I was going to suggest that, but I've found that when you're diangosing issues that high in the rev range, even with a choke circuit that you know works, it has little affect on that operation... I know that doesn't seem to make sense, but it's just what I found when trying to use that as a troubleshooting help... and I'm not saying don't try it, maybe it will work for you, and you've got nothing to lose!

It's really hard to convey in words how to tell if it's lean or rich, for me, it's just something I've learned over the years, and the only way for me to tell you for sure if it's one or the other, would be to ride the bike myself, which obviously can't be done in this case!!

One helpful item is this - let's say you're running in 3rd, 4th or 5th gear, with wide open throttle, and you approach an RPM where it begins to stutter, surge, etc... at that exact place, if you slightly back off the throttle, and begin to pick up speed again, then that is an indication of a lean setting for the fuel circuit you're running in.

Plug reading is another way, but you have to work very hard to diagnose the plugs correctly, for the range your working in - I'll explain:

Let's say you're diagnosing your main jet - the only way to truly get a good plug reading is to install new plugs and start the bike in a place where you can get right to a long stretch of road, imediately after warm-up, then run through your gears with wide open throttle through, let's say 4th gear, though this would vary depending on the length of your stretch, and your ability to run at high speeds safely - when you get to the top of whatever gear you can safely finish in, you shut the bike off, and use brakes to get down from speed, then let the bike cool and pull your plugs for inspection... this requires a lot of planning, as well as circumstances working out in your favor, like, little to no traffic on the road you're on, etc.
I would say the best place to manage this, woud be on an old runway, a closed portion of rideable highway, or a drag strip... it's not convenient, and is kind of labor intensive no matter what.
Again with this bit, I'm not saying that plug reading without the above scenario is useless, but that it is the most precise, reliable way to get an accurate reading for the given circuit you're trying to test

Anyway, blah, blah, blah, I hope you can get this sorted - I can't imagine having to ride regularly with fueling issues in any range... that would definitely take some of the fun out of things, for sure!

 

Ok, so I started drafting my last reply hours ago, but was really busy with work, and just got the chance a little bit ago to post it, and missed your last post in the meantime.

Awesome, I'm glad the choke was a helpful troubleshooting aid, but keep in mind, 7500 to redline does involve the circuits below to some degree, but the ultimate limiting factor in metering of fuel when running wide open throttle in that rev range, is your main jets, not your needles - the rich/lean adjustments in this range need to be done with your main jet sizes, and when you get the "yank your arms out of there sockets" pull without the choke, then work on your needles, which governs your wide open throttle fueling from roughly 5,000 to 7,000.
I will not stop emphasizing the importance of working from the top down, you have got to get the mains right, before working on the lower circuits - yes, the lower circuits have a slight affect on the above circuits, mostly on transition, but for 7,500 to redline, it's main jet, main jet, main jet!

I don't know if I ever posted this link for you before, but it's been around for 1000 years, and it is good, accurate information:

CV Carb Tuning Procedures

Just ignore the step about float height, as the F2 floats are non-adjustable... that said, our floats can be damaged, and there is a procedure for checking the height, but if they're off, it requires replacing of the floats, since they cannot be adjusted.

 

I've found the same thing through all my trials and tribulations. Thats a good way of describing it.

I'd do that if I had a place to, but I don't. Theres no where around here I could do that. But great advice for anyone else reading or me for that matter if I ever end up in a rural area

Yea it does take away some of the fun

That's been my go to for this whole process. I thought the 135s (DJ 126s) I had in there were correct because of their good pull from 10-redline but I guess not.

So after moving the clips down two positions, its wayy to rich from 5-6k, and still has the 8-9.5k lean stumble but a lot less severe. I guess my next step is actually 138s and moving the clips back up. I already tried 140s and they were too rich. Thanks again for all the help guys. If 138s dont solve the problem I'm putting a stock header/slip on and stock jetting back in

 

After reading your post im starting to wonder if your issue is coming from the home made muffler you have on it.. i have tried to tune a few bikes with cut down mufflers and there always was an area of concern and never seemed to be worked out... if i am correct on this and you still want to run that muffler then look for the happy medium.. the best way i could explain is......................
An engine needs the highest flow velocity possible for quick throttle response and torque throughout the low-to-mid range portion of the power band. The same engine also needs the highest flow volume possible throughout the mid-to-high range portion of the powerband for maximum performance. This is where a fundamental conflict arises. For "X" amount of exhaust pressure at an exhaust valve, a smaller diameter header tube will provide higher flow velocity than a larger diameter tube. Unfortunately, the laws of physics will not allow that same small diameter tube to flow sufficient volume to realize maximum potential power at higher RPM. If we install a larger diameter tube, we will have enough flow volume for maximum power at mid-to-high RPM, but the flow velocity will decrease and low-to-mid range throttle response and torque will suffer (the "back-pressure" myth probably arises from a misunderstanding of these factors). This is the primary paradox of exhaust flow dynamics and the solution is usually a design compromise that produces an acceptable amount of throttle response, torque and horsepower across the entire powerband. ..

 

Huh, a lot of what you said went over my head . Am I right in gathering that my 4-1 header and cut pipe are allowing too much flow on the top end possibly causing my problem? At this point would it be wise to just get a stock header and some kind of basic slip on?

Edit: re-read what your post a few times, I think I've decided to get a stock header. Anybody selling one?

 

In short, what squale posted up is part of an explanation on how different exhaust configurations "move the power band" around a bit - meaning there will always be a compromise between your low-end, mid-range, and top-end power - this is an age old conundrum for racing/tuning, and is the same for any internal combustion engine - it is one of the decisions that must be made by every tuner/mechanic/developer, that being, "where do I want my peak power, and which/how much of another power range do I want to sacrifice to have it there?"
If you want to read the whole thing in context, just search for some of the text he posted, and you'll find the rest of the total read, which is considerably more verbose, in various places on the internet.

Bottom line, cut down exhausts bring a challange, and personally, I am not a fan of extremely cut-down units, like the ones which basically amount to a car end pipe connected to the header, as there's no point then in running anything at all! Now I'm saying this without seeing what end can you're working with, but you should have no issue tuning your carbs with a header... maybe you could go with a little more conservative slip-on, if it's super-duper-uber short, but once again, I'm not sure what you're currently using.

I have tuned both of my bikes, with relative ease, in several changes of configurations, like with OEM header and OEM slip-on, then with 18 inch aftermarket slip-on, then with race header and same slip-on, then with the same race header and the slip-on shortened over 6 inches, etc.... I've run into no real problems with any of these changes, you just have to adjust accordingly.

Just how short is your muffler anyway? How much packing is in it, and how good is it's condition?

 

You know what, if you can do it, I can do it. I'll keep working with it, I don't have 200 bucks to drop on a new header/exhaust

It's really not that short, here it is:





Half of the can (in the middle) has packing, the rest does not. It is in pretty good condition and doesn't leak

JNSRacing another question for you. How much extra main jet did you need for the race header over stock? How about for the k&n filter over stock?

 

sorry for the long scientific theory of it but just wanted you to have a clear understanding of it... but like jns racing said there is alot of good info on the internet.... i also agree with what jns racing said about using several changes of configurations on my bikes and customers bikes and never had any issues that could not be corrected... so i think your set up can be tuned but like any other bike((carbs bikes especially)) your going to have to make adjustments and changes.... just like marc at factory says... carb tuning is a combination of science, art, intuition and and at times, a fair dose of wizardry. There is no dyno that "tells" one how to assemble or modify the carb to deliver proper power and response...

 

^well put

So what do you guys think of my next plan: right now with 135s and the clips on their second positions from the top, my idle-7.5/8k is perfect. from 8-10k it leans out and sputters, from 10-redline it pulls pretty hard but not as hard as I know it could. Next, I plan on upping to 138s and leaving the needle position alone. Sound good?

 

i think that sounds good...start there and report back and we will go from there...