now thats more like it!! cool looking stuff.
Service Honda- 2013 KX500AF Build Project
- Thread starter mtn-doo
- Start date
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mtn-doo
Well-known member
The carb chosen by Corey Dyess, of APT is the straight 40MM. Corey is the head Tech and "mad scientist" of APT. He is very easy to talk to and will explain all the technical features clearly. The installation was a simple swap. The intake boot to the reed block and the boot from the air box are all the same size. My clean air, high flow system slipped right on. The fuel line connects just the same as your stock carb. No other assembly or parts to install. The only piece that may differ from bike to bike, is the throttle cable. It comes with the standard fittings to receive the cable no different that a conventional carb. Adjusting the length may vary on other bikes. My cable length worked perfect with a slight modification to the carb end.
It started on the second kick and idled noticeably smoother than my stock carb. I warmed it up then adjusted the idle again. It idles silk smooth. Very impressive. The throttle response is crazy fast!
It started on the second kick and idled noticeably smoother than my stock carb. I warmed it up then adjusted the idle again. It idles silk smooth. Very impressive. The throttle response is crazy fast!
Ride it
Hurry up and ride it so we can get field report. Do u plan on a heater of any sorts? I'm pretty pumped to get the kx going again. In need of a good vibration I guess. Lol
Hurry up and ride it so we can get field report. Do u plan on a heater of any sorts? I'm pretty pumped to get the kx going again. In need of a good vibration I guess. Lol
Can't wait what kind of results you get from testing that carb, looks good. As for me I have had no issues running the stock honda FCR carb. The only thing I have done to it is install a Factory Pro emulsion tube, FP needle and jet kit and had it tuned on dyno. Made the FCR more efficient, we actually brought the main down quite a few sizes. I think the FP emulsion tube helps atomize the fuel better just like the ATP carb. No over fueling issues in cold temps either, also seems to have a quicker throttle response too.
C
coreyd396
Member
C
coreyd396
Member
The SmartCarb incorporates an altitude correction circuit that "vents" the float bowl to directly communicate with the venturi. Currently our billet performance SmartCarb holds roughly 57ml of fuel in the bowl, which is certainly enough to make for a hard to start engine after a complete tip over and takes a little time to clean out.
We've always had the option to eliminate the altitude correction circuit and just run standard venting to eliminate the tip over flooding issue and still have a nice running carburetor. However the circuit really does a lot more than just correct for changes in ambient air pressures and densities; it also balances the fuel driving pressures to provide very precise air/fuel ratio control as the engine goes in and out of efficiencies, i.e pipe effect. These same features also augment the fuel driving pressures to work in conjunction with throttle position and the shape of the venturi.
All of that said to say it has been a challenge to find a way to trap all the fuel into the float bowl during a tip over and keep it from running straight down the vent tubes and into the engine. Different tip over conditions can create different scenarios of course and we are finding that those with a little lower setting of the fuel level have much less problem with flooding after a tip over. Conversely those running a little high on the float level have more of a problem because of a greater volume and a little longer to shut the inlet needle seat. The needle and seat are shut when tipped over and no more fuel can enter the bowl.
We are getting good results with the first design of our check valves that both allow the altitude correction circuit to remain fully operational, and contain all to most of the fuel in the float bowl during a tip over. These are designed to fit inline with the current vent line fittings and are easily interchangeable on the billet SmartCarbs. These valves will be incorporated into the vent passageways on the new cast carbs.
The greater challenge is overflow if the floats stick open, and totally fill the engine up with fuel. This requires us to find a way to either stop fuel flow from the tank while the engine is stopped. Vacuum petcocks/valves have been around for awhile and are met with mixed feelings, but certainly doable. The other solution is to put a stand pipe in the float bowl that is float operated to let out the overflow, which is less desirable as it would let fuel run out onto the ground. BTW with just the vent line check valves the only way fuel can overflow into the engine is up the nozzle with the throttle closed and really slows it down but still not a complete solution.
Mike Rosso (KTM North America) says that KTM would probably be accepting of a vacuum high/flow petcock, but would be best to apply any device solely to the carburetor. Which I agree and is what we are doing. It's very hard to get a manufacturer to accommodate a supplier, but we are also in a time when EPA/ARB is forcing a clear emissions strategy from manufacturers and necessary steps will no doubt come along to better accommodate what has to be done. It would however make for a nearly fully contained fuel system and EVAP emissions would likely be on par with EFI. We did this on our 150 cc scooters during EVAP testing for EPA and showed in this category to be the lowest evaporative emissions of any carburetor.
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mtn-doo
Well-known member
Great test ride today. With baselines previously established, I had a clean idle, mid range was that typical danger zone, a little lean, in the 1200F range, and wot stable in the high eleven's. Those base line figures were at a "fixed" altitude. My first test with the APT 40mm, started out with a simple start at the parking lot, 3100 ft, msl. Temp was about 18F. I let it idle and warm up while I geared up. Headed up hill going through the gear and throttle ranges closely listening to the exhaust, feel in the seat, and my trusty KOSO EGT. The first thing I noticed was the aggressive response. Very impressive. The next was the mid range lean was gone. It held a constant egt in the 700F range. Never varied either way. I didn't have enough room to open it up....yet! After reaching the alpine at about 6800ft, I noticed nothing had changed at all. It ran just like it did at 3100ft and reading the same egt's. The fun began when I left the road and headed straight up through the trees in untouched powder. Over revved in second, over revved in third, grabbed fourth and loaded the engine hard at wot. It held full rpm, ski in the air and a hand full to hang on to for the long pull. The egt's peaked out at 1230F. It never got fat or faded. I repeated pounding that area with the same results. My first impression was totally awesome with the "consistency"! No changes from start to finish. The changes I want to make,... lean out the mid range a bit, and that's all. Then just fill it with gas and start pounding the woods. APT gave me the simple instructions on adjusting the metering rod to lean the mid range a bit. We have a long two day demo scheduled in Missoula next week. I will be reporting back. And some vid's coming soon.
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That is great
So do u do base jetting for your starting elevation? What kind of eft temps r u wanting?
So do u do base jetting for your starting elevation? What kind of eft temps r u wanting?
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mtn-doo
Well-known member
Well, You simply raise or lower your metering rod until you have good plug color, egt temps, etc. then you are done. Nothing to do. Kinda strange. I laughed at myself for going on a long ride up the mountain to set it. It is hard to realize that you don't have to. Today I adjusted the rod in my pasture and was done. It will be the same on the top of the mountain. Amazing... and for all us "old school jetters" it is hard to get in our head that we can dial it in at home on the driveway, and be spot on tomorrow at the top of the mountain. Something we have never known. It is very cool. I feel i should be jetting something! ha! I re- set the rod to lean the mid range today. I was running in the high 900's and plug color was caramel color. Will do a test rip to the top of the mountain tomorrow. If all is correct and "consistant", I think i'm done! I will up date.
demo ?
so, Missoula demo meaning your will be out riding in the area, or down to da bike shop where they sell the Mtn horse ?
so, Missoula demo meaning your will be out riding in the area, or down to da bike shop where they sell the Mtn horse ?
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mtn-doo
Well-known member
You set the metering rod initially for your application. Get it spot on. No jetting required. You simply dial a knurled knob with "clicks" . Left for "lean", right for "rich". Once set, you're done. It will maintain that ratio all day to the top of the mountain and back. Very amazing. Read your plug. You want from a little rich, "chocolate color" to no more than a tan "caramel" color. Those colors should cross check against your egt's in the high 900's to 1200. Below 900 is getting a little fat, and above 1200 is getting too lean. Note; with the way this carb atomises fuel, it will burn cleaner, which relates to a little higher temp's. I am slightly over 1200 in a long pull, and in the 900's everywhere else.
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mtn-doo
Well-known member
We will be demoing on LoLo Pass Friday and Saturday. The demo is being sponsored through our local dealer, Big Sky Motorsports in Missoula. If you are interested, ask for Nate at Big Sky.
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mtn-doo
Well-known member
Hey Guys, Great test on the new APT Smart Carb. I slowly, one click on the "metering rod" at a time, leaned it, until i was running EGT's in the mid 10's to upper 11's. I pulled my plug 6 different times to cross check my progress. Color was a caramel brown. Clean and crisp. I had to make two runs to the sky line on top to check everything again at altitude. I ran the same temps and color's. This thing is truly amazing. The other thing I noticed was starting. As per their instructions, I never touched the throttle or choke, and it starts in one kick! I was so thrilled with easy starts, I would shut it off and start it as a test multiple times. In 6 attempts, It started in one kick. When I got home and after some dinner, I couldn't resist the temptation! I went to the shop.... Ha! and yep! It started in one kick! I am going to love this thing. Heading to Missoula for a company demo weekend. It will have a lot of hours of hard thrashing. I will keep up the progress reports.
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mtn-doo
Well-known member
I was asked for more details on the "carb jacket". We used a Gortex outer shell and lined it with "thinsulate insulation". The closures are heavy duty Velcro. A pattern was made first from some simple fabric laying around. Then that pattern was used to make the final product. The bottom is all sewn closed, sides and top Velcro. There is a 1/2 inch hole in the bottom for drainage. This jacket on a conventional carb with a KTM carb heater worked perfect. Carb was warm and dry. No ice. The jacket fits the new APT Smart Carb perfectly. I will be using it this weekend. A BIG thank you to Amanda in the Carb Jacket R&D! She made a very nice finished product. 
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love the reports
so when r they going to have a little cheaper not billet unit ready for sale? this really has me thinking about ripping on the kx again man its fast!!!
so when r they going to have a little cheaper not billet unit ready for sale? this really has me thinking about ripping on the kx again man its fast!!!
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mtn-doo
Well-known member
Not sure? I know they are working on new products. Well worth the investment. They don't wear out. Brings the old tech up to date and even ahead of the simple EFI systems. Keep an eye on APT. They will have what you need I'm sure. These units aren't cheap but you have to remember what you're getting. Equal to/ and in some cases better than EFI for half the price! They flat work. People have been waiting for a test, well I have been testing and it is just like my EFI bike. Even better in some ways. I will report after this weekend of heavy use.
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