KLX250S vs. KLX300 carb
#11
09-03-2013, 05:10 PM
Join Date: Oct 2009
Location: Sonoran Desert, Arizona
Posts: 262
I would like to see some of the jetting people ended up with if they will chime in. I'm not a novice on jetting but this one has been more difficult than most to jet.
I'm running a KLX300 header and muffler with the tip in place and a K&N filter, KDX200 snorkel.
I remember seeing a couple of pages of jetting records but can't seem to find it now..... That might give me an idea of the next move if someone can point me to it. It was actually for the 250 motor I think but might be of help.
I'm running a KLX300 header and muffler with the tip in place and a K&N filter, KDX200 snorkel.
I remember seeing a couple of pages of jetting records but can't seem to find it now..... That might give me an idea of the next move if someone can point me to it. It was actually for the 250 motor I think but might be of help.
IMHO intake velocity is critical for proper jetting, particularly with CV carbs. Changes to the intake tract, i.e. removing the air box lid, greatly affect the intake velocity, unfortunately in an unknown manner. A tuner may be able to increase power at some particular throttle opening, but that increase will most likely be offset by a decrease at some other opening. What usually happens is that the air box cover is removed, or a larger snorkel is employed. Then the main jet size in increased until the bike runs reasonable well at full throttle. The intake velocity (without the lid, etc.) is now not optimal at lesser throttle openings and driveability goes down the toilet. To try to make the engine run at least half way right the "tuner" has to resort to excessive rich pilot screw adjustments and rich needle settings to cover up the flat spots and hesitation caused by the erratic intake velocities.
I know I'll receive some heat for those comments. Blast away.
For what it's worth, here's my setup:
351cc.
Thermo-bob (consistent engine temperatures allow consistent jetting).
300 muffler with custom tip.
Unifilter (or Twin air, don't remember).
OEM snorkel.
120 main jet.
300 carb emulsion tube.
300 carb slide.
Mixture screw 1 3/8 turns
These settings probably won't work for others. However they work very well on my bike. It runs like a striped *** ape (seen any of those lately?). The throttle response is clean and crisp at all throttle openings with no hesitation or surging. My mileage generally is 72-75 mpg.
Good luck with your tuning.
Ron
Last edited by Ranger Ron; 09-03-2013 at 05:24 PM.
#12
09-03-2013, 07:03 PM
Thanks Ranger Ron, good info.
I changed to the KLX300 header and muffler and to the KDX snorkel while the bike was still a 250 and each made a significant increase in the motors ability to rev into the higher rpms. Before those changes I had gone to the stock needle and 118 main from the Dynojet Stage 1 needle setting and larger main, I forget which DJ main it was but at my altitude it was so rich it blubbered.
It ran nicely with the 118 main and stock needle shimmed.040"
When the 330 kit was installed it had a bad lean surging as described in my previous posts. It pulled good wide open and I went up several main jet sizes trying to stop the surge to no avail with the larger mains and the needle in notch 4. Hoping in notch 5 it will run properly but haven't been able to test ride it yet. I may need to go to the emulsion tube from the 300 carb to get it sorted out, I was wondering about the differences in that fuel circuit when I asked about the 300 carb.
I changed to the KLX300 header and muffler and to the KDX snorkel while the bike was still a 250 and each made a significant increase in the motors ability to rev into the higher rpms. Before those changes I had gone to the stock needle and 118 main from the Dynojet Stage 1 needle setting and larger main, I forget which DJ main it was but at my altitude it was so rich it blubbered.
It ran nicely with the 118 main and stock needle shimmed.040"
When the 330 kit was installed it had a bad lean surging as described in my previous posts. It pulled good wide open and I went up several main jet sizes trying to stop the surge to no avail with the larger mains and the needle in notch 4. Hoping in notch 5 it will run properly but haven't been able to test ride it yet. I may need to go to the emulsion tube from the 300 carb to get it sorted out, I was wondering about the differences in that fuel circuit when I asked about the 300 carb.
#13
09-03-2013, 08:55 PM
And Ron, please correct me if I'm wrong, but IIRC your main jet is a Keihin #120 jet, just a step up from the stock #118, and comparable to a dynojet #114 (https://www.kawasakiforums.com/forum...e2/#post442610).
Also, I thought you changed from the stock needle to the N1TC or something similar. Is that correct?
Also, I thought you changed from the stock needle to the N1TC or something similar. Is that correct?
I have no experience with the Dynojet needle for the KLX, so can't really comment about that. I will say that I have used Dynojet kits on other bikes and the kits were all ridiculously rich.
IMHO intake velocity is critical for proper jetting, particularly with CV carbs. Changes to the intake tract, i.e. removing the air box lid, greatly affect the intake velocity, unfortunately in an unknown manner. A tuner may be able to increase power at some particular throttle opening, but that increase will most likely be offset by a decrease at some other opening. What usually happens is that the air box cover is removed, or a larger snorkel is employed. Then the main jet size in increased until the bike runs reasonable well at full throttle. The intake velocity (without the lid, etc.) is now not optimal at lesser throttle openings and driveability goes down the toilet. To try to make the engine run at least half way right the "tuner" has to resort to excessive rich pilot screw adjustments and rich needle settings to cover up the flat spots and hesitation caused by the erratic intake velocities.
I know I'll receive some heat for those comments. Blast away.
For what it's worth, here's my setup:
351cc.
Thermo-bob (consistent engine temperatures allow consistent jetting).
300 muffler with custom tip.
Unifilter (or Twin air, don't remember).
OEM snorkel.
120 main jet.
300 carb emulsion tube.
300 carb slide.
Mixture screw 1 3/8 turns
These settings probably won't work for others. However they work very well on my bike. It runs like a striped *** ape (seen any of those lately?). The throttle response is clean and crisp at all throttle openings with no hesitation or surging. My mileage generally is 72-75 mpg.
Good luck with your tuning.
Ron
IMHO intake velocity is critical for proper jetting, particularly with CV carbs. Changes to the intake tract, i.e. removing the air box lid, greatly affect the intake velocity, unfortunately in an unknown manner. A tuner may be able to increase power at some particular throttle opening, but that increase will most likely be offset by a decrease at some other opening. What usually happens is that the air box cover is removed, or a larger snorkel is employed. Then the main jet size in increased until the bike runs reasonable well at full throttle. The intake velocity (without the lid, etc.) is now not optimal at lesser throttle openings and driveability goes down the toilet. To try to make the engine run at least half way right the "tuner" has to resort to excessive rich pilot screw adjustments and rich needle settings to cover up the flat spots and hesitation caused by the erratic intake velocities.
I know I'll receive some heat for those comments. Blast away.
For what it's worth, here's my setup:
351cc.
Thermo-bob (consistent engine temperatures allow consistent jetting).
300 muffler with custom tip.
Unifilter (or Twin air, don't remember).
OEM snorkel.
120 main jet.
300 carb emulsion tube.
300 carb slide.
Mixture screw 1 3/8 turns
These settings probably won't work for others. However they work very well on my bike. It runs like a striped *** ape (seen any of those lately?). The throttle response is clean and crisp at all throttle openings with no hesitation or surging. My mileage generally is 72-75 mpg.
Good luck with your tuning.
Ron
#14
09-04-2013, 01:32 AM
I just got in a test ride with the latest setup, 120 Keihin main, Dynojet needle in 5th slot, KDX200 snorkel, KLX300 header and muffler with stock tip, K&N filter. Temp about 55 degrees. Just a hint left of the lean surge at about 6500 - 7000 at about 3/4 throttle. Throttle response is excellent from any rpm or load or from any throttle opening. Just the lean surge is the only problem. Haven't been able to ride enough to check fuel mileage and not concerned about it until I get it running like it should.
I will next put the stock snorkel back in and see how it runs.
Ranger Ron, I see you are using the KLX300 emulsion tube and slide. Does the 300 slide have a different cutaway? What needle are you using? What clip? What elevation are you riding at with the 120 main?
The Kustom Kraft kit has a lower compression piston than Bill Blue's kits but I wanted to be able to run regular fuel rather than need premium. I also wanted the Nicasil cylinder coating of the Kustom Kraft kit. With the lower compression my tuning likely will be close but slightly different.
Thanks, L D
I will next put the stock snorkel back in and see how it runs.
Ranger Ron, I see you are using the KLX300 emulsion tube and slide. Does the 300 slide have a different cutaway? What needle are you using? What clip? What elevation are you riding at with the 120 main?
The Kustom Kraft kit has a lower compression piston than Bill Blue's kits but I wanted to be able to run regular fuel rather than need premium. I also wanted the Nicasil cylinder coating of the Kustom Kraft kit. With the lower compression my tuning likely will be close but slightly different.
Thanks, L D
I have no experience with the Dynojet needle for the KLX, so can't really comment about that. I will say that I have used Dynojet kits on other bikes and the kits were all ridiculously rich.
IMHO intake velocity is critical for proper jetting, particularly with CV carbs. Changes to the intake tract, i.e. removing the air box lid, greatly affect the intake velocity, unfortunately in an unknown manner. A tuner may be able to increase power at some particular throttle opening, but that increase will most likely be offset by a decrease at some other opening. What usually happens is that the air box cover is removed, or a larger snorkel is employed. Then the main jet size in increased until the bike runs reasonable well at full throttle. The intake velocity (without the lid, etc.) is now not optimal at lesser throttle openings and driveability goes down the toilet. To try to make the engine run at least half way right the "tuner" has to resort to excessive rich pilot screw adjustments and rich needle settings to cover up the flat spots and hesitation caused by the erratic intake velocities.
I know I'll receive some heat for those comments. Blast away.
For what it's worth, here's my setup:
351cc.
Thermo-bob (consistent engine temperatures allow consistent jetting).
300 muffler with custom tip.
Unifilter (or Twin air, don't remember).
OEM snorkel.
120 main jet.
300 carb emulsion tube.
300 carb slide.
Mixture screw 1 3/8 turns
These settings probably won't work for others. However they work very well on my bike. It runs like a striped *** ape (seen any of those lately?). The throttle response is clean and crisp at all throttle openings with no hesitation or surging. My mileage generally is 72-75 mpg.
Good luck with your tuning.
Ron
IMHO intake velocity is critical for proper jetting, particularly with CV carbs. Changes to the intake tract, i.e. removing the air box lid, greatly affect the intake velocity, unfortunately in an unknown manner. A tuner may be able to increase power at some particular throttle opening, but that increase will most likely be offset by a decrease at some other opening. What usually happens is that the air box cover is removed, or a larger snorkel is employed. Then the main jet size in increased until the bike runs reasonable well at full throttle. The intake velocity (without the lid, etc.) is now not optimal at lesser throttle openings and driveability goes down the toilet. To try to make the engine run at least half way right the "tuner" has to resort to excessive rich pilot screw adjustments and rich needle settings to cover up the flat spots and hesitation caused by the erratic intake velocities.
I know I'll receive some heat for those comments. Blast away.
For what it's worth, here's my setup:
351cc.
Thermo-bob (consistent engine temperatures allow consistent jetting).
300 muffler with custom tip.
Unifilter (or Twin air, don't remember).
OEM snorkel.
120 main jet.
300 carb emulsion tube.
300 carb slide.
Mixture screw 1 3/8 turns
These settings probably won't work for others. However they work very well on my bike. It runs like a striped *** ape (seen any of those lately?). The throttle response is clean and crisp at all throttle openings with no hesitation or surging. My mileage generally is 72-75 mpg.
Good luck with your tuning.
Ron
#15
09-04-2013, 01:47 AM
Since quite a few KLX riders with 250s or with 330 cc kits are using the NT1C needle and Ron is using the 300 carb emulsion tube and slide that is the reason I asked about the 250 vs. 300 carb at the beginning of this thread. By the time I bought a tube, needle and needle jet and maybe a slide I could buy a good used 300 carb and all that would already be there for about the same price it seems. And that carb is already set up closer to 330cc than the 250 carb.
Comments welcome......
Edit:
Okay, I just bought a KLX300 carb off eBay, will post results when I get it and install it......
Looking for a 100% power increase.... and 6th gear wheelies..... LOL!
L D
Comments welcome......
Edit:
Okay, I just bought a KLX300 carb off eBay, will post results when I get it and install it......
Looking for a 100% power increase.... and 6th gear wheelies..... LOL!
L D
Last edited by thinairflyer; 09-04-2013 at 03:08 AM.
#16
09-04-2013, 02:55 PM
The Kustom Kraft kit has a lower compression piston than Bill Blue's kits but I wanted to be able to run regular fuel rather than need premium. I also wanted the Nicasil cylinder coating of the Kustom Kraft kit. With the lower compression my tuning likely will be close but slightly different.
Thanks, L D
Thanks, L D
#17
09-04-2013, 03:01 PM
Join Date: Oct 2009
Location: Sonoran Desert, Arizona
Posts: 262
Oops. Forgot to mention the needle. 
It's the N1TC with the clip on the second groove (from the top). The main jet is a Keihin.
The slide on the 300 carb is a little different than the 250 slide. I'm going from (bad) memory here. It was over three years ago that I did the carb work. If I remember correctly, the slide had the same cutaway. I think it had the same lift hole as the 250 carb, but also had an additional lift hole in the back of the slide facing the engine. At least that's where I think it was.
I think the biggest bang for the buck is the emulsion tube. It has additional air bleed holes which allow for better mixing of gas with air which in turn provide for better atomization.
I've ridden the bike from 500' ASL to over 8500' with no issues at all other than the normal reduction of power at high altitude.
Ron
It's the N1TC with the clip on the second groove (from the top). The main jet is a Keihin.
The slide on the 300 carb is a little different than the 250 slide. I'm going from (bad) memory here. It was over three years ago that I did the carb work. If I remember correctly, the slide had the same cutaway. I think it had the same lift hole as the 250 carb, but also had an additional lift hole in the back of the slide facing the engine. At least that's where I think it was.
I think the biggest bang for the buck is the emulsion tube. It has additional air bleed holes which allow for better mixing of gas with air which in turn provide for better atomization.
I've ridden the bike from 500' ASL to over 8500' with no issues at all other than the normal reduction of power at high altitude.
Ron
#18
09-05-2013, 12:28 AM
Thanks Ron, I'll have to hope the 300 carb I bought hasn't been tampered with, it is a gamble but only paid $50 for it and in the pics it looks nice and clean. I'll be able to compare parts with the 250 carb I have to hopefully find a stock emulsion tube and needle...
#19
09-05-2013, 12:32 AM
IDRIDR, I can't hear well enough anymore to tell if an engine is pinging so opted for the std. compression ratio for that reason as well as peace of mind running regular fuel. I'll be 74 in a couple of months and age sure enough shows in my hearing.... :-)
L D
L D
#20
09-05-2013, 12:52 AM
Oops. Forgot to mention the needle.
It's the N1TC with the clip on the second groove (from the top). The main jet is a Keihin.
The slide on the 300 carb is a little different than the 250 slide. I'm going from (bad) memory here. It was over three years ago that I did the carb work. If I remember correctly, the slide had the same cutaway. I think it had the same lift hole as the 250 carb, but also had an additional lift hole in the back of the slide facing the engine. At least that's where I think it was.
I think the biggest bang for the buck is the emulsion tube. It has additional air bleed holes which allow for better mixing of gas with air which in turn provide for better atomization.
I've ridden the bike from 500' ASL to over 8500' with no issues at all other than the normal reduction of power at high altitude.
Ron
It's the N1TC with the clip on the second groove (from the top). The main jet is a Keihin.
The slide on the 300 carb is a little different than the 250 slide. I'm going from (bad) memory here. It was over three years ago that I did the carb work. If I remember correctly, the slide had the same cutaway. I think it had the same lift hole as the 250 carb, but also had an additional lift hole in the back of the slide facing the engine. At least that's where I think it was.
I think the biggest bang for the buck is the emulsion tube. It has additional air bleed holes which allow for better mixing of gas with air which in turn provide for better atomization.
I've ridden the bike from 500' ASL to over 8500' with no issues at all other than the normal reduction of power at high altitude.
Ron
But on a serious note, did you ever do much research with that fancy air/fuel/exhaust or whatever magic analyzer that you showed a pic of one time? It would have been interesting to see a comparison of some of the carb jetting issues between DJ, OEM needle, and the 300 needle...and yes...even your special little emulsion tube setup there.