[mcdonaldsb0i]

hello first time posting on the site. i have a 03 400ex and going to bore it to a 426 i have a stage 2 hotcam big gun rev box white brothers e-series slip on exhaust im having gt thunder hd head studs installed and a 88mm wiseco 11:1 piston and have the head mating surface trued up and a port and polish atm with a 10:1 piston stock bore i have 168/42 jets in the carb with choke removed and an opend air box with a k&n airfilter with a precharger need a little help on starting position with the jets ive read alot of forums and think a 180 185 and 190 should be what i try any advice?

 

[misterclean59]

Welcome to the site. I don't know the specifics for your question but several here know this wheeler well.Just wait.....you'll see!

 

[TBRider]

I'm sure slammed ranger will be along to talk jetting with you, he seems to have it down to a science from what I've read....

 

[SlammedRanger]

45 pilot jet. And 185-190 main jet would be a place to start. Your gunna want to put the needle down one clip also. And i suggest some sort of cooling mods or your gunna run the risk of over heating. Are you doing a bore on stock sleeve? Or having the jug sleeved with a LA sleeves and then bore? Welcome to the forums!

 

[mcdonaldsb0i]

thanks for the help and im allready 1 clip down on the slide pin and i bought a bored stock cylinder and a 11:1 wiseco 88 mm piston and the cooling i have air fins and an oversized oil tankand i am putting a spal fan on the rad with a thermo switch for automatic cooling no idea what else to do atm unless i put an extra rad on it and a 45 pilot will i really need to go that big?

 

[SlammedRanger]

Oh yeah. I was running a 45 in my carb when i had a stock carb. And mine is a 416ex. Stage 2 cam. And +1 valves. I wouldnt be surprised one bit if your 426 needed more. But i would think 45 should cover it.

Your cooling mods will be plenty sufficiant. Though. I have very similar just no over sized oil tank.

 

[TRX2fiveO]

Do not bore your stock sleeve to 88mm. You can purchase an 88mm sleeve from LA or Wiseco. Make sure you upgrade the timing chain to a 2002-2008 CRF450R/450X- 2006-2008TRX450R/450ER chain part # 14401-MEB-671. Replace the guides too.

 

[mcdonaldsb0i]

ok ill guess ill buy a couple of jets and the cylinder i bought presleeved idk if it is a stock sleeve or not what would be the difference ive spent almost $500 so far tring to get everything to make my quad a 426 and i allready have a 450r timing chain that happened when it got a stage 2 hotcam

 

[SlammedRanger]

If its a stock sleeve bored. (Which i would bet money it is) the sleeve at the bottom would be very thin. I mean sketchy thin. If its a sleeved jug it will be roughly a 1/4 inch thick maybe alittle more.

 

[mcdonaldsb0i]

is there any good go to spots for jets and yeah i looked its a bored stock sleeve is that gonna be a problem?

 

[SlammedRanger]

I always use jetRus. And yeah you run the risk of the sleeve cracking being that thin. Do alot of people do it? Yes. Would i ever suggest anyone to? No.

 

[mcdonaldsb0i]

ok well i just took the head and cylinder and studs to the machince shop its gonna be $275 for gt thunder studs installed true up the mating surface on the head and port and polish and and a valve job and clean up the head and i bought jets from 180-195 just to be sure and 45-48 just to be sure dose that sound like a good price for all of that machine work ( theyve been in buisness for 60 years and have amazing reviews even from a friend)

 

[SlammedRanger]

Its a tad steep. But if the work is done right its worth it!

 

[SlammedRanger]

I paid 120 for the gt thunder studs installed at snure interlocking. And my family friend owns a machine shop that did the bore, hone, and decking for 40 bucks. Valve work and flow beanching head with p&p was another 40 bucks. And that was installing my +1mm valves, high rev springs, titanium retainers, new valve seals.

We wont talk about how much it cost to fly cut the piston though. That hurt alot lol

 

[mcdonaldsb0i]

ok so another thing im going to bore open the exhaust header not to much just a little to help flow but i was using a DPR8Z ngk plug should i go to the DPR9Z ngk plug?

 

[SlammedRanger]

The only reason you would need a dpr9z plug is if your riding at wide open throttle for a long period of time. Or if tuning it makes it necessary. Reading the plug will tell you if it needs to be a colder or hotter plug.

 

[mcdonaldsb0i]

ok sounds good thanx slammed and others for your help ill update when i get my parts back from the shop

 

[SlammedRanger]

No problem! Glad to help!

 

[mcdonaldsb0i]

ok i got it all back together today and i did 185 and 45 jetsand 1 clip down from stock on slide it started excelent but it back fires with flames could an exhaust leak make it do this?

 

[SlammedRanger]

Yes an exhaust leak can do this.