Smart Carb

[2stroke]

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.

 

[john r b]

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.

 

[Dirt Dud]

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 ?

 

[2stroke]

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?

 

[pscook]

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.

 

[2stroke]

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.

 

[john r b]

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

 

[john r b]

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.

 

[2stroke]

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?

 

[Jakobi]

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.

 

[(F5)]

To add the head mod should reduce squish to about 1mm but also parallel to the piston which it is not.

Read my head mod thread with a search.

Of course we are talking idle when warm. Always a bit ropey when cold but that's only at the start of the day.

Laughed (and felt guilty) PSCook. Not the fist time the flimsy silencer perforated tube had displaced or collapsed. Hardly expected. .

 

[pscook]

Laughed (and felt guilty) PSCook. Not the fist time the flimsy silencer perforated tube had displaced or collapsed. Hardly expected. .

Don't feel guilty, I had a good chuckle after a good long face palm. What's the point of research if you can't find the resolution? And, it's much (MUCH) better to resolve it myself than to have to source out the troubleshooting at $$$$ per hour.

 

[muellersq]

Regarding the bad idle, maybe you should look for obstructions in the reed cage and boot section https://youtu.be/bUEfs3cOI9s

 

[SpirosZ1000]

Slide height should be exactly or near to 2mm and you fix this with the idle screw.
Also check what metering rod you have. Before ordering the smartcarb searching the net for info I read about lots of 2strokes working with Q11 rod but mine came from them with Q09 rod which is richer.Gas Gas have also bigger jets than Ktm's for example as from stock.
Fingers crossed mine is working surprising well for it's first hours.

 

[Jakobi]

Slide height should be exactly or near to 2mm and you fix this with the idle screw.
Also check what metering rod you have. Before ordering the smartcarb searching the net for info I read about lots of 2strokes working with Q11 rod but mine came from them with Q09 rod which is richer.Gas Gas have also bigger jets than Ktm's for example as from stock.
Fingers crossed mine is working surprising well for it's first hours.

The Gas Gas uses bigger jets because it uses a 38mm carb vs a 36mm on the Ktm. Bigger carb = lower air velocity = less fuel picked up = larger jet required to supply similar volume of fuel.

I'm well off the mark with where smart carb is up to. I had a 38mm billet and could never get it to run right. I might look at sending it back for an update at some point. Been sitting in storage a long time while both my bikes have their stock carbs in use.

 

[SpirosZ1000]

The Gas Gas uses bigger jets because it uses a 38mm carb vs a 36mm on the Ktm. Bigger carb = lower air velocity = less fuel picked up = larger jet required to supply similar volume of fuel.

I'm well off the mark with where smart carb is up to. I had a 38mm billet and could never get it to run right. I might look at sending it back for an update at some point. Been sitting in storage a long time while both my bikes have their stock carbs in use.

You are correct and believe me I have read your troubles with smart carb thoroughly in your thread and together with some other information I found around the web I was very skeptic at first but every bit of info I found was at least 2 - 3 years old when the changes from apt to tech elevated happened and the product was still new without the new cast model in line.
What made me to give it a try was some recent posts I read from people who use them both on dirt bikes and snow bikes (mostly) and on newer posts more and more of them went that way.

 

[Jakobi]

I hear you.

Time passes and things develop. Lots of data was gathered once APT rolled out the early models and they were all over addressing issues, updating models, and working with customers to get things running right.

While I could find flaws in the product, I couldn't in the service. Being in Australia it took time though, waiting on parts, and even more so if I was to send the whole carb back for updates. Introduce a 2nd child to the family around the same time and riding was more important than tinkering. Easier to go with what worked.

Like you, I also get great economy out of the PWK.

Also had a Lectron of similar vintage to play with, got similar economy, similar power, and similar issues with finding the sweet spot (metering rod position + boost jet).

 

[SpirosZ1000]

I was very pleased by my pwk except the fact that my bike had lost it's torque with the particular setup I had, it had a steady idle nice revving and great fuel economy for a gasser. The thing is that I live in Athens where altitude is sea to 800 meters (there it worked excellent) but we have many friendly races and events around Greece (different conditions) where the bike needed tinkering and as you said with two kids and a very time consuming job, time is limited.
I am also far away from them and having things shiped from US is money and time consuming for me as well.
I was sold by the new gasser but after reading about only 3000 units production (next model said that will have a new motor as well) and the fact that the 2stroke scene is going efi I think I will wait 1-2 more years and buy a new one but I really want to keep this one.
Finally I think (and really hope) I am one of the lucky ones who have the carb working good.

 

[2stroke]

Well I finally got my head cut. I called the most local shop I could, Bill Bune in Minnesota. I talked for a bit, and they seemed knowledgeable. They actually wanted the piston as well so they could change the squish angle to 2 degrees from the piston dome angle. They recommended .040" squish clearance, to which I said perfect. I went through all the extra trouble to pull my jug, drain coolant, etc. 2 weeks go by, and I was out hunting. I had killed a turkey just 10 minutes earlier, and I was packing up when they called. The guy said my squish angle was 15 degrees, and my piston 10. As well my squish was about .090" (Which is true, I measured my solder tests before I sent them). I said, cool, please CC the head so I can keep the compression the same. Guy says he plain cant do it. The clearance is too big (no S&!t, that's why I sent it in), and there is nothing he can do for my squish angle. I said talk to your boss and call me back when you figure something out. Later that day I get a call from another guy saying my head was ready, should he ship it back. I told him that it couldn't be, I was told it was impossible. I talked with the original guy and he had cut my head down .030", and cut some of the dome out. I should have took a picture. All they did was put it in a lathe, and spend about 30 minutes cutting it. They never did CC my head, but they sure took my $100. What they did, I could have done myself on any lathe, and should have. Absolute waste of time and money. Do not use Bill Bune in Minnesota.

Anyway I got it back together, and running. Its not quite ready for a ride yet, but first impressions are not great. It pretty much runs the same, has to idle high or it dies.

 

[(F5)]

OK you need to measure the compression ratio right now. Read my head thread, its not hard, but clearly they could have put you crook.