400ex jetting help

[pj88]

i have a 01 trx400ex with a 11:1 piston with a magnum stage 2 cam, air box mod, 6 degree adv key, and removed the choke. stock exhaust with spark screen cut off, Fresh build hasnt been fired yet. looking to jet the carb. i live in il at 720ft above sea level. looking for some recommendations on a good starting point on jetting? plan on running a 50/50 mix of 98/100 oct, to start and see if I can get it down to just 98 without detonation?

[tri5ron]

couple of things wrong here that need to be corrected before you jet it.
with 11:1 & stg 2, you should not be running a +6 key, and you should be running at least a slip-on.
Change those before you try jetting it.

btw,
what brand of headlight fluid do you use, what is the air temp's and humidity you'll be riding in, and are you running air or nitrogen in your tires ???
(Just Kidding)

[TheAwesomehonda]

What the heck is the voting thing for :huh :huh

[chronicsmoke]

Originally posted by TheAwesomehonda
What the heck is the voting thing for :huh :huh

:rolleyes: the guy is new and this is his thread..

I voted for help jetting :)

[JOHNDOE83]

Originally posted by tri5ron
couple of things wrong here that need to be corrected before you jet it.
with 11:1 & stg 2, you should not be running a +6 key, and you should be running at least a slip-on.
Change those before you try jetting it.

btw,
what brand of headlight fluid do you use, what is the air temp's and humidity you'll be riding in, and are you running air or nitrogen in your tires ???
(Just Kidding)

I had just got done reading this and thought. "Ha!...blinker fluid."

Then I went to craigslist and saw this directly after.
http://orlando.craigslist.org/mcy/3056675918.html

I cant believe it actually comes with a powerband, I thought of rons lil website and this made me laugh my a#$ off.


Sorry to jack your thread man....:chinese:

[TheAwesomehonda]

Originally posted by JOHNDOE83
I had just got done reading this and thought. "Ha!...blinker fluid."

Then I went to craigslist and saw this directly after.
http://orlando.craigslist.org/mcy/3056675918.html

I cant believe it actually comes with a powerband, I thought of rons lil website and this made me laugh my a#$ off.


Sorry to jack your thread man....:chinese: LMFAO I'm still not sure where to find the power band on my quads or dirt bike. lol

[pj88]

tri5ron could you please explain to me why I shouldn't be running a stage2 cam and 11 to 1 piston?I'm using a stock head gasket so won't be a true 11 to 1. As for your ****ty coments the more info you post the better the help you will get. If I had posted "looking to jet my 400ex" there would have been a bunch of posts asking what I had done to it. I skiped that BS. elevation matters as for humidity unless you jet it for the rain forest and run it in the dessert won't matter much. Of corse it will run leaner in cool crisp air but I was just asking for a starting point

thanks
PJ88

[Stickman400]

Ron didn't say anything about your stage 2 cam. He said you shouldn't be running +6 key with an 11:1 compression piston and the stage 2 cam because the key makes it run hotter, and that in combination with 11:1 compression piston and cam will make it run too hot and you risk burning up your top end because of all the heat.

[JOHNDOE83]

Originally posted by pj88
I skiped that BS. elevation matters as for humidity unless you jet it for the rain forest and run it in the dessert won't matter much.


thanks
PJ88

That was hillarious.....lol.

Only 3 posts and this guy fits right in here, welcome to the family....:devil:

[Rohr397]

Here's right from Sparks website:

"The 400EX in stock form is very low compression and responds extremely well to advancing the timing 6 degrees. The Sparks Racing Ignition Advance Key advances the timing 6 degrees. There are no side affects from the installation of this key. It must only be used in conjunction with a stock piston. This key works great with any other modification, Hi-rev CDI's, performance camshafts, carburetor kits, etc. Just not high compression or big bore pistons. We also include a flywheel puller for your convenience."

[pj88]

well it's done and runs like a raped ape!! Haven't had a bit of ping or any over heating! So to those that said "you can't" thanks you made me want to even more. Spent a little more time on the no brainers. Probally not for the bolt on babies but it works and works well!!

[300exBorg]

So you came on here asking for help. People told you what their opinions were and ya ignored them.... Oh well I guess, good luck with your bike man.

[pj88]

Came here poking around for some info but every now and then when you poke around you poke some sh_t . don't need luck, luck is for the lottery. By the way what did you gain with those brake levers, gold chain and fancy gas cap?

[JOHNDOE83]

Ya unfortunatly sometimes here you have to sift through the chit to get any real answers and sometimes alot of misinformation is put out there because of what dealers and mechanics tell people, Its best to ignore the BS around here.

Essentially you can make any mods work in conjunction with each other if you know what to do.

what did you end up with jetting wise and what method did you use?

I only ask because its nice to know what people with certain mods are running.

It also help future thread readers try to get a better grasp on jetting.

I would like to know to....:blah:

[pj88]

OK here is what we did. Started with a namura 11-1 stock bore piston. (used stock head gasket not a true 11-1) went with a magnum stage 2 cam mainly for the extra few degrees of duration over a hot cams stage 2 probably a little more sensitive to valve lash but worth it if you ask me (Longer the valves are open the more fuel and air you get in) sparks 6 degree advance key removed the choke spent a lot of time (blistered fingers) with 500 and 1000 grit wet/dry paper taking all the casting and rough edges out of the intake and exhaust. (like glass now) port matched the intake to the head with a dermal and 500/1000. Our exhaust welds were very clean so just cleaned them up a bit started out with spark arrestor out but quieted it down by just whacking off the screen. Four 2 9/16" and four 1" holes in the airbox lid. Stock 148 main and stock pilot. Have been reading the plug and it still has a black haze to it not the golden brown I'm looking for but a little ritch is better then lean no signs of detonation. It starts just fine after bumping the throttle a few times then cranking. This started as a top end with a cam and piston last year because it was starting to smoke. Just did the piston, cam, valve seals and lapping then after a few days of hard riding wouldn't hold 2nd gear. So figured what the hell if were going to split the case lets see how much bang for our buck we can get. We are running 100 octane right now but hope to tone it down to 98 with the right jetting.

Piston 80.00
Cam 100.00
Full gasket kit 60.00
Hours (including bench racing with friends) 80hrs
The look on your sons face when it still wants to stand up going into 3rd.

PRICELESS!!

[Stickman400]

OK, so you are running an 11:1 Namura piston with a 6 degree key AND on 100 octane???? Let me know when it melts that piston and ruins your motor........ Seriously though dude, you CAN'T run a 6 degree key with an 11:1 piston, it makes to much heat and will melt a normal piston, let alone a Namura. And you also don't need 100 octane on 11:1, you only need 93 pump. 100 octane is for 12.5:1 or higher.

[pj88]

well haven't been here since my last post. I figured I would give all the nay sayers an update. But first off have to comment on stickman. The higher the octane the more controlled the burn is. When you run more timing it is more important to have more of a controlled burn then an explosion. Anyways since early Aug. till late Nov. We beat the hell out of it. (that's what it's for) so at the end of Nov blew the head gasket and parked it. Well just got done tearing it back down and low and behold....... The piston............... WAS FINE!!!!!! NO DEONATION of any kind! if fact will be going with a thin copper head gasket. Going to do a little work on the stock head pipe and smooth out the welds a bit.
Remember compression + fuel = HP Get the motor to flow and you CAN up the compression and timing1718102949

[Stickman400]

Back when I typed that a few guys on here (and around where I live) had a similar setup and they melted their Namura's. Glad that it's held together for you but I'd say you just got lucky. And I'm not saying the way you built it is wrong or anything, it's just that piston. That same build with a Wiseco or JE would be great, but that Namura is just a wild card.

[Blodg]

I never saw anyone say that they thought you would have a problem with detonation. By running 100 octane on an 11:1 you would never have a problem with detonation. What people said is that by running 11:1 and a 6-degree key that it would run hot and could cause problems which is true. And then you tell us it blew the head gasket after 3 or 4 months which is a sign of running hot so it sounds to me like the naysayers may have been spot-on.

[quadmanw]

I run the sparks key with an 11:1 piston.. Does run a little hotter but nothing too extreme.. I'm willing to take the risk since I've best the chit out of the engine so far.

[Stickman400]

You've got an oversized oil tank quadman, I'd say that helps keep the temps down enough to be manageable.

[quadmanw]

Yeah, it should Stickman. Still runs a little hot but it's a quad.. With an air cooled engine lol. When I have the time to throw a cam in, then I will see if still running the key with it will over heat it.. And if it does.. I will go Spal fan lol

[cheater13]

Mine runs super hot. I guess I'll get that aluminum oil tank if it actually helps.

[quadmanw]

Deffiently not a bad idea... But it isn't a must

[forestbrian88]

Hey i have been all day Googling about jetting and carbs and ive been learning a few things but im still a bit confused my bike looks like its burning its Fuel correct i check the old plug in it and it was brown tan color
so tomorrow after an other beating ill get a look at the new one
so here my question is im planning onhaving a look at the carb in the near futur
and im Runing a Stock engine with the Namura 11:1 stock bore piston, Stock cam, with stock head pipe and rear Stock 450R exaust
Airbox lid is on (its cracked), and im Using a UNI filter
ive never had a 400ex and id like to get the most out of this with the carb i plan on putting a cam in it but still confused about wich one to go for...
but here with what i have for the moment what Carb setup do you think i should go for?

[cheater13]

Hey i have been all day Googling about jetting and carbs and ive been learning a few things but im still a bit confused my bike looks like its burning its Fuel correct i check the old plug in it and it was brown tan color
so tomorrow after an other beating ill get a look at the new one
so here my question is im planning onhaving a look at the carb in the near futur
and im Runing a Stock engine with the Namura 11:1 stock bore piston, Stock cam, with stock head pipe and rear Stock 450R exaust
Airbox lid is on (its cracked), and im Using a UNI filter
ive never had a 400ex and id like to get the most out of this with the carb i plan on putting a cam in it but still confused about wich one to go for...
but here with what i have for the moment what Carb setup do you think i should go for?
Take the airbox lid off and get a Hotcam Stage 2. Most likely everyone else will tell you the same about the choice of cams.

[forestbrian88]

and for jetting i think the bike is still stock... so i wonder if its too lean for the 11:1 piston and 450R exausth?

Edit:

Im getting an AEM Wide Band O2 sensor kit ill be checking it later on and ill update what current jets i have

[JOHNDOE83]

A wide band sensor is not needed at all and doesnt really work on these types of motors.

stock jetting is already to lean from factory, you need to buy multiple jets start big and work your way down until the jetting is right.

check out the how to jet section on www.jetsrus.com go to the FAQ section and read about main jet tunning, you should also get a 42 pilot jet.

[forestbrian88]

Is there anybrand of jets i should or should not consider?
im just new to the jetting thing been doing my own mechanic on cars and atv but never had to touch a carb... so even for the past days reading and learning i get the concept but still a bit confused

[forestbrian88]

i dont understand why the o2 wideband wont work? heard lots of good thing about it good tool for carb tuning

[Stickman400]

Order your jets from here: http://www.jetsrus.com/a_jet_kit_atv/honda_400_TRX400EX_1999-2008.htm

Or if you have a local dealer get genuine Keihin jets, don't buy a Dynojet kit or anything like that, they make jets in different sizes and make it harder for us to guess what you will need. And a few guys on here have installed wide band O2 sensors on their 400s and have had good luck with them.

[forestbrian88]

Allright so to sum this up.. Il be going Keihin 42 pilot I just finished dismantling my carb and had the Choke removed... I still had the factory 38 pilot and 142 main so i guess its lean for sure... with the 11:1 Piston and Uni filter and 450R exaust
so ill order the kit on jetsRus do some trial and error when i get my Wideband O2 controller and ill post some A/F RPM stats (if the RPM works with the 400ex...)

[JOHNDOE83]

Im not gonna say they dont work at all. "02 sensors"

Im just saying that generally they are designed to work with computerized fuel systems and multiple cylinders that produce HP differently then a air cooled, single piston atv motor thats basically a glorified lawn mower engine. "like a 400ex"

One of the largest jet maufacturer's reccommends that any 2 or 4 stroke should generally run at optimum performance when its just under being to rich "the high rpm stutter" once you get the stutter/stumble from being to rich you only go down 5-10 jet sizes.

Whats cool is now your gonna have the ability to test it out for us :muscle:

You could tune it both ways and see what the actual difference is and compare both.

[forestbrian88]

1718103223

ok just a little question here... im reffering to my manual... and i cant understand if this goes in there or not???

A is my main jet
B is what i dont know or cant see in my manual
C is my pilot jet
D is the needle jet

Can someone correct me if im wrong and help me identify B

[forestbrian88]

Im not gonna say they dont work at all. "02 sensors"

Im just saying that generally they are designed to work with computerized fuel systems and multiple cylinders that produce HP differently then a air cooled, single piston atv motor thats basically a glorified lawn mower engine. "like a 400ex"

One of the largest jet maufacturer's reccommends that any 2 or 4 stroke should generally run at optimum performance when its just under being to rich "the high rpm stutter" once you get the stutter/stumble from being to rich you only go down 5-10 jet sizes.

Whats cool is now your gonna have the ability to test it out for us :muscle:

You could tune it both ways and see what the actual difference is and compare both.

well im getting the A/F gage with usb data loggin so ill keep a chart of the A/F ratio i get recorded from the o2 sensor with diffent carb setting so ill go from there after ...
i know i have to set it around 12-13.1 because 14.7 would be better off for FI setups
but ill do some trial and error when its all installed and keep a log