Running rich

I have an 04 XR400 with a FCR carb off of a 2002 YZ426.For jetting 160 main 36 pilot, needle 3rd slot down.

I am in Baja so limited parts here. I can get some stuff brought down if I can figure out what I need

The float was not shutting gas off so I pulled the seat out and found a dried flat oring. I replaced that with a round oring and reinstalled and the needle and seat now seal. Now as the bike starts great cold and as it warms up it starts to run rich. I can turn the fuel screw all the way in and not have the bike kill. I think I am getting fuel from some other source. I can run with the fuel screw 1/2 to 1 turn out and it runs pretty good. I am at sea level2 and run these jets before and no problems. fuel screw 2 turns. I also ran it in Utah last summer at 4500' to 9500' and could go to about 1 turn and still run good. I don't really think it is a jetting problem but siphoning fuel from somewhere else. Wide open the bike runs great.

Thanks for any help Mike

Have you tried one size smaller pilot jet,mike?

If you can screw it in all the way in and no change usually means the pilot you have in it currently its too big.

Hope this helps

Leaky choke plunger (corroded/dry plunger)

Dribbling accelerator pump nozzle (dirty nozzle)

Partially clogged air jet (at the intake bell)

Thanks guys.

No choke, So at least I can check that one off the list. It's either getting fuel from somewhere else,Acel pump nozzle? Work on that tomorrow.

Not enough air Yea. More checking and I'm already in there.

Thanks again Mike

Well got it running good, Went for a 50 mile ride today. mixed some dirt road, some singletrack, some river bottom bushwacking. Bike ran good. First or second kick hot or cold. Good power down low chugging. no pop on decel, Ran good wide open. .now I have to figure out jetting. The plug looks weird to me. Pretty lean on electrode and soot at bottom of threads. What do you guys think?

Thanks MikeP1000158.JPG

That plug says that you are too rich, and the plug is way to hot.

But, you have to remember, that the gas you are using is probably full of additives, so you have to pretty much ignore the color of the insulator.

http://www.braigasen.com/howtoread.htm

Another question. Could it be possible the oring on the slide is deteriated and causing a vacuum there? To remove the slide do you remove the small screw on top and then remove the hex screw the small screw came out of the center of? Hope this makes sense.

Thanks Mike

If the bit still idles with the fuel screw gently seated (and the screw/spring/washe/oring) in good condition, the idle speed low enough to ensure you are off of the needle, then you may want to drop a size in pilot jet. This will only affect idle and if you are too rich elsewhere, have to adjust the corresponding carb circuit.

By the way, ignore how the plug looks. All that matters is how the bike runs.

Well just did a 250 mile ride. Mixed singletrack, rough 2 track and some wide open roads. Bike ran great, good fuel mileage.I ended up dropping the needle 1 slot and am a about 1 turn on the fuel screw. I don't know if its perfect but the bike runs good, easy to start hot or cold and after a fall.

I'm done fiddling until I get home and parts are available.

Thanks to all Mike

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now