Throttle valves/slides and Air Striker Carbs

[Chopperpilot]

I got an epic deal on a genuine Air Striker carb on Ebay. Now reading that they come with richer (4? 4.5?) slides than a standard PWK has me wondering a few things.
My understanding of slides is that you would go with a leaner cutout... if you had a nearly perfectly tuned setup, but it was a little (how little??) too rich from 1/8 to 1/2 throttle. That for some reason you couldn't fix with a needle/PJ/MJ change?
Why does an Air striker carb use 'richer' throttle valves/slides than a standard PWK when an Air Striker is supposed to have a better part throttle signal across the jets? or is it the richer throttle valve in conjunction with the fins that create the better part throttle snap?
Why do some KDX owners get from running a #6 or #7 throttle valve that you couldn't get from the factory #5?
Do most of the Air Striker users on here just stick with the supplied #4.5 throttle valve? Should I anticipate jetting issues using it?

[John_S]

In my experience with a brand new genuine 35 air striker, the 4.5 slide worked great with an 18mm float setting. For my hot temps and humidity in Florida it ran a 40 pilot, JD jetting red needle 2nd clip and a 145 main. That's on a 220 with V force reeds and FMF pipe, air box lid but no snorkel.

I bought and installed a #7 slide and had to run the air screw nearly closed even to rev it slightly in neutral without a lean bog. I installed a 42, 45 and 48 and the screw was eventually 1 turn out for proper response. I now have a 50 in it (for a year or more) with the air screw about 1.25 out and it runs just as good but no better than it did before I messed with it. I also had to lower the needle clip one position. The reason I will go back to my original setting (4.5, 40, 1.5 turns out) next time the carb is out is that the air screw is finicky compared to before.

Others that I've read about have not had this problem at all with a #7 slide. I believe that slide is a better replacement on a carb that's seen better days or for one with a worn out OEM slide. Just my opinion though on that last part. The other stuff is real world messing around over and over to get it to run right. It wasn't worth it at all. Not better at starting, idling, or off idle response.

[Chopperpilot]

Thanks! that's what I wanted to hear, some real world experience swapping them out. I actually just got my factory 35mm PWK tuned 'just about perfect' with the factory slide needle (40 PJ, 155 MJ, needle #2 clip position). I could probably go 160 on the MJ (I think) on full throttle runs for a little over rev so we'll see. I also have a CEK needle to try (and now a DEK that came with the Air Striker). I'm probably going to keep on experimenting with the factory PWK (with the needles) to see what I can get out of it. Then swap in the Air Striker and really have a back to back comparison between a great running PWK and a new Air Striker.

[Chopperpilot]

Ok, installed the 35mm Airstriker last night and just took it for a ride. Now I have a KDX200 (2001) and had the factory PWK running pretty much perfect. Could do power wheelies in first and second (40PJ, 155MJ, and #2 position on the factory needle). I put in the Airstriker with a 38PJ, 158MJ, and DEK needle at #2 (I got a screaming deal on this carb, hence why I got it).
First impressions: bike is easier to start. Dead cold it's less kicks to get going and don't have to 'restart' it. With the factory Carb tuned great for riding, cold starts became a few more kicks and would usually die after starting requiring a restart (this is when the bike is overnight cold or not run in a couple of days). If I stalled the bike it may start first kick or may be 2-4. Keep in mind whenever I stall it's on a hillside of some sort so there's the added complexity of 'did I give it a good kick?' With the airstriker in current tune it was always a 1 kick and it fired up on a hillside.
General running seemed about spot on. Not a lot of difference from the properly tuned factory PWK. I think it did have slightly better off idle throttle response, but also I think a little bog. 1st gear off idle power wheelies seemed to not come as easy. I'm thinking maybe moving the needle to position #3 to give it a little more fuel earlier? So I know that sounds weird to say off idle response was better, but not........ even with the little bog, I felt I was still getting better response once it got past it. This may also be a function of the DEK needle maybe.

Routing all of the vent hoses smoothly takes a little thinking. I'm not sure if it was the hoses causing the issue, but I've gotten pretty good at taking the carb in and out with all the tuning. The airstriker seems to be a slightly tighter fit. Seems like it was just a touch longer and taller, so it was a little harder to get it back it the 'spot'. I used the KDX upper cap (with the 90* bend).

So my initial impressions are:
if you can get one cheap like I did ($110 on ebay, yes its an actual Keihin!) I think it is better than a well running factory carb. So far the easier starting is nice, and I think with a couple of tweaks to the tuning it'll be a more noticeable difference from the factory PWK.
If I had a good condition PWK and knew I had it tuned correctly, I probably wouldn't pay full price for an Airstriker. I went with the 38/158 because the supposed increased signal from the Airstriker made me think going down one on the pilot jet would be spot on. According to the airscrew, my thinking is correct (2.25 turns out has of now). I went 158 on the MJ because I thought I could go 1 up from the 155 I had in the old carb anyway and it runs about the same WOT.
The Airstriker is probably a no brainer for the 220s?

[kdxdazz]

Sounds like the starting is easier because you are running the very rich dek needle, like having the choke slightly open compared to the factory needle but up to temperature bogs because too rich, just my guess

[Chopperpilot]

Sounds like the starting is easier because you are running the very rich dek needle, like having the choke slightly open compared to the factory needle but up to temperature bogs because too rich, just my guess

I was wondering about that (+ the 4.5 slide on the Airstriker). I need a touch more testing to see if it's a lean or rich bog (it's very very slight, I notice it because I had the factory Carb really dialed in). I can play with the air screw to see which way makes it get better or worse. I did wonder about the DEK/CEK needles I'd read people getting and liking. I'd think with the factory slide a DEL or DEM/N would perform better. People claim the C/D needles give much more throttle response/power. The good thing is that the factory #5 slide fits in the Airstriker with the same amount of play/slop that the slide has in the Airstriker. So I could always revert.

[Chopperpilot]

OK, did a much longer ride (had to wait on weather) plus some more training on the bike with the new airstriker PWK. I think it's a pretty noticeable difference from the factory PWK (even when dialed in good like mine was). Full disclosure I'm getting much better at riding this summer so that could have an affect about how I feel about something too (for instance I learned how to climb hills by being 'retarded' with the clutch!). However, yesterday I did a ride on some 2 track trails and noticed the bike would pull up hills (not hill climbs) in higher gears and I never ended up feathering the clutch (although I was ready to) and this was relatively low speeds and low throttle openings. I feel the bike was slightly harder to stall and pulls harder at WOT (maybe going from a 155 (factory) to a 158 MJ(Airstriker) was the key??).
Again, this was coming from all indications of a factory carb in tune and in great working order. I'd changed the jet block gasket too. The only thing I didn't try was other needles in the factory carb and the Airstriker comes with a DEK, I'm pretty much running the same jets. So there's that to consider.
kdxdazz : I did turn out the airscrew a 1/2 turn for this ride and that pretty much got rid of the bog, so you were probably on to something. Bike still starts easier (all though now, like my KLX650R, it has a trouble area when it isn't cold, but not hot either engine running wise and it takes a few more kicks or the choke as I found out).

[kdxdazz]

OK, did a much longer ride (had to wait on weather) plus some more training on the bike with the new airstriker PWK. I think it's a pretty noticeable difference from the factory PWK (even when dialed in good like mine was). Full disclosure I'm getting much better at riding this summer so that could have an affect about how I feel about something too (for instance I learned how to climb hills by being 'retarded' with the clutch!). However, yesterday I did a ride on some 2 track trails and noticed the bike would pull up hills (not hill climbs) in higher gears and I never ended up feathering the clutch (although I was ready to) and this was relatively low speeds and low throttle openings. I feel the bike was slightly harder to stall and pulls harder at WOT (maybe going from a 155 (factory) to a 158 MJ(Airstriker) was the key??).
Again, this was coming from all indications of a factory carb in tune and in great working order. I'd changed the jet block gasket too. The only thing I didn't try was other needles in the factory carb and the Airstriker comes with a DEK, I'm pretty much running the same jets. So there's that to consider.
kdxdazz : I did turn out the airscrew a 1/2 turn for this ride and that pretty much got rid of the bog, so you were probably on to something. Bike still starts easier (all though now, like my KLX650R, it has a trouble area when it isn't cold, but not hot either engine running wise and it takes a few more kicks or the choke as I found out).

You guys in the US run incredibly rich jetting compared to close to the equator where I am so any jetting suggestions I give could be wrong but an important thing I have learnt, and I am still learning,is the relationship of the straight diameter of the needle with the pilot jet , you can't really talk about one without the other and this is where people get confused, they set the pilot jet based on idle and air screw but the straight diameter is also supplying fuel at idle so you can think you are right with the pilot jet but aren't due to incorrect straight diameter, also the air screw affects the whole rev range but more strongly at idle, it's a very complex relationship which I still haven't mastered
Glad you are making progress

[Chopperpilot]

Agreed on the straight diameter part of the needle and idle/off idle performance. A friend gave me a couple of needles (CEF and DGG)..... I tried them in the original carb on the bike (that was pretty dialed at that point) and the bike wouldn't start or run at all with just changing to those much thinner needles. Which is why I think a DEL or DEM or DEN would be a better setup that the DEK on the Airstriker.