KTM 520EXCessive power 4U

KTM400MAN · May 11, 2001

Hi James, Erik here again, as for the 9000ft altitude, I also have a ocem-r needle. Would that be a better choice than the stock needle or the ocem-n needle dropped down to a lean clip position?? Which portions on the various needles are richer and leaner? Do you still have a chart you can post that describes which needle sections are lean/rich by the letter-codes on the needles?? Your time and help are GREATLY appreciated. Thanks in advance, Erik

James Dean · May 12, 2001

A PICTURE IS WORTH A THOUSAND WORDS

Here is a graph of needle profiles. The EMN is 1 step leaner than EKN (to the right). The last letter "N" is for the straight diameter, which is 2.72mm.

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See: http://www.trailtech.net/redicart/needle1.jpg
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Bultaco290, Before you do anything else, clean your accelerator pump diaphram top & bottom and make sure it is squirting. Then move the clip down which lifts the needle up. This will be equivalent to shifting
the sloping line to the LEFT.

We don't have a spreadsheet for altitude changes. This is a relatively new setting for the KTM 400/520 and only a few are using it. Your feedback is appreciated.

James

azcourt · May 13, 2001

What effect will this have on mileage? I currently can go about 70 miles on my 520EXC.

James Dean · May 13, 2001

Mileage

My WR400 went 105 miles on 3 1/4 gallons which is no change from before. The needle saves turning the throttle as far. I will have a better idea about the 520's mileage after this weekend. My freind with the 520 will be doing a 75 mile ride with the EMN needle as described. Maybe both days... (Right Bob? :eek: )

wazzafrom oz · May 15, 2001

For James Dean, the Guru

James, the 520 exc imported into Australia, according to the book have the mixture screw out 2.5 turns. I have changed the jets as you have descibed and first started it without adjusting the mixture. Man it blew smoke, I then set it at 1.25 turns out and the smoke went. Now after a couple of rides the pipe is looking a little sooty, it goes better. Should I move the clip from 4 down to 3 down or try a different mixture screw setting. Humbly yours wazza from oz.:confused:

KTM400MAN · May 15, 2001

James Dean A.K.A. MR.JETTING

Please check your e-mail! Thanks Erik:D

James Dean · May 15, 2001

WAZZA

Both directions are worth checking. My friends 520EXC was at 1 1/4 from the factory, NOT EVEN CLOSE to what the manual said. Where was yours set when you got the bike?? Try turning the pilot screw in first, 1 - 1 1/4. Then consider the leaner clip #3.

If performance drops you will know which way was better. Fuels, conditions, and manufacturing tolerances make a general setting for everyone hard to pick. Sounds like you are close to getting it dialed in.

James

wazzafrom oz · May 18, 2001

Tried the mixture screw

James, Backed off the screw to one turn and the result was negitive, it didn't rev as before, lost it's urgency. Next I will move the clip to #3 and see how it goes. Cheers Wazza:(

drehwurm · May 18, 2001

OBEKN needle

Servus,

If you REALLY want an OB needle, Yamaha ( :think ) has a part # 5JG-14916-EN which is OBEKN.

I can happily report that those part# finally work in Europe also (had our own # before) and that Yamaha Europe is not sold out of those needles! Still, the need to play with my jetting isn't big enough yet ...

Michael

BENT · May 18, 2001

Jumped in and need help

Well, I've installed the Yamaha needle & a #168 main jet, the clip is 3 from the top. Now I have a flat spot off idle. It almost seems like my accel. pump is not working. The bike has 10-12 hours on it and I turned the carb sideways to install the parts. I only rode it a couple minutes so it may need time for the carb to recover from being dried out?
Is my clip settng correct?
I think it's lean?
Is there a simple fix?

drehwurm · May 18, 2001

Re: Jumped in and need help

Servus BENT,

I don't like the term ' turned the carb sideways' - I don't think this would be possible on my 520EXC without damaging or bending something. Especially check on the overflow tube which exits from the bottom of the float bowl. There is so little room between the fitting for the tube and the engine cases that it is easy to pinch the tube. If this tube is partially blocked or flow restricted the symptoms you describe can occur. If you are not sure, just remove the tube and ride again!

The carb can NOT dry out in such a short period of time. To check on your ACP (accel. pump) just remove the black plastic cover and look if the actuating arm is moving.

Michael

James Dean · May 21, 2001

BENT

:eek:

The most common reason for that flat spot is usually lean jetting. Yes, like the accel pump is not working.

You are headed in the same direction wazza is going. Try turning out the pilot (fuel) screw to help richen it from idle, about 1 1/4 to 1 1/2. I am uncertain whether or not clip #3 (counted from top, #1 is top) will be better than #4 unless you are at higher altitudes. For comparison the YZ426 is using clip #5 on the Yamaha version FCR carb.

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Has anyone compared WOT performance with different main jets using the EMN needle?? ---- To the point: Does a #170 or #172 main jet give a better top speed than a #168 main jet??

James

drehwurm · Jun 13, 2001

I knew it

Servus,

I really was reluctant in doing this, but finally my curiosity won. I changed the jetting of my 520EXC to OBEKN needle 3rd position, 165 main and 48 pilot and it didn't work! Bike was bogging bad and I didn't really feel and improvment in power in the midrange. Changed to a 170 main and the bogging almost went away, but still not impressive. BTW stock exhaust.

I've been so happy with my jetting OBDTM/2 , 175 main, 52 pilot and I will be again. There is ABSOLUTELY NO USE to change anything on the 520EXC apart from the 52 pilot and making sure the ACP is working - leave the jetting games to the Yamaha owners (been there done that) and enjoy your power. Sorry James, but I don't buy the improvement on the 520 with the E-series needles.

Michael

scottyr · Jun 13, 2001

sputtering 400EXC

OBEKN needle 3 rd clip. 172 main. 1.25 turns out. Pulls hard off the bottom end but has a sputter on the top end? Is it the rev limiter? It feels like it just runs out of guts really fast on the top end. What gives? Is it now revving so fast that I'm hitting the limiter that easy? Thanks!

KTM400MAN · Jun 13, 2001

Scottyr, Try a leaner main jet. The stock needle works best with a 172 main, and the new needle lets much more fuel through the main jet. Try a 162 or 165 main
jet, and let us know what you come up with. By the way, how's the midrange? is it really better than stock? Do you have better bottom end too? or is it just more noticeable due to the lack of top end? Erik

scottyr · Jun 13, 2001

I put the stock needle in for comparison but left the 72 main in and the EKN needle definitely has more power down low and crisper throttle response than stock. With the stock needle, the sputter isnt there. I will try a 162 main tomorrow and report.

James Dean · Jun 14, 2001

Try once and give up?

Drehwurm,

Your EKN needle is richer than the EMN and will need a leaner clip position#2 or #1. When you were using the #52 pilot jet what was the pilot screw set at? Did you take the time to adjust it to different settings with the #48? Lastly a #162 main jet will give you more revs.

While you ride your 520 with the DTM, take note of what happens at 1/2 throttle on uphills. Feel the lag and slow throttle response, try to roll it on for a wheelie. Keep it in mind because the jetting is weak/lean there. The Keihin charts show it, my graph explains it, and other riders are certainly convinced by their results.

I will forward the EMN dyno results and another riders perspective on this via email.

James

drehwurm · Jun 14, 2001

Re: Try once and give up?

Servus James,

Try once and give up?

This time yes - as there is no need there is no motivation also.

When you were using the #52 pilot jet what was the pilot screw set at? Did you take the time to adjust it to different settings with the #48?

I change between 1 1/4 and 1 3/4 depending on temperature. With the EKN and 48 pilot I couldn't find a setting to get rid of a severe bog down low - only the change to the 170 main helped, which in turn makes it to rich on top. As I wrote in my e-mail I think I'm just not 'compatible' with the e-series needles. You should know best how different riding styles and conditions affect jetting.

I will forward the EMN dyno results and another riders perspective on this via email.

Thanks, but not really helpful because of the missing comparison to the DTM needle and the open exhaust. Sorry for wasting your time :(

Michael

James Dean · Jun 14, 2001

I Can Respect That

Michael,

I understand what you mean and value your opinion. There are many differing conditions to jet for and rider preference is most important. The 520 makes great power and its not worth spending a lot of extra time getting the last bit of power out of it. Thus the title of the thread "520EXCessive". This is not a waste of time for me. It is more a point of reference, another piece of information to help others with.

Thanks for giving it a try. Sorry for wasting YOUR time. :(

James

JohnnyMac · Jun 14, 2001

Well James you didn’t waste my time.

I finally got a chance to try the new OCEMN needle and main jet today at the track. I’ve spent a lot of time jetting this carb (never thought I’d be saying that!) and wasn’t looking forward to starting over again after finally getting the early hesitation/cough under control. But I think this jetting has made a pretty substantial change in my bike. It’s the first time in a while that I wasn’t sure what gear I was in at times. It gives it a stronger, longer pull. On my bike the biggest change is ¼ throttle to full. I didn’t get it wide open that often to make sure the main was fine but I’ll play more this weekend. Seems good though.

I went with the new needle in the 4th position, 162 main and ¾ of a turn out on the fuel screw. My 2001 520SX has the ProCircuit t4 silencer with the p38 lightning. Started first kick no choke. The track was about 85 degrees 3,500 foot elevation.:D

drehwurm · Jun 21, 2001

new convert

I couldn't rest and I finally found the holy grail. Yes, the EKN needle gives a better midrange and which is best of all, more overrev! I still have a slight bog occasionally which wasn't there with the DTM needle, but overall the EKN is the better choice. I have to admit, I was wrong!

Here are my settings: 2001 KTM 520 EXC, stock exhaust

162 main
EKN needle 2 clip
48 pilot, 1 1/2 on the fuel screw
ACP stroke reduced by 0.7mm

Michael

James Dean · Jun 22, 2001

Thats great to hear Michael, very cool! :cool:

Max Factor · Jun 22, 2001

Please refresh my memory, what's the difference between the EKN & EMN needle?? I thought this whole post started off focussing on the EMN needle and jetting as the winner?:confused:

KTM400MAN · Jun 22, 2001

EKN #2 is the same as EMN #3, I believe. Remember that E is the taper,
(steeper taper than "D") whereas the middle letter, (K, for example,) is the clip position. K being richer than M, therefore K on clip position#2 is the same as M on clip position #3. The last letter is the straight portion and is richer to leaner starting with lower letters going up to higher letters.

James Dean · Jun 23, 2001

EKN#2 = EMN#3

The last post is mostly correct.

In order of code: (DTM,DVR,EKN,EMN,EKP, etc.)

E- taper is 1 degree, D- is .75 degrees, F is 1.25 degrees

H,J,K,L,M,N,P,Q,R,S,T,U,V,W,X... - each is 1/2 clip difference in taper location(not taper start unless identical straight diameter and taper angle)

M,N,P,Q,R,S - straight diameters in .01mm increments(rich to lean)

Therefore- EKN#2 = EMN#3
EKN#3 = EMN#4
EKN#4 = EMN#5

Also to note that FHP#4, EMP#4, and DVP#4 have tapers starting at nearly the same location. :eek:

James :confused:

KTM 520EXCessive power 4U

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