Have an 06 Yz250 i've been riding for about 6 months. Havent changed the jetting or anything, i believe it has some porting work done to it. Current jetting is pilot:50 Main:185 and clip at the third from the top i believe. Live in Fl in the hot temps. I run a mix of 60/40 100LL and 93 pump mixed 40:1. Has and SST pipe and shorty silencer. Should i tweak anything? thanks

If it runs Ok why tweak it? I'd have a look at tghe plug. At piston change control the pool of fallen out premix if you got some 1- 2 mm you should be OK
Also piston crown and head will tell you how your jetting is. with 50/NP3/185 you are good so far I can tell.

Runs good, except for that cutting out issue. Pulled the carb apart and cleaned it, didnt look bad at all. Havent fired it up yet though. You ever heard of a choke not working? When i pull it to start it, it doesnt really change the idle but will bog the bike out on the track if i try to get on it like it normally would if it was working. Evrything is clean and not clogged

The choque could be clogged, could you elaborate the cutting out issue? Maybe its the plug and not the carb.

I'm betting it's cutting out at high rpm due to the big main. You need to experiment.

Edited by LILBIT, 21 June 2012 - 05:42 PM.

Honestly, for Florida riding conditions at this time of the year your bike is really rich on the pilot and the main. The #3 position on the stock N3EJ needle, if it is the OEM needle, is in a good position to start with, and I would keep it there to start with. Give this a try.
48-pilot
178-main
N3EJ Needle, start at #3 slot,but may need to go to #4.

That bike, especially with the SST pipe, requires that you keep using that good gas, or it will detonate alot when under a load.

I'm in FL too and I have a 2010

Premium from the pump was not working good so I started to mix 50/50 with Sunoco 110
40:1 motul 800, stock pipe
Slow vet C, Mx only and stock jetting works pretty good on mine (48 pilot/178 main and N3EW #3)

It's a tad rich and I might play this setting as it's getting really warm and humid but shouldn't be to far off from current settings

I couldn't get my jetting right when using only premium for the pump. I met a fast local on the same bike who told me about adding a bit of 110 and it did the trick.

ill see if i can get some of those jets and ill keep you all posted, choke isnt clogged blew it out with air and carb cleaner. Does it pull any fuel through the bottom or anything? Or it just opens up that channel around the mouth of the carb? Ill try a new plug also. Thing runs good when its this rich hows it gonna run when i lean it up?

I guess I'll hi jack the thread a little.  I just bought my bike and it had the stock jetting (50 pilot, 178 main, N3EJ needle 3rd position I believe).  I havent even really ridden yet but just from riding it in my neighborhood for a a couple of minutes it felt rich.  I switched it to a 45 pilot, 175 main, N3EW 2nd clip based on reading the jetting thread in the FAQ section.  I'm in Texas where it's getting close to triple digits and at about 500-1000 feet elevation.  I'm running Motul 800 32:1, stock pipe and silencer, all stock motor exept a No Toil Super-Flo air filter and cage.  Thoughts?

Edited by RiderX, 22 June 2012 - 04:37 AM.

Street riding cannot be compared to be on track or offroad, that what I found out the hard way.

TAG -

With the SST pipe guys are usually ending up with a little bigger main than most. Also, the porting thing can throw off jetting. You need to do some WOT chops, plug readings, etc, and determine what your bike needs.  Might find lots of guys running 175 mains, but with stock pipes and porting, and going from a 185 to a 175 might be death for your bike, or perfection.


RiderX - like arnego2 said, a few minutes of street riding and using the bike under actual riding/racing conditions will bring you very different jetting requirements.

Yeah I know that I can't judge jetting on a bit of flat ground riding, I'm mostly referring to what others have posted works for them at the same elevation in stock trim. A 50 pilot sound pretty rich.

Just a quick update incase anyone cares:

I rode all day Saturday and the jetting worked great.  I started at 1 turn out on the pilot screw, which seemed to load up a bit at idle after the motor was nice and warm.  I ended up at 1 3/4 to get it perfect.  It ran flawlessly after getting the pilot screw dialed in.  It was 100 degrees here and very dry.  Where I rode was at about 800ft.  No spooge.  This bike rips, way more lively than any KTM I've ever owned (I've had 5 of them).