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 klx 450 jetting. Brisbane 
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TRAIL HACK

Joined: Wed 23 Jun, 2010 9:11 pm
Posts: 84
Post klx 450 jetting. Brisbane
Hey guys just wanted to start a thread on the klx 450 jetting here in Brisbane.
Im running standard motor with air box snorkel removed.
FMF 4.1 ti exhaust with standard klx header. just installed r&d powerpump setup to equivalent of a 40 leakjet. with 50 leakjet had bog from idle to wot.
About to install an fmf powerbomb header.
There was two issues i was having. Initially i had a 170 main jet. However under wide open throttle there appearred to be a stutter. It would run clean then die out like it was starving for fuel then run clean again. So i figured it was running lean. went to a 180 mainjet and from #1 to pos #3 on the needle problem solved. Or so i thought. was fine for a while then Took it out in the fresh cultivation high load wide open. stutter is back at wot. I have two theories on this. One is that the absense of a main air jet (which i beleive is equal to around a 200) is creating a lean condtion at wot. The other is that the oem manifold is operating outside of it design charicteristics at that rpm (overrev). (long skinner header high air speed down low looses effieceiency up high.) Hence the reason for purchase of the powerbomb header.) I'll list my current jetting and if anyone can spot anything they think or preferably know is way out please comment. My suspicion is to put a 175-180 main air jet (none currently installed equal to a 200) then drop the mainjet back to around a 170-175 ( currently 180) and see if that clears it up. I know there are a couple of klx450's floating around on this forum very interesed to see what you have to say....

(as a side note i am also suspicous on the klx clutch. one of the trailrider mags is currently doing a review of the 450. One of there articles noted to remove the small shim behind the clutch cover. Apparently there is 2 shims. remove the small one. I dont want to change too many things at once so just working through one by one till i have a win.) Although i think jetting is the main issue i have.

leak jet - R&D powerpump set at 1-1/2 turns out equivelant to a 40 leakjet.
Starterjet-55
pilot jet- 45
pilot air jet- 100
mainjet-180
MAJ Not installed = 200 (i believe stock from Kawi)
Mixutre screw 1-3/4 turns out
Needle- NCVU #3 position from top

Ill post a link to a couple of intersting points.

http://www.thumpertalk.com/forum/archiv ... 06890.html
http://www.thumperfaq.com/jetting.htm

Also has anyone installed a highcomp 13.1 piston in there klx. what were the effects. Did it make the power unusable in the trails.

Gotta thank Shane-o for his help so far


Wed 25 May, 2011 12:10 pm
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TRAIL GURU
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Joined: Sat 26 Sep, 2009 11:00 am
Posts: 841
Post Re: klx 450 jetting. Brisbane
Pm LMB, between him and Wildhorse they would have the advice your looking for, both are well modded klx's. (The PM might get a earlier response)

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Wed 25 May, 2011 1:58 pm
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Post Re: klx 450 jetting. Brisbane
Hey Nitro,

I am running a DEP powerbomb header with a DEP S7 silencer and a hi comp piston. Found the klx hard to jet and am still not 100% happy.
Currently running #45 pilot, #170 main with a JD blue needle, 'O' ring mod on accel pump. If the bike is loading up then clearing out sounds to rich to me, shouldn't need any bigger then a 170 main jet so start there and look at the needle. The standard needle is to lean and maybe give you a bad transition onto main. Will see if I've got some spare ones for you to try. Left MAJ standard. I still have a splutter just of idle, only notice when crusing firetrail at low throttle, never bogs though so put up with it. Seems to be a traight of the powerbomb headers.

Am running a STM slipper clutch so can't help you there.

Are you running the full R&D power bowl or just the accel pump cover?

Wildhorse is running the R&D power bowl with full procircuit gp system, highcomp piston, stage 2 hotcams and head work. Same jetting specs as me but with a #38 pilot, adjust leak jet to stop bog and all good..


Mon 30 May, 2011 10:19 am
TRAIL PORN STAR
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Joined: Wed 15 Jul, 2009 12:27 pm
Posts: 3351
Post Re: klx 450 jetting. Brisbane
LMB how come you and Wildhorse picked the Klx 450 to do up with some goodies


Mon 30 May, 2011 6:27 pm
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TRAIL PORN STAR
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Joined: Sat 22 Aug, 2009 11:11 pm
Posts: 4013
Location: Brisbane
Post Re: klx 450 jetting. Brisbane
LMB from what dan and i discovered the KLX doens't have a Maj installed. and its MAj is like a 200 instead of a 150 something. that's where all its issues lay. and there jetting is way of for them to meet LAMS or some shit.

But ill let dan tell you what had to be done cause i cant be ******

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Mon 30 May, 2011 6:50 pm
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Post Re: klx 450 jetting. Brisbane
Yea ther jetted lean for ADR's, but the throttle stop and spare needle should be fitted by the dealer..


Mon 30 May, 2011 8:08 pm
TRAIL PORN STAR
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Joined: Sat 22 Aug, 2009 11:11 pm
Posts: 4013
Location: Brisbane
Post Re: klx 450 jetting. Brisbane
more rich since there is no MAJ. and the PAJ is a 100... Well rich in the top end and of the needle

Im 50% once Dan's got it sorted he'll share the specs.

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Mon 30 May, 2011 8:14 pm
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TRAIL HACK

Joined: Wed 23 Jun, 2010 9:11 pm
Posts: 84
Post Re: klx 450 jetting. Brisbane
Thanks for your post lmb.

When i got my bike it had a 170 main in it but would detonate at wide open under load. Thats why we went to a 180 which was heaps better but less power from 1/4 to 3/4 throttle. in saying that it was on the #1 postion on the standard needle. I went to number 3 when i change the main. Ive done a fair bit of reading and im confident the Main air jet issue certainly contributes to the lean at wide open. There is no thread in the MAJ circuit to install one either. So i got a fitter at work to help come up with a solution. I drilled out the maj (cast into body 2mm) to 3mm then stepped the hole out. We then machined and pressed in a brass bush and drilled and tapped it to suit a 393 air jet that comes standard in the MX bikes. I have a range to try. (no drilling or soldering jets neccesary which is a pet hate of mine from when i worked on drag cars, (top fuel, Supercharged outlaws) From what i understand a 200 main air jet is fine when the bike has the standard cork (exhaust) and choked up air box. (and has to meet adr) but with the snorkel removed and a fmf 4.1 installed it created some drama for me. So when they breath better the lack of restriction in the main air jet creates a lean out at wide open with a 200 MAJ. I spoke to a couple of people about the jd kit and there thought was the jd kits needles were to rich for australia. Again just talk i have not tried it or have any proof. Dan from show and go suggested i try the EMR needle which i now have possesion of but he hasnt tried one in a klx just mentioned he has a lot of succes with them.

Also check the timing of the accelerator pump. mine was coming in way late creating lean bog. I think from what i believe to be right your 170 main will be spot on with about a 170 main air jet as well. Its hard to find info on what air jets to run with what main jet but one theory is that for desert racing you minus 10% of the main jet size then thats is your MAJ size. for better than average riders you you use about the same main jet to main air jet size and for average weekend jo's you add 10%. So if i was desert racing with a 170 main i would use a 153 or 150 main air jet. I spoke to a couple of MX mechanics and they wondered what the hell i was talking about with main air jets. Why? because they all run 160 to 180 from standard. From what i believe to be true. so they just concentrate on primary, mains, and needle position. They dont deal much with bikes that had to meet adr.

for primary jets they say 45MJ/100PAJ 42MJ/85PAJ. I can send you the link if you want to read more.

I have a 13:1 woosner pistpn ready to go in it, but i want to have a play with jetting a bit more 1: to get it right 2: to learn from it.

I just installed the r&d powerpump not the powerbowl and the r&d flex jet. I tried an alloy one an it was vibrating loose on the stand. So i didnt risk running it. I agree that just adjusting leakjets would have got me there eventually however its a pain in the ass pulling the carby out all the time so i bit the bullet and bought one.

Dont take too much i what i have said here as truth cause i have yet to prove it, but is simply the path i am going to follow and see if i can make it work on my bike. Ill be sure to post any findings. Shane-o and i were going to try and plan a day where we muck around with jetting for a bit of an experiment. if you wanted to try some stuff maybe you could join us. We just have to find some land to wind them out and access to a hose to clean them down before pulling carbies apart.

Its very hard to find good info on trail bike tuning but Shane-o gave me some awesome links that have help formed what i have just posted. Hopefully be running sweet soon thanks heaps for your input as well.

Dan

Shane-o - TPS voltage is .719 at idle. different to the WR'S but if it try's to advance the ignition curve to early it may cause some drama down low... Thinking, thinking, thinking..... Got a factory workshop manual on its way... Hope it shed's some light....


Mon 30 May, 2011 10:31 pm
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TRAIL HACK

Joined: Wed 23 Jun, 2010 9:11 pm
Posts: 84
Post Re: klx 450 jetting. Brisbane
Shane-O wrote:
more rich since there is no MAJ. and the PAJ is a 100... Well rich in the top end and of the needle

Im 50% once Dan's got it sorted he'll share the specs.


Larger air jet=more lean out

200 air jet = way lean... @WOT


Mon 30 May, 2011 10:33 pm
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TRAIL HACK

Joined: Wed 23 Jun, 2010 9:11 pm
Posts: 84
Post Re: klx 450 jetting. Brisbane
LMB

Who did the port wok on your cylinder head? Im thinking of getting the seats blended in and casting marks removed. I have had some movement on the intakes of late as well. Keeping a close eye on them.


Mon 30 May, 2011 10:44 pm
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Post Re: klx 450 jetting. Brisbane
I just had a mate do my head work, blended the seats, cleaned up the bowl, removed the cast marks, modified the guides short turn and divider. Replaced valves at 110 hours as they where had it might have sucked a bit of dirt. Bought KX 450 S/S valves and lathed the down to fit as I couldn't get klx s/s valves at the time.

I would fit your new header, fit a 180 MAJ, 170 main and try some different needles first then fine tune with maj if needed. My bike will happily run from 1/4 through to limiter with no hesitation with no maj. I don't think you will get it right using std needle.

The high comp piston will give you alot more mid range punch added with the powerbomb header can make them a bit of a handfull but lots of fun!! With the head mods bike will now make power through to the limiter instead of dying off, nothing like wildhorses though with the hot cams! I can pull a bike length on him out of a 2-3 gear corner but by the time you grab 4th he's going past..

Let me know a day and I can organise a place near Beerburrum.


Tue 31 May, 2011 8:41 am
Post Re: klx 450 jetting. Brisbane
(as a side note i am also suspicous on the klx clutch. one of the trailrider mags is currently doing a review of the 450. One of there articles noted to remove the small shim behind the clutch cover. Apparently there is 2 shims. remove the small one. I dont want to change too many things at once so just working through one by one till i have a win.) Although i think jetting is the main issue i have.


Remove the clutch pack should only be 1 washer between pack and basket, some had 2.
http://www.dirtbikeworld.net/forum/show ... hp?t=51733


Tue 31 May, 2011 9:30 am
TRAIL HACK

Joined: Wed 23 Jun, 2010 9:11 pm
Posts: 84
Post Re: klx 450 jetting. Brisbane
tried a couple of things today. 180 main 180 air, powerbomb header standard needle. Lazy power, lazy top end, just a bit of a pig really.

Went to 170 main 180 main air jet powerbomb header standard needle picked up top end power but couldnt hold it on for long. was running out of track fast. mid range felt better. Bottom end bit better but still lazy. felt lean.

Put in EMR needle, with above jetting. holy shit........... first gear would instantly go to the limiter if traction was even slightly compromised. 2nd gear pulled like a freight train that nearlly pulled the arms out of my shoulders third gear revved clean all the way up top. I really need to take it for a good ride now. the area i had to ride wasnt much. only about 200m of up and down hill with rocky technical stuff on the way in and out.

I think its more in the ball park now but need to take it for a good run out at beerburrum.... Anyone wanna come out tommorrow...... R&D powerpump and flex jet really make it easy...


Tue 31 May, 2011 2:06 pm
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Post Re: klx 450 jetting. Brisbane
occasion14 Now just throw the high comp in, tidy up the head and you'll be a happy man!!


Tue 31 May, 2011 6:55 pm

Joined: Mon 12 Dec, 2011 7:29 am
Posts: 1
Post Re: klx 450 jetting. Brisbane
Hey guys,

Just wondering where you got your main needles from? Is there a company here in OZ that can help us out?

I too have been toying with the carb on my John Deere.

At the moment, after a head rebuild I have;

#45 Pilot
#150 Main
Needle clip 3 down from the top

FMF power bomb/pro circuit slip on

Snorkel removed

If anyone wants to give me a couple of ideas that would be great.

Currently,
Its not too bad, still fades a bit top end and bogs a little off idle but is pretty torquey low to mid range then runs out of breath a little up top.


Mainly I'm after a clean crisp bottom end, the top end isn't too much of a concern for me as I ride mainly single tracks.

let us know what you think.


Cheers,


Troy


Mon 12 Dec, 2011 7:53 am
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