Here is a little blurb I copied off the forums a couple years ago.. forgot who the original author was.. Quote The Low speeed jet is a 37.5. The High speed jet is a 77.5. The high speed jet is located inside of the float bowel. Remove the "fuel filter" screen and you will be able to see it. It is screwed into the larger nozzle. When I tweak one of these engines for someone. I will start by getting two new stock jets. Then drill the low speed to 38 and the high speed to 78 to start. Then go .5 larger at a time until the surging stops. When that is achived. I will go back and drill the main jet out +1 oversize as I did the low speed jet. Example. If I drill the low speed jet from 37.5 to a 39. Which is 1.5 larger. I will add 1 to that 1.5 which of course is 2.5. Then drill the main jet and take it from a 77.5 to an 80 jet. If you have surging at idle. What do you think is happening when you apply full throttle where you do most of the work? The funny thing that I have saw with many DuraForce engines when working on them. When the head is removed. The cylinder and the top of the piston are dry and the cylinder is a dull flat color. Which is mostly caused by a lean condition or running to hot. Then once I have rejetted the carb to where they are running a richer fuel/air mixture. The cylinder and piston top become shiny and damp looking from the extra oil that is reaching the parts after running for awhile. The normal rule of thumb when dealing with a 2 stroke engine rejetting. 1 size up on the low speed jet, 3 up on the main jet. You do not want to have a rich low speed (idle to mid prm range) dumping fuel into a lean top end (mid to top RPM speed). You must achive a balance with the fuel system. Once the carb is rejetted correctly. You will have a very happy engine that will run much smoother, cooler and provide more power to the blade. The 5 or 6 that I have rejetted for people here have been very happy with the results. Even with their fuel comsumption going up a little. But who is really going to complain because it now takes 36 oz of fuel to mow the same area that use to take just 32 oz? Not me when I know that my 2 stroke mower will not burn up and be around to mow another day.

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.

Well, I had a few minutes to check a few things over last night. Gotta love these things, engine shroud off, removed carb, float bowl....tools used, 1 screwdriver.. :-) So..float bowl was clean and crud-free, so signs of gunk in the needle valve, moves freely, etc. Cork float is all in one piece, and once the surface gas dried upp it doesn't seem saturated. The air vane moves freely, spring not broken. Throttle is held wide open, vane will close throttle, spring back to wide open, seems fine. I blew through the ports I could with the carb off....did NOT touch mixture screw (I assume it's the brass one sticking straight up behind the throttle through-shaft?) The mixture screw has not been touched at all (as long as I've had the mower, and it worked well since I've had it). Exhaust port is clear. Pulled the plug out, cleaned it up, a fair amount of wet sludge (from running so rich)..cleaned it up like new, reinstalled. So, that all checks out.....put everything back together, same issue. It's running rich to the point that you can tell it's sputtering when you move the air vane...it should rev up but it sputters instead, like it's way too rich. It ran a few minutes while I tried each direction on the click wheel (it changes the idle speed but it remains rich and doesn't want to rev up...sputters instead), and it left a big oily spot on the lawn under the exhaust port....so..yeah, rich... Also, it's spitting gas out the intake. Not a huge amount, but enough that it gets the air filter wet, and will fire drops into your eyes if you stick your head down there with the air filter off. LOL I didn't fiddle with the mixture screw. (Any time I fiddled with carb mixtures in the past ended with a trip to the small engine shop to have them fix what I screwed up.) If someone can confirm how many turns from bottom it should be, I'll pull it out in case there's a piece of dirt or something in it... As for the adjustment..it 'should' be good..it was never changed... So...recapping::: rich, will idle not too bad, but as soon as you cut any grass it just slows right down and stalls. Will not rev up any significant amount when moving the air vane..it wants to but just loads up with fuel and sputters instead. The issue came on slowly over 2-3 mowing sessions..it wasn't there all of a sudden...it came on slowly and got worse and worse over time. Feel free to toss the hints at me....thanks in advance!!

Hi. I just wanted to revive this thread for a bit more clarification. I copied the url for the parts list of my 10323. I have the wire drills bits and am ready to rejet, but wanted to know why the pilot jet is not listed in the parts list. The part number (98-7041) is also not listed. The mainjet is clearly identified and is not a problem, but is there another name for the pilotjet. Slowspeed, idle and 37.5 also do not appear. Does the 10323 simply not have a pilotjet? I haven't looked behind the sticker on the carb yet, so I have no idea yet. Thanks in advance. Regards, Stevan Here is the Link: https://lookup2.toro.com/request/getpub1.cfm?PubID=13009&PubNum=3321-570&Lang=EN&Cust=anonymous_user&xCaller=lawnboy&Filesize=2394941&vKey=1983392&PubType=11