Smart Carb on my CR500

[rodgini]

I Finally got my shipping confirmation on a 38mm smart carb. I'll have it this Wednesday. I have read good things thus far. i'll be posting detailed info once i get the install done. The carb is going on my 2006 cr500af. The motor is fresh 1998 bone stock. I built the bike this winter. Because i knew the smart carb was coming i stuck baseline jetting in the pwk carb and ran it. i have a feeling it was pretty far from perfect. Having never ridden a properly jetted cr5 i have very little frame of reference. i imagine going from ball park jetting to optimum is going to be drastic. I'll keep you all posted. Here is the monster it is going on.

Edited June 24, 2013 by rodgini

[HRC27]

Look forward to your feedback.

[HRC27]

Look forward to your feedback.

[harryhandshake]

i dont know, theres been quit a few people on other forums sayin the smart carb aint all its cracked up to be. good luck to ya

[2coldnpagosa]

Huh, I'll have to look up Smart Carb. On another note.....what a picture tells about somebody..?? Your loaded with 2strokes !!,! :-)

Envious in Colorado

[Redlined]

I'm interested to hear the test report too. Still running the PJ on mine, but figured I'd upgrade at some point.

[c-slak]

I Finally got my shipping confirmation on a 38mm smart carb. I'll have it this Wednesday. I have read good things thus far. i'll be posting detailed info once i get the install done. The carb is going on my 2006 cr500af. The motor is fresh 1998 bone stock. I built the bike this winter. Because i knew the smart carb was coming i stuck baseline jetting in the pwk carb and ran it. i have a feeling it was pretty far from perfect. Having never ridden a properly jetted cr5 i have very little frame of reference. i imagine going from ball park jetting to optimum is going to be drastic. I'll keep you all posted. Here is the monster it is going on.

Billet Smart Carb correct? I preordered the cast a few months back. I keep going in between waiting for the cast and stepping up to the billet for my 265. I am still running the pj on my 500. Good luck! Make sure and post your feedback.

[rodgini]

i dont know, theres been quit a few people on other forums sayin the smart carb aint all its cracked up to be. good luck to ya

well they will take it back for a full refund so what's to lose really?

[rodgini]

Huh, I'll have to look up Smart Carb. On another note.....what a picture tells about somebody..?? Your loaded with 2strokes !!,! :-)

Envious in Colorado

i'd trade you all of them to live in colorado (i'm originally from new mexico)!! All those 2-strokes and jack shit to ride here in Va. Can you pick out the lowly 4-stroke?

[rodgini]

Billet Smart Carb correct? I preordered the cast a few months back. I keep going in between waiting for the cast and stepping up to the billet for my 265. I am still running the pj on my 500. Good luck! Make sure and post your feedback.

yeah man....i reluctantly upgraded when they offered me $50 bucks off. i have a 38mm billet coming. Didn't hurt as bad paying for it 2 installments. lol.

[rodgini]

Well I got my smart carb yesterday evening. My wife had to work this morning. As soon as she left for work, I headed out to the shop to do the install. I had one minor snag specific to the cr500 where the throttle cable is a touch too short to allow the slide to close all the way. I had to counter sink the top of the carb 3mm to allow the slide to seat properly. This was per Corey with apt recommendations. I was a little concerned with the fit as this is a custom bike. It fit no problem and the thing sure is a pretty. Corey sent me 2 metering rods with the carb. I went with the richer one as I have heard from other folks that the cr500 liked a pinch more fuel up top with the smart carb. I set it to 75 clicks out from full rich which was the recommended setting with that rod. The adjustment system for the low to mid range is the clicker on top of the carb. You hold the throttle wide open to engage the adjuster, push down on the knob and start clicking. Ingenious really. Anyhow, I finished putting the bike together. Other than changing the metering rod and having the minor cable issue, it installed just like any other carb. Here are a few pic of the install

So I rolled the bike out in the driveway. I pulled the choke, turned the fuel on, and kicked her over. I didn't use the decompression button just to get an idea of hit started with the new carb. This is what happened. Fired up first kick and idled great.

http://i262.photobucket.com/albums/ii120/rodgini/1DF5C38F-81C0-438A-950A-52F58BD380B0-3041-000001FD0316E63D_zps8a3e396e.mp4

My inital obervation was the motor seemed quieter and smoother at idle. I let it idle for thirty seconds while i put my helmet On. It would not idle like this until warm with the pwk. i then took it for a ride on a grass track near my house. It rained 1/2" last night so things were swampy. I noticed the bike did not seem as cold natured like it was before. It seemed to take forever to warm up before. It also didn't seem to make much smoke, no spooge and the exhuast just smelled different. The power off idle is completely different. It pulls right off idle and the Low end torque feels stronger and smoother. The bike had a pretty violent hit in the mid range before and a slight hesitation right before which made it worse. It now pulls smooth from the low end to mid range. Suiting up now to go test the top end and over rev! More to come. Very impressed so far.

Edited June 29, 2013 by rodgini

[rodgini]

. Just put 1.5 hours on the meter. Mix of Mx, trails, and practice clearing logs + a few wide open runs on Tarmac. No hiccups what so ever. I had a hard time timing wheelies for log crossings on this bike before. I was nailing them today! No need to find the sweet spot just roll it on.

Also keep in mind I suck at jetting a carb and spent minimal time setting up the pwk because I knew this was coming. If you are blessed with jetting skills and stay on top of it the smart carb may not blow your mind like it is mine. It really feels like a completely different bike. The lack of a power valve is not nearly as evident.

[CamP]

Also keep in mind I suck at jetting a carb and spent minimal time setting up the pwk because I knew this was coming. If you are blessed with jetting skills and stay on top of it the smart carb may not blow your mind like it is mine. It really feels like a completely different bike. The lack of a power valve is not nearly as evident.

I was going to mention this. I would be very surprised if a properly jetted Keihin air striker wouldn't perform as well, or better. The Lectron/APT carbs are very simple. I have a lot of experience with the Lectron's, in particular. They are good carbs that make excellent peak HP, but in my experience, the Keihins are better for MX.

[mynewcr250]

I was going to mention this. I would be very surprised if a properly jetted Keihin air striker wouldn't perform as well, or better. The Lectron/APT carbs are very simple. I have a lot of experience with the Lectron's, in particular. They are good carbs that make excellent peak HP, but in my experience, the Keihins are better for MX.

That descripion of the lectron is well documented. However, Apt posted their dyno tuned keihin vs their smart carb, there is no way the keihin will perform better. Similar? Yea you can get it close but then you gotta stay on top of it. Which isnt that hard if you attempt to learn what your bike is telling you. The keihin will also never atomize the fuel to the same level.

They are similar but are not the same. With that said the OP description of the keihin power band shows that he did not try to jet the bike and that's fine cause he was already set on the smart carb.

The Lectron is widely recognized as a “drag race” carburetor because it works very well in applications where maximum power is desirable. Which it does well, what it does not do well is provide high signal to the metering rod throughout the whole range of throttle opening and therefore smooth throttling suffers, requiring many different venturi sizes (every 2mm) and has thus gained a reputation as not being very streetable. The reason: Throttle opening and closing is symmetrical in relation to the throttle bore area, which is more or less round. While there have been small improvements over the years with Lectrons, the SmartCarb has a patented variable venturi shape that concentrates and accelerates airflow past the base of the metering rod under all throttle opening positions. This shape provides an extremely high pickup signal to the metering rod in all conditions and is also specific to enhancing air/fuel flow balance in both two cycle and four cycle engines.

Edited June 30, 2013 by mynewcr250

[rodgini]

I was going to mention this. I would be very surprised if a properly jetted Keihin air striker wouldn't perform as well, or better. The Lectron/APT carbs are very simple. I have a lot of experience with the Lectron's, in particular. They are good carbs that make excellent peak HP, but in my experience, the Keihins are better for MX.

Well I'm not a complete dunce when it comes to jetting and my pwk was close just not perfect. With previous bikes i often found myself chasing a condition throughout the throttle range and i felt i was always compromising somewhere. Also temps and humidity change so much around here that you almost have to pick a happy medium with jetting. I have to be honest I was skeptical of the smart carb regrading bottom and mid range power. I asked a lot of questions about this before I bought one. It delivers and its not a drag race carb. i wouldn't lump the smartcarb with the lectron until you try one. I tried everything I could do today to find a flaw in the jetting. I couldn't find one anywhere. The thing pulled clean off idle and never stopped pulling until I got scared. I tried chopping the throttle suddenly, quick downshifts, it just wouldn't make a hiccup. It started easier, vibrated less, no spooge even when lugging, zero surge on decel etc.

Edited June 30, 2013 by rodgini

[rodgini]

headed from sea level to 3500' tomorrow. not a huge altitude change but much cooler temps and far less humidity. in the past this always required a change in brass. we'll see how she runs.

[pieplatesnductape]

Quick question for anyone in the know..Im wondering specifically about the slide itself. I read somewhere that the slides need to have a certain coating to prevent sticking. I know nothing about what Kehin or mikuni or APT use for theirs. The first photo looked like there may be some scratches? Im actually really interested in the smartcarb for my 03 250, so not trying to bash...

[rodgini]

Quick question for anyone in the know..Im wondering specifically about the slide itself. I read somewhere that the slides need to have a certain coating to prevent sticking. I know nothing about what Kehin or mikuni or APT use for theirs. The first photo looked like there may be some scratches? Im actually really interested in the smartcarb for my 03 250, so not trying to bash...

i'm not sure about coatings? The slide in the smart carb appears to be billet? i think the photo makes the scratches looks worse than they are. The throttle pull is as smooth as the pwk if not smoother.

[pieplatesnductape]

i'm not sure about coatings? The slide in the smart carb appears to be billet? i think the photo makes the scratches looks worse than they are. The throttle pull is as smooth as the pwk if not smoother.

Seems like most slides are listed as having some type of chrome plating.. Not sure whats better, a slide that looses some plating and possibly sticks, or an unplated slide?

[rodgini]

Seems like most slides are listed as having some type of chrome plating.. Not sure whats better, a slide that looses some plating and possibly sticks, or an unplated slide?

I posed this question to Corey. We'll see what he has to say.