426 carb, couple questions..

[PhatDave]

hey everyone! longtime lurker, first time Poster..

So I am tuning my carb after sitting for the majority of the winter.. I want to change my pilot to a 42 (right now it's a 38) and I was looking at my main (from a DynoJet kit) and it says 170.. Looking at Steve's jetting placement, the Dynojet's 170 is equal to a 190 OEM Main jet?

I have a 426, and it seems to be running fine.. it just kind of surprised me to see that comparison on the other page.. You'd think that i'd be jetted WAY fat like that??

Also, my dealer (genuine Honda/Yamaha/KTM Dealer) said that it is impossible to order a 42 pilot :huh

that's exactly why I hate going there, I know more then those stupid **cks do..

Where do I find the proper Pilot?? would a mild port and polish change my main jetting??

[flyboy1294]

Originally posted by PhatDave
hey everyone! longtime lurker, first time Poster..

So I am tuning my carb after sitting for the majority of the winter.. I want to change my pilot to a 42 (right now it's a 38) and I was looking at my main (from a DynoJet kit) and it says 170.. Looking at Steve's jetting placement, the Dynojet's 170 is equal to a 190 OEM Main jet?

I have a 426, and it seems to be running fine.. it just kind of surprised me to see that comparison on the other page.. You'd think that i'd be jetted WAY fat like that??

Also, my dealer (genuine Honda/Yamaha/KTM Dealer) said that it is impossible to order a 42 pilot :huh

that's exactly why I hate going there, I know more then those stupid **cks do..

Where do I find the proper Pilot?? would a mild port and polish change my main jetting??

Welcome to the forums!

First off, every engine is different so don't stress too hard over your setup. I am currently running a 185/42 setup in my 440 carb, but I have seen guys running as high as 220 with similar mods. You may be closer to sea level than other members on here, and thus requiring larger jets to compensate for the denser air.

Anyway, 42 pilot jets are very common for these carburetors. I buy my jets from RMATV. And yes, a P&P may change your jetting since the engine has less restriction and can move more air.

About a year ago my dealer asked me about the 'powerband' on my quad, and I never went back. (True story. :rolleyes: )

Here is a link to what you need: http://www.rockymountainatvmc.com/productDetail.do?navType=type&webTypeId=80&navTitle=Intake%2FFuel&webCatId=16&keyword=400ex+pilot&prodFamilyId=24375

Some other people also speak highly of JetsRUs.com.

[chronicsmoke]

Welcome to the site!

Double check your jet and make sure it's not a OEM Keihin, you're better off fat than too lean..

I stopped going to the dealer when they charged me 1500 to change my wiring harness when I was 14-15.. I vowed back then I'd never let them **ck me again.. so don't feel bad, most dealers are crooks and dont know what they are talking about outside the repair manuals.

[CJM]

www.jetsrus.com They sell the pilot and the main jets you need. Genuine keihin jets. 400ex/450r carbs are PICKY with thier jets.

[kt1148]

Instead of paying more for shipping than the actual part(unless you order more than just the pilot jet) I took my pilot jet out and said this is what I need. I'm lucky, I have a few small bike shops around here that will get me what I need too..

[PhatDave]

thanks guys! I managed to find a local guy that is trying to stock all jets. was able to get a #42 pilot for 9.99..

And he said he's got all sorts of mains for 3-6$

Funny the genuine Honda dealership said it couldn't be done..:rolleyes:

[CJM]

Speaking of dealers, for a good laugh check this:

1. I asked once at the local dealer how much they would charge to tune the carb seeing as how they have a dyno. Guy told me 250 bucks at least and that it might take 2-3 visits (odd, dynos can dial you in pretty good period since your actually loading and running the engine-least last I checked). When I asked were return visits discounted or covered if they needed it for a few runs they told me nope, pay each time full price.

2. A dealer that actually has racers there and sponsors others tuned the carb for me once. I just lacked the time to do it myself. I told them EXACTLY what I had done to the quad. What did I get back-they turned the air/fuel screw out a few more turns. Mind you I asked the service guy did they jet it, he said yea. I said what mains, he says he dunno the mechanic is out to lunch atm. They took a a stock bore, with an open airbox, exhaust, cam, etc, etc and LEFT THE STOCK MAIN IN THERE. Not like I didnt tellt hem and the service writer NOTED everything down too (I saw the sheet, said jet for the specs provided so forth and they noted them!) It promptly blew up, needing rings and I never had them work on it again. I mean really, you have people who race on mechanic staff, you sponsor and work on race quads. And you cant jet a bike??

I refuse to go to the dealer. The one by my house closed, nearest one is an hour away and they usually dont stock anything. I rather order the parts online or make it work myself rigging it up if I gotta.

[punk rock kiel]

i have a 426 with stage one hot cam, full lrd exhaust, uni filter, ehs covered air box lid and changed mine, 42 pilot, 172 main, 3rd clip (back fires a little on downhills so might go back to the 4th) and 2 turns out on a/f screw.
i am at 400 elevation and still runs fine down here in hatfield which is anywhere from 800-1600 we seen so far.

[honda400ex2003]

Originally posted by PhatDave
hey everyone! longtime lurker, first time Poster..

So I am tuning my carb after sitting for the majority of the winter.. I want to change my pilot to a 42 (right now it's a 38) and I was looking at my main (from a DynoJet kit) and it says 170.. Looking at Steve's jetting placement, the Dynojet's 170 is equal to a 190 OEM Main jet?

I have a 426, and it seems to be running fine.. it just kind of surprised me to see that comparison on the other page.. You'd think that i'd be jetted WAY fat like that??


Where do I find the proper Pilot?? would a mild port and polish change my main jetting??

my thoughts on it would be start with a 178(end up at a 175), 3rd notch on the needle, 42 pilot and 2.5 turns out on the f/a screw. with a slip on, open box, and a 426 bore.

a port and polish would change jetting once again. this would be the case for any flow change to the engine.

you are correct on a 170 dj being a 190 keihin main. imo that is too big and is overkill for 99% of the engines out there. you would be amazed at the change in performance dropping it to the proper size will do for you.

steve