new SmartCarb SC3 34mm advanced metering rod carb option

[SpruceItUp]

Yep! Got it all setup today and it is running great! It idles beautifully. I just did some little test rips around the yard and it seems to be pulling very well!

In regards to fitment we finally got it to where it is not hitting the frame whatsoever. It is close, but it is not hitting it. The thumbwheel is now adjustable as well without moving the carb in the boot at all. I'll get some more detailed information once I run it up in Ohio, but so far all is looking good!!

[tosaw]

Nathan called me last night to tell me they're shipping the parts out that I will need to install my carb today. He's a really nice guy and I am impressed with the customer service.

Can't wait to try it, glad it feels strong Spruce!

[springstever]

Do the H series installations require any mods to the air boot?

[Nsign]

Do the H series installations require any mods to the air boot?

As a rule of thumb we suggest checking for and, if necessary, trimming any rubber lip inside of the airboot that may block the SmartCarb's vent scoop or otherwise direct airflow away from it. Some bikes are worse than others. The Shercos, for example, have a really thick rubber lip in their boots that requires a substantial trim. Some bikes require no trim at all, like Betas.

That said, we're using an extension ring adapter in our KDX kits, which means the vent scoop is positioned lower than it would be in a SmartCarb kit without that type of adapter. From what I've seen the lip in the KDX boots is minimal. Combine that with the use of the adapter and lower relative position of the vent scoop and I would say no, you do not need to trim the boot. But going back to the rule of thumb it's always a good idea to check by looking through the boot into the carb (filter removed of course) and ensure you can see the full scoop or the upper edge of it. If you can't get a direct look a phone camera typically does the trick. That or a bore scope if you have one.

Here's what we're seeing in our long-term H series tester, no trim required:

[springstever]

Thanks for the great feedback with the included picture. That is close, so checking is prudent. I just ordered one, and can't wait, hopefully it won't take forever to get to Alaska, our summers are freaking short. The days are long though!

[SpruceItUp]

As a rule of thumb we suggest checking for and, if necessary, trimming any rubber lip inside of the airboot that may block the SmartCarb's vent scoop or otherwise direct airflow away from it. Some bikes are worse than others. The Shercos, for example, have a really thick rubber lip in their boots that requires a substantial trim. Some bikes require no trim at all, like Betas.

I stuck my phone camera in my airbox yesterday and it looked like it was clear to me. I could only see half of the vent, but the other half should be the same. I'd say trimming shouldn't be necessary but check just in case.

[Chuck78]

I'm very eager to get a SmartCarb fitted to my bike...
I'm packing up some 220 cylinders to send off to Boyko Racing for mild porting work and port chamferring corrections (PowerSeal USA failed to do anything with the less than desirable factory port chamfering on the one cylinder I had them re-plate, major bummer), so that I can have a fresh top end when it comes time to test out the new SC3 34mm....

The SC3 34mm should prove to be a great fit for my 220(s) and my riding terrain preferences.
We don't do short rides (fuel tank range is critical), and we generally seek out the more technical trails anywhere we go here in the Eastern/Appalachian regions of the USA (throttle response & smoothness are also quite critical).

The SmartCarb SC3 34mm should suit this terrain very well... These photos are from the closest worthy trails for us based here in Central Ohio, 57 minutes drive time East/Southeast from our home not far from the edge of the glaciated plains transitioning into rugged Appalachian hills:





Also, the added fuel efficiency of a dialed in metering rod carb like this will really help with running a KX 125 / KDX hybrid, as the factory KX tanks are only 2.2 gallons capacity. I don't want to have similar fuel range to the modern 300's... The 220 displacement as well as porting versus the 200 even, as well as the metering rod's very well known superior fuel atomization will help my KDX 220's & my KX/KDX hybrid build project go a lot longer on less fuel. Major bonus.

[SpruceItUp]

I had some free time on the drive up here to do some thinking. I took a look at the video and got a good still frame from it, it almost looks like the air boot starts dipping down the further to the right you go. Or maybe it's the photo, but maybe I need to take a closer look tomorrow. It definitely doesn't show signs of lean running or too rich, but just seeing that bothers me and I can't get my mind off of it. Too bad it's almost 12 o'clock.

Also, I need to verify my idle/slide height, as when I got the carb I adjusted the idle a bit once I got it on to get it to idle properly (stupid of myself) as I forgot metering rod carburetors are very sensitive to idle/slide height. I don't remember how much I turned it, so I do need to verify it's close to the stock height it was when it was sent to me. Again, it's running perfectly fine, but just not knowing bothers me.

Here is that still frame:

[Tommo32]

Hi Spruce, apologies if I have missed this somewhere but have you got a V force reed block fitted? If you don't I'm wondering whether it would make fitment more difficult?

[SpruceItUp]

Hi Tommo. I do have VForce3 reeds. Unsure if it makes fitment more difficult, but it may. It does fit, though!

[tosaw]

Good to know, I've been running vforce 3 reeds with my legacy Lectron and don't want to have to change back to OEM.

[Tommo32]

Hi Tommo. I do have VForce3 reeds. Unsure if it makes fitment more difficult, but it may. It does fit, though!

Ah fantastic. I too have V force reeds so glad to know it will go in with them. Hopefully those without them can enjoy some extra clearance. Looking forward to hearing how people get on with the SC3 so do keep us posted!

[springstever]

To those who have V Force 3 Reed valves, did you put both gaskets that came with them on your bike? One on either side? I know when I took off my original reed cage, I only had one gasket, and was wondering if the extra mm or two of a second gasket would change atomization or the venturi at all, given the minimal extra distance fuel had to travel through the cage. Just curious. Probably no effect whatsoever.

[tosaw]

I did end up using both gaskets and RTV on my 1990. I tried with just one but had terrible air leaks. Always always always perform a leak down test when replacing reeds!

[Nighthawk016]

Its been a minute, had any one got any good ride updates?

[tosaw]

I finally installed mine on Saturday and although I still need to dial it in a little, it runs amazing and smooth with great power delivery. I'm happy with the purchase but the fitment has been tricky at best on my 1990. Look where the choke knob sits...


PXL_20260530_180540113 by The Real Guy Photography, on Flickr

[Chuck78]

I finally installed mine on Saturday and although I still need to dial it in a little, it runs amazing and smooth with great power delivery. I'm happy with the purchase but the fitment has been tricky at best on my 1990. Look where the choke knob sits...


PXL_20260530_180540113 by The Real Guy Photography, on Flickr

Have you communicated that choke/fuel line clearance issue to Nathan @ SmartCarb?

Is that a stock E-Series petcock?

A 2016-2022-ish YZ250X fuel petcock will sit close up to the tank probably like that but has a bottom outlet fuel tap, if that could be made to work.

I would not have figured that there would be any clearance issues with the choke knob but then again I personally don't own an E-Series, although I have worked on several for friends.
We'll get through these growing pains and have a better outlook on exactly what needs done to fit these properly. Now that the thumb wheel adjuster size is reduced to fot the E Series, this may be the last hurdle.

I haven't seen one test fit to an '86-'88 air cooled / KIPS C-Series 200 yet, but I do know the choke is on the opposite side on those, I don't think it would have any clearance issues like this because the E-Series Center spine frame type tank hangs down quite low, which is seeming to be the source of this issue.

The side choke knob is a new one here for me, that wasn't something that I would've anticipated or expected to cause issues versus trying to fit the older SmartCarb SC2 36mm to a '95-'06 KDX frame, where the carb was just entirely too bulky and had hard interference with the frame crossmember & rear head stay mount bracket. That's why they came out with these for the KDX instead.

So far I've only heard very excellent positive feedback on the performance of them.
I've got one here now, but the bike is torn down for a top end. I'm very eager to try it out though!

[Nsign]

We'll get through these growing pains and have a better outlook on exactly what needs done to fit these properly. Now that the thumb wheel adjuster size is reduced to fot the E Series, this may be the last hurdle.

I haven't seen one test fit to an '86-'88 air cooled / KIPS C-Series 200 yet, but I do know the choke is on the opposite side on those, I don't think it would have any clearance issues like this because the E-Series Center spine frame type tank hangs down quite low, which is seeming to be the source of this issue.

Yes, we are learning as we go but the community has been excellent in providing feedback. If any issues are to be had it's good that they're easily solved with tweaks to a few components for fitment. Performance-wise we are hearing nothing but praise.

Speaking of fitment we've actually pivoted to providing right-hand or mirrored models for the C Series 200s where the choke and adjustments will be on the right side of the bike just behind the kickstarter (incidentally the same right-hand config we'll be selling to Tecate owners). So far we only have a couple of C Series customers but they are aware and will be swapped out as soon as possible.

Look where the choke knob sits...

Could you give us another angle on how close the petcock is to the choke, more from the left relative to the pic posted? From what I can see you might benefit from replacing the fuel line with a length that is a half inch or so longer yet so that it's not strained over the choke and/or the fuel inlet. Give it just a little more slack so to speak.

[KDXGarage]

THANK YOU for all you have done! To hear that "C" models will get an option is terrific news also! OUTSTANDING. Thank you again!

[tosaw]

Chuck - Thanks for the tip on the YZ250X petcock, I just ordered one. Not sure if mine is stock or not.

Nate - I'll get some different angle photos when I get a chance. If I set the carb level the petcock is pointing directly at the choke knob, I angled it down but now the adjuster wheel is impossible to turn because the throttle cable is pushed into it by the fuel tank. I was going to try angling it the other way but I'll use the Yamaha petcock instead. I hope that solves it because otherwise I'm loving the carb.