Taffy or LarryCo!! I need your help please.

I'll second that suggestion. I bought the JD Jetting Guide a little while back and it has already been very helpful. I can now print out graphs of the jetting profile as I change them and then correlate them to all the notes I take when I go out testing the changes in the field. In my mind, this is the *only* way you will get the bike dialed in and understand the effects the changes have.

For example, after I pulled all the restrictions off my bike, I was running too lean (plug pure white, bike running very hot) and my first goal was to get back to a "safe" baseline jetting profile. I decided that going for a new jetting profile that would enrichen things about 5% from approximately 1/4 to WOT would be a good gradual starting point. I used the JD Jetting Guide to get me a graph that translated my original profile richer by about 5%. I made the jetting changes and the bike runs fine. Is it optimized? No way! But I now have a new profile that is safe (not too lean) and runs great for trail riding.

The next step is to start to understand how to get more "snap", quicker revs, and all the other seat o' the pants stuff that everybody talks about. I will now use the JD Jetting Guide to help me correlate a different needle, for example, by looking at the graph, testing the bike and then I will understand what the graph means in terms of response from the motor.

You gotta experiment but you gotta do it in a scientific manner or you'll just spin your wheels (pun intended). The other important thing to remember is to only change one thing at a time. Graph it, test it, understand it, before you do anything else.

Good luck and have fun!


Jeff :)

Hey JD- this needle is a NCVQ. The acc pump is working fine too.

Taffy- I took the ET tube out per your request. It was pretty easy; it just unscrews. :D It has no numbers or marks whatsoever. I was playing with the et and the dut needle, and even with the needle bottomed out on the main jet, there was still about 1/4 inch until the straight went in. The et doesn't stick out into the throttle body. It sits about 1mm below the surface with an alluminum shield looking thing up stream about 1/2 way around the hole the et sits in. The et inner diameter is just a hair smaller than the straight of the dut needle. If I pushed and twisted the needle, I could push about 2mm of the straight portion into the et (with the main jet out). This is what I don't get. Why make so many different needles? I mean, if you have needle a and b, and you make needle b fatter and move the taper further up, then the two needles should be identical, right? Something like the emm is the same as an ekn. Who cares where the taper starts? That point never enters the et. If it did, the little lip might cause the throttle to stick open. :D

I'm :D:)

I just took it up the street a few times and I still think that the 40 pj is too lean. It ran best at 2 1/2 turns out, but the idle was still going all over the place. Maybe it is because of the 100 paj. I think I'm done for a while though. This jetting stuff is still giving me a headache. I am having such a hard time telling if it is lean or rich. :)

The bog still seems better since I put the yz cam in. The yz needle made it a little better too. Now it is only a problem at really low rpm and really quick throttle openings. Button starting is still no where near as good as it was with the wr cam.

Oh, I also took a picture of the et with the needle touching the main jet. I have no idea how to post or attach it though.


Sorry to hear you are having so many problems. I may have missed it, but what was the baseline jetting you started with after the new cam was in? I am assuming you started with the baseline YZ jetting but maybe not?

I have been considering the same modification, but I am concerned about ending up with a power band that is less manageable on the trails. I don't want to end up feathering my clutch all the time - may as well get a two stroke if that's the case. One of the nice things about the WR power band is that it's predictable, albeit kinda boring. All that low end torque is great for climbing steep, rocky hills though... :)

Good luck and keep us posted.

rohar- you can go back in this thread to follow where my jetting started and where it has gone. The yz cam made my throttle response much better. It is much snappier than before. I would describe it as sleepy and slow response with the wr cam, and now it is more instant. It is definitely more tiring with the yz cam, but when I twist the throttle, I want it to go right then. I don't want to wait for the bike to gather itself and then go. I rode some single track yesterday and I would have prefered the wr cam for that. I haven't ridden in the more open desert yet, but I think I will like it better. I may switch back though because I may not be able to hang on for long rides. :D

I just switched from the 100 paj to the 70 paj. I couldn't tell any difference. :) So now I'm at 155 main, 40 pj, 70 paj, ncvq needle clip 4, and 2 turns on the fs. It seems to be pretty good, but I don't think it will be happy at the high elevations I'll be riding at on saturday.

* * * * * James Dean * * * * * * *

I purchased yur jetting guide over a year ago, I lost it in a computer crash and would really like to get another copy, can you look in your records and see that I paid and perhaps email me another copy?

Please let me know as I am struggling with jetting again. I just did a big bore job on my bike and I am having trouble from 1/4 to wide open blips.

However I have not got the needle Taffy suggested yet from my dealer...perhaps monday it will be there for me.

Anyway heres where im at:

BK mod

155 MJ

EFN Needle c3 (waiting for the EKP and EKN to arrive)

35 Pilot

Pilot Air Jet(screw) @ 1/4 turn

1 turn out on the pilot screw

I started with the EMM needle and had a stalling/bog issue from closed to 1/8 throttle, then I went to the EFN and the stalling when cracking the throttle went away but it still has a heavy bog when trying to stab the throttle open from 1/4 to FUll open.

If i rev it slowly it feels crisp from closed to Full open however.

Anyway...let me know what you think?>

Long time since I have seen a post from you!

I gave up on the 35PJ and Adj.PAS, seemed to create problems above 1/4 throttle. Had two weeks of trial and error, multiple needles, main jets and clip positions. My bike runs great now with a 40pj and 75paj, even runs great at 5k in elevation. Taffy and JD's advice really helped me understand the FCR and it's circuits. But I'm not going to miss anymore riding time trying to get the last two percent out of the old yami. Good luck....Domenic :D

PS..My bike is a wheelie monster even with the rich pilot and no missing, popping or bogs :)

After some more tinkering, I think I've got the jetting pretty good.

I put the 40 pj in like I said, and the idle is way too lean. I went to the 70 paj to try to richen things back up and I couldn't tell any difference, so I put the 42 pj back in. Much better.

I was still having a sputtering problem at 1/4 throttle just kinda cruising at high rpm. While I was comparing the two needles when I first got the ncvq, the ncvq seems to have a steeper taper than the dut. I decided to put the dut needle back in on clip 6 to see if it would work if it was a bunch richer. Supposedly that would allow the idle to stay rich, but not increase the fuel flow as much as the ncvq as the throttle opened. I was hoping this would cure the richness while cruising at ~1/4 throttle. While throttle response was better than the dut on clip 4, it wasn't as good as the ncvq needle on 4. It did fix the sputtering though.

So this time I put the ncvq back in a clip leaner this time at position 3. Throttle response was better than the dut ever was, but still kinda boggy again. The sputtering while cruising was pretty much gone too.

I changed the paj from the 70 back to the 100 and the throttle response got much better. I don't know why I didn't notice that it got worse when I went the other way. I guess it was because the 40 pilot was messing things up.

So now I'm back where I was yesterday, but with the needle one clip leaner. That seems to have fixed the richness/sputtering at steady throttle between 1/8 and 1/4 throttle and leaned out the idle enough to put the fs back to 2 turns out. The bog is still slightly worse than with the needle at clip 4, but it is way better than the dut ever was. I'm chucking that thing. It is running pretty dang good now. It will start with the button if I just bearly crack the throttle, but not in any other senario. The bog is still present if I open the throttle way too fast while the engine is idling. It is still MUCH improved. I think I'm going to call it good, but I still have no idea if the main needs to go up or down.

Next I'm going to try different leak jets to see if I can get the bog back where it was at clip 3. I put a really small piece of wire in the leak jet to see what would happen if I put a smaller one in. It seemed to help, but that was back when I was running the dut needle. I'll try the 50 and the 40 if I can get them.

Thanks to everyone for the help! :D :D


Team Scream,

Yes, I can send another guide to replace the lost one. Send me a PM with your email and about what date or month it was.



The needle clip #3(NCVQ) is a step leaner than stock YZ and close to DUT#4-#5 at 1/4 throttle. NCVQ is richer everywhere else giving better power. Makes more sense to be a step leaner than the stock YZ for altitude. A few YZ450 owners are running 2 clips leaner.

Same as the 42/100 without disabling the air bypass (or Air Cut Valve- ACV). It should run a little leaner than a stock YZ450 for altitude.

Last fall I was riding high altitudes in Colorado and tried a #42PJ with #85 PAJ, 1 turn out, and had good results with quick E-starting. The KTM 400 usually starts quicker when the fuel screw is closer to 1 turn. Something to consider if the starting is a problem. I might have cracked the throttle too without thinking about it, looking back... :)


Cheers! :D

Thanks James, PM sent

live to ride

you're at leastone clip too rich on the needle, drop it again please.

if the highere gear the duller the top end = your MJ is too small, if revs out fine then obviously you're ok.

your pilot settings are everywhere because the needle has been wrong. when you lower the needle again you will have leaned off the pilot area a tad. something to bear in mind.

JD. good to know you're alive! we haven't spoken for over a year i should think. i too lost my chart in a crash last august.

Q; this NCVQ needle/ is this a 'C' taper, V clip and Q straight? i can't believe that they're running 'C' tapers!


Taffy- my guess would be that it is an E taper. I have no idea why it is coded this way, so maybe you're right and I'm seeing things. I'm pretty sure that the taper is steeper than my dut was. They looked about the same at the straight, but more narrow at the point. :)

It is raining today, but I'll try dropping the needle tomorrow. Thanks for your help! :D

Taffy- I put the needle one clip leaner, and it didn't run so well. It was too lean and it was sputtering again at 1/8 throttle while just cruising at a steady speed at about 4000 to 9000 rpm. I had the fs out 4 turns and it was still way to lean at idle and wouldn't even stay running if it was turned in more than that. I could try a size bigger on the pilot, but I think it would still sputter at high rpm. Do you think a bigger pilot would help this? :)


The new NCVQ needle code only has the last letter of any meaning. It is the "Q" diameter (2.745mm). The tip is the same as EMM and taper is close to .9 degrees, so the taper start is about the same as a DTQ.

I can send another jetting spreadsheet. Send me a PM with your email.


thanks JD that tells us a bit about the needle taper. just about inbetween a 'D' and an 'E' needle.

i think LTR that you could put your MJ up to 160 or 162 and the top end will be a lot better, the knock on effects all the way down will be good.


I just miked the two needles I have. The DUT is .1141 inches thick at the straight. The NCVQ is exactly the same diameter. The tip on the DUT was about .0895 1mm from the end of the main taper. The NCVQ was .0835 at the same point on the taper.

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