Major stutter after rejet. Help.


46 replies to this topic
  • JCORMI

Posted March 28, 2006 - 04:18 AM

#1

Well I finally did the JD jetting kit last night, I did the air box cut outs, snorkle removed, 170 main jet, 48 pilot jet, and put the Blue needle on the 4th clip, I also have the baffle pulled out of the stock pipe. Oh yeah zip ty fuel screw and TT ais removal, and throttle stop cut. Compared to stock settings the bike actually has a ton more power, and alot of the off idle bog seems to be gone. BUT, and a big but it is, the bike is missing horribly at constant speed, probably about 1/4 - 1/2 throttle it is just surging and stuttering very badly.
Oh and also, the fuel screw doesn't seem to make any difference in how it idles unless I back it almost all the way out. I turned it all the way in and the bike was still idling fine. Any body have any ideas.
By the way it was about 40 degrees when I was riding if that makes a difference.

  • Matty05

Posted March 28, 2006 - 04:30 AM

#2

put the needle back to the 3rd clip.

Search on how to set fuel screw, but basically turn bike idle up so it sounds a bit high (this is for fuel flow and why it only worked for you wound a lot out) then adjust the fuel screw in and out till you find the place with max rpms and best throttle response.

  • JCORMI

Posted March 28, 2006 - 05:24 AM

#3

http://www.thumperta...0&highlight=TPS

Just found this in the jetting forum.

  • odonnks

Posted March 28, 2006 - 07:55 AM

#4

Is it missing under load or on the stand?
Check the AP squirt and the AP linkage. The owners manual has a very simple adjustment (not sure which page). Probably not the cause but it help the off idle bog more.
If the fuel screw does notmake a difference, reduce the P- jet. back to the stock 45 to see if it helps.
Run it in the zone where the problem occurs for a minute and kill the engine from there. Pull the plug look for indications of fuel mix. Plug electrode should be tan.

  • MotoGoalie

Posted March 28, 2006 - 08:51 AM

#5

Well I finally did the JD jetting kit last night, I did the air box cut outs, snorkle removed, 170 main jet, 48 pilot jet, and put the Blue needle on the 4th clip, I also have the baffle pulled out of the stock pipe. Oh yeah zip ty fuel screw and TT ais removal, and throttle stop cut. Compared to stock settings the bike actually has a ton more power, and alot of the off idle bog seems to be gone. BUT, and a big but it is, the bike is missing horribly at constant speed, probably about 1/4 - 1/2 throttle it is just surging and stuttering very badly.
Oh and also, the fuel screw doesn't seem to make any difference in how it idles unless I back it almost all the way out. I turned it all the way in and the bike was still idling fine. Any body have any ideas.
By the way it was about 40 degrees when I was riding if that makes a difference.


I've had this problem back last summer when I was fooling with my jetting.

You may be rich in the midrange.

What is your needle set out right now, while it is surging and sputtering?

Lean it out.

If that is better, you might also try a slightly leaner PJ. 45 ish?

The sputtering of a rich jetting is more annoying and cumbersome than what you would think of overly lean jetting. Overly lean jetting makes the bikes power seem flat. Overly rich makes it jerk, bog and sputter. Of course you want to find a perfected setting.

I know this is the YZF jetting specs but consider that NCmountainman went with a bit leaner jetting on his bike and has cured this stuttering problem. You, of course dont want to COPY this jetting but just try experimenting with a bit of a leaner setup till you home in on a better range of jets for your situation.

http://www.thumperta...49&page=2&pp=10

  • JCORMI

Posted March 28, 2006 - 09:19 AM

#6

I have my needle set at 4 from the top right now, you think go up one and go back to the 45 pilot, keeping the 170 main for now?

  • MotoGoalie

Posted March 28, 2006 - 09:31 AM

#7

I have my needle set at 4 from the top right now, you think go up one and go back to the 45 pilot, keeping the 170 main for now?



Only make one change at a time. Being one size off might be your answer.

Try JUST going to a 45.

And perhaps a 168 on MJ.

Once you get it close you can play with the needle height.


but only make ONE change at a time. It's tedious but you'll be rewarded with a strong running, properly jetting bike.

  • odonnks

Posted March 28, 2006 - 09:31 AM

#8

I may even goto a 168 main.
With pretty much the exact same set-up on my 06 I went from a main of 165 to 170 and back to 168. It felt like it ran better there. Without a aftermarket pipe I don't think the engine will flow enough air for a 170 though you are in a cooler climate.
I droped the leak jet from the stock 50 to 35. This helped the off idle response too.
Keep in mind that warm weather is due any day and jetting you adjust to run well at 30 deg will bee too rich at warmer temps.
If you haven't yet replaced the phillips head screws on the bottom of the carb bowl, do it before you strip out the head. Allot of us did this.
My preference is allen head since a bondus tool will turn them off angle.

  • JCORMI

Posted March 28, 2006 - 09:40 AM

#9

So do you think the pilot is the cause of the mixture screw having no effect? I changed the screws on the float bowl last night with some good stainless philips heads, because the hardware store down the road didn't have any with allen heads. I did strip one of the stock ones out taking it apart. These stainless should hold up alright.

  • MotoGoalie

Posted March 28, 2006 - 09:47 AM

#10

So do you think the pilot is the cause of the mixture screw having no effect? I changed the screws on the float bowl last night with some good stainless philips heads, because the hardware store down the road didn't have any with allen heads. I did strip one of the stock ones out taking it apart. These stainless should hold up alright.


Generally if you have to move the FS more than 2.5 turns out to get any effect you need to then look at your PJ. So, yes, if you are turning your FS out 4 turns to get any effect, you are out of wack on you PJ. The symptoms you describe I think, are more likely being too rich.

The position of your throttle in relation to your jetting is also important. I've noticed that overly rich PJs lead to harder starting as the bike gets hotter. Cold starting is easy, but through the day the bike becomes more finicky to start.

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  • JCORMI

Posted March 28, 2006 - 10:34 AM

#11

I am at work right now, but am going to attack this thing again tonight. If I move down on the pilot and main and still have that steady throttle sputter I will try unplugging my tps. Report back tomorrow.

  • odonnks

Posted March 28, 2006 - 05:42 PM

#12

Look over this link.
The graph / map is pretty handy to figure out which jet to adjust based on where the problem is.
This is a really good article and applies to both the 250 and 450.
http://www.thumperfaq.com/jetting.htm

  • FOZZ

Posted March 28, 2006 - 07:39 PM

#13

Sorry for the non related input but saw this through the above link..

Any one use one of these ?

http://www.motionpro...oduct/carbmate/

  • OneToGo

Posted March 28, 2006 - 10:55 PM

#14

Re your stutter or what sounds to be ' hard stumble'

Also check the thread in Jeting by gassrx on Part 1 Jetting - very good basic intro. Sorry, cant paste thread as borrowing Hotel laptop...

This recommends setting your MAIN Jet correctly FIRST, makes sense as you want the motor to produce max power and run wellat WOT foremost and most jets overlap in influence... So, run WOT and see if the mottor stumbles. If so too rich - go one down on main - 168 in your case. If NOT, set a richer main - probably not in your case - then work down until no hard stumble

Then, start from the bottom and work up from pilot. I feel the 48 is right for the recent WRs. Then set the needle for mid range throttle.

PUT tape marks on your throttle grip so you can accurately guage where the problem lies in throttle setting. Remember, JD recommend 170 with BLUE 3 and 168 with RED 5. If this helps (and I think it will) if not then I suggest disconnect TPS. I'm doing same this weekend just for FUN! :thumbsup:

  • Matty05

Posted March 29, 2006 - 02:28 AM

#15

I am at work right now, but am going to attack this thing again tonight. If I move down on the pilot and main and still have that steady throttle sputter I will try unplugging my tps. Report back tomorrow.

Don't touch your TPS!!!!!

drop the needle 1 clip (go to #3) and your problems will be solved.
Your pilot and main look right, but your needle looks rich.

  • odonnks

Posted March 29, 2006 - 03:05 AM

#16

Fozz
The real benefit of that tool is wihen adjusting multi carb bikes. If your going to do that its pretty useful. I can't see much use on a single carb bike.

  • Matty05

Posted March 29, 2006 - 03:14 AM

#17

Fozz
The real benefit of that tool is wihen adjusting multi carb bikes. If your going to do that its pretty useful. I can't see much use on a single carb bike.

better using a lambda meter or "CO2 sniffer".

  • JCORMI

Posted March 29, 2006 - 05:11 AM

#18

I ended up dropping the pilot down to the stock 45. Mainly to see if that would help with my problem of the screw having no effect. I also went down one clip on the needle. I only had time to take it for a very short ride, but I can say that the midrange sputter I was experiencing was not nearly as bad. changing the pilot jet however did not make any change in the mixture screw. I started the bike up and it idled fine with the screw all the way in. Am I mistaken or is the bike supposed to run with the screw all the way in.
I am going to go out tonite for a full on test run and see how it feels, like I said it was a very short ride last night, but just from the few minutes I was on it, it did not seem as strong off the bottom with the 45 pilot as it did with the 48 pilot. If that is what I feel tonite I will go back to the 48.

  • yamageezer

Posted March 29, 2006 - 08:46 AM

#19

I went through the same thing as you, all of the same mods same problem but when I switched to a 168 main ,48 pilot, red needle at the 4th position, and Zip-Ty 1.5- 2 turns out depending on temp and altitude. The bike runs fantastic and no more stumble. James Dean gave me these settings because I was having such a hard time with my jetting :thumbsup: I think the blue needle is just too rich for some bikes. Good luck...

  • odonnks

Posted March 29, 2006 - 08:49 AM

#20

Are you sure the fuel screw is in the whole way?
With the stock 45 PJ and scew in and engine on a 'fast' idle, you should see some difference from a few turns out to the whole way in.
The first time I installed it I thought it was in teh whole way and it wasn't. I took it out completely (don't loose the sprong, washer or O-ring !) and ran it in again. That time it went the whole way.
The know should almost touch the bottom of the carb bowl when its in the whole way.
If your sure it is, don't crank it too hard. You can damage it or the carb.




 
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