02 400ex

[foreman 450]

Hey guys help please???? I put hmf pipe on my ex put in the 155 they sent with pipe. Ex runs fine until you let off the throttle then it pops and cracks. The mixture screw is 2 half turns out needle is 2nd clip down. When your running 2nd 3rd gear poking along it acts like its trying to die or run out of gas.I have a uni air filter on it also.Its an 02 still has the factory tires on it and I gave $600 for it. Did I do good or what.

[bkelley]

155 is pretty big just for a slip on. I would try going down to a 150 or 152.

[clemsonteg]

155 might be a little on the rich side, I would keep it in though and go 3rd clip down on the needle and 3 turns out and see what that gets ya.

[foreman 450]

Ok I will try it both ways. I have extra jets. Thanks for the info.

[dalejiw25]

Sounds lean on the pilot jet. Whats in it now ??? Try a 42 and put the needle on the third clip. AF screw 2-1/2 turns out.

[honda400ex2003]

Originally posted by dalejiw25
Sounds lean on the pilot jet. Whats in it now ??? Try a 42 and put the needle on the third clip. AF screw 2-1/2 turns out.

x2 that was going to be my guess. steve

[foreman 450]

Its got the stock 38 pilot in it now.

[TRXRacer1]

Originally posted by foreman 450
Its got the stock 38 pilot in it now. 3 or 3 1/4 turns is closer to where you should be with a 38. Before you buy the suggested part finish tuning what you got. Most likely you'll be fine once you open it up.

[JOHNDOE83]

You need a 155 just for a pipe...believe me.

the poping comes from the pilot like stated above, they say if you go more the 2 1/2 turns you need a biggger pilot, but honestly if it works 3 1/2 turns out, its good enough.

Saves you from having to buy one.

[foreman 450]

Ok thanks you guys are great. Im a new be at this stuff.The guy I got the ex off of gave me a box full of keihin jets. I will check it and see if there is a 42 pilot in it. If not I will turn the screw out to 3 or 3 1/2 and try that. When I get some pics I will post them and you all can tell me If I got burnt or not .

[TRXRacer1]

Originally posted by foreman 450
Ok thanks you guys are great. Im a new be at this stuff.The guy I got the ex off of gave me a box full of keihin jets. I will check it and see if there is a 42 pilot in it. If not I will turn the screw out to 3 or 3 1/2 and try that. When I get some pics I will post them and you all can tell me If I got burnt or not . Don't even look for the 42, if you're poppin' you're lean. Turn it out to that 3+ range and see what happens.

[foreman 450]

Ok Im gona go mess with it see what happens I will post back later when I get done with it.

[foreman 450]

Ok I put the needle on 3rd setting put the A/F screw out 3 turns rode it down the road and it helped it alot totally different ex.I looked in my box and there is a 40,42 pilot and a 150 and 152 main in there if I need them to.

[dalejiw25]

Originally posted by TRXRacer1
Don't even look for the 42, if you're poppin' you're lean. Turn it out to that 3+ range and see what happens.
Wow Can't believe this statement. 3 1/4 turns out is good.... Dude drop in the 40 min. I'd go 42 myself. You gotta start at the pilot when tweakin a carb. 3 1/4 turns outand the jet is right .... Please.

[TRXRacer1]

Originally posted by dalejiw25
Wow Can't believe this statement. 3 1/4 turns out is good.... Dude drop in the 40 min. I'd go 42 myself. You gotta start at the pilot when tweakin a carb. 3 1/4 turns outand the jet is right .... Please. What can't you believe? That's what the mix screw is for. If he can get all the fuel he needs for the pilot circuit with a 38, 3 turns out then there's no advantage to installing a bigger pilot jet and choking it back. Either way is the same amount of fuel. If his pilot circuit is still lean at 3 1/4 turns out then he needs to go bigger.

[beags86]

Originally posted by TRXRacer1
What can't you believe? That's what the mix screw is for. If he can get all the fuel he needs for the pilot circuit with a 38, 3 turns out then there's no advantage to installing a bigger pilot jet and choking it back. Either way is the same amount of fuel. If his pilot circuit is still lean at 3 1/4 turns out then he needs to go bigger.

x2, listen to the cheese head, he knows what he is talking about.
i couldn't have said it better myself.

[foreman 450]

TRXRacer1 what you told me to do helped my EX alot. Starts better runs better.No more popping. dalejiw25 your way would of worked to im sure,but I dont know alot about carbs It was easier for me to do it the TRXRacer1 way. Thanks alot for both your alls suggestions and know how Help me alot THANKS.

[01 400EXer]

Running a little rich is good.

I have a 2001 400EX with an HMF Slip on. My set up is a 158 Main jet with a 42 Pilot jet and the needle in the stock position. In the winter I bump the Main jet up to 160 or 162. Without counting I think my air fuel mixture screw is around 2 out. I have never counted them I just listen to until it sounds good and I can chop the throttle without a bog. I know I don;t have it turned out very far. I also have 6 air box lid vents.

My 400 seems to start and run great just about all the time unless it is really humid. My starting method is 3 pumps of the throttle, full choke to start and once it starts 1/2 choke for about 10 to 20 seconds and then no choke and wait for it to warm up.

I have had a pipe on my bike since the first year of ownership (2001) and have only had to change the plug 3 times. My plug is always a dark tan / chocolate color.

[JOHNDOE83]

changing the pilot out for a bigger one is more for when you remove the choke....then you can use the pump the throttle and hit start method and start right up with no choke.

removing the choke helps add a lil more unrestricted air flow, not nessesarily adding horse power but deffinetly helps throttle respose...just figured id throw that out there.

I always run slightly rich also.

[dalejiw25]

They ship these things with lean pilots in them to Please the EPA and the Tree Huggers. The small jets are no different than the lousy exhaust and the terrible suspensions on them. As soon as you get em home tear em down, Make em right and have a huge Garage sale with the crap they put on at the Factory. The only reason I suggested a larger pilot jet is if your in there replacing the main and you have a bigger pilot in your hand, Why not. It'll only make it better. Just my opinion, Everyone has one.

[01 400EXer]

I disagree with you for only changing the pilot out for choke removal. Honda's are jetted lean from the factory to make California happy. Every Honda I have had I have always richened the pilot circuit to make starting easier. Starting is not so difficult in the summer but in the winter (depending on where you live) it can be a pain if the pilot is not increased. I was just letting him know what works for me and my Honda's and I swear by it.
changing the pilot out for a bigger one is more for when you remove the choke....then you can use the pump the throttle and hit start method and start right up with no choke.

[dalejiw25]

Originally posted by 01 400EXer
I disagree with you for only changing the pilot out for choke removal. Honda's are jetted lean from the factory to make California happy. Every Honda I have had I have always richened the pilot circuit to make starting easier. Starting is not so difficult in the summer but in the winter (depending on where you live) it can be a pain if the pilot is not increased. I was just letting him know what works for me and my Honda's and I swear by it.

Oh Hell Ya !!!!

[JOHNDOE83]

Originally posted by 01 400EXer
I disagree with you for only changing the pilot out for choke removal. Honda's are jetted lean from the factory to make California happy. Every Honda I have had I have always richened the pilot circuit to make starting easier. Starting is not so difficult in the summer but in the winter (depending on where you live) it can be a pain if the pilot is not increased. I was just letting him know what works for me and my Honda's and I swear by it.

I wasnt disagreeing or trying to disprove anything, Ive been saying the same thing my whole time on exriders, they come lean from factory for sure.

[foreman 450]

Guys there isnt any need in arguing bout it. Both ways would of worked fine one was just easier for me. I will tell ya this tho when I took the plug out It looked real gud on the electrode fireing great but the outer ring were the threads start was black

[JOHNDOE83]

Theres a new thread on plug reading, you should check it out?

[01 400EXer]

I wasn't arguing, I was just stating my experience. I am not one to worry about plug color unless it is white or light gray. Also if you run race fuel or gas with a lead substitute the color of the plug will ususally be in the gray range and not tan / brown. I listen to my machine. Just like where you started with listening to the popping and cracking on decel and you knew you needed to do something about it.

[TRXRacer1]

Originally posted by dalejiw25
It'll only make it better. Just my opinion, Everyone has one. This is where you're wrong, it's not an opinion. He's either getting enough fuel or not and right now he is. Maybe with future mods or conditions he may need to go bigger but right now it's pointless.


foreman 450. glad it all worked out for you. Just remember, the only time you need to up the pilot is when the one you have can not offer enough fuel. A 38 3+ turns out is similar to a 42 2 turns out. It's still the same amount of fuel. One is just opened up while the other is choked back. You're searching for a "range" when adjusting the pilot circuit and I don't know if it's a secret to most or if people would rather internet jet rather then learning how to do it right (nothing meant towards you). It truly is the easiest area on a carb to tune once you learn how.

Shoot me a PM sometime with your email and I'll scan a page from the Honda tech manual that explains it quite well.