02 YZ426 Rebuild carb or swap to new-er year?


8 replies to this topic
  • Spartan426

Posted August 27, 2014 - 06:56 PM

#1

Hey everyone,

the tittle pretty much says my question. I have a 2002 YZ426 and My gaskets in the carb are pretty worn, flat and hard, I've had some inconsistant starting issues and my valves are in spec. seems like It's time for a rebuild or swap to a new-er year carburetor? I'd just like some opinions on which would be more benefitial to more power, idleing or perhaps starting?

I know the inconsistant starting could be due to jetting, however I'm not very knowledgeable about it yet. I'll be doing some reading on jetting stickies but I'm still wondering if rebuilding the 02 carb is worth it vs buying a 07 or 08 carb?

thanks alot!



  • x_JT_x

Posted August 27, 2014 - 07:10 PM

#2

Hey everyone,

the tittle pretty much says my question. I have a 2002 YZ426 and My gaskets in the carb are pretty worn, flat and hard, I've had some inconsistant starting issues and my valves are in spec. seems like It's time for a rebuild or swap to a new-er year carburetor? I'd just like some opinions on which would be more benefitial to more power, idleing or perhaps starting?

I know the inconsistant starting could be due to jetting, however I'm not very knowledgeable about it yet. I'll be doing some reading on jetting stickies but I'm still wondering if rebuilding the 02 carb is worth it vs buying a 07 or 08 carb?

thanks alot!


The carb made for your bike will work best. Just rebuild that one. It's really not hard.

  • grayracer513

Posted August 28, 2014 - 06:33 AM

#3

I beg to differ.  First, the earlier FCR's are a PITA to try and "rebuild" once they reach a certain state of wear.  You can always try it and see what you can accomplish, since in any case, it's cheaper than another used carb would be, but you can also spend a lot of time, and sometimes money, not getting anything but frustrated.

 

Secondly, the carbs from '05 and later YZ450's work far better on the 426 than the original.  It's essentially a bolt-on operation, too, but you will need to get the correct throttle cables for the carb, and always try to buy one that includes as much of the hot start assembly (plunger, cable, lever, etc.) as possible, or you'll nickel and dime the project into being more expensive than it should.  In every one of these swaps I know about, the owners report that the bike never ran so good as with the later carb. 



  • Spartan426

Posted August 28, 2014 - 09:46 AM

#4

Thanks for the replies guys!

I know it's cheaper to rebuild it but since the 02 carb sill works right now. I think saving up for a newer one will probably be the route I go. I'll make sure to find one with the hot start assembly.

I've heard different responses of having to stretch the boots to fit newer years? Or the boot being to loose? Any thoughts on that?

Any idea What's the latest year carburetor before Yamaha went to EFI? Or does it really make a difference as long as the carb is newer then 05?

Edited by Spartan426, August 28, 2014 - 09:47 AM.


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  • Shawbridge Husky

Posted August 28, 2014 - 11:48 AM

#5

On the '05 and newer cab, would the old style YZ400 hot start plunger work instead of

the newer style cables and everything ? I like my things to be diminutive, I'm in no hurry

to restart a dead engine as I don't really race.


Edited by Shawbridge Husky, August 28, 2014 - 12:07 PM.


  • grayracer513

Posted August 28, 2014 - 12:50 PM

#6

At minimum, you need the hot start plunger, the seal, the spring, the retaining nut, and something to plug the hole in the top. 

 

The boot is the right diameter, but the carb is shorter, so the boot doesn't quite reach to the mouth of the carb.  All that's needed is to clamp the boot to the carb first, then push the carb forward into its socket and clamp that.



  • Shawbridge Husky

Posted August 31, 2014 - 10:24 AM

#7

Thanks Greyracer, I kept the original YZ250/450F boot, so I guess it could be used if ever I update the carb.

It does seem to reach further ( longer ) than the stock 400/426 one. I'm going to

order a carb kit for the '99 400 and hope for the best. Bike has sat without gas for last

10 years ( last time I used it ) It does not have a ton of hours, I may luck-out.

If I do the carb mod while I do the 450 mod it well get overwhelming.

But I will keep the spare parts for it. Thanks.



  • Spartan426

Posted October 27, 2014 - 10:45 AM

#8

At minimum, you need the hot start plunger, the seal, the spring, the retaining nut, and something to plug the hole in the top. 

 

The boot is the right diameter, but the carb is shorter, so the boot doesn't quite reach to the mouth of the carb.  All that's needed is to clamp the boot to the carb first, then push the carb forward into its socket and clamp that.


Sorry to revive an old thread, I wanted to clarify since I'm now going this direction after admitting defeat to rebuilding the 02 carb like I wanted. (No middle body gasket set exsists, they are only for the years of 03 - 09) I'm just a little confused as to which boot your referring to, does the 08 boot stretch to fit. or do the stock 426 boots stretch to fit the 08 carb?

This question may need to be put in the jetting threads but I'd just like to be pointed to the right direction. Since this is an 08 carb in a 02 bike Should I start it off with stock jetting numbers for the 426 or stock jetting for the 08 450? I'm guessing I will need to rejet to get it more spot on as well since I've added intake and exhaust Hot Cams during this rebuild.

Thank you for the responses!



  • grayracer513

Posted October 27, 2014 - 11:12 AM

#9

The 426 air boot is what needs to be stretched.  Attempting to use an air boot from a later model may not solve anything, since the air box could be located at a different distance from the carb.   Start with stock jetting for the year model carb used.  It will be very close.







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