yz426f 02' carburetor question/reference

[davidroxx23]

Hello all, i'm new to the board here and new to riding. I recently purchased a 2002 yamaha yz426f. When purchasing the bike, the previous owner told me it needed the standard carb cleaning and whatnot. After having a buddy at work rebuild and clean the carb, he's having an issue.

After starting the bike and running it for a bit, the carb will leak gas out of the overflow on the bottom bowl when attempting a 2nd/warm start. He's confident he has all goods installed right and thinks the bottom bowl may be cracked from getting water in it and sitting over time.

Does anyone know of any common issues with these carburetors? Any other possibilities besides the bowl being cracked?

Last of all, are 2000 and 2001 carburetors compatible with this 2002 model? Thanks in advance for all the help!

[Stinger1133]

I had that happen once and found the float setting was off. After I got the correct setting the leak stopped and the bike hasnt leaked since. Might double check that float setting. Also check the diaphgram for cracks. I had that problem as well and it leaked out of the top of the push rod tube and ran down the side of the carb. It would only leak when the throttle was twisted.

Here are the links for the service manual.

http://www.yamaha-motor.eu/eu/services/owner-manuals/index.aspx

http://www.yamahaownershandbook.com.au/?r=0

[davidroxx23]

Thank you. I cant quite seem to get the manual to download. I will inform my buddy at work about this possibility. Does anyone else have any input?

[grayracer513]

Does anyone know of any common issues with these carburetors? Any other possibilities besides the bowl being cracked?

Last of all, are 2000 and 2001 carburetors compatible with this 2002 model? Thanks in advance for all the help!

The '00 and '01 carbs are directly compatible, but if you want a major bolt-on upgrade, buy one for an '05 or later.

Common problems other than obvious wear items like the AP diaphragm are the slide vacuum release plate wearing/cracking/chipping and causing idle and part throttle troubles. Pilot jet varnishing can result from sitting, as can seals drying and cracking. If the TPS is removed or loosened, it can be a pain to get back to where it should be, too, and they have been know to develop faults of their own. If in doubt, try running with it disconnected.

In your particular case, the things that would cause the fuel overflow might something as silly as a loosened drain screw (3mm Allen near the hose at the center of the bottom of the bowl. More likely it's due to a worn or cracked float needle tip, a shrunken or cracked O-ring between the needle seat and body, or a float hinge binding because of varnish deposits.

Try the manual again from the Euro site now that the link is fixed.

Here are the links for the service manual.

http://www.yamaha-motor.eu/eu/services/owner-manuals/index.aspx

http://www.yamahaownershandbook.com.au/?r=0

You can't copy/paste the links that way. I already edited it, but wherever you see a "..." in a link on this site, you have to right-click it and do a "copy shortcut" or "copy link location" and paste that. Otherwise, part of the address will be missing.

[davidroxx23]

The '00 and '01 carbs are directly compatible, but if you want a major bolt-on upgrade, buy one for an '05 or later.

Common problems other than obvious wear items like the AP diaphragm are the slide vacuum release plate wearing/cracking/chipping and causing idle and part throttle troubles. Pilot jet varnishing can result from sitting, as can seals drying and cracking. If the TPS is removed or loosened, it can be a pain to get back to where it should be, too, and they have been know to develop faults of their own. If in doubt, try running with it disconnected.

In your particular case, the things that would cause the fuel overflow might something as silly as a loosened drain screw (3mm Allen near the hose at the center of the bottom of the bowl. More likely it's due to a worn or cracked float needle tip, a shrunken or cracked O-ring between the needle seat and body, or a float hinge binding because of varnish deposits.

Try the manual again from the Euro site now that the link is fixed.

You can't copy/paste the links that way. I already edited it, but wherever you see a "..." in a link on this site, you have to right-click it and do a "copy shortcut" or "copy link location" and paste that. Otherwise, part of the address will be missing.

Thank you for the response. I sent a PM as well

[grayracer513]

Please don't send PM's regarding technical questions when they can be answered in the forums for the possible benefit of others. Your question was:

what model bike should I be looking for if i were to purchase an 05' or newer carb. are all the larger 4 stroke carbs compatible in this situation? thanks

The information applies to YZ426/450 carbs only. Some others may very well fit and work, but you'll need to do your own research on that.

[davidroxx23]

anyone else on this?