i need loads of help from users who have real exp. in crank swaps...

Alright.... As we all know the yz 426 has this really shitty cage bearing in the bottom end of the crank... Also known as the big end. long story shot my bike blew up. I know the pin size for the yz 450 crank is the same and the bearing is bigger for the 450. My question is will it fit the 426 and take the crank parts such as the balance shaft and the magneto and ect. I dont mean to be rude but ive looked thru this forum a bunch for other things such as shocks and ect for my bike and i only need people to help me solve this issue because next week im buying either a used 426 crank because theres no such thing as a new one anymore... Not even from yama anymore. Oor im buying a new 2001-2-3ish 450 crank for my 426. Thanks guys for the help in advance... If all goes well next week ill be posting vids of me rebuilding the engine in about 3 hours to youtube.

Or people who can atleast measure the main bearing surfaces o the crank from the 450 and the 426 to give me and idea of the bearing size i need to get.

The 450 starts at '03, BTW.  The Yamaha parts book still lists the '02 YZ426F crank (5JG-11400-20-00) as available.  The '00 crank was discontinued long ago, and the '01-'02 replacements feature an upgraded rod bearing.  The later crank uses a splined balancer drive gear rather than keyed.  

 

As far as I know, the 450 crank won't drop in, but the '03-'05 450 rod and bearing can be used with the 426 crank if you also use the 450 piston and pin for the same year.

The real problem im having is finding somewhere that can rebuild it locally. And isnt the piston size different for the 450... By more than 2 mm. The 426 is ... Only.... A 95mm and to make it a 446 you need to go 2mm over on just the piston.

So...if i were to get a 2002 crank it should drop in but would it hurt the balancer? Or should i replace it too?

You would need the balancer drive gear for the '01-'02 to go with it.  

 

The 450 is a 95mm bore as well.  The displacement difference is in the stroke (63.4 vs. 60.1)

Thanks... Im going to buy a used crank today just to get it running and see if i need anything else and next week or so im going to buy the 02 crank. And of course the drive gear. Thanks man!

Well the update is i wound up getting a new crank and installing a hot rods kit on it works good. The compression is so strong i can jump on the kicker and it wont budge till i hit the decomp valve. Fires up first kick everytime after some carb adjustments im very happy woth my 426.

Well the update is i wound up getting a new crank and installing a hot rods kit on it works good. The compression is so strong i can jump on the kicker and it wont budge till i hit the decomp valve. Fires up first kick everytime after some carb adjustments im very happy woth my 426.

Since it's been so long since this thread started how many hours do you have on the new crank? I have read some negative comments regarding HotRods cranks however I had the crank on my 2009 CRF450R rebuilt with a HotRods rod kit and it never missed a beat. I raced it for two more seasons and it was still running strong after I sold the bike to the new owner.

Hotcam with auto decompression made my friends 426 much easier to start.

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