Smart Carb

Maybe I didn't find the right thread, but I see you posted something about using fork oil to measure the area at top dead center. I don't see any real detail, but it seems you found TDC, then poured oil in the spark plug hole, possibly with a syringe or measuring cup, and filled until the second thread up the spark plug hole?

I ran it as hard as I could today in the yard. I closely listened for pre detonation, but did not hear any at all. This was with 91 octane. I will continue to play with the smart carb, but so far it's the same. It's fantastic mid-top, but off idle and midrange are no better than the Kehin. There is still the off idle blubber unless you are far into the throttle. Rolling on the throttle makes it worse.

I'm asking for my money back Monday. I just wasted a month, and gained a few more gray hairs. Working on GasGas bikes is a royal PITA.
 
I've spent most of the day riding, and I'm convinced the compression is plenty low for 91 octane. Absolutely no knocking, not even a pipe knock when you get off the throttle. I don't think its worth it to me to take it apart again to check the compression ratio.

The more I play with the smart carb, the more I am unimpressed. One odd thing is sometimes it seems to change tune if I shut it down, for a minute, and start it again. There is nothing I can do about the 1/4 throttle blubber except ride harder. When riding hard, the thing runs great. As good as any Kehin carb, maybe better. I always run a rich main jet in my Kehin, I don't need the top end, and it was safer. The big difference is when just kind of putting around it really loads up bad. Worse than the Kehin. Another thing is that the clicks don't seem to do much. So many reviews say they just went one or two clicks from where it came, and it ran great. For me, I can do 5 clicks at a time without a huge change. I have gone up to 15 clicks lean and rich from what I have found to be best, and the change is not gigantic.

I think at this point the only thing is to "jet" the smart carb, which I am not willing to do. Instead, I think I'll put my Kehin back on, and live with it until I can afford the new fuel injected KTM's in a few years.
 
Spent yesterday sloping around in some muddy Forrest, seriously slippery. 3rd gear near stall speed worked well. It runs like a trials bike with the head mods I found. N3 something needle pwk.
 
I got my 38 mm Kehin back in today. Runs WAY better than with the Smartcarb. I'm running a 42 pilot, NECJ needle, and 180 main, although I think a 178 or 176 main would be better. Air screw at 1 1/2 turns out it runs clean until it gets on that rich main jet. A simple swap and it will be good to go. As the weather changes I'll have to adjust it, which sucks, but its just the way it is.

The Smartcarb would be good for motocross. Compared to the Kehin, the Smartcarb runs like mad when you are riding hard. Enduro, what gasgas was made for, no way. You can run it far too lean and it does ok, but no matter what, you will never get rid of the part throttle rich condition without modifications. The worst part is that it comes right off that rich blubber, right into an insane mid-top end. I tried for days with the smart carb, from so lean it won't start, to barely running pig rich, it just plain doesn't run good on my bike.

My bike does seem to idle better now with the head mod and the Kehin carb. It doesn't like to idle down too low, but it seems like a much stronger idle, and most importantly, it doesn't seem to want to die the minute you pull in the clutch. I'm not a great rider, middle of the pack C rider, but its hard to ride smooth with a bike that wants to die.
 
As kind of an update to the head mod, which put my squish at about 1.6mm, it is not a big improvement. When I put my Kehin back on, it was about 40 degrees Fahrenheit, and was about 65 yesterday. The bike is still very sensitive to temperature. It still runs better than the Smartcarb, but its rich everywhere. On top of that, the idle is no better than when I first bought the bike. It has to idle say 2500 rpm or it won't idle consistent. If you turn the idle screw just an 1/8 of a turn out from that, it will die. To those sending your heads off to have the squish adjusted, make sure they get those clearances as tight as you can. Gasgas engines do not like to idle.
 
On my 13 300xc with a Cast SC 38mm Q11rod (it came 57clicks from full rich) and it ran ok after brake in. Played with it and got great fuel mileage but alway's had a burble off idle and then clear up and ran like a champ. Then started talking to Barry on KTM talk did a few things like trimmed the inside of the airboot to reed cage, set the slide air gap from 2mm to 1.3mm played with the clickers and ended up at 97clicks from full rich and it run like a spotted ass ape. I bought a Lectron HV to compare and I can't get it to run as good as the SC and the fuel mileage sucks
 
I found a video of exactly what my bike does. Like me, the guy in the video has made his bike idle high so it doesn't stall. The guy uses his clutch to simulate the problem, but for me it happens when riding, or even just sitting there. Sometimes if I just let it idle, after 30 seconds it will drop low like that, or die if the idle is set too low. Lots of times it wont. The cable isn't binding, I'm not running lean, my pilot jet is a 42, and I think a 40 would be better now that its warmer. To the best of my knowledge, my crank seals are not leaking. I am at a loss why this is happening.


https://www.youtube.com/watch?v=k7FGbWzs2TY
 
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