Author Topic: Jetting, a pain in the D! (Read 10154 times)

fearlessfred · « **Reply #15 on:** July 13, 2013, 01:49:26 PM »

If fuel is coming out of the overflow,it could be causing your problems.the fuel level ,when correct is even with the seam ,if it is to low it would cause poor throttle responce (not what your describing),to high to were its coming out the overflow that would cause what your describing.I think the diff. in the ign. would have an effect ,but I don't believe that is bigger problem

363 stroker · « **Reply #16 on:** July 13, 2013, 02:06:00 PM »

It is possible it could be the difference between the two ignitions. Maybe try an counterbalance holder that is adjustable where you can add or take away a little timing and see how it feels.

pinned250r · « **Reply #17 on:** July 13, 2013, 05:03:11 PM »

Well upon inspection I had a Rees chip, I picked up some vf2s and installed today. throttle response is better, but didn't get a chance to ride it. Going out tomorrow and bringing all jets along. I will keep y'all updated. Thanks for the variety of answers!

rsss396 · « **Reply #18 on:** July 13, 2013, 05:14:37 PM »

All great advice given previously, I would still first adjust the float level if its wanting to spill a little fuel, before you do any jetting changes or even leave the house, then go after the plug gap then needle and maybe air screw to fine tune the lower bottom end range of throttle pull.

sanddunesaddict · « **Reply #19 on:** July 13, 2013, 06:01:10 PM »

What intake setup is on his bike and what is on yours??

pinned250r · « **Reply #20 on:** July 13, 2013, 06:43:41 PM »

Sounds great. I will follow instruction Dave.
I have vf2 reeds, 40.5 kehin, and esr airbox elim kit.

Morse250r · « **Reply #21 on:** July 13, 2013, 08:18:01 PM »

Mine has a upp intake v force3 reeds esr eliminator kit

sanddunesaddict · « **Reply #22 on:** July 14, 2013, 05:32:58 PM »

ok my idea is out then

pinned250r · « **Reply #23 on:** July 15, 2013, 03:43:37 PM »

played with the float, all set there, went down from a 150 to a 145 pilot, really cleaned up the low end, now it cuts out on the top, like a lean cut. It never did this before, possible i need to go up a size on the main then? maybe down a needle clip rather?

Tbone07 · « **Reply #24 on:** July 15, 2013, 04:43:08 PM »

What about an air leak?

pinned250r · « **Reply #25 on:** July 15, 2013, 08:58:35 PM »

Update. Today I went down a clip on the dgh needle(rich) and i couldn't get it to cut on the top end, so that's a bonus, but it's still a little doggy on the bottom end, just not as responsive at johanns, very well could be the cr ignition I think :/ I took the airscrew out another 4 turns for a total of 5.5 turns out(4 turns=1 size lower pilot) and it didn't make as big a difference as going from the 48 to 45. Any other suggestions to help on the bottom End?

Polonda · « **Reply #26 on:** July 15, 2013, 09:10:50 PM »

I'm slightly confused. 148 and 145 are main jet sizes. Pilots for that carb would two digit numbers like a 48 or 52. And you should be no more than 2.5 turns out on the air screw.

Start bike and let it warm up. Then turn the air screw in all the way. This will richer the pilot circuit and may cause the bike to stall. Start turning the air screw out quarter turn at a time until you get the highest idle. At a point the idle wont go up anymore. (Make sure you give the motor some time to react to your change) Then turn it back in a quarter turn. If you are more than 2.5 turns out on the screw you need a smaller pilot. If you are less than 1.5 you need a larger pilot.

Start with the clip on the second groove from the top of the needle.

Put at very minimum a 160 main in it as I'm pretty sure a 145 is way to lean.

.018 spark plug gag is key also as stated before.

Polonda · « **Reply #27 on:** July 15, 2013, 09:12:20 PM »

This may explain it better than I can.

http://www.duncanracing.com/TechCenter/KeihinCarbJetting.pdf

rsss396 · « **Reply #28 on:** July 15, 2013, 10:58:50 PM »

good advice Polanda!
I forget the amount of turns on the air screw but its always stuck in my head as 3 turns and 1-1/2 turns was ideal so you had equal adjustment open or closed but I have not messed with the pwk in a long time since I run lectrons all the time now.

Yeah your pilot number are wacky maybe drop the first digit?

If you are cutting out on topend then always up the main jet first that is primarily what it affects. and you should get the main jet sized properly before tuning the needle to much.

pinned250r · « **Reply #29 on:** July 16, 2013, 12:24:21 AM »

I apologize guys, i am aware the pilot jet is just a 2 digit number. Typo.

I do not plan on running the air screw out that far ever, I remember hearing/reading somewhere than 4 turns out is equal to 1 size down on the pilot, any confirmation of this?

I have a 175 main in it currently and the top end is now good, no cutting out.

My current set up in the carb is as follows
40.5 kehin
175 main
45 pilot
dgh needle, 2nd clip from the bottom

My issue now is on the bottom end, from no throttle to about 1/3 throttle, its just weak. I do have an "aggressive drag port" from RB racing, but as stated previously, Johanns rideability on "the same" port and head work is 10x better than mine, it has a bottom end like an mx bike, where mine lacks that significantly. It could be the ignition difference, but i cant imagine it making such a significant difference. Do i dare go down to a 40 pilot or lower?