Good tip. Seems like we may get the optimum mix of boring and replacing with experimentation.

So you're saying pilot jet replacement alone took care of all Duraforce lean-running problems?

So far, it has on mine. However, mine had its original carburetor, including all gaskets, replaced under warranty this past July. Even with its stock pilot jet, the new one didn't surge anywhere near as badly or as often as the original carb did---making me wonder if the original one had an air leak from overtightened mounting bolts. After all, as many of these engines as Toro built during the last year of production, it's possible that quality control suffered some as a result of the increased volume.

Based on its behavior, I think my 10424 was borderline too lean with its new carburetor and stock pilot jet (and dangerously lean with the old carb---I hope no damage was done). Consequently, going up 5mm in size on the pilot jet has provided enough enrichment to stop the surging, which is all the enrichment I wanted.

Sounds good to me, and there's nothing to lose by trying it - if it doesn't cure it, the new jet can stay and the main jet will have to be bored. BTW, check your decimal points on those jet sizes!

Oddly, my '98 10525 doesn't seem to have any of the lean running problems that others have talked about. My aunt has the exact same model, though I think hers might be a '99. I bought mine late in the season, and she bought hers in spring, so I'm not sure as I've never compared serial numbers. I prime mine 3 times, and it will always start on the first pull, then after a very brief little lean sag, it smooths right out and even 4 cycles a little bit till it gets under load.
I see no reason to mess with the jets on mine whatsoever. My plug is a light tan color and I only just changed it this year, even though the original one was probably still good for quite some time. It showed virtually no wear on the electrodes.

Maybe I was just fortunate enough to get one that had jets that were on the large side of the error margin?

I just don't want to dive into this and jet it richer only to have a sputtering, stinky, too-rich running mess when I'm done. If it ain't broke, don't fix it, right?

saxman--

Regarding the jet sizes, here's where my lack of mechanical knowledge/skill shows itself! :)

Mike--

I think you're right---you were probably fortunate enough to get one that had jets that were on the large side of the error margin. If your DuraForce isn't surging, then I agree that you don't need to re-jet. Like you said, the phrase "if it ain't broke, don't fix it" definitely applies here.

If it ain't broke, fix it till it is.

Heh.

Reminds me of my favorite torque setting.

"Tighten it until it strips, then back off a 1/4 turn."

My 1998 or 1999 LB just started to search for the smooth running speed 3 weeks ago. It has run great and started easy till then. Took the carb off to clean and still runs bad. Guess I'll be looking for the new jet. Does the jet go under the bottom cover of the carb? I did not take it off for the cleaning.

One jet is screwed in from the outside. That's the low speed jet. The main jet is inside the bowl area of the carb. Cleaning the jets, the bowl, and the needle seat is the main goal of carb cleaning. Dirt on the outside is unimportant.

Even with a change in jet size, atmospheric changes could still cause some surging at different times of year or baro pressure. I wouldnt over do it if it ran fine during the summer.

Hmm, interesting. this matches up well with my rejetting experieince and is easier to execute. I had drilled both jets one wire bit size larger and found that the jetting was close but not spot on. Since the jetting was so close to perfect I went up one more wire size on the only the pilot jet and found jetting bliss. Now my mower starts with 3 to 5 primes, hums great while mulching, burbles at the end of a swath when I'm doing a 180 turn or when I am standing still (no load).

It makes sense that this can work because I believe the pilot jet delivers fuel under all throtle settlings while the main jet is resricted to middle and full throttle settings.

If you are curious about your fetting you can do a plug check. While at full throttle underload (mowing) just letting the bale go to immediately kill the motor. Pull the plug to inspect the colr of the electrode insulator. If you idle back and then shut it down or do the check while under no load you will get a reading for condition that does not exist while mowing. Regular/regular gas mix should be a nice golden brown. Fromulated (oxygenated fuels) might show a littel more brown grey. You should see no oily deposits and modern 2 cycle oils will not show any ash deposits.

I also read the plug should be "wet" at the tip. Is this also true of correct operation? If it is dry...it is starved.

I'm not too sure that in actual operation it should be wet at the tip of the electrode insulator, but may be an artifact from the testing method. When you kill the motor in a plug check you want to do it under the load and throttle settings for the conditions that the motor is under at the moment. In a perfect world that would include instantly stopping the crank from spinning. Even with a blade brake that is not really possible, so when you release the bale the spark is removed instantly but the crank still turns a number of times and pumps some raw fuel/air mixture through the combustion chamber which could leave a wet residue on the tip. Maybe with older motors running at 16:1 and 20:1 gas to oil fuel blends the residual oil may give a wet look from oily residue. Also I think that modern 2 cycle oils mixed at 32:1 and leaner should be dry looking with no oily residue. I guess if you go fully old school you could do a sniff test and decide if the odor is unburnt fuel (gasoline smell) and a test artifact, or partially burnt oil (char smell)which may be an indication the heat range for the spark plug is too low as the electrode insulation is there to keep the tip hot enough to burn off any residue but cool enough to avoid pre-ignition (pinging). Personally, this is a step farther than I care to go......we're talking lawnmowers here not some race engine your about take on the competition with. I'll just stick with the OEM spark plug.

Now you got me to wonder when lawnmowers will be required to be OBDII compliant (or something similar) and you just plug in you PC when doing a tune it up. Then re-jetting will require downloading a new fuel/air map into flash memory. No more wrench spinning and grime under the finger nails, just a computer and some type of serial cord.

"No more wrench spinning and grime under the finger nails"

Even in todays highly technical automotive world, this is utterly impossible. Nothing works forever and anything that is exposed to fuel, oil, air will always become a greasy mess to work on. Sure you can do part of the diagnostics with clean computers, and reprogram with them as well. But identifying the mechanical fault/causual part and replacing parts has never and will never become automated. Hands on is the only way. And you have to be a contortionist to even squeeze in to make the repair with all that garbage "under the hood"... LOL

Tarheel,
I know this is an old post, but I just bought a new Duraforce and it does surge. Do you still think the R-Tek pilot jet is the best. I took your advice earlier and used the Suzuki 40 mm in my first mower and it runs fine. So for the new one, I am not sure if I should get the 40 or 42.5mm jet. What do you think/suggest?
Thanks for your help.

Joe--

Since both jets cost about the same, I'd go ahead and use the larger one (the R-Tek jet). Because it's bigger in diameter than the Suzuki jet, the R-Tek pilot jet should provide extra insurance against having to enlarge the main jet---a process that requires removing and disassembling the carburetor (which is beyond my mechanical ability).

Hope this helps.

tarheelman; Did you experience higher RPM as a result of enlarging the pilot jet?

dkr497,

Don't touch that drill!! At least not until you have removed the carb and completely cleaned it out including all the orfices and passage ways. If your mower was running alright before and then started surging, most likely you have a plugged or partialy plugged jet or orfice. Disassemble the carb and clean with carb spray, also check for a bad float and inlet valve needle and seat. It is a good idea to install an inline fuel filter and shutoff valve on the duraforce, I like the Briggs and Stratton filter #5065 and have them on all my LB's. One thing I have found out is if the carb is flooding due to a bad float or inlet valve the engine will behave similar to a lean running surger only you will see a lot more smoke and sometimes the fuel tank will self drain while sitting for a period of time. Good luck!

just talked to my dealer that handles Toro and Briggs. Neither part number exists alone. He says you need to buy a kit now to get the R-Tek jet. Also just checked RCPW on-line. It is not there either.

Kit ?? What is in the kit and how much ?? I would drill them out rather then support their games.

Yea. I did not go for it either.

SEPW has the jets separately

Joe--

Fordtech is correct, sepw.com sells the R-Tek jets by themselves. I ordered mine from there in late summer/early fall last year using the Toro part number and it arrived in a Briggs package.

saxman--

I didn't experience an increase in engine RPM when I installed the R-Tek pilot jet. However, I was able to back off on the air vane governor's spring tension by one click since the engine no longer surged. (I had increased the tension to an engine speed higher than I like shortly after I bought the mower in order to minimize the surging.)

Good deal - I think I'll try it. I used my 10550 the other day and couldn't wait to be through so I could put it away. It runs okay but as my expectations of what is a good mower for me have developed, it no longer fits the bill. I think I'll try this pilot jet, but my plan is to disable the drive, change to regular rear wheels and use it in place of the old 10201 for my rough work (leaf mulching, undergrowth control). Can't use the geared wheels for this as debris clogs and jams them. This way I can always put everything back if I decide to use it for the lawn again, or I could just push it.

It is funny how you guy never mention a Part Number for this R-Tec Pilot Jet in this thread !!

Visited TORO's web site & downloaded the parts manual and found B&S # 801308. This would be the pilot jet for L-B 33005 & 06 (6.5HP) and TORO 38515 & 16 (5HP) and 38517 & 18 (6.5HP). What is interesting is the engine assemblies are different (5HP vs. 6.5HP) yet they use ALL THE SAME PARTS !!

TORO also shows a 38600 & 02 that use a H.O. 7 HP engine ... this uses different main & pilot jets than the 6 listed above, as well as different cylinder, piston, crank. Otherwise, all other parts are common between these engines. Based on the parts differences, you would assume this 7 HP has more displacement but the TORO literature states it as the same 141 cc.

Searched both SEPW & RCPW for "801308" and got no matches. Do you guys have a different (I.E. old TORO) part number ?? Tried to find an OLD TORO parts list, but all (back to 2001 anyway) have been up-dated to B&S part numbers.

Doug

Toro #98-7025. They have them at SEPW.

Doug--

I gave the Toro part number for the R-Tek pilot jet in my original post at the start of this thread.

"I gave the Toro part number for the R-Tek pilot jet in my original post at the start of this thread."

My 42 yr old eyes must be going ... I swear I read the whole thread before posting my ignorant question !!

Thanks Tarheelman

"It runs okay but as my expectations of what is a good mower for me have developed, it no longer fits the bill"

Saxman...post that puppy on ebay...or sell here to us junkies.

Two people have offered up thier LawnBoys on this forum this week and no junkies have jumped on them.

As I mentioned above, Toro also has a H.O. 7 HP R-Tek Engine ... this uses different main & pilot jets than the 6.5 & 5 HP versions, as well as different cylinder, piston, crank. Otherwise, all other parts are common between these engines. Based on the parts differences, you would assume this 7 HP has more displacement but the TORO literature states it as the same 141 cc.

Now here is the question:

Pilot Jet is B&S # 801309 ... anyone know what size this is ??

Doug

HOLY COW!
I just joined this forum after web-searching for a solution to my surging LB. I cleaned the carb and replaced the jet with the part suggested. The surging is very much reduced and the engine sounds so much more "alive" and strong. When I started it up for the first time after the work I did, my wife came out and said it sounded like a motorcycle in the garage (insert Tim Allen grunt here). Thanks for the tip!
-Scott

Scott, glad it helped. I know I didn't contribute to this thread but these guys really know how to get the duraforce engine running better. In my opinion this should have never had to be done. People should not have to re-jet a lawnmower engine. Toro should have went with a higher quality carb.

I realize they had to meet EPA emmisions tests but I'll bet some other carb could have made the grade. Those plastic carbs on that engineering marvel just threw the whole engine off for me.
I've heard people say that the D-400's were a tinkerers engine but I'd say the duraforce is in there too.

Good luck with it, Neal

agreed -if toro had used the metal walbro carb-this could have been a contender for best 2 cycle engine of all time and could have been a huge money maker for them but we can blame the epa for the fiasco of the plastic carb

I have three 10515's all with walboro carbs. Never had a surge, never will. I chose to rid myself of duraforce powered mowers because I had a job to do. I was embarased when I would run my 10324. It would run up and down up and down. I ditched it and the 10247 I picked up used for the same reason.
Don't get me wrong folks I'm a lawnboy guy, I didn't want to hassle with jets and little tiny drill bits etc. I'm not running motocross here. When was the last time you heard of someone having to re-jet a Briggs or Tecum?
I think that this could have been solved inside Toro.

Neal

I have a 10518 with F engine and it has a craptastic plastic carburetor that the airvane sticks on. Even brand new replacement carb does the same. So its not just Duraforce, its the carburetors. And MANY 10515 and 10518 have the plastic carbs. All of the 5HP ones do. Sticking air vanes are just as large a problem as a minor surge. I have 6 Duraforce mowers and only one has an annoying surge. The rest quit surging within a minute or two.

Great Info. Does anyone know if the R teks run larger main jets like they run larger pilot jets? It would be great to replace with the larger jet than having to drill out the main jet. I know this must have aleady been looked at. Is the R-tec main jet 77.5 also? Thanks

I believe the main jet in the R-tec is a smaller 73.8 vs the 77.5 in the Duraforce. I'm getting this info from the Toro engine service manual. In Fla I don't have need of a snow blower.