jetting for neow mods on 440?

[spec]

I just picked up the mod quad air flow kit, and so am now running my airbox lid off, with a K&N on it. I went to re-jett and kept stepping it up from a 158 to a 168 ( trying every one betwen there). Up untill the 168 when I'd go to punch the throttle it would dog way down, then finally start to pick back up. Finally when I got the 168 in there its pretty much right on for throttle responce. My question is, firts off, when it would dog like that, that ment that it was burning to lean right? Secondly, on my spark plug the bottom side of the threads(the ring right around the bottom) is a dark brown/blackish color, and the little post that goes up( that the spark transfers to/from) is a white ash color. Am I still to lean on it? I have pictures if that would help more. Let me know if the info I provided was good enough, or if you need more.

Thanks for any help.

[GPracer2500]

Originally posted by spec
I just picked up the mod quad air flow kit, and so am now running my airbox lid off, with a K&N on it. I went to re-jett and kept stepping it up from a 158 to a 168 ( trying every one betwen there). Up untill the 168 when I'd go to punch the throttle it would dog way down, then finally start to pick back up. Finally when I got the 168 in there its pretty much right on for throttle responce. My question is, firts off, when it would dog like that, that ment that it was burning to lean right? Secondly, on my spark plug the bottom side of the threads(the ring right around the bottom) is a dark brown/blackish color, and the little post that goes up( that the spark transfers to/from) is a white ash color. Am I still to lean on it? I have pictures if that would help more. Let me know if the info I provided was good enough, or if you need more.

Thanks for any help.

That's pretty good info--TONS better than, "I put a filter on my 440. What jet do I need". lol :p

..."I'd go to punch the throttle it would dog way down, then finally start to pick back up..." From that description alone it's hard to say exactly what's happening. But if it wasn't doing this before the intake change, and it kept getting better as you went up in main jet size, then you'd have to think the it was doggin' because it was lean.

Your post is cool becuase it's a great example of the RIGHT way to jet: You make a change on your quad. You know that increasing the airflow pushes jetting lean, so you pretty much know your going to jet richer. So then you got out your jets and started stepping up the sizes. And between each change you tested--looking for rough running and (hopefuly) what throttle positions is was happening at. You kept testing until you found the best performance. THAT is the procedure that will get most people the farthest in getting their jetting right.

There are a few things you didn't mention but should be considered:

What throttle postions have you been testing at?
What throttle postions does the rough running occur?
(awareness of throttle postion is essential for figuring out what's going on inside the carb)
What are your other jetting specs?
Stock carb? Is the choke removed?
What about your elevation and type of exhaust?
Are there any other relevent engine mods?
It's not 30 degrees wherever you are, right?

It never hurts to mention stuff like that. Sometimes there will be something really significant that you didn't realizes WAS significant.

I don't put much stock in plug readings as a useful tool in many situations. Getting accurate and specific information from a plug isn't as easy as it seems.

ETA: Is a 168 the biggest you have? It's certainly possible that continuing to go up will improve performance. However, if were the case it might mean that you were running a little lean before the filter change. 158 to a 168+ is starting to be a pretty big change for just an airfilter. Are you pretty sure your jetting was correct before? Be sure to check your pilot circuit and you might want to try a step richer on your needle just to see.

[spec]

As of now It has a T-4 slip on, and then the 440 kit, hot cams stage 2, and the air filter. Also no the choke is still on and its the stock carb. Also when the rough running occured, it was at about 1/4 throttle. After that it first chopy spot it seemed to run fine though. As for the jetting, I bought this quad used form a guy last summer, and so the jetting was in there from when he had it, so it could have been off from the begining. Yes I do have a 170,175,and 178( my local dealer was all out of 172s:( ) that I could still put in there. And no it's not 30 degrees here, it's been in the 80s this whole last week.:p

[krt400ex]

Originally posted by spec
As of now It has a T-4 slip on, and then the 440 kit, hot cams stage 2, and the air filter. Also no the choke is still on and its the stock carb. Also when the rough running occured, it was at about 1/4 throttle. After that it first chopy spot it seemed to run fine though. As for the jetting, I bought this quad used form a guy last summer, and so the jetting was in there from when he had it, so it could have been off from the begining. Yes I do have a 170,175,and 178( my local dealer was all out of 172s:( ) that I could still put in there. And no it's not 30 degrees here, it's been in the 80s this whole last week.:p

from around 1/4 throttle? did u check/mess with ur pilot jet? that may be lean