Carberator trouble

I got an new 04 from the dealer, took it home fired it up let it run for less than a minute. Took the choke off, the bike ran like crap. It would cough backfire and then die, pulled the choke back on run the bike up and down the street take the the choke off and it still does the same thing. Put in fresh gas in set the jeting as per manual 172 main 40 pilot 2 1/2 turns out on feul screw for 4800 feet 50 deg F. No change, took it back to the dealer. They Put back in 168 main set feul screw 2 turns and changed gas. Bike seamed to be all better, had to wait a week for wheather to clear then went to the track and it did the same thing. Played with the feul screw changed main to 172 no change. Took back to the dealer , they cleaned the carb. put 168 main back in (to lean). Ran good when i Picked it up , had to wait a phew days for weather to clear again! but it did the same thing, runs great with the choke on runs like *^%$#@:"?< with the choke off. It seams like one moto it runs differant than the next, im baffeld and dont trust the dealer any more. Any help would be appriaciated

Sounds like you have an airleak. No matter what jetting you have in there, it won't run good for long.

check your hot-start valve to make sure it isnt sticking open.Water can get in there from the cable junction.

What is the best way to check for air leaks. I heard of spraying WD-40 around the intake area. Is there a better way.

I don´t think it´s an air the bike brand ner or?

I think it´s the carb setting....i don´t know how much 50 degrees F seden we use celsius...But i´m prettey sure your bike is running BIKE TIME to lean!

When my bike is running to lean it starts backfireing and i have to run it on the said you had 172 main...that is ******* lean....damn man...i have 190 and it´s 12-13 degrees CELSIUS in sweden and pilot jet 48!

What i had done if i were you...get out and take the spark plug off fast as hell and get you ass back here and tell me how it looks!

If its white/grey, that bike needs biiiiiiigger main jet and pilot jet!

the spark plug should be like..choklet-brown.. if its black its running to rich..the spark plug tells you everything!!

What is the best way to check for air leaks. I heard of spraying WD-40 around the intake area. Is there a better way.

First of all, check that the hot start is not stuck open. Next, make sure the carb is in the boot all the way and the clamps are tight. If you still suspect an airl leak, use ether (hot start), not WD40. Spray the hot start where the suspected air leak is while the bike is idling. If there is an air leak, the idle will change.


Check this once. This happened to me. My bike when I got it some dirt got past the filter so I took off the carb and cleaned it. Afte I put it back together it did the same thing yours is doing, would run fine with the choke on but wouldn't run at all without it. I cured the problem by putting in a 50 pilot jet and that fixed it but just recently I took my carb back apart and realized that the plate on the throttle slide was on upside down haha. The plate is actually the same shape as the slide so it'd be easy to put it on wrong if you're not paying attention. The plate actually goes on upside down compared to the shape of the slide itself and a way to tell if you have it on right is if you look into you're carb with the slide closed there should be a small opening at the bottom of the slide on both sides that allows fuel through when the slide is closed so the bike can idle. Check that out dude and see if that's your problem b/c it happened to mine. I switched the plate around and put jetting back to stock and it runs fine.

I did check the hot start, I am sure it is not sticking. I sealed the boot on the cable with vacuum grease and put a light film of pro circut assembly lube around the plunger and set the free play a little more than what the Manuel calls for. The spark is more of a tan color than a grey or white. Haven't tried the WD-40 trick yet, Ill try that tomorrow. The carb boots are not loose I'm sre of that. 13 deg c is about 5 deg less than 50 deg f i think. The dealer checked the plate on the slide and it was on the correct way I whatched them do this the first time I took the bike bake to them Oh and by the way did I say Awesome bike yet!

From reading your post it seems they never changed the pilot jet to a bigger size. You need a #42 for 70 degree days to get the bike over it's too lean factory setting. At 50 degrees you would need to go even larger. These bikes are sensitive to temp changes. Changing the main never helped because that only comes into play from nearly 3/4 throttle to wide open. Also make sure the accelerator pump circuit is working all the time. Without that squirt of fuel when you crack the throttle it will lean out, bacfire and die. Get you a T handle fuel screw so you can adjust the fuel setting as minor temp changes occur easily.

Do you think a 42 pilot would run OK at my elevation. The tracks I ride at are between 4800 and 5100 feet.

Don't know alot about the elevation change except that would make it richer which might help at the lower temps. The owners manual has a chart to adjust jetting size for temp change and elevation change as well.

whats the stock jetting?

i'm running 178 main jet, 3 rd clip needle @ stock postion and 42 pilot with 2 -2 14 turns out. our elevation is about 4600 - 5000 above sea level. During the winter i was even up to a 180 main jet needle to 4 th clip and 2 1/2 turns out @ 0 degrees and colder.

The stock jetting is 178 main 40 pilot 3 clip and 2 1/4 turns on the feul screw. The dealer put in a 168 main same pilot and clip and 2 turns out. I just put in a 42 pilot 172 main 2 clip and it ran best at 3 3/4 turns, Im headed to the track Il let you now how that deos.

I would check the sparkplug gap. Then goto the jetting.

any time you start turning over 2 1/2 turns go up a pilot size.

With the 42 pilot and the fuel screw at 3 3/4 turns out the bike ran really good, a major step in the right direction. It seams to me the pilot is a little big for the elevation but the bike is telling me thats what it needs

Just bought a RM-Z250 a couple of weeks ago and I'm having the same problem. Initially it was difficult to start and didn't really want to idle, especially once I pushed the choke in. But once I got it fired up, it ran great for the hour that I rode it. Took it home to change the filter and oil (per the instruction manual) and had a hard time starting it to warm up the oil. After changing the oil I again had a tough time starting it. Eventually it fired up, but died after I pushed the choke in. Kicked it (I know it sounds bad) until my foot was sore from hitting the peg and my calf was sore from the kick lever hitting me in the back of the leg. Figured I fouled the plug, so I changed it and the bike started up, but only ran until I pushed in the choke. Perplexed, I took the bike back to the dealer where the last I heard, they still had the carburetor apart. Hopefully I'll get it back this week and I'll let you guys know what they came up with.

i made a mistake on mine once. there is a plate that goes on the slide on the carb. Look at that plate. When you are looking at it, there is a letter stamped on it. It is the letter "M". If when you look at it the M is a W then it is upside down. It will make the bike run like crap all the time. Take the slide out and flip it around and put it back together. I did this and my bike worked great again. Simple mistake made when putting my bike back together late at night.

try turning up your idle speed, also.

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