap, clogged fuel line, or fuel line shutoff valve

These are my top 10 issues that I suspect on my Lawnboy F-Engine. Of course there can be other deeper issues, but home mechanics can check these and make sure they are all up to snuff. Then if there is STILL issues, you call out the big guns or have a shop look at it.

I've also thought that it may be that the new CDI is defective on the high speed portion of it, but the only way to determine that now is to purchase another CDI. I was hoping that the old one would work at least one more time to determine if that was the case or not, but it's apparently dead now.

Lawn-Boy states in the E Series Service Manual to not soak the carb, to only leave it in the cleaner long enough to clean it. As to cleaning/rebuilding the carb, there's a possibility that I might be able to do it before the weather gets much worse. For that to happen I would need to get the necessary parts and supplies to have on hand when a nice day presented itself. Right now I'm feeling like I've had enough of playing mechanic and would probably be more likely to want to do it in the spring. I can't do it during the winter as the only place I would have to work would be in the house and I don't think that's a good idea.

 

[dewguy1999]

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

On the advice of bt3 and others I bought a can of Seafoam even though I thought the claims were "too good to be true". Since I had about a half a tank of gas in the mower and only a quart to quart and half left in my gas can I added 1/2 ounce of Seafoam to the tank and filled it up. Since the temp was around 50 and the mower hadn't been used in almost 2 weeks I had to prime it twice and it started on the first pull after the 2nd priming and ran normally. It was no longer surging and skipping (or whatever it was doing) at medium to high speeds. It's back to running like it did before I did the work on it and I guess I owe it to Seafoam. :smile:

 

[guitardude1998]

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

just wondering I have the same model does yours have the high rear wheels

 

[guitardude1998]

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

I have to shut off the fuel to mine or it leaks out of the air filter and the muffler and it runs like crap till I empty out the carb bowl