lol... yeah, Im not doing trials with the bike, just using as an example. Some trails may require a bit of putting, or sometimes Im just lazy.

In any case, do you notice any tradeoff with lack of control at lower rpms?

Also, anyone running an N1TC also changed the needle jet to go with it, or still running stock 250s needle jet. Of all the threads here on needles, there are very few mentions of changing needle jets. Im running the N1TC with stock needle jet, seems to be working pretty well.

 

Josh, my testing and charts are using the DJ2152 kit - so it's the DJ slide spring, DN0228 needle, and a final determination of a DJ140 main jet.

There is no information on the use of other needle jets.

Your use of the K138 (while lidless) will create a quite lean top end. It is the equivalent of a DJ128. A K138 would work better with the lid on and snorkel removed - This is because the lid offers enough restriction to airflow that the pressure gradient between the ambient air above the fuel in the bowl and the air entering the needle jet from the MAJ causes an enrichening of the AF in the needle jet. The pressure of the air entering the needle jet becomes lower which increases the de facto pressure on the fuel from the ambient air pocket above it - all of which makes the AF in the needle jet richer. Pulling the lid is a radical mod due to the fact that we cannot re-size our MAJ to compensate for loosing the above described gradient. We can only increase the main jet size until the needle jet AF is restored to "proper" and then use springs/holes/needles and clip positions to avoid overfueling the low and mid range.


This is the link to the x-over chart that has been used successfully by members to duplicate my slipon+lidless recipe - https://www.jetsrus.com/FAQs/FAQ_mik...ihin_sizes.htm

A K152 will target 12.8-13.0 to 1 AFR throughout the RPM range with N1TC@2N and 7/64th slide lift hole on a stock slide spring.

 

This is very strange- I have some brand new Dyno Jet mains from a Mojave DJ kit-- it contained DJ122, 126, 130, and DJ134 mains-- A stock Mojave uses a Keihin 132 main-- the Keihin 138 is visibly larger than the DJ 130 or 134 jets-- its pretty damned big.

Unless DJ makes different size jets with the same numbers for different kits (same carb), something doesnt add up-- the Keihin 132 looks about the same size as the DJ 130, the Keihen 135 is slightly larger and the 138 is very easily larger visually.

I honestly cant imagine running a 150+, that is a gigantic jet compared to anything in the DJ kit, let alone stock.

As I said though, it runs very strong now, and Ill be adding a bit more restriction with the 6db baffle. K138 is the largest I have on hand ATM. I was also planning to put the lid back on and try this afternoon-- I ran out of time (and electricity) last night-- I have drilled a bunch of 1/4" holes under and around the baffle for more air flow while trying to keep the airbox noise down-- seemed to work good for the DJ 126 with stock exhaust. We'll see

 

Yeah the whole issue of comparing DJ jets to K jets is old news in here - DJ jets are not built like K jets, they have a venturi cross section and flow quite differently. K jets are holes drilled in brass. That link impresses me due to the fact that they know fully well, and talk about, the fact that DJ jets do not have a direct x-over to K jets. They do present x-overs that perform similar to DJ jets. And as such, apparently, the chart is accurate.

 

With that restrictor stuck in the end of your DG-O and MCM'less, I would go with a K148.

Oh, BTW, you might want to know that DJ uses "mules" to develop their kits that may not conform to what is in your garage.. When I was testing and calling DJ on a regular basis, we finally figured out why we could not see "eye to eye" on fueling the KLX - They created the 2152 kit using a dead stock KLX - not even equipped with a slipon.. So what my dyno charts kept showing (leanness) was in direct conflict with their data.. You put a slipon on your KLX and you are off the DJ reservation. Add MCM and lidless and you might as well call Larry the Cable Guy for fueling help..

 

Both my brother and I have done the KLX300 jetting hop up
including the KDX200 snorkel, which has an opening area almost identical to that of the air boot between the carb and air box, thinking it isn't hurting things too much. I did a 40 pilot, drilled air jet and drilled slide, 125 main (at 900 ft elevation), and the N1TC needle on 2nd notch from top. Idle mix at 2.5 turns was adequate. He rode his before doing the last change, installing the Dial-A-Jet fuel adder from Thunder Products. He said it smoothed out the power delivery over the jetting done. I think he did a 128 main. I went with the leaner jet to bring in the Dial-A-Jet a bit more in the mix, per their recommendation.

I have about 35 years experience running the Dial-A-Jet, having them on my old Nighthawk S to smooth out a glitch in the jetting around 4000 rpm without having to remove and tear down the carbs. Have one on my KLX650, a notoriously lean jetted bike It has compensated for cutting the air box lid, going to a Vulcan big bore piston, and a full reverse cone megaphone Baja Designs pipe without adjusting anything. Works similar to the Mikuni power jet, but adds some air into the fuel mix. Well proven by Dick's Racing, DirtBike!, MXA and Motorcyclist in the work they've tested. The ATV and Snowmobile markets are much stronger on it, probably because the newer industries are more open to new products. Bike people seem so much more enamored with brass.

I've been over a range of 5000 ft and temps from 18-95 deg F without any noticeable issues on the 650. Still need to get out and about more with the 250 to see about the elevation and temp changes, but it carbs smooth pretty much all through the range.

 

Did some testing this afternoon with the airbox lid on and off. Last night I had it off, had VERY noticeable power increase, arm jerking acceleration, I would say. This afternoon, made another quick run, same hard, strong pull.

Decided to put the lid back, and despite the 20+ quarter inch holes I have drilled in the lid with stock snorkle, there was no comparison. Bike still ran OK, no noticable sputtering or big flat spots, but the arm-jerking pull was gone. I may try completely removing the snorkle-- that plus the extra drilled holes might be as good as pulling the lid, while possibly reducing the airbox noise a little.

KLXster, Perhaps I will try a couple sizes up main. I definitely want to try 3N on the needle, as right now the low to mids are quite good, but WOT brings a definite increased rush of power. If the main is still a bit lean, as you believe, yet WOT pulls so hard, its very possible that the midrange could use a little more fuel as well. Got hold of a 7/64 bit today as well, will probably break down and drill the slide.

The incoming baffle is yet another variable thrown in the mix. Ill be glad when I get it as good as I think it will get so I can button it up and start riding and stop tinkering.

Thanks for the help and responses guys, sorry to go OT a bit as the last few posts arent really MCM related.

 

Yep, lidless running gets the biggy power potential.. But right now your small main jet really requires the lid sans snorkel. Until you drill your slide, pull the lid, and go with at least a K148, you're not going to get the low and mid fueled correctly for max power.. That stock spring + stock lift hole just won't allow it.. The KLX will run perfectly fine with a "less than optimal" fueling curve - You have a taste of what happens as you approach optimal fueling.. A K148-K152 will extend that hard pull up over 9K rpm before slacking off into over-rev.. Once done, you'll be running the N1TC on 2N or 1N - I suspect better low/mid power could be found with 1N instead of 2N on a non-MCM application.. Your dyno-butt will decide..

 

Couple things on and off topic.

First on topic-- KLXster, I read when you first did the mod you had some audible chattering in the engine, but you were sure you hadnt dropped anything in it. This concerned you. I never did see if you posted a solution or reason behind it. What did you find?

In your honest opinion, do you think the MCM is worth the time and potential troubles that one might run into doing it? Also, do you really think it increases peak HP at all, or just moves it into a more usable range? In any case, Im getting weary of tinkering and am just ready to ride. Ill def wait till I finalize my jetting/exhaust clearance check time before touching the cams in either case.



Second, off-topic:

I drilled the slide with a 7/64 bit AND dropped the needle to 3N yesterday, as well as installing the 1" DG baffle.

Bike still runs good, hard pull might even kick in a bit earlier in the RPM, but I do feel a rich spot around 5000 to 5500. I think Ill probably have to go back to 2N, but I didnt have much time at all to test, so Ill probably leave it till I get my new jets. I have a 145 and a 148 jet coming in soon.

BTW I removed and cut the intake screen on my bike, not real sure if that really makes a difference, but one thing I can say is that it is a REAL PITA!

I understand that upping the mains can have an effect on the midrange even if the needle is not touched. Im guessing the 145 or 148 (damn Im scared of that 148, especially with the hottest time of the year coming upon us) will help the entire range a little even at 2N.

KLXster, any feedback is appreciated.

 

Yes, I did have a scary chatter right after buttoning up the MCM. Good research Josh. It was the cam chain tensioner. I backed off on the tensioners' screw and the chatter went away. It is possible that I did not reset the tensioner properly before reinstallation.. No damage was done and my dyno chart last week shows 23.6hp.. My bike is finally "broken in"..

I did the MCM as my very first mod on a brand new bike - I know how much power it adds, it's BIG powah. But I can't prove it with a Dyno chart. What I can tell you is that the MCM creates cam timings that serve up increased power to the entire RPM range. While the increased TRQ ramp-up is quite noticeable, the increased overlap of the intake/exhaust valves carries the biggy power out to the very top end. Your own research comparing the Mojave timing is very significant in validating the basic tenet of the MCM. Look into the effects of increasing valve overlap on performance - it's an ancient subject.

Should you do it..lol.. It's this question that has bloated this poor thread for years.. So here you go - MCM works, very noticeable difference. For some it is a simple 1-2 hour project. For others, its' impossible. Members delude themselves with all make and manner of criticism and questioning in order to personally justify not doing this scary MCM mod. And that's actually ok, I don't have a problem with folks suffering that delusion if it keeps someone from destroying their engine with a flawed MCM mod.. If you CAN do it, do it - you'll never regret it, you'll never look back.

You got some skills with CVK fueling. Going 3N after drilling indicates you're going for a significant enrichening of the low/mid with your smallish main jet. You went too far but hey, you took a shot.. I surmise non-MCM wants a low/mid AFR in the 13-13.5:1 range @ WOT.

You know the N1TC is short. It'll overfuel the hell outta the low/mid even with a small main jet. Overfueling kills TRQ production even though the bike will usually run perfectly fine.. Main jet selection affects fueling across the board once off idle. Based off my testing results and knowledge, your best power solution should be lidless+K148+N1TC on 1N or 2N. I'd try 1N first due to the "quiet tip"restriction you're putting in your pipe. However, my testing also shows the KLX will run perfectly "fine" with all kinds of crazy fueling curves - so if you "go it alone" with your setup, it'll probably run ok..