Smart Carb
 

I just bought and installed a 38 mm smart carb on my 2006 EC300. I have been fiddling with it, and I have to say I am not all that impressed. I hate jetting with a passion, so I was hoping this would solve that. While it runs fantastic mid to top, say above 3500 rpm, down low I can't quite get it. It seems off idle you can either have it run clean and sacrifice torque, or set it for max torque and it will smoke and spit spooge. Also, no matter what it has a pretty bad blurble until it clears out in the mid range.

On top of that, I still cannot get my bike to idle. This is a problem I had with my kehin as well. My crank seals are good, no airleaks, and it has a fresh top end. With the kehin, I had to run a too small pilot and crank the idle screw almost all the way in. With the smart carb its not much better. It either idles high or doesn't idle at all. Even with a high idle it will easily die if you are not careful. The most annoying is when riding and coming to a stop, you have to blip the throttle or the idle will drop low and quickly die. This is made worse by the fact that the gasgas kickstarter is just awful. I will be buying a yamaha one soon, but for the past year I have been riding with the kickstarter off. I just take it out of my fanny pack and use it to start the bike. Its better than mid ride having it stab you in the calf.

Is this a New Smart carb? cast or billet? Have you read the installation booklet.?
Has the float and slide been set? I'm very Happy w/ mine.

I also have 3 of them 2 on enduro bikes one on my trials bike and they all work much better than my stock carbs . It sounds like there may be another problem with your bike ?

It's not brand new, but rebuilt. From the paperwork, it looks to have been new in 2014, but was recently sent in for updates. I think it was the check valves for tip over. Everything in the carb is new, and the float height I think is at 23mm. I will have to check again, but I did set it. It is a cast model. I have read the book front to back multiple times, but have to admit its not that much help. The videos on youtube are much more helpful.

I'm not sure what problem my bike could be having. I noticed it does smoke a lot, and it doesn't smell that good (Klotz R50 is pretty distinct good smelling), maybe my clutch side crank seal went?

I went through two CDIs, three spark plugs, two coils, a Keihin AS2, and a Lectron before I figured out that I had a plugged silencer. I'm not saying that you have a plugged silencer, but you might want to check the packing.

Another consideration is excess oil in the expansion chamber. I had a PW80 that would NOT run properly, but it sure knew how to smoke. A lot. I decided to take off the pipe and remove the choke washer from the pipe inlet, and when I took off the pipe about 8 oz of nasty smelly two stroke oil came out. Best I could tell is that they couldn't start the bike, flooded it, and the excessive gas/oil collected in the expansion chamber, and the gas eventually evaporated leaving the oil behind, which choked the bike (and my neighborhood) something awful.

Regarding the possibility of the right side seal leaking, drain your gear oil. Put in a specific amount, ride for a while, then drain and measure. That should tell you if you have a leaking right side seal.

Whatever you decide, good luck, as I know how frustrating these inconsistent gremlins are.

I'm fairly certain it's not the silencer. Mine doesn't even have a full season on it. I guess its possible my pipe is filed with oil, but I never had any flooding problems, and I bought my pipe brand new along with my silencer last summer. I had the same idle problem even when the exhaust was brand new. I always measure my clutch/tranny oil, and its always in the center of the sight glass. I guess I would have lost more by now if the seal was leaking.

I just hate getting called lazy with my jetting. I've tried 3 or 4 needles, and plenty of jets with each, and never did get it figured out. I'm sure Kehin carbs can be great if you spend a ton of time figuring out what works in what temperatures (and elevations if you live in the mountains), but I just don't want to spend that time. I was hoping the smart carb would be better, but so far it is not. Its as good as a half decent jetted kehin.

I'm ordering the solder to measure my squish, and assuming it needs it, I'll have my head cut. Maybe that will help me out. I hope I don't have too high expectations for my idle. I would like to at least be able to start it and put on my helmet. Mine will die in seconds. I've had bikes in the past and they would idle nearly forever.

Have you set the slide height? it's 4 or 6 mm can't recall

Another issue I had was the cable would loosen at the throttle housing,lowering the slide. took me awhile to figure that one. Ended up using pliers to tighten the nuts at the housing and indexed the cable,so i could tell if it moved.

I don't see anything about setting slide height not in the book or online. The only thing I see to adjust it is the idle screw. Your throttle loosened, lowering the slide? Why would the throttle cable be propping it up at all?

I had a billet SC (early model), which I paid a motza for and never got happy with it. Worked with APT/Corey for a while with different metering rods and adjustments but always found that I couldn't get it to run well across the board. It was either too fat for slow tech work, or too lean for hard runs.

In regards to your idle issues. The squish clearance if excessive will do exactly that. I chased myself in circles until I was dizzy with intermittent issue idles. Measured squish at 2.8mm. After head work brought back to 1.25mm and compression adjusted and it idles like a sewing machine.

The only other thing that really impacts on my idle is the clutch drag. There is a bit there, and I set it so it only just ticks over with the clutch lever pulled, on a hot engine. Sometimes I need to give it a little blip to keep it going. In neutral it idles very nicely, low and slow.