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Rejetting XR400

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I have a 2004 XR400 and I am in the process rejetting it. Now I purchased a new main jet which is probably about and inch long and when i pulled out the stock main jet, this thing is like 2 inches long, whats the deal? I have never rejetted a bike before so either I got the wrong thing...or who knows. Any help would be great

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Your stock carb is a PV(pump valve) carb. If it is a California model you will need a new needle. I'm not for sure on the model number for the needle, but if you do a quick search (carbu* needle* Cali*) you should find it pretty quick, it is something like A16. A good clip position is 3rd from the top to start with. Raising the clip(higher on the needle) leans out your fuel flow and lower richens your fuel.

As for your jets depending on your elevation and mods it will vary. The type of jets you need are Keihin 13 series for your main jet and Keihin 21 series for you pilot jets. (The pilot jet is the long jet you pulled out)

I have removed my air filter box snorkel, ground header welds, UNI air filter, and drilled the 3 holes in the exhaust. I run 160 main and 60 pilot at 1800 feet elevation and the bike runs great and starts cold usually on 1 kick.

I have found a great place to get jets is Dennis Kirk. You can get the Main jets in a 5 pack for 20.99 and individual pilot jets for 4.99. I would get the main jet pack in the 150/152/155/158/160 kit and several of the pilots 52/55/58/60. That should cover your jetting range.

Don't forget the needle, from what I've read it is very important on the California model bikes.

Good luck

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I have a 2004 XR400 and I am in the process rejetting it. Now I purchased a new main jet which is probably about and inch long and when i pulled out the stock main jet, this thing is like 2 inches long, whats the deal? I have never rejetted a bike before so either I got the wrong thing...or who knows. Any help would be great

The tube the main jet screws into often comes out with it. If so, swap the jets, then put the whole thing back in.

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Wow, that sounds very involved...this is my first rejet so pardon me if i get lost in the terminology. Are you sure that was the pilot jet i pulled out? The reason I ask is the number on the jet was something like 133 0r 138 and I thought pilot jets were in the 40's and 50's. Perhaps it is best and i have a pro do this, but I really don't wanna have to spend money that doesn't need to be spent

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that thing that was 2" long was the main jet plus the jet holder. The holder should not have come out. That means the jet itsself was tightened tighter than the holder was. You want it to be the other way around so that when you want to change the main jet, it comes loose from the holder without loosening it too.

What makes you think your bike needs rejetting? I would find some local help(besides a dealer/shop) that can help you jet it properly and so you can learn a thing or 2 also.

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Depending on the intake/exhaust mods you have done, the bike will need different jetting.

There should be an outline of what jets to install in my FAQ at the top.

Pull intake snorkle and Unifilter = 55 pilot and 155 main.

Full Gordons mods = 58/60/62 and 160/162 main. 60 and 162 is most common.

Every bike and riding condition is slightly different, this is pretty close.

Altitude and TEMPERATURE makes a difference.

The CA needles should be swapped out for the 49 state needle.

This is a bit more involved and I only have met one person that

can do it without removing the carb.

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On my bike the snorkel is pulled, uni filter and white bros E2. The main jet i pulled out was a 138 so im guessing the pilot jet was a 52. Should I bump it up to the 162 main jet/62 pilot jet? By the way, where is the pilot jet on the carb?

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I think 162/62 may be a tad rich but run it and see. The pilot jet is in the float bowl just to the rear of the main jet but a little higher up. It's round, not hex like the main. Comes out with a straight slot screwdriver.

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I have a Calif. 2004 model XR400, too. From the factory this model comes jetted 138 main and 52 pilot and is horribly lean. I punched three holes in the stock exhaust, removed the snorkel and put in a Unifilter. Then bumped up the main and the pilot to a 158 and a 58, I think - I'd have to check my manual were I wrote it down to be sure. At first I had a smaller pilot jet and it was still too lean - when I had my valves adjusted post break in the mechanic said I should probably go up one more size on the Pilot. So I had to do the rejet on the pilot twice.

It was my first time rejetting a bike. Since it sounds like it will yours, too, my advice is to not touch the needle jet or clip position until you get the main and pilot jetting set up just right. If you do it all at once, and it doesn't run right, too many variables to isolate may drive you crazy.

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On my bike the snorkel is pulled, uni filter and white bros E2. The main jet i pulled out was a 138 so im guessing the pilot jet was a 52. Should I bump it up to the 162 main jet/62 pilot jet? By the way, where is the pilot jet on the carb?

Go with a 60 pilot and 162 main. That will be in the ballpark.

To put in the pilot jet, you need to remove the float bowl. The little white slosh guard is a PITA to put back on.

Want to know how a really rich bike rides? Warm up the bike and ride it a bit. Then put the bike on choke on 1/2 and do some riding for a very short time. (It's not good to ride with the choke on. Too much gas washes away the oil on the cylinder walls, per Honda manual.) You'll find what an overly rich bike is like.

You'll know if the pilot jet is right or not by adjusting the fuel screw. See the FAQ on how to adjust it.

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Did you change the needle? I have a 2004 Cal. XR400R too and I'm considering a Uni filter, maybe pulling the snorkel (prefer to keep the noise down by keeping it in), and leaving the exhaust stock. I'm not going to drill any holes in it. I'm hearing 155/55 is around the correct combo for this. But I also hear you have to get a A16A needle to make it all work right.

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Wow, that sounds very involved...this is my first rejet so pardon me if i get lost in the terminology. Are you sure that was the pilot jet i pulled out? The reason I ask is the number on the jet was something like 133 0r 138 and I thought pilot jets were in the 40's and 50's. Perhaps it is best and i have a pro do this, but I really don't wanna have to spend money that doesn't need to be spent

here's a pic:

http://www.ronayers.com/fiche/200_0345/carburetor/carburetor.cfm?man=ho&groupid=14720&parent=14710

#3 is the needle you need to replace. cali only have a less than deseriable needle oem. putting the 48 state needle in (a-16) makes the bike run better. the main jet would be 138, 160 etc (you want 160) and is in the middle of the carb. it's held into place by a carrier tube that has holes into it. the needle slides in and out of this carrier tube and provide fuel when a lot of throttle is applied. the pilot jet is smaller (get the correct smaller flat head screw driver!!!) and has number like 38, 60 (you want 60). this jet control fuel when you use light throttle. there is also a fuel screw at the bottom of the carb to fine tine the pilot jet.

elevation & engine tune are a factors to determine proper jetting. as you go up you have less oxygen and thus need less fuel. lean is when an engine does not have enough fuel and the engine run too hot. rich is when it has too much and the engine stumbles. here's a starting point chart using honda's jetting charts:

0000 ft > 160 / 60

1600 ft > 158 / 58

3200 ft > 155 / 55

5000 ft > 152 / 55 (54 act., turn pilot in more)

6500 ft > 150 / 52 (53 act., turn pilot out more)

9800 ft > 148 / 50

others will use a 162 main with a 60 pilot jet. another thing you'll want to read about and do is gordon mods.

this stuff is all standard intermidate carb tuning work. if it seems confusing or difficult, stay out and pay some to do it right. don't fack up your carb.

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On 8/2/2006 at 8:55 AM, Kev_XR said:

Depending on the intake/exhaust mods you have done, the bike will need different jetting.

There should be an outline of what jets to install in my FAQ at the top.

Pull intake snorkle and Unifilter = 55 pilot and 155 main.

Full Gordons mods = 58/60/62 and 160/162 main. 60 and 162 is most common.

Every bike and riding condition is slightly different, this is pretty close.

Altitude and TEMPERATURE makes a difference.

The CA needles should be swapped out for the 49 state needle.

This is a bit more involved and I only have met one person that

can do it without removing the carb.

Resurrecting old thread here.  I need help jetting a 2000 XR400R that I am shipping from Colorado to my friend in West Virginia.

Here is the skinny.

Bike:  2000 XR400R California model with Uni filter and Big Gun exhaust

Stock jetting (California model) - 142 MJ, 52 PJ, A2E needle

Current jetting (done by PO):  158 MJ, 60 PJ, and non-California needle A16A

I haven't changed the jetting from when I bought it used a few years ago.  It seems to run fine in Colorado, but I can't recall if I've taken it to high elevations.  It hasn't been my primary dirt bike.  

The PO replaced the lean California needle.  However, I also see from the parts diagram that the needle jet part number is different between the California and non-California models.  Should the needle jet be replaced to?  It looks like it is about $27.

Any other suggestions on jetting for West Virginia (roughly 1000 feet elevation).  My friend isn't super mechanically inclined, so I'd like to get the jetting sorted out before I ship it to him.

Also, why are the jetting recommendations that I am seeing for the post 1997 models SO much richer than stock?

Thanks all!

 

 

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After '97, Honda leaned the stock jetting out for emissions purposes.

When you mod the airbox and exhaust you have to jet richer. Your bikes current jetting should be very close to what it should need for 1000' with those mods. The pilot may need a 60. That Big Gun exhaust is the question, as far as what's going to be needed for jetting, but 160/60 at 1000' should be real close. Needle 3rd from top.

I would not replace the pressed in brass needle jet. The difference between the two can probably be made up with clip position of the needle if required.

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96-97 were jetted assuming the customer would remove the intake snorkel and exhaust quiet core, then go race.

1998-2004, the bike was jetted assuming the intake snorkel and exhaust quiet core would remain in place.   When the bikes are opened up, the jetting needs to revert to the 96-97 jetting.

"Current jetting (done by PO):  158 MJ, 60 PJ, and non-California needle A16A"

This will actually run fairly well at sea level.   XR400's are very tolerant of "ball park, not perfect" jetting.

To improve...

You might add a 162 main jet.  It will probably run fine with a 158-162.  You will just notice it has more top end with a larger jet, until you go too big, then it blubbers.

60 or 62 pilot jet should work.  See the "How to adjust the fuel screw" to see if you have the correct pilot. 60 will work.  62 might be better.

You have the right needle, A16A.  Find a nice safe place for the California needle.  Leave it there for ever.

You can change the PJ and MJ by removing the float bowl.  Changing the needle requires removing the carb, though a few can do it in place.

Edited by Kev_XR

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On 8/2/2006 at 10:55 AM, Kev_XR said:

Depending on the intake/exhaust mods you have done, the bike will need different jetting.

There should be an outline of what jets to install in my FAQ at the top.

Pull intake snorkle and Unifilter = 55 pilot and 155 main.

Full Gordons mods = 58/60/62 and 160/162 main. 60 and 162 is most common.

Every bike and riding condition is slightly different, this is pretty close.

Altitude and TEMPERATURE makes a difference.

The CA needles should be swapped out for the 49 state needle.

This is a bit more involved and I only have met one person that

can do it without removing the carb.

Yea - if memory serves, I have a 58 pilot and 155 main in mine with a pulled snorkle, stock filter, and stock exhaust at roughly sea-level.  Hi Kev.

JayC

Edited by jayc250x
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23 hours ago, jayc250x said:

Yea - if memory serves, I have a 58 pilot and 155 main in mine with a pulled snorkle, stock filter, and stock exhaust at roughly sea-level.  Hi Kev.

JayC

The Unifilter helps.  I ran stock and UniFilter back to back.  The UniFilter is better.

XR400's are jetted so far all over the place, a local tuner offered me to put my XR400 on a dyno and tune it for free.  I wish I had done it. 

When I did a race at 5,000 feet in Nevada, I was too lazy to rejet.   Nevada is more relaxed about noise, so I pulled the "Vortex quiet core" to open up the exhaust.  Made the sea level jetting good enough for the race. 

My XR400 is plated, so I could do test runs on the freeway.  Swap jets, get up to 65-70 mph.   More top end speed, I have the right main jet.  Blubbers,...too big.

62 pilot and 162 main is what Honda put into the XR400 when the idea was to pull the intake and exhaust restrictions.  So the jetting needs to be balanced for your XR400 intake, exhaust, elevation, temperature, humidity, etc. 

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