Dialing back on the HP, focusing on torque under 6.5k
#32
06-26-2017, 08:28 AM
Greetings all. The info on this forum about the MCM and Klxster's tuning work led me to purchase a Canadian 2006 KLX250s. A very clean low mile bike. The seller had a very steep paved driveway and the bike almost needed clutch work to get up. On the 50 mile ride home I found the bike had trouble holding 6th on any kind of hill, and BC is full of hills.
I did the mcm mod a few days later and immediately felt an improvement in low to mid revs. I then got a DJ2206 kit and installed the needle N1,dj132, air screw 3.5 , stock pilot, lidless and punched some holes in the stock muffler. I'm at 1500'asl and took it up to 6000' where we ran into snow.That setup ran cleanly at all revs and throttle openings. I noted that on the highway the bike maintained the speed limit with much reduced throttle opening. The bike could now easily hold top gear on most grades.
The 2206 kit only goes up to 132 so I ordered 134 136 and 138. The 134 and 136 are back ordered so I installed the dj138 and punch out the muffler three baffles deep. Only one ride so far, up to 5000' and it ran good, more power overall but it is possible that will be to rich at 7000' as summer warms up. The bike will lift the front a few inches at 4000rpm no clutch no pull.Not as strong as Klxster's. I think I'll try a 38 pilot and I have a slip-on on order.
Even if I don't get further gains from the slip-on an further tweeks I'm pleased with the gains so far, and I would like to thank Klxster for his efforts in testing and chronicling...........invaluable.
ps My power is up and the MPG is holding the same, the bike is so much stronger at 1/4 throttle.
I did the mcm mod a few days later and immediately felt an improvement in low to mid revs. I then got a DJ2206 kit and installed the needle N1,dj132, air screw 3.5 , stock pilot, lidless and punched some holes in the stock muffler. I'm at 1500'asl and took it up to 6000' where we ran into snow.That setup ran cleanly at all revs and throttle openings. I noted that on the highway the bike maintained the speed limit with much reduced throttle opening. The bike could now easily hold top gear on most grades.
The 2206 kit only goes up to 132 so I ordered 134 136 and 138. The 134 and 136 are back ordered so I installed the dj138 and punch out the muffler three baffles deep. Only one ride so far, up to 5000' and it ran good, more power overall but it is possible that will be to rich at 7000' as summer warms up. The bike will lift the front a few inches at 4000rpm no clutch no pull.Not as strong as Klxster's. I think I'll try a 38 pilot and I have a slip-on on order.
Even if I don't get further gains from the slip-on an further tweeks I'm pleased with the gains so far, and I would like to thank Klxster for his efforts in testing and chronicling...........invaluable.
ps My power is up and the MPG is holding the same, the bike is so much stronger at 1/4 throttle.
#33
06-26-2017, 02:09 PM
Howlinsage, the altitude correction chart I use only goes to 6k, but that's ok - the CVK will quite easily "auto compensate" for +1k (to 7000 ft ASL) ..
BTW: It cannot compensate at all for "lower altitudes than jetted for. Given an altitude that you've jetted for, you can go higher with your bike, but not much lower before top end leanness begins.
Here is the chart - pick a Alt and Temp box. For your bikes' setup (DJ140/1N), multiply the correction factor in the box to 141.41 for the corrected jet size ( always try to round down, not up, however a calculated 131.5 should logically round to a 132..).
Main Jet Correction
Since you must choose an altitude AND a temp, I'll call it "A/T"..
Usually, you just jet for the A/T you spend most of your time at. However, in a worst case senario where jetting needs to work "ok" over a given altitude spread, there is hope.
So, lets say you regularly ride from a low alt to a high alt, and that there is no predominate alt to target with jetting. See below.
Jet for 1k-2K above your starting A/T - choose the value that gets you to the halfway point in your alt spread, but never exceed a 2K correction.
In your case, (1.5k - 6k) the spread is 6k-1.5k=4.5k. So you use the max 2k correction. And that would be 1500 ft + 2000 ft = 3500 ft..
So choose an A/T box for 3500 ft and calc the jet size. Yes, you have to interpolate... E.G. 3500 @ 68° ≈ .96
So 141.41 x .96 = DJ136
For extreme spreads, like 1500 ft to 10K ft, you have to calc the 1500 A/T main jet, the 10K A/T main jet, and choose a jet size in between.
BTW, getting a Kouba fuel screw would allow you to quickly readjust your pilot system for changing altitudes - giving you a perfect idle and low throttle opening performance at any altitude..
BTW: It cannot compensate at all for "lower altitudes than jetted for. Given an altitude that you've jetted for, you can go higher with your bike, but not much lower before top end leanness begins.
Here is the chart - pick a Alt and Temp box. For your bikes' setup (DJ140/1N), multiply the correction factor in the box to 141.41 for the corrected jet size ( always try to round down, not up, however a calculated 131.5 should logically round to a 132..).
Main Jet Correction
Since you must choose an altitude AND a temp, I'll call it "A/T"..
Usually, you just jet for the A/T you spend most of your time at. However, in a worst case senario where jetting needs to work "ok" over a given altitude spread, there is hope.
So, lets say you regularly ride from a low alt to a high alt, and that there is no predominate alt to target with jetting. See below.
Jet for 1k-2K above your starting A/T - choose the value that gets you to the halfway point in your alt spread, but never exceed a 2K correction.
In your case, (1.5k - 6k) the spread is 6k-1.5k=4.5k. So you use the max 2k correction. And that would be 1500 ft + 2000 ft = 3500 ft..
So choose an A/T box for 3500 ft and calc the jet size. Yes, you have to interpolate... E.G. 3500 @ 68° ≈ .96
So 141.41 x .96 = DJ136
For extreme spreads, like 1500 ft to 10K ft, you have to calc the 1500 A/T main jet, the 10K A/T main jet, and choose a jet size in between.
BTW, getting a Kouba fuel screw would allow you to quickly readjust your pilot system for changing altitudes - giving you a perfect idle and low throttle opening performance at any altitude..
Last edited by Klxster; 06-26-2017 at 02:25 PM.
#34
06-26-2017, 04:31 PM
Thanks for the reply. I guessed I would end up at dj136, good for 1500' to 6000'+. If I went down to sea level ,I assume a loss in power but nothing bad would happen unlike a 2 stroke that might burn up. Is that correct?
I will order the Koubo screw. For my setup, which pilot would be better 38 or 40? I'd like a tad more grunt off idle.
My neighbor has a gen2 KLX250s and is keen to mod but doesn,t want to wrench.
I have offered to help.
I have seen here where some Canadian bikes have different carb parts. I checked a parts fiche and at least some years of gen 2 had different needles and and needle holders but the same slider and spring. For his bike should he order the 2006 needle holder and follow my tuning? We ride the same terrain.
I will order the Koubo screw. For my setup, which pilot would be better 38 or 40? I'd like a tad more grunt off idle.
My neighbor has a gen2 KLX250s and is keen to mod but doesn,t want to wrench.
I have offered to help.
I have seen here where some Canadian bikes have different carb parts. I checked a parts fiche and at least some years of gen 2 had different needles and and needle holders but the same slider and spring. For his bike should he order the 2006 needle holder and follow my tuning? We ride the same terrain.
#35
06-26-2017, 06:29 PM
Yes, all is well with the DJ136 at sea level.. Summer temps @ 7000 ASL might be a little rich..lol
#40 + Kouba = total control + the transition fueling MCM likes..
Well "needle holder" .. I guess you mean the little white plastic do-hicky.. lol
The goal of the DJ needle washers is to perfectly (or near) mimic the thickness of the stock needles' "retainer". You must do this in order to allow the holder to stabilize and secure the needle properly. It would stand to reason that different needle holders would be required if a given needle had a different thickness retainer..? As long as the DJ washers are used properly, as noted above, there should be no problems with a Dj needle in your buds bike..
Geo has stated that his Canuck CVK carries a different needle, needle jet, emulsion tube, etc.. If your buds bike has this "condition", it is unlikely that your setup will work the same as it does for you.. If this is the case, I think I know that simply putting in one of your leaner DJ jets will fix it..
Anyway, do-up his bike exactly like you've done yours.. If your DJ136 comes in before his carb parts, do-up his silencer, MCM it, pull his lid, and install your DJ138 into his carb.. If yall can't wait, do-him-up and install your Dj132..
#40 + Kouba = total control + the transition fueling MCM likes..
Well "needle holder" .. I guess you mean the little white plastic do-hicky.. lol
The goal of the DJ needle washers is to perfectly (or near) mimic the thickness of the stock needles' "retainer". You must do this in order to allow the holder to stabilize and secure the needle properly. It would stand to reason that different needle holders would be required if a given needle had a different thickness retainer..? As long as the DJ washers are used properly, as noted above, there should be no problems with a Dj needle in your buds bike..
Geo has stated that his Canuck CVK carries a different needle, needle jet, emulsion tube, etc.. If your buds bike has this "condition", it is unlikely that your setup will work the same as it does for you.. If this is the case, I think I know that simply putting in one of your leaner DJ jets will fix it..
Anyway, do-up his bike exactly like you've done yours.. If your DJ136 comes in before his carb parts, do-up his silencer, MCM it, pull his lid, and install your DJ138 into his carb.. If yall can't wait, do-him-up and install your Dj132..
Last edited by Klxster; 06-26-2017 at 06:32 PM.
#36
06-26-2017, 07:17 PM
OK 40 pilot it is. The kawasaki fiche called the emulsion tube a needle jet holder. My carb knowledge is minimal but growing. When his bike is done up I'll report the result.
As an aside, I never rode his bike but I had the impression his bike stock for stock ran a little stronger.
As an aside, I never rode his bike but I had the impression his bike stock for stock ran a little stronger.
#37
06-26-2017, 08:14 PM
You can acquire as much or as little CVK knowledge as you want - at least partly by reading my "stuff" to learn how the internal parts interact to fuel the engine.. Or just stay with what is already known to work for max performance.. Geo points out that many other bikes use CVK's - I've never "gone over" to other forums to see what others have learned or know.. At this point, I probably know all I need to about our particular CVK's and I have no need to "crusade" in other bike forums..
Anyway, if your buds' bike has a different emulsion tube, it may not respond well to the CVK setup you are using. Add in a different needle jet and possibly MAJ (main air jet) and you've got real problems.. The MAJ is not replaceable, and if it is different, it would be due to the different emulsion tube - as they must interact properly. After his MCM and silencer mods are done, I think I would just go with the DN0352 needle @ 1N (2206 kit needle) , and one of your biggy DJ jets and check the performance. If it runs horrible, a DJ132 or DJ128 main jet could fix it.. This means his emulsion tube and MAJ create a far richer AFR than the other, I guess US spec, parts..
BTW, if you can verify that his bike has a different needle jet than US spec, he should buy the US spec needle jet.. A mismatch of needle and needle jet can't be worked around. And all needle fueled ops will be affected..
Anyway, if your buds' bike has a different emulsion tube, it may not respond well to the CVK setup you are using. Add in a different needle jet and possibly MAJ (main air jet) and you've got real problems.. The MAJ is not replaceable, and if it is different, it would be due to the different emulsion tube - as they must interact properly. After his MCM and silencer mods are done, I think I would just go with the DN0352 needle @ 1N (2206 kit needle) , and one of your biggy DJ jets and check the performance. If it runs horrible, a DJ132 or DJ128 main jet could fix it.. This means his emulsion tube and MAJ create a far richer AFR than the other, I guess US spec, parts..
BTW, if you can verify that his bike has a different needle jet than US spec, he should buy the US spec needle jet.. A mismatch of needle and needle jet can't be worked around. And all needle fueled ops will be affected..
#38
06-27-2017, 03:08 AM
So about that stuttering.... It's happening. I tried spending alot of time between 5 and 6k and there seems to be a surge or something... feels like I'm dragging a rope. It's not all the time, but certainly isn't happening above or below 5-6k
#39
06-27-2017, 08:51 AM
RHITB. '08 on had the NNLA set-up that is familiar here.
KLXster. 16.5 thou #50 MAJ. Needle jet (choke height and orifice size) are different part numbers between 300, '06 '07 CDN 250s, '08 and on North American 250s as well as emulsion tubes.
I had dynos available to me in he 70's and 80's when I was still in the biz. I used O2 wide band when EFI took over. In the end it was a help but fine tune was still reading plugs and piston and most importantly rider input.
The transition stutter (that I read so much about lol, hint, I had it) is a slight rich condition. More info on harley and scooter forums than you can shake a stick at lol. MCMing amplifies it by adding to the pressure threshhold at which the slide begins to rise. With MCM my slide begins to rise at 2000 to 2200 rpm and at stock timing it starts at 3200 to 3500 (with stock spring, drilled and standard vacuum hole made no difference here).
To prove this to myself after observing it on the bench and to try to cure it, I stretched a stock spring 3/8". This extra preload would hold rpm back a 2000 when applying light throttle on the bench. Not a stall because more throttle plate opening began the lift. With MCM the lift started with about 3/16th's to 1/4 throttle grip twist and with stock timing about 1/4 to 3/8th's twist, same stretched spring.
Interesting enough to me that I looked at my other 2 stock springs and there was an 1/8th" difference in overall length. Maybe overlooked sometimes but spring rate is very important on a slide controlled by it. Little bit makes a difference when you open that box.
To fix the stutter (3 different slides, 2 different cv carb bodies) at transition on MY BIKE with MCM required changing slide cutaway from .5 to 1.5 (approx, 8% more air in the cutaway range) and 1/4" added spring length). This changed the reaction rate in the field from a pop up wheely that ended as soon as it started to 60 to 90 feet of front wheel 1 foot high. Noticable, better control, FELT slower, but it wasn't lol.
Cam timing, who knows eh. Part numbers may be the same on the hard parts but things can change over the years with specs and manufacturer. MCM added spit back a higher rpm (I run dyed fuel off road and it is real easy to see when fuel goes to the wrong spots on a rejet lol) on MY BIKE and took away 1500 rpm (even if it is weak) of powerband up top but the little kick between 5000 and 8000 is fun. I should add I have stock exhaust 1.75 " outlet, stainless screen, with the last plate drilled three more times and spark arrestor left intact (live in wildfire country).
I only joined in because I researched this forum with the desire to make my new to me '07 250s (my plated CRF 450X is too much like cheating when out and about with my senior friends lol) the best it can be lol. I tried, with intense hope, that the easy way was the best way but it didn't work on MY BIKE. So for others out there, every bike is it's own so like mine your's may be different.
In the end MY BIKE works best with close to DJ's recommended lidless 300 set-up and the tweaks I needed to do to fine tune. Hopefully after I install the 300 this afternoon i can drop to clip 4.
On a side note, and speaking of cheating lol, I ordered a Chinese 300 kit (256.95 loonies to my door and 6 days delivery). It's not bad. Look for the one that has 299 stamped on the cylinder.
Piston is lower compression (good cause even the 250 has given me some knocks during testing with our fuel up here) , 8 gr lighter that OEM 300 but pin just about equals it out, same taper, fit is 1.9 thou. Rings good quality with good gap. Barrel casting is a little less finished externally but structurally sound and equal to OEM in dimensions. Machining on base is excellent, head surface has a bit of light milling chatter (probably fine but I lapped it anyway), honing is a little rough looking at it magnified, they should add to coolant flow to help with build up. Steaming hot water and soap wash is needed to get the bits out.
Gaskets are a no go (get OEM, work perfect). Besides fit a bit off, two coolant holes in the head gasket are punched out wrong and would cause an overheat due to restriction. Too bad because the quality and material would of been fine.
All in all a darn good deal for up here.
KLXster. 16.5 thou #50 MAJ. Needle jet (choke height and orifice size) are different part numbers between 300, '06 '07 CDN 250s, '08 and on North American 250s as well as emulsion tubes.
I had dynos available to me in he 70's and 80's when I was still in the biz. I used O2 wide band when EFI took over. In the end it was a help but fine tune was still reading plugs and piston and most importantly rider input.
The transition stutter (that I read so much about lol, hint, I had it) is a slight rich condition. More info on harley and scooter forums than you can shake a stick at lol. MCMing amplifies it by adding to the pressure threshhold at which the slide begins to rise. With MCM my slide begins to rise at 2000 to 2200 rpm and at stock timing it starts at 3200 to 3500 (with stock spring, drilled and standard vacuum hole made no difference here).
To prove this to myself after observing it on the bench and to try to cure it, I stretched a stock spring 3/8". This extra preload would hold rpm back a 2000 when applying light throttle on the bench. Not a stall because more throttle plate opening began the lift. With MCM the lift started with about 3/16th's to 1/4 throttle grip twist and with stock timing about 1/4 to 3/8th's twist, same stretched spring.
Interesting enough to me that I looked at my other 2 stock springs and there was an 1/8th" difference in overall length. Maybe overlooked sometimes but spring rate is very important on a slide controlled by it. Little bit makes a difference when you open that box.
To fix the stutter (3 different slides, 2 different cv carb bodies) at transition on MY BIKE with MCM required changing slide cutaway from .5 to 1.5 (approx, 8% more air in the cutaway range) and 1/4" added spring length). This changed the reaction rate in the field from a pop up wheely that ended as soon as it started to 60 to 90 feet of front wheel 1 foot high. Noticable, better control, FELT slower, but it wasn't lol.
Cam timing, who knows eh. Part numbers may be the same on the hard parts but things can change over the years with specs and manufacturer. MCM added spit back a higher rpm (I run dyed fuel off road and it is real easy to see when fuel goes to the wrong spots on a rejet lol) on MY BIKE and took away 1500 rpm (even if it is weak) of powerband up top but the little kick between 5000 and 8000 is fun. I should add I have stock exhaust 1.75 " outlet, stainless screen, with the last plate drilled three more times and spark arrestor left intact (live in wildfire country).
I only joined in because I researched this forum with the desire to make my new to me '07 250s (my plated CRF 450X is too much like cheating when out and about with my senior friends lol) the best it can be lol. I tried, with intense hope, that the easy way was the best way but it didn't work on MY BIKE. So for others out there, every bike is it's own so like mine your's may be different.
In the end MY BIKE works best with close to DJ's recommended lidless 300 set-up and the tweaks I needed to do to fine tune. Hopefully after I install the 300 this afternoon i can drop to clip 4.
On a side note, and speaking of cheating lol, I ordered a Chinese 300 kit (256.95 loonies to my door and 6 days delivery). It's not bad. Look for the one that has 299 stamped on the cylinder.
Piston is lower compression (good cause even the 250 has given me some knocks during testing with our fuel up here) , 8 gr lighter that OEM 300 but pin just about equals it out, same taper, fit is 1.9 thou. Rings good quality with good gap. Barrel casting is a little less finished externally but structurally sound and equal to OEM in dimensions. Machining on base is excellent, head surface has a bit of light milling chatter (probably fine but I lapped it anyway), honing is a little rough looking at it magnified, they should add to coolant flow to help with build up. Steaming hot water and soap wash is needed to get the bits out.
Gaskets are a no go (get OEM, work perfect). Besides fit a bit off, two coolant holes in the head gasket are punched out wrong and would cause an overheat due to restriction. Too bad because the quality and material would of been fine.
All in all a darn good deal for up here.