springstever wrote: 03:34 pm Jun 15 2026
I found that my throttle cable rubber boot is against the adjusting knob, making it hard to adjust the knob. I have to pull the boot up to adjust the knob. Again, not a big deal. I have to use a lot of fuel line to add the filter, and it makes it hard not to have a big loop sticking out, just asking to be grabbed by a branch or boot buckle. That said, I should get a lower-profile petcock valve that everyone is discussing to help with that issue. Do I really need the filter?
You can tilt the carb up to 15° either side without issue so you may want to play with the tilt just a bit to see if you can get some better clearance between the frame, cable, and clicker.
The filter is included as a courtesy and is recommended, though not required. The gist is to keep your fuel clean going into the carburetor however you do it, whether with just the petcock screen or via adding the in-line filter.
springstever wrote: 03:34 pm Jun 15 2026
Instructions say it needs a short break-in before you try adjusting. It idled great at first. After a two-hour ride, it wouldn't want to idle when warm. It would idle real low until it stalled, indicating that I am too rich. It seemed a little fat, too. Is this by design, Nathan? It definitely had more power and ran way better than what I had going on with the old carb.
Yes, we tend to set them a bit rich out of the box for two reasons:
1. SmartCarbs have a very tight tolerance between the metering rod and the brass fuel nozzle it rides in. The bars the rods are made from, for example, are precision ground and require no more than a .0003 diameter deviation over their entire 12' length. During the initial break-in period the metering rod laps into the nozzle. They wear in so to speak over that first hour or so. Settle in. This is important because the metering rod is designed to rotate axially about 15°. As the metering rod breaks in the fuel nozzle it becomes more free to rotate. That rotation is crucial for maximum fuel atomization as the rod will "flick" back and forth on its axis at a high frequencies based on intake airflow wrapping around it and engine pulses. The result is finer fuel atomization than even most fuel injectors.
2. And to generally err on the side of caution. Better to be a bit rich than a bit lean.
springstever wrote: 03:34 pm Jun 15 2026
I am currently 8 clicks left of factory settings (lean). I rode last night, and it's still too rich, won't idle. I will keep adjusting via the knob, which is really hard to do because of the lack of room up there. Maybe I need to turn more clicks at a time, but I wanted to start with small adjustments. When I pulled the plug, it looked a little rich. Sorry, no pic, I forgot. Any advice on how many clicks I should do at a time, Nathan?
Note that each click only moves the metering rod up or down (richer or leaner respectively) just over a thousandth of an inch (.0012). We recommend only adjusting 1-2 clicks at a time and we don't get too hung up on the number you have to go. There are ~150 total clicks in the range of adjustment and you may ultimately go 5-15-25 clicks or more as needed to clean/brighten up the bottom end and bring the idle RPMs up to your liking. Moreover the clicker adjustments really only affect the bottom end and have little effect mid to top so you can go leaner with confidence knowing you're not going to go lean on top. Additionally it's always recommended to assess performance and response while riding, in gear, under load, and with an engine and pipe that are at operating temps. Not on the stand/in neutral and not cold. Lastly when going from richer to leaner there is a bit of a lag in the effect of your clicker adjustments, particularly if you were quite rich to begin with, due to residual fuel in the crank needing cleared out. Best to ride a few minutes between clicks.
If you go too lean on the clicker you start to get softer bottom end response, a bit of hesitation, a bog on quick throttle opening (in gear), and sometimes a bit of a hanging or erratic idle.
Below are the instructions to what we call the Loaded Lean Bog Test. They can help you quickly dial in your SmartCarb after it has been broken in from new (1-2 hours of moderate riding time at or near the as-delivered settings):
1. Ensure the carb is broken in, the engine and pipe are up to temperature, the engine does not have any residual loading up, and you are able to ride in a safe environment.
2. While riding the bike, in 2nd gear, moving about 7-10 miles per hour or jogging speed with zero throttle, lean forward and whack the throttle open quickly from 0 to full open. Do not hold the throttle open or pin the bike for any long period of time. You are simply assessing the off-idle or 0 to 1/4 throttle response in a max load scenario (only as much as you would load the engine during normal riding for a given gear before downshifting). It should pull through and be clean, crisp, and responsive.
3. Using the Clicker, adjust the metering rod lean or counterclockwise 1-2 clicks at a time.
4. Keep performing the test and clicking leaner 1-2 clicks at a time until you find a decided bog when whacking the throttle. That’s what we call the Lean Bog.
5. Once you have found the Lean Bog, use the Clicker to adjust the metering rod rich or clockwise 1 click at a time and repeat the test until the bog goes away and you are left again with crisp, clean, and responsive throttling while performing the test.
6. From there go 1 or 2 clicks richer yet to arrive at a Clicker adjustment or metering rod position for best bottom end performance.
7. Only then do we recommend making fine adjustments to the Idle Set Screw to fine tune your idle RPMs. The Idle Set Screw is very responsive if the metering rod is dialed in to a proper setting using the Clicker. If the rod is off, you may find the Idle Set Screw has little effect on idle RPMs. Lead with the Clicker and follow with small Idle Set Screw adjustments. You may need to repeat the Loaded Lean Bog Test a couple of times as you balance these two settings. (Note that the Idle Set Screw setting should stay between the as-delivered settings and up to 2 full turns in – any adjustment outside of those parameters indicates a non-optimal metering rod setting using the Clicker or some other installation related issue).
8. Once the bottom end is dialed in using the Loaded Lean Bog Test, you can assess the mid to top by feel and plug readings.
