This is fun. The slide controls the fuel the same as if it has a cable hooked to it. The fuel don't care how the slide is lifted cable or vacuum. The CV carb is good for the EPA as it kinda meters the fuel on how much air is moving through the carb not how much gas the rider wants it to get. CV open the throttle half way and the vacuum says wait till the air gets moving. fuel is metered as needed, smooth but slow[lag]. Pumper carb squirts fuel when you open/lift the slide and your milage goes down and front wheel goes up[not much on the stock 250 tho]. CV smooth; pumper not. Come on up to Sedro Woolley and you can ride mine. Or get a pumper carb and try it your self.

I never rode my bike with the stock set up and I didn't put the 120 main jet in so I have no idea how it ran stock. It has never missed a beat except for the fuel screw thing I messed up on.

 

You have to be aware of the different sizes of jets from different manufacturers. A 125 jet from Keihan is not the same as a 125 jet from dynojet.

You keep saying you have a 125 main. Dynojet doesn't have a 125 main. So that makes me think you have a keihan jet. Which is actually equivalent to a 118 dyno jet main. Which would be too small easily explaining the problems you are having. Your bike should run great on a 124 or 128 dyno jet.

For example, Kawasaki has a hop up performance article from the factory for our bikes. It says a 140 jet with no lid is the best at sea level. But they use a keihan jet. So that actually comes back to a 130 dyno jet.

Here is a conversion chart


Width------Kehein # -- DynoJets # -- Mikuni #
0,0350---- 92,5--------- 92----------- 86,3
0,0360---- 95----------- 94----------- 88,1
0,0370---- 97,5--------- 96----------- 90,0
0,0380---- 100---------- 98----------- 91,9
0,0390---- 102,5------- 100---------- 93,8
0,0400---- 105--------- 102---------- 95,6
0,0410---- 107,5------- 104---------- 97,5
0,0420---- 110--------- 106---------- 99,4
0,0430---- 112,5------- 108--------- 101,3
0,0440---- 115--------- 110--------- 103,1
0,0450---- 117,5------- 112--------- 105,0
0,0460---- 120--------- 114--------- 106,9
0,0470---- 122,5------- 116--------- 108,8
0,0480---- 125--------- 118--------- 110,6
0,0490---- 127,5------- 120--------- 112,5
0,0500---- 130--------- 122--------- 114,4
0,0510---- 132,5------- 124--------- 116,3
0,0520---- 135--------- 126--------- 118,1
0,0530---- 137,5------- 128--------- 120,0
0,0540---- 140--------- 130--------- 121,9
0,0550---- 142,5------- 132--------- 123,8
0,0560---- 145--------- 134--------- 125,6
0,0570---- 147,5------- 136--------- 127,5
0,0580---- 150--------- 138--------- 129,4
0,0590---- 152,5------- 140--------- 131,3
0,0600---- 155--------- 142--------- 133,1
0,0610---- 157,5------- 144--------- 135,0
0,0620---- 160--------- 146--------- 136,9
0,0630---- 162,5------- 148--------- 138,8
0,0640---- 165--------- 150--------- 140,6
0,0650---- 167,5------- 152--------- 142,5
0,0660---- 170--------- 154--------- 144,4
0,0670---- 172,5------- 156--------- 146,3
0,0680---- 175--------- 158--------- 148,1
0,0690---- 177,5------- 160--------- 150,0
0,0700---- 180--------- 162--------- 151,9
0,0710---- 182,5------- 164--------- 153,8
0,0720---- 185--------- 166--------- 155,6
0,0730---- 187,5------- 168--------- 157,5
0,0740---- 190--------- 170--------- 159,4
0,0750---- 192,5------- 172--------- 161,3
0,0760---- 195--------- 174--------- 163,1
0,0770---- 197,5------- 176--------- 165,0
0,0780---- 200--------- 178--------- 166,9
0,0790---- 202,5------- 180--------- 168,8
0,0800---- 205--------- 182--------- 170,6
0,0810---- 207,5------- 184--------- 172,5
0,0820---- 210--------- 186--------- 174,4
0,0830---- 212,5------- 188--------- 176,3
0,0840---- 215--------- 190--------- 178,1
0,0850---- 217,5------- 192--------- 180,0
0,0860---- 220--------- 194--------- 181,9
0,0870---- 222,5------- 196--------- 183,7
0,0880---- 225--------- 198--------- 185,6
0,0890---- 227,5------- 200--------- 187,5

 

Ok well it took me awhile to get to it but I have changed my 124 main to a 128 but I am still getting the hesitation from 3/4 to full throttle. It might even be worse. I am going to mess some more with the air screw and I am going to make sure my gas tank breather hoses arn't getting pinched off or anything....from there I have no idea

 

I kinda find that hard to believe that i have the 128 main kawasaki jet and its equal to the 120 DJ... A friend just put in a 128 main DJ jet in his and he says its still flat wide open... mine runs great. So he is getting that much more fuel but it still needs more? Something doesnt make sense there...

 

You can keep messing with it all you want if you like doing that.
If you'd like to get rid of than stumble, put the snorkel back and MJ back to original.

--
Mikko

 

My 09 has stage two jetting (stock Pilot) and the snorkle removed and a good AC and it runs greart at any rpm and has no issues at all, Just lucky I guess. Or maybe it has to do with following the directions supplied by the manufacturer of the parts I'm using.

 

Hey Mikko...just curious on your suggestion about the snorkel. Are you saying that one can't get smooth jetting response without the snorkel or just that in EMS' case, installing the snorkel will help him? I can't think of a scenario I've had with several bikes with CV carbs that couldn't be jetted to optimum performance with open airboxes and such. I could definitely see where a clamp-on air filter setup could cause some tuning grief with a carb...especially a CV...but barring some pretty serious hacking on the airbox, I'd think he should be able to find the sweet spot for his bike's jetting needs.

I run an open top airbox, and the bike is crisp and clean throughout the range.

 

TNC, like we know it is POSSIBLE to find a jetting setup that works with opened up airbox, plenty of testimonials to that effect here on this board.

But it is also pretty well established that CV carbs tend to be easier to jet when there's a stock airbox behind it. Extreme example is clamp-on filter element that you mentioned, good luck anyone making it work properly with a CV. Some bikes (with CV carbs) are pretty much impossible to get running properly if stock air box is not present.

OP, (seth) has "messed with" main jet size and found no improvement there.
Adjusting the pilot screw is not going to fix a jetting issue at 3/4 throttle and 7000RPM. Sounds like he's pretty much exhausted his jetting skills trying to resolve it.

The bikes do not hesitate or sputter 3/4 throttle in stock condition.
Yeah, they are little cold blooded to start so drilling the enricher jet helps, and so might opening the pilot screw a little.
But there is absolutely nothing wrong with the stock jetting above say 1/4 throttle.
I think some here pretty recently posted A/F plots of the stock jetting, darn close to constant 13 - 14 above the very low RPM range. Perfection.

OP wants to cure the half throttle hesitation, I say quickest way to do it is put the snorkel and stock main jet back.

--
Mikko

 

I can try putting the snorkle back in and see if it changes anything but I would loose allot of power by going back to the stock main would I not? Maybe I would not notice the difference...please inform

 

Do the best thing and try it yourself.

While you still have the 128 in there and snorkel removed go and do a top speed test. 6th gear, test top speed on a given stretch of road to both directions (to average out any head/tail wind).

The go and quickly swap the MJ back to stock and pop the snorkel on. Should take no more than 1/2 hour tops.
Repeat exactly same top speed test.

If you lost or gained any power the to speed will show it.

--
Mikko