yz 426f seized motor

Good luck. I'm working on my 426 now. Complete rebuild. Stock parts are hard to find and really expensive...

That's exactly what it turned out to be.......not surprised. But that's all part of it if u play u gotta pay. It got so hot that the crank itself turned blue. Thanks for the help.

It got so hot that the crank itself turned blue. Thanks for the help.

The blue color around the crank pin on the YZF crank flanges is a result of the factory using heat to assemble it in the first place, and is present on every brand new YZF crankshaft ever built by Yamaha. It's not a result of any fialure in operation.

+1 on what grayracer said. A brand new crank assembly will have the same color marks.

So the interesting question is: "What do you plan to do about it?"

I assume you had the bad con rod bearing problem. You could buy the bearing and pay someone with skills to pull the crank apart and reassemble it with the new bearing, but that might cost nearly as much as a new crank, and you better really trust whoever reassembles it to get it lined up perfect. You have the opportunity to buy a 2002 crank and counterbalance shaft, which will drop in, has a better con rod bearing, and drives its cb off a splined gear instead of a keyed gear. That's what I did, and it resulted in a much quieter bottom end.

I would agree with the others. The same thing happened to me last year. Riding then all of a sudden died and the kick starter seized. Ended up being seized crank. if you decide to do it yourself, you will need so special tools to get to the crank i.e clutch holding tool and case splitter. best of luck to you and hope you get it running soon.

I would suggest you have a professional install the new rod and rod bearing, that way it's straight and true. And as far as taking the engine apart and rebuilding it, the only special tool you will need is a flywheel puller. I use a cordless impact to remove and install the clutch, works great. I just rebuilt my 426 about 2 weeks ago and did 4 yz250f motors this year. Good luck!!!

Thanks for the help. I think I'll go with the whole crank assembly ....i believe its part # is 5jg100 or something like that that way it looks to be just a matter of splitting the cases and replacin the bearings and seals. Hoping to be riding by next month if all goes well. Maybe next year I'll do the big bore kit with stage 2 cams on both sides . Btw I priced the assembly on yamaha's website an they list it $439 if remember correctly if that helps u at all.

I was going to order a crank when I did my bike, but I was told there was only 1 remaining in the U.S., so I opted for just replacing the bearing and rod since the timing gear was in good shape. I ended up spending $200 for parts and labor to repair the crank. I just finished my rebuild a week or so ago, here's a pic. Let me know if you need anything.

bikepics-2210011-full.jpg

Awesome pic! FMF Powerbomb exhaust? Did u notice a difference in performance? Mine has yamaha pro moto billet exhaust on it but that is the same exhaust i was considering. As far as i know the crank can be overnighted here from wherever it is. Lol what is ur thoughts on a big bore kit?

I just baught the bike in april and rebuilt it. It's my first time really riding anything over a 250f, so I can't say much about the stock exhaust. I just got home from my first ride on the bike and absolutely loved it. The power is amazing. I never shifted out of 1st gear on smaller windy trails.

My thaughts on the big bore are fix the bike stock, sell it and buy a 450. I'm not a big fan of major engine mods, especially if they make a bigger bike like the 450.

I had the big end bearings go out on my 426, so I sent the crank to Mr Crankshaft for a rebuild. I believe it was $180 including return shipping, all parts and labor included. I shipped the crank to him in a USPS flat rate box for ~$12 I think, so right around $200 for a complete rebuild. I know of at least one other person that did this, and he is just as happy as I am. They used a Vesrah rod and bearing, and sent me the remains of my original. I also replaced every single bearing in the cases as they were suspect due to oil starvation from the previous owner. Got those from Boats.net or something like that, great prices. Although, Thumpertalk has a meet-or-beat policy, so you might want to shop around and give the TT store a call.

Don't forget to check your piston clearance and bore dimensions as most likely not just the crank was affected by this issue. You need to check everything out, cams, etc. A new piston with pin is only ~$130, might as well drop that in, too. Try to avoid Wiseco pistons, as they are very, very noisy and might mask true concerns inside your engine. I think that JE makes a nice piece for about the same price as Wiseco.

Once you get the cases apart don't be afraid to ask for help. Lots of very experienced users on this forum, and they are happy to help someone find a solution (as you have recently noticed). Good luck!

I had the big end bearings go out on my 426, so I sent the crank to Mr Crankshaft for a rebuild. I believe it was $180 including return shipping, all parts and labor included. I shipped the crank to him in a USPS flat rate box for ~$12 I think, so right around $200 for a complete rebuild. I know of at least one other person that did this, and he is just as happy as I am. They used a Vesrah rod and bearing, and sent me the remains of my original. I also replaced every single bearing in the cases as they were suspect due to oil starvation from the previous owner. Got those from Boats.net or something like that, great prices. Although, Thumpertalk has a meet-or-beat policy, so you might want to shop around and give the TT store a call.

Don't forget to check your piston clearance and bore dimensions as most likely not just the crank was affected by this issue. You need to check everything out, cams, etc. A new piston with pin is only ~$130, might as well drop that in, too. Try to avoid Wiseco pistons, as they are very, very noisy and might mask true concerns inside your engine. I think that JE makes a nice piece for about the same price as Wiseco.

Once you get the cases apart don't be afraid to ask for help. Lots of very experienced users on this forum, and they are happy to help someone find a solution (as you have recently noticed). Good luck!

Just to clarify, our policy is 110% off the difference: http://shop.thumpertalk.com/help_answer.asp?ID=21#21 :smirk:

Thanks for the help fellas. I got my crankshaft out and sent off to Mr Crankshaft with no trouble I just got an email from Vince he got my crankshaft today and said they would be shipping it back out later today. So I should be airborne this time next week if my gasket set gets here in time. :ride:. :thumbsup:

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