Jetting

[Rastus]

Well, i checked my plug today after about a 3 hour ride and its a light red color. This is with a WB E-series, with the stock headpipe.
I had a DG close circuit racing exhaust, and it was jetted right, and I still have the same jets.
I do have the White Brothers headpipe, i tried running it, but it just runs worse.
Could i be running lean? It back-fires on deceleration. Would i have to go bigger to an even bigger jet if i put the White Bros. Headpipe on?

Thanks in advance.

[Rastus]

Any help would be helpful.

[BornOnFire]

If you are back firing on decelleration, you are definately lean. try a bigger jet or turn in the fuel screw on the carb 1/2 turn.

[Rastus]

Thanks.
I tried running my WB headpipe, and i checked the plug. This time it was a black color on the threads, and a dark brown on hte electrode.
Does that make any sense? Seems like a bigger headpipe would increase the flow.


Stock Headpipe+ WB E-series Pro-Meg = lean

WB headpipe +WB E-series Pro-meg = rich

(these are on the same jetting.) Weird?
Ill be taking the carb off tomorrow, and checkin to see what the main jet is.

My problem isnt with the needle jet, or the slow jet, its the main thats running rich, because it acts like it has the choke on. The Low to mid power is great, but the topend sputers.It only does this at 3/4 to full throttle.

Thanks for the help guys.

[BornOnFire]

You may be having a problem with the back pressure created by the new head pipe and the silencer. You can try removing a few discs from you silencer and tune it that way or mess with the fuel screw a little. Don't depend on that spark plug too much. It can give false readings depending on the brand of gas you are running. Also, you should be using a fresh plug for these tests as well. A fool proof method to use would be to go up on the main jet size incrementally until the engine begins to make a "warbling" sound while accellerating. At that point the engine is telling you that you are rich and you should be able to go down one jet size and be right on the money. Good luck

[Rastus]

Thanks, it already does that when i have it full throttle.It acts like I have the choke when the throttle is 3/4 to full. So just try getting going down a jet size?

Thanks

[spliffy]

hey man... You Can Change The Main Without Taking Off the carb... On The Bottom Of The Bowl... There Is A large Nut... Take That Off & Ur Main Is Right There... Takes 5 Minutes To Change It That Way Instead Of Taking The Tank, Carb & Bowl Off Seperately.... Let Me Know What You have in There... im Running a 150 Main Right Now & 40 Pilot... Im A Little Rich On the Low End .. But Top End I'm Good At That.... We Have Similar Mods Except For The Pipe.... Im Just Running A Stock Pipe With The Welds Ground Out On the Head Pipe..... I am thinking Of Going Back Down To The 38 For Pilot Cuz When I Give It Gas On the Lowend She Kinda Sputters But On The Mid Up... She Takes Off Like Crazy..... I have Some New Scratches On the Bottom Of the Back Grab Bar... If you Know What I mean hehe :p

[BornOnFire]

I would go down on the jet size until it stops "warbling". Then put in a new plug and test it out by getting into a large straight away. Open her up into 5th gear for at least ten seconds and then pull the clutch while you hit the kill switch at the same time. Coast to a stop and let her cool a little. Then check your plug. It is important that you kill it while in the WOT position otherwise you will not get a "pure" main jet result. Good luck.

James

[Rastus]

Im running a 130 main right now.
So jsut try a 129 main and see what happens?

[Blake24]

sometimes bumping up the pilot will help backfiring during deceleration

[BornOnFire]

Yeah try the 129. See if it still "warbles".

[spliffy]

there is no 129... you will have to get a 128.... thats just seems to small to me.... but i spose its different for every machine

[Rastus]

Theres no 129? Man, that sucks if it doesnt exist.

About adjusting... Does the needle jet holder do anything?
I was just wondering b/c its adjustable, and i was just wondering if thats what you guys are refering to.
If ya want to get technical, i have a manual somewheres around here, and can find the part, just need some help finding the right jetting.


Thanks guys for the help.
Or, should i go ahead and order, or get a 128 main jet too?

[spliffy]

I Would Just Get A Couple Different Size Jets.... They are $4 A Piece.... maybe Get Like The 128 , But Also I Wold Get A Couple Bigger Jets Too... Like A 132 & A 135 Just To Have As Long As You have To make The Trip To The Dealer/Shop The Stock Jet Is a 122 or a 125... Depending On The Yr Of The 250x ...... A 128 Still Just Seems Way To Lean To Me.... With The Mods You have Listed..... The Cam Mod Alone Should Call For A Much Bigger Main Jet IMO :)

[Rastus]

Yeah, I thought it would mean it has to be richer.But the plug shows its rich, and it kind of warbles on the top end.
Course, some things are just weird.
Ill mess around today, and ill let you guys know what happens.
Thanks

[honda250xrider]

if u dont really want to mess around with the jetting and stuff i would get a lectron carb i think it works well with my 250

[Rastus]

How much do those run?

[honda250xrider]

i think they are 250$ im not sure but i think that is how much i paid for mine i will have to try and come up with the recipe and tell u where i bought it from but really they are great carbs...but the down side no choke they are ment for racing

[TRX250EXER]

when is the last time you did a valve adjustment? my buddies 300ex had this problem and was dropping main jet sizes like crazy until he finally adjusted his vavles. those can cuase the backfiring upon decelleratio too. he went from a DG exhaust to a Eseries also. that is what my problem was anyways, the vavles. my 250ex was doing the same thing too. check your valve clearance before you go and spend money on smaller jets you might not need.