Slide Theory, Carb Models, and Jetting

[Jakobi]

Looking for peoples settings and the slides they are running, along with the carb model. This is a bit of a continuation of GMPs findings in his 2012 model, along with some info from another forum where 2 x 36mm carbs have reported good results using the JD Blue and a 40 pilot. One has a 6.5 notched slide, unsure on the other.

My particular bike required the idle to be turned in all the way with the stock F diameter needle and a 40 pilot just to substain something that you could barely call an idle. After trying all combinations, a 40 pilot and W diameter gives the best idle, which doesn't hang, and only lightly burbles off load. Going richer to a H diameter needle I get more burble and only slightly more torque. This is all with a non notched #7 slide in an 38mm ASII carb.

You'd imagine the smaller 36mm ASII would prefer leaner jetting due to an increased air velocity, along with the richer slide, so it has me wondering, does the notch make that much difference??? or are their other variables at work.

[GMP]

Borrow a notched slide if available and run it with known jetting for a comparison. My point was that it seems to have more effect on my older carb than what you hear about on the new carbs. I'm pretty good now with my standard JD Blue jetting I've used for years. I will go back and try some of the Suzuki NED/NEC series though. Screw top carb is easy.

[twowheels]

Originally Posted by GMP

Screw top carb is easy.

Show off

[swazi_matt]

Where is the notch, how can I tell if I have a notch or not?

[Jakobi]

Based on your bikes jetting preferences I'm going to guess yours has no notch. Just a guess though!



The number is stamped in the bottom, the notch is visible below that. Basically just a small window where the neelde runs past.

[swazi_matt]

Ok yep no notch on my no7

[Jakobi]

Originally Posted by swazi_matt

Ok yep no notch on my no7

And 38mm PWK ASII with the shallow bowl and flat top?

[n_green]

I have a 36mm carb with the notched 6.5 slide in my '11 300.

Using 42pilot, AS 1.5 turns out, 165 main, NEDW #2. Was quite snappy with this jetting, may have been ever so slightly on the crisp side on the pilot or straight section. Also hung on occasion coming back down to idle for a second or two. Pulled quite hard though and had a good top end.
Video:
http://youtu.be/Lv8RNTB9d5E


Using 40 pilot, AS 2.25t.o, 172 main, JD Blue #3. Has bucket loads of torque and an inability to stall that pulled with tractor like grunt through to the top end. Perfect idle, though was a bit low compared to previous jetting with idle screw left untouched. I think I could go one step leaner on the pilot and maybe even on the main as the top end wasn't as impressive as the NEDW jetting.
Video:
http://youtu.be/X2QAzqjk7F8?hd=1

In 2 weekends time I'm going for a weekend ride with a mate on a '11 KTM 300. It has a 36mm carb and is running a non notched #7 slide. I'll fine tune my current jetting to where I love it and then whack in his #7 and leave everything else and report back. I'll grab a comparative video and post up as well, might be able to hear the difference if any?

[GMP]

Yes that would be interesting. I'd like to try a #6.5 notched in my older carb but its not a standard slide and I'm not paying KTM big bucks for it. I suppose I could make one from a standard #6.

You go from a NEDW to a JD Blue with the same slide, wow, thats a huge jump in needle dia. If your bike runs the Blue good down low, try the NEDH/NECH, NEDG/NECG. Maybe that will balance the good top end with more grunt than the W dia that sounds lean from your description. The 300s have so much low end you can afford to drop some in a trade for linearity, as long as the bike is not too lean, but you have to be careful as the reason the torque falls off is the bike is slightly lean. The 250s go flat fast if you attempt this. I do not like the way they feel with super clean jetting, better a little fat down low with good grunt into the mid. JD Blue does this, with a hard pull through the mid.

[Jakobi]

Originally Posted by GMP

Yes that would be interesting. I'd like to try a #6.5 notched in my older carb but its not a standard slide and I'm not paying KTM big bucks for it. I suppose I could make one from a standard #6.

You go from a NEDW to a JD Blue with the same slide, wow, thats a huge jump in needle dia. If your bike runs the Blue good down low, try the NEDH/NECH, NEDG/NECG. Maybe that will balance the good top end with more grunt than the W dia that sounds lean from your description. The 300s have so much low end you can afford to drop some in a trade for linearity, as long as the bike is not too lean, but you have to be careful as the reason the torque falls off is the bike is slightly lean. The 250s go flat fast if you attempt this. I do not like the way they feel with super clean jetting, better a little fat down low with good grunt into the mid. JD Blue does this, with a hard pull through the mid.

I noticed this when I did the 300 to 250 change. The smaller engine needs the fuel to make the torque where the 300 can get away with being a bit leaner. Also agree it sounds like the bike was a bit lean if hanging idle and such. Maybe due to clip position, maybe due to the diameter. I'm guessing a combo of both.

I'll be super interested to hear the outcome of the slide test and also to hear how anyone gets on running a richer diameter on the suzi needles.