Jetting Question for my New *Whacky* Head

So I got my 05 X back together. Here’s the scoop:

Dr D. SS Pipe & Header

J&E High comp piston

07 R Head

Ron Hamp SS valves

08 R OEM Cam

Polish & port (compliments of AS Racing)

Took it out today for an easy 50 mile break in (run it through the range, try to kepp the RPMs mellow, don’t lug it, yadda, yadda, yadda).

The bike purrs like a kitten when I start it and has a decent response when I crack the throttle (no real bog). There’s zero pop on decel and aside for slightly rough delivery at the bottom end (I’ve just written that off to having sacrificed a bit of bottom end due to the mods), everything is beautiful.

Here’s the rub, the bike bogs out & sputters like a sorority girl after one too many Red Bull & Vodkas on the top end. The transition from 4th to 5th bogs pretty bad and anything past about ¾ throttle is just non-existent.

Now, I don’t know much, but I do know what I don’t know, and I don’t know carbs. I’ve got an unreasonable fear of carbs and generally try to avoid them. For some people it’s clowns, fir me it’s carbs. I know, I have issues…

I think it’s time for me to face this fear head-on and figure this out.

I’m relying on the collective brain-trust of ThimperTalk Inc. to help me out with this one. So, any thoughts???

Thanks guys!! :thumbsup:


What jetting do you have? Just of the top of my head I would say up the main to 165- 170.This can be done with the carb on and twisted through the drain cap.Also what needle clip position are you at and what needle.Even if it's a stock needle you should be in the 3rd- 4th(most likely) clip.Sounds to me with all the mods you did R cam,ported 07 R head,and high comp piston you need more fuel.The needle can also be addressed with the carb in and a slight twist to access the two allen bolts on the cover.I found it is easier to only remove one of them and losen the other one enough to spin the cover.Hold the throttle open with the help of a freind or vise grips and the needle slides right sure when you remove the allen bolt cap over the top of the needle you don't lose the spring underneath it.It normaly sticks to the cap.To grab the needle there is a tool that came with the X's if you don't have one or lost it,all it is is a small piece of tubing on a thick piece of wire the tubing is big enough that when you press it on the top of the needle it grabs it and out you pull.


Thanks guys!

I'll crack 'er open early next week and see if I can figure out what I'm currently running (assuming I can).

As soon as I do I'll report back!


PS Paul - My pleasure!! That was in part for all of the help and good info you've provided the past. :thumbsup:


After removing the carb & spraying my brother in-law with copious amounts of gas (the 1st time was an accident, the 2nd, 3rd, 4th, 5th & 6th times were not) I’ve made the following discoveries: :ride:

The main jet (thing #1 from the bottom) is a #158

The neddle (thing #2 from the top) is a NCY Q and the clip is in the 4th notch from the top.

Hopefully this all means something to you, because I’ve got nuttin’!

Thanks again! :thumbsup:

I have basically the same mods as you with slight differences in pipe and cam.

The NCYQ is an 05 R needle and the 158 main is bigger than the 130 stock jet.

So The clip position on the needle sounds fine,I would definitely go up on the main jet to 165-170 which is basically the R jetting.What size pilot jet is in there?The one next to the main? Since your in there if it's not a 42 I would put one.If you look at Ramz's 250X jetting chart it shows you the R & X jetting Specs.You've basically made your bike as close to an R as possible motor wise.Is your air box opened up?Just like you and I,what comes in one end goes out the other.:thumbsup:

Thing #3 (the thing next to thing #1) is a #42.

Aside from having taken the little rubber cover off on the opening on top of the air box, no - I have not cut open the top...

Removing the snorkel only, is not enough air for what you got going on.

Cool, so I'll up the main to a #168 & cut my air box open.

Thanks for all the good info - I appreciate it :thumbsup::ride::rant:

Can't wait for an report!:thumbsup: Don't forget to start your fuel screw at 2 turns out.If you don't have an easy adjust screw nows the time.

Keep that air boot clean when you cut the air box.

Can't wait for an report!:thumbsup: Don't forget to start your fuel screw at 2 turns out.If you don't have an easy adjust screw nows the time.

Keep that air boot clean when you cut the air box.

Air box is cut - sub-frame was already lifted, so I just removed the filter & covered the opening with a clean rag. Done & done.

Already have the easy adjust fuel screw - thanks for the heads-up. I'll bottom it out and take it out 720.

I'll report back when I button it back up.

Thanks again!

I agree with Stallion on most everything. Your bike should be flowing as well as or better than a stock R. The 08 cam is pretty hot and the 2008 R calls for a 188 main. That bike uses a larger carb so things don't cross over. The last R to use a 37mm carb was the 2005 and that calls for a 172 main. I think I'd start there.

That thing should be wicked fast when you get it dialed in...

Wow - OK good to know. I'll start with the 172 then - Sounds like my local Honda Dealer has them all in stock, so :thumbsup:

Dr D. SS Pipe & Header

J&E High comp piston

07 R Head

Ron Hamp SS valves

08 R OEM Cam

Polish & port (compliments of AS Racing)


I really want this setup, but don't have the funds yet. Tell us how this beast runs when you get it dialed in.

So… I grabbed the 172 main, buttoned it all back together and the only way I could get it to start was with the choke off and a fist full of throttle.

After I got it to go I pulled out the choke let it warm up, turned the choke back off and it just dies. Repeated attempts to start it (both with choke on & off) create all sorts of bad burping, popping & back firing noises (not to mention a decent amount a smoke out of the pooper).

What do you guys think? Adjust the fuel screw, try a different main jet, grab some holy water :thumbsup:

As always, Thanks!!!

EDIT: So after some Scotch,, I tried tightening the fuel screw little by little and it progressively got better. Only now I’ve got the fuel screw completely bottomed out and the bike starts a lot better, but won’t idle – it just dies…

So, smaller jet???

OK – Carb boots were tighter than a virgin on prom night…

Now, this is where I push my “Thing #1, #2 & #3” vernacular comfort zone :thumbsup:

I’ve got an ass-load of jets, and even a pilot screw, but I can’t find anything called a “pilot jet” :ride:

So I yanked the main jet, jet needle & the “slow jet” (that’s what Stallion told me to make sure it was a #42). It’s got the little holes in the top “needle” portion of it.

I rubbed it, blew into it, ran a wire through it, caressed it… you get the idea.

Looks good, but what do I know…

EDIT: I threw the little slut back together but need to wait until the AM to fire it back up lest I piss off the neighbors. I’ll report back…

If it still isn't working after you cleaned it out and made sure everything was nice and tight you may need a 45 pilot/slow jet. I'm actually running a 45 pilot jet with my set up. For some reason after installing my hot cam the 42 pilot just didn't cut it. I could close the fuel screw entirely and the idle wouldn't change. Put the 45 jet in and booooom works perfect. Just something to think about if cleaning it doesn't help.

Paul you should start a religion man, ‘cause L Ron Hubbard ain’t got nothin’ on you! (Please don’t kill me Tom Cruise!)


I just got off my DS 450 before I took the X for a rip up the alley, and that bitch is hotter that a black cat on a tin roof. I said DAMN!

I don’t know if is was the jet or what, but whatever I did it worked!!!


EDIT: JTmach1 - Pass some of that gas along for me to the Agent - I'm tapped!! :thumbsup:

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