Mowers, weren't your going to sell your L-B and get a Snapper?

I was planning to use it for the remainder of this year to give it a fair try. I posted a listing of all the things I hate with my LB, and was blasted, so I thought I would give it a fair try to try and be understanding and learn why everyone loves these things. Do not get me wrong..I still have major issues with this thing. But the surging drove me totally nuts.

tarheelman, you arent the 89tarheelman on Ebay that won the lawnboy deck last week?

I did some serious internet mining a month ago...but have not found any sites that are fully developed or have the selection of parts of RCPW or SEPW. There are hundreds of sites...but when you go into them and enter the part numbers...nothing is available. I guess if you call, they may have the parts? RCPW wanted $8.99 to ship jets. I got mine locally instead.

The Sears Parts Store is a pretty good place to look for parts too if they arent too special.

http://www3.sears.com/

They are pretty close in price with RCPW and SEPW and possibly cheaper on shipping.

Here is a link that might be useful: The Parts Store

Mowers & Blaise--

Thanks for the encouragement. Unfortunately, I'm not a total novice to L-Bs, I'm a total novice to carburetors. I don't even understand how they work, much less how to take one apart and put it back together correctly.

FordTech--

You guessed it---I was the winning bidder on the L-B deck last week. It's for a long term project to make use of a nearly new F series engine I have.

Tarheelman, the carb on the Duraforce is almost as simple as they get (like the L-B 2-stroke itself). How about getting a used carb and rejetting it if you're concerned you might mess up yours?

Tarheelman...everyone is correct...very easy. The detailed instructions at the top say it all. If you are putting engines onto decks..you can certainly do the jet job. Be a convert. Now we just have to work on Saxman...

OK, guys---you've convinced me. The next time I see a good DuraForce carb for sale on eBay I'll bid on it. If I win it, I'll re-jet it and try it out on my 10424. However, I think I'll go with a new Mikuni jet for the pilot jet (it's easier than re-jetting the DuraForce pilot jet).

Is there a good source (other than eBay) for new bits this small?

Tarheelman, hobby stores usually have bits and pin vices.

Saxman is the only one left holding out. He has been silent, so it is suspect he is working on his at this time and will reappear with comments on how it turned out.

My Jets came in yesterday $9.37 for the two jets, two intake manifold and a float bowl gasket.....I still need to hunt down the wire drill bits, the 1st hardware store (same place that ordered up the parts for me) had them only down to #60 at $1.99 each. I will check another HW store that is a monster of a place that always seems to have what youÂre looking for. I may bring this project in for under $15.

On the pilot jet I see the two holes to drill are offset by 1/8 inch so it appears you have to ream them separately.

One question. Do you ream both holes on the pilot jet or just one of them? OK, two questions. If it is only one hole that is reamed, is it the one closer or farther from the threads?

The pilot jet has a slotted top for a screw driver and a bored bottom. It also has two side ports. Dont touch the side ports. The hole at the bottom tip end is what you bore and it only goes in so far.

Thanks FT,

I bought the bits outlined above at lunch today. When I saw the size of those little suckers I knew I was off track on where the pilot jet needs to be reamed. I think I'm straightened out now. Damn fading eye sight, I'll have to get the magnifying glass out and look.

It may be well worth the bucks to just get the Mikuni pilot jet, but I am all set to do the deed on the stock L-B parts.

I'll report back as to my results.....vroomm, hummm burble, hum burble, burble.

Well guys, my 10550 now sounds like a by God real 2-stroke now! I found the bits at Radio Shack of all places...wasn't even what I was looking for, but there they were, complete with a pin vise to hold them, for like 13 dollars with a lifetime guarantee! It doesnt have the 78 to do the low speed, so I only did the high with a 66, and she gurgles and purrs now, and even has just a hint of smoke when I hit the heavy stuff! Thanks to all of you for providing info on doing this! The bit sizes range from 54 to 74, even sizes only. Tarheelman, it only took about 35 to 40 minutes to do, but it made all the difference in the world!

Got 2 sets of #61-80 bits w/pin-vices from Widgit Supply on e-bay for less than $20 ... ordered 7/4 and received 7/7. I did both my 1999 10323 and 2003 10424 yesterday and then cut the grass with the 10424.

Findings durring modification:
Got one Mikuni/Suzuki Pilot Jet (81-1030) ... #78 drill too big as it should be, however bit o.d. measures 0.0156" or 0.3962mm which SHOULD theroretically fit in the 0.400 mm jet (possibly the combination of cheap China made Bits & Dial Caliper).

Drilled out one L-B Pilot Jet with #78 (o.d. measured 0.0004" smaller than it should as stated above). #79 did fit in original orifice and actual o.d. of bit measured 0.0145" or 0.3683mm as it should.

Drilled out Main Jet with #67. #68 did fit in original orifice ... however "theoretically" 0.031" / 0.7874mm should NOT fit in a 0.7750mm jet, but actual bit o.d. measured 0.030 / 0.7620mm which explains why.

Adjusted Governor: 1 click slower (counterclockwise).

Pilot Jet: I tried both the stock Suzuki and the (now) slightly larger drilled-out L-B and think it ran slightly better on the Suzuki jet.

As dry as my lawn is, it really did not NEED to be cut but guess what ... it got cut any way. Since my 10424 has nothing else to do but spin the blade, it pretty much ran under no-load the whole time. It sounded much better than before and there was barely any surging, but it did seem to smoke more than I'd like to see (however less so with the Suzuki Pilot Jet). I'm also running Amzoil at 50:1 rather than L-B oil at 32:1.

I'm kind of wondering if we are richening these engines up too much. I've ordered 2 new main jets and I'm going to try and find a "true" #68 drill (which should theroretically be slightly larger than stock) and give this a try as well.

Sure wish these engines had an adjustable main jet like on my 7024 ... hey a guy can dream can't he ?? Sounds like a business oportunity to me ... design & make a Duraforce replacement carb with an adjustable main jet !! Any takers ??

Dougmac, I'd wait until you have some real grass to cut before making any more changes. When you get the noload 2 stroke sound, it seems the engine does smoke a little - maybe because of incomplete combustion. I don't know why 2 strokes do that but it does seem they smoke a little when they are 4 stroking.

Regarding drill bits...my ebay purchase were "cheapie" ones and I believe the sizes may not be right on the money. Everything was OK on the pilot..but on the main jet, a #69 fit but not the #68. Regardless, I just found the one that fit and went up "one" bit in size...for me that was a #68.

Other tips I recall may be helpful for folks doing it the first time.

1) Make sure you clean you mower off very good BEFORE starting. All the light tan dust accumulation will get into your carb if you are not careful as you start removing parts. You do not want to drag your carb through junk as you lower and remove it and allow junk to enter the body.

2) Watch out for the micro plastic pieces that fall out of the 4 carb bowl threads when you remove the 4 bolts. They are light and clingy and hard to notice because they are black. A big of a chessy design in my opinion.

3) Remove the PP (if you have one) plastic shroud cover on the deck to give you more room to drop and reinstall carb.

4) Do not forgot the primer hose...this should be installed on the carb before it is installed back onto the engine, otherwise it is next to impossible to install because it needs to make a 90 degree turn and there is no room for big fingers. Yes, I did this on mine. Remove hose from the shroud and install onto the carb. Then when you reinstall the tank, then install the other end of the primer house.

5) Job takes very little time. The biggest time killer for me was cleaning parts.

6) On the pilot jet boring...it will feel like you are doing nothing as you turn the bit. Just be patient and take your time and apply little pressure. It is boring although it does not feel like it. It will all of a sudden break through.

7) Definitely install an in line gas filter!!!! I am very anal at cleanliness, and despite this, I still found a decent amount of particle build up at the main jet screen filter. I used a Home Depot Briggs filter part # 5018. Worked great. There is plenty of room for this. You do not need extra gas line. Just cut the existing hose about 2 inches from the carb connection and install it.

8) I did 2 mowers and did not need any new gaskets. Mine were fine. So if you want to save money, try with what you have.

9) Just lightly snug up your bolts. The unit is plastic...do not go crazy.

Picture of the fuel filter...Fit perfect.
{{gwi:132574}}

Reguarding Fuel Filter ... I am also trying to put a shut-off right at the tank. Was trying to find a filter / shut-off combo but all the ones I've seen are 1/8" NPT for screwing in the bottom of a tank (like my 7024 uses).

Anyway, found a Stens 120-228 (Briggs 494769) 90Deg Shut-Off with hose barbs both ends that will fit nicely, but will limit me to a 2.5" o/a long filter between the shut-off and carb. I remember seeing a couple like that Briggs filter you used Tom, but I think they may all be too long.

Regarding RPMs...after I rejetted, I backed off on the vane adjustment.

Can someone explain how to correctly determine the RPM of a mower? Are tachometers expensive and required..or can you just make adjustments basedu upon engine sound. What brand would you recommend?

All,

My gaskets and jets came in Friday, I ran down to my friendly neighborhood hobby shop and picked up the bits and... WOW! Now that's what I'm talking about! Ahh, the sounds of the Lawn-Boy making sweet love to the fescue (aka Lawn-Girl). Now that's how I remember Lawn-Boys sounding! (This is my first Lawn-Boy, although I use a couple while mowing a cemetary when I was a kid)

If you have a Duraforce with any hint of surging you gotta do this mod!

Regarding the recent comments about the belt rubbing the deck on a 10550. I noticed the exact same problem on mine during the re-jet. It is disappointing but should not cause long-term harm except to the belt possibly, but even though it had been rubbing for a while the belt was in fine shape.

Pete P,

I picked up a Vibra-tach from my dealer. Around $20. It's Briggs p/n 19200. They are simple and inexpensive and as an added bonus is goes up pretty high and I can use it on my model airplanes! Not the most precise but well with-in the +/- 300 RPM spec on the Duraforce.

Happy Re-Jetting!

AJY

Tom,

That's the same filter I put on my 'V' even though I believe it's supposed to only be used for engines with a pump.

Pete,

I've got a Vibratach on order now, Tecumseh part no. 670156. It's the same tach as the B&S (part no. 19200) but a few bucks cheaper.

As far as checking RPM, can an old Autotune Multi-tester (Dwell, Tach, Points) be used on a mower ?? It has 2 leads, one that goes on the primary side of the coil and one to ground.

I still own the 2 cars I used to use it for, but they have had Mallory Unilite conversion kits since the mid-80's, so this thing has been sitting in my tool box un-used for 20 years !!

I re-jetted the 10247 this weekend. I ran into a few bumps but it was only my 3rd time working on a carburetor. I opened the drill bit case wrong and all those small bits fell on the bench. By process of elimination (length and size) I took my best guess at the bit to use. Be careful with those bits.

I only drilled the main jet. Took my time, used oil and backed it out many times. Put the carburetor back together. It started right up, however while adjusting the governor back the spring came loose inside the governor. I think if you hold the air vane in a position to keep the most resistance on the spring while adjusting, this won't happen. Took apart and attached the spring. Adjusted the governor so full throttle is 3800 rpms. Based on the tach it runs very steady (on concrete) anywhere from 3400 - 3800. Has a slight surge at 3200 rpm, but not much. It smokes more, like an F or D motor. It sounds different, hard to explain, a bit more exhaust noise, an overall lower tone, and more exhaust ping.

Been dry here but I'm going to use it this week. Don't have to run at 3900-4000 rpm to avoid the surge. 3400 rpm seems about right. Going order Mikuni pilot jet replacement. May even order another main jet and bits so I know exactly how much is drilled out.

A couple of questions;

1. I pulled the sticker off by the pilot jet on the side of the carb. Is that jet supposed to be covered with the sticker?

2. After re-jetting anybody post their rpm range

Thanks everybody for all the tips and instructions, KenMc

Here's my update - I have 2 DF's I'm modifying. I bought the new Toro pilot jets and replaced them - no change at all. So, I might suggest this is not needed.

I did buy some small bits but didn't realize I got even sizes only. I really want to get a size #67 for the main if that's all it takes. Has anyone only gone one over on the main with good luck? Sounds like most are going 2 over to #68. Is that correct?

THS,

I replaced the pilot with the suzuki and only went up one on the main to a #67. (note: the larger number the smaller the diameter) Mine surged very bad at the specified 2900 RPM but is was almost tolerable when I set the speed to 3200.

Going up only to #67 is almost perfect for my machine. Juuussst a touch rich. I wish I wouldn't have reamed at all. Although the #66 bit did not fit when I was done.

I'm considering getting another main jet and and not "reaming" at all and see if it likes that a little better. Either way the change was music to my ears!

I gather from all the posts here that there is some variation from engine to engine and if I had unlimited tinkering time I would start again and step the diameter in as small increments as I could and try until I found perfection. Last night I had dreams of an externally adjustable carb!

"I really want to get a size #67 for the main if that's all it takes. Has anyone only gone one over on the main with good luck? Sounds like most are going 2 over to #68. Is that correct?"

Actually 2 sizes over would be a #66 not #68. I drilled mine out to #67 and am using the Suzuki Pilot Jet and it is running good.

At the top of this thread, Tom P states ... "a 10% increase in orifice size is all that is needed."

Well, I finally did the math ...

Main Jet Stock "77.5": 0.7750mm i.d. = 0.4714904 sq-mm
drill #68: 0.7874mm i.d. = 0.4866987 sq-mm (3.2% larger)
drill #67: 0.8128mm i.d. = 0.5186052 sq-mm (9.9% larger)
drill #66: 0.8382mm i.d. = 0.5515246 sq-mm (16.9% larger)

Pilot Jet Stock "37.5": 0.3750mm i.d. = 0.1103904 sq-mm
Suzuki "40": 0.4000mm i.d. = 0.125600 sq-mm (13.7% larger)
drill #78: 0.4064mm i.d. = 0.1296512 sq-mm (17.4% larger)

Drill bits also don't make perfect holes, and in brass it is real easy to end up with a larger hole than the actual drill bit size. Taking this into consideration, going 2 sizes up could end up closer to a 20% increase in actual orifice size !!

dougmac - you're right, I mispoke on the size. Also, thanks for doing the math. I was curious about that, too.

Sounds like I am better off to try the 67, then see how it runs before going to a 66.

I am tempted to go back to the original pilots when done.

Basically if you go up 2 on the low go up 2 on the main so you don't get a rich low speed and a lean hi speed condition. The low speed jet is still feeding some feul at full throttle so it is good to have them balanced.
Ideally a engine is jetted at 70 deg.normal humidity and at sea level. Higher temps,humidity and altitude make the a/f ratio richer.
I learned all about jetting back in my teens to late 20's when I used to race motocross. In morning pratice I would get my bike set up a tid lean ready for the heat and humidity to rise for the first moto. Then after qualifying I would lean again as the temps ,humidity increased for the moto. Always gave the sponserd guys fits and never had a seizure or fould plug.

THS...why are you considering going back to original jets? I would only go up one on each, and see how it runs. Do not go by the sizes on the drill bits. Mine were off. Just go up to the next larger size from the one that fits. My bits were cheap ones on ebay and I am sure not precision machined to perfect tolerances.

I was just noting that the change to the pilots made little difference (not really a surprise). I am going to enlarge the main jet, and based on what Two Cylce Nut says, I will probably just leave in the bigger pilots as well.

I think I'll go and buy a #67 bit now....

Thanks!

Just installed a shut-off AND fuel filter on both my 10424 & 10323. Don't have a digital camera, so I'll just have to explain it ...

* 1-1/4" long hose tank to shut-off
* Stens 120-228 (Briggs 494769) 90Deg Shut-Off with hose barbs both ends
* 1-7/8" long hose shut-off to filter
* Briggs short round red filter; approx 2" long (don't have a pt#, dealer grabbed them out of a bulk bag).
* 1-1/4" long hose filter to carb

Looks and fits great.

By the way..what is everyone using to clean their carbs with? I had nothing else at my house when I rejetted...I used brake cleaner to blast the junk off the carb body. I was concerned a bit about the effect it could have to the plastic. I just love brake cleaner though. I mowed my lawn again today...I just love my 10550 now without surging. The surging and ES was awful together Now the ES ain't that bad anymore except for backing up.

Brake cleaner wont hurt the body. I use Berryman Chemtool B-12 carburetor cleaner. No effect on the parts.

Holy Crap! So THIS is why there are so many 2 stroke LB nuts around?!?!?!

I just re-jetted my 10550 yesterday, went up two sizes to 66 on the main jet and it really, honestly UNLEASHED a MONSTER. Totally different machine. (Saxman, if you haven't done it, I really recommend you do). I hadn't mowed my extra lot in weeks so the grass and weeds were thick and tall and I was giggling and smiling the whole time. Wow, unbelievable. Some really thick, deep zoysia is creeping in from the neighbors on one side and when the mower hit that, the engine just settled into this wonderful amazing buzz or hum and left behind the most beautiful cut I've ever gotten from a mower. In another location, some tall fescue and grassy weeds had reached over a foot high and were incredibly dense. The 10550 didn't flinch when I roared into it. Totally obliterated it with no discernable strain. I have to admit that it did smoke quite a bit at first start up which had me thinking I screwed up and oversized the main jet but within a few minutes the smoke disappeared. Starting was incredibly easy, only one pull...and I stopped and restarted it quite a few times.

Oh, and I tweaked the control cable for personal pace/easy stride, gave it a little more slack (as per recommendations here) and along with the re-jetting (i.e. no more surging) the personal pace operates MUCH more smoothly. I was a convert to the 2 stroke LB's before but this is now a truly amazing machine.

I didn't pick the best day or location to do the re-jetting, hottest day of the year so far, swimming in humidity on an asphalt drive in the direct sun. But it still took less than an hour and I didn't screw up anything. Kinda tricky getting the air vane spring re-attached and holding all the parts during the reassembly. But this is one SIMPLE carb when it comes right down to it which only increases my respect for this LB. As for the heatshield, it wouldn't be difficult at all to get a thicker piece of aluminum transfer the holes and drill them out. But with the engine running richer and therefore cooler, is this now necessary?

Again, rejetting completely changed the performance characteristics of this machine. Everything from the sound of the engine to the quality of the cut to the operation of the PP was improved. This is a necessary mod.

Thanks to everyone....

jarrall

"Saxman, if you haven't done it, I really recommend you do"

Saxman has been very silent on this post...I do not think he is convinced.

DO IT!! I was hesitant at first, I mean, I had just bought my 22260 about a month prior and I sure as hell didn't want to screw anything up but I just couldn't stand the surging. It was just downright embarassing. In fact, I stopped using my commercial and used my 8270 instead. My neighbour was giving me strange looks and he told my kid that my mower "sounded sick". This is the same daughter that said my old 5024 "smelled like cookies" when it was running. The shame! Now, not only does it smell like my old boys, it runs better than any mower I've ever used! I can't understand why anyone with a surging duraforce wouldn't do this simple, wonderful modification.

Even if the engine has little to no surging, I would do it. I had a 10323 that ran fine, but kicks butt now that it was rejetted.

Tarheelman,

I hope you've read jarrall's post and are inspired to re-jet yours. It can't be that difficult even for a "mechanically challenged" guy. If I had a Duraforce, I'd do it without hesitation.

Maybe I will. I'm back and forth on it. Mostly out of laziness, I guess. Just don't want to tear it down. Actually, I have to get into the carb on my old 10201 first, because it runs so rich it 4-cycles. It will go into the 'power hum' but only under max power demand, like chewing up a leaf pile. It smokes a lot even with my modified Opti-2 mix. It's either dirt in the carb or a high float. The thing has great compression and clean ports.

I wonder if the jet from a 'V' carb will fit a Duraforce? If it did, that would be an easy fix. There are lots of 'V' engines being sold and disposed of these days, so there should be plenty of carbs available.

I have a couple of what I believe are V carbs and they do not have compatible jets. They are one piece and the main jet and idle jets are different types altogether. They are black plastic and look similar but thats as far as it goes from what I can tell. That is IF the ones I have are indeed the V engine carbs.

I DID IT! Like everyone says, you MUST do this!!

I actually did this on two DF's this evening then mowed a great deal with both.

My #68 bit had to be turned in on both, and the #67 just took out one tiny shaving. I stopped there. Both engines had just the slightest hint of a tiny surge afterwards, but only something I would notice and only once it a while. That tells me I didn't over-do it. Most of the time, they had the perfect, smooth hum and burble sound.
Here are some other observations:

1. This was about the third or fourth time I've taken carbs off of DF's - I'm getting better but they are a pain in the butt! Have patience.

2. I actually noticed less smoke and a better smell, if you can believe that.

3. They just sound, smell, and run like a Lawn-Boy should. I'd even bet that they burn cleaner now.

4. I'm tempted to go up one more size. I feel confident it would not be too much for the engine, as others here have noted.

Thanks to everyone who's commented on this post. A year ago, I was scared to try this. Now I know process is easy (took me less than an hour to do 2 engines). It makes the DF run the way it was meant to run. What a difference 1/1000th of an inch makes!

Troy, did you leave the larger pilots in? Do you think they are necessary now?

Yes, I left them in based on what TwoCycleNut said. One of the engines now just purrs at all speeds. The other one isn't as good, but it's older and I know it needs a new needle and maybe a float adjustment. I do get an unpredictable surge from it now and then. Otherwise, they are both running great. The change to the jets is so slight, but makes a world of difference.

Does this put and end to the thread? We need to keep it going. Many people are benefiting from it.

Just bringing it back up! As I'm finally getting to my Duraforce surge.

I want to let you know that my neighbor uses the 10424, I think, its a DF of course, and for a couple years I have been listening to him severely surge his way through his lawn. Well, one saturday a month or two ago I go over to talk with him about the lawnboy and find out he knows nothing about the re-jetting, or properly maintaining the LB for that matter. So, since I already have the drills I suggest that he allow me to rejet it, mainly for my satisfaction so that I dont have to listen to that annoying surge every week, and he accepts. Now I only rejetted his idler jet, so there is still room to rejet for him. A week or two after the modification he came over to let me know it is working real well, and to tell you the truth I haven't had the chance to listen real well to it as he cut so I have to take his word for it. The next step is to remove his carb and do it right by rejetting his main jet, so this is something to look forward to.

...Keeping the thread alive!!!

There is a new post looking for rejet info...

Just wanted to chime in, I've had a model 10323 since 98 or so and it ran pretty decent for many years though always had a lean surge most of you speak of but cutting through the grass it would power through well.. One thing I did last year was changed out the plug with an E3 plug from Lowes and that made a noticeable difference, not quite as bad but I knew it could run better. A couple of weeks ago the surge got worse, cleaned out the carb which looked pretty good but found the pilot jet (under the sticker) clogged, in the meanwhile I found this thread and went ahead picked up some bits at Hobbytown USA ($21) and did the jet bore out mod as mentioned and it is a totally different machine! As jarall described unleashing a monster, no friggin joke! It felt so good I wanted to cut the whole neighboorhood! This baby is good for another 20+ years the way its running, have another of the same model I acquired when I found out 2 strokes were no more. Would be nice if they would bring 2 strokes back with a simple fuel injection, there is 2 stroke technology supposedly that is cleaner than existing 4 strokes, or how about a small clean diesel? I know I'm dreamin, I wont need another lawn mower for the rest of my life, dont think this thing is breakable.