Its a long story so I apologize in advance. As many of you know, I am an ardent fan of the Lectron Carb. I doubt that I will ever run a conventional carb again. I was also the 2nd guy in on the early order Cast 38mm Smart Carb. I stuck it out through a year of delays that had many dropping out of the buy. I finally got my smart carb a little over a year after I initially placed the order. APT rushed the carb to market through many manufacturing issues with several still to be resolved. My initial operation of the carb was short and over. The rod delivered with the carb was far to lean and wouldn't run above ~3/4 throttle regardless of adjustment. Corey at APT immediately shipped me 3 new rods and when I went south early this year I had it installed with the richest rod and was ready to adjust. Unfortunately 7 miles into my first ride, I had a confrontation with a barrel cactus that was in my landing zone off a little rise and so much for my effective riding. I had made a couple of adjustments to that point as the carb was too rich on the bottom. I gutted it out a couple of more tries but I just couldn't effectively work with the carb. On to the second issue with the as delivered early release carb. The tip over valves that stop the carb from flooding the bike when tipped over(read endoed) stick closed. It is just like having the vent lines plugged on a lectron...it doesn't want to run. Corey sent me the details on the fix and a small massaging with a milling bit and problem solved. So in the last few weeks I have been using the supplied rods and still could not find the happy place where it was crisp on the bottom and still rich enough on top. Well it turns out that the rods are made long so the same rod can be used in any size carb no matter adjustment height. Enter the third issue fix. APT sent me the shorter rod to be used with the 38mm Smart Carb. I have been using that rod and it is so damn close to perfect. I ride a lot of the time on the bottom and mid. I want my carb to work perfect in this area of 0-1/2 throttle. So much of our crappy burned trails are constantly covered in down fall from the last wind that the bike just has to run well down low. Even with the new shorter rod if I have the bottom/mid perfect the very top is still too lean and if held WO for any length of time will be lean enough to bog. Granted this isn't my priority but when you need it to fly, you need it to fly. This issue is complicated by the small bores lack of signal strength at higher rpms/at higher altitudes. The Lectron had the same issues but Kelly quickly made adjustment and Kevin created the MS-3 rod that solves the issue. Enter the massaging tool. I made a very similar re-grind to the supplied shorter Smart Carb rod that I had previously made to the Lectron rod with advice from Kelly......Bingo we have a winner. I can have the rod adjusted for the ultra crisp bottom/mid and it will still pull to the moon with no lean issues. So I now have a Smart Carb that runs as cleanly as my perfect Lectron. How do they compare? First, I think the SC has a distinct advantage through its keyhole design for first half throttle response. This is born out through my initial impressions. Response is immediate and controllably explosive. Where the Lectron is all about smooth, consistent, rip the SC seems to just explode up obstacles with the flick of the wrist. Whether this is better for the individual is a personal decision. Second, I think the SC produces more top end than the Lectron. This is just from my observations on the county road pulling wide open runs. The SC pulls a little further, a little more willingly. I don't know that there is an advantage to either carb in that 1/2-3/4 throttle but I just haven't been able to ride with them back to back in a real gnarly trail environment where you are rolling on and off and living on using that 1/2 to 3/4 throttle up a nasty climb. Adjustability, while the lectron really seems to be a set and forget carb, I think you would possibly make minor adjustments at times if it was as easy as the SC. It literally is a matter of shutting the motor off, leaning over and while holding the throttle open clicking the adjuster one way or the other. Start the bike and ride off. Don't get off, don't remove any tools, 5-10 seconds and you have made your fine tuning adjustment. So that is the story even though it is incomplete. I still need to get up into the gnarly and ride them back to back. I also need to compare fuel economy in the same way. Once I am sure that my rod grind is working in the nasty stuff as well as in the fields and bumps, I will forward it to Corey and see if he is as responsive as Kevin at Lectron. More tales later, Thanks for your patience
I concur! On one of our WB165s I have a 36 billet APT that runs perfectly as it initially came. On the other WB165 I have a 36 Lectron that needed the PowerJet tube trimmed. It runs great. On the WR144 I have a cast 38 APT that needed the short rod, just as you described. It runs perfectly, but we don't ride at extended WOT at all. Not sure what I'll put on the WR360, but it won't be a Keihin or Mikuni!
Looking forward to hearing more, I also have an early production run carb that hasn't really delivered. As tempting as it is to throw it and go lectron, I really want to be able to justify the big spend.
Just saw a post on KTM talk that APT is 'almost' there with delivery of the cast 38's mmm … it's now the middle of June 2014
I have put mine on my saw bike and went back to the Lectron on my 177. The Lectron just works great everywhere. I couldn't get the SC to work perfect bottom to top. Either the bottom is rich or the top is too lean. Just not ready for the small bore Husky demands with current rods. I will revisit it at some point when there are more rod options.
Been following this as I am running a 40 billet smarty on my 300 timbersled. I have tried the q11 through q5 needles and am currently running the q7. If I run the needle at 60-65 clicks from full rich setting my wide open egt's stay at 1250 but idle and fuel economy sucks, way rich, I don't even need choke to start bike at 25 degrees. If I set q7 needle at 90-95 clicks from full rich( 100 being end of threads) economy is good and idle and throttle response is great, but egt's are 1350 and climbing when I back out of it. Have to much time invested in this carb to start over, lectron, so could I modifie my other needle to richen up the wide open like lectron users have, or install a power jet that would only add fuel at wide open? Please help, tried to pm wallybean one here but can't figure that out either. N
hi farmer, you probably have to be here so long or make so many posts to pm. thats my guess. sound like you know what youre doing with jetwork and being able to watch egt is very helpful. however, there are very few apt users here and many lectron guys, im not sure theres anyone here that can help. if you could install an adjustable powerjet like the lectron has im sure that would fix you up. on a lectron, it can be set up to work in that top 1/2 or top 1/3 of throttle...
The beauty of the Lectron is the 40 years of sorting out rods for all applications and the external PJ. With the SC you are fixed 0-100. IMHO sounds like your solution would be to use a rod that is lean on top but idles and works well on the bottom and mid and then sand the rod (which makes it richer) until you get the top end you want. Or better yet SC should make you a rod that works. To sand the rod you need to identify what throttle position it starts to go lean at and mark the rod. Then take a hone stone and carefully sand and measure with a micrometer. Its going to be all trial and error and you are going to want to sneak up on it as there is no going back. This is how I designed some custom rods and it works. Hope that helps. Oh, early on SC was touting how basically one or 2 rods and their super fancy all compensating carb would do the rest and acted like one setup was going to work for everything. Hence smart carb. We on the Lectron side just smiled and waited for the fall out. Motor requirements and fuel vary so much there is no such thing. I really liked the SC billet one I tried but in the end found Lectron way easier to work with and understood this type of carb (they invented it 40 years ago) and had it sorted.
Motorsports were you the one that modified the lectron rod to richen up the wot? I read the lectron post where someone modified the rod and then shortened the power jet noozle? To make it work better for wide open. I believe the snowbikers load these motors longer than most bikers do, I think anyway, so was just hoping to mod my needle, just wanted so info on how to. Thank you
yes that was me. did a lot of early development on the Lectrons for your specific requirements as off road riders.
would you share how you modified the needle? I have a thunder products power jet, but hesitate installing it as I am convinced the flat needle does a better job of atomizing the fuel, therefore would rather modifie the needle. I have a q11 needle, that is .080 at the rich end, q9 is .078, and a q7 that is .076. All these needles have the same taper, and I can raise all but the q11 high enough with the clicker to richen the wide open throttle egt temps. With that setting though idle is way to rich. I am hoping to get some insight on how I can grind my own needle....ie what to use to grind it, where I can purchase stone ect. Thank you for our help.
A honing stone like one you do bores with or a knife sharpening stone ultra fine i assume would be suitable to creep up on the needle.
First I marked the throttle housing and grip with hash marks. Then what I did was ride the bike and noted the lean area. I looked down while riding to see where I was throttle wise when the lean area showed up. Then I removed the carb with the throttle still hooked up and turned it to where I could feel a lean spot and marked the metering rod in the carb with a sharpie. So now I knew where the lean spot ion the rod was (roughly). Then I took a fine hone stone and sanded the rod at that location and past. The stone takes it off slow enough to not get carried away. Took me a few attempts but could feel it getting better where I needed it to. Ended up with a perfect rod for my bike. I had started with one that was very close so did not need a lot of tweaking. So now I use the PJ adjustment very sparingly and still have it to add fuel if I ride dunes or something.
