426 motor siezed....


18 replies to this topic
  • Kyle Prior

Posted November 23, 2006 - 12:27 PM

#1

So today was a bad day for me riding. I was out at a dry lake bed and surrounding trails, and as I was headed back to the truck on the lake bed, going around 75mph, my motor decided to sieze itself out of nowhere. My oil was full, as was my coolant, and the motor was cool to the touch within 10 minutes of seizing. Does anyone have any idea on how that happened, and tips for rebuilding? Thanks.

  • mudhog426

Posted November 23, 2006 - 05:17 PM

#2

How many hours were on the bike when it seized? Did it completely lock up or was it gradual? Several things could result in this, blockage in an oil line/passage causing bearing failure, timing chain breaking, etc. I would think that starting with the top end and working down would be the most logical course of action. Please post what you find to be the cause. Good luck:thumbsup:

  • Kyle Prior

Posted November 23, 2006 - 11:04 PM

#3

I tore it apart, from the top down, and have come to find its the connecting rod siezed to the crankshaft. The block is coming out tomorrow morning, and im gonna go ahead and split the crakcase. It was full of oil, and coolant, and wasnt all that hot when this happened, so I dont know how it happened. Any ideas? The connecting rob is now a redish color, which i know isnt normal.

  • Matt96xr6

Posted November 24, 2006 - 07:47 AM

#4

did not change the oil frequently enough.

Also with enough hours the crank does need replaced.

  • yz426em

Posted November 24, 2006 - 07:49 AM

#5

The exact same thing happened to my 426, which had alot of hours on it. How many hours are on your bike? Hopefully you will get it back up and running again.

  • Kyle Prior

Posted November 24, 2006 - 08:22 AM

#6

Ive had 20hrs on it since I got it, and changed the oil 3 times. The guy I bought it from had an unknown amount of hours, but I suspect somewhere well over 100. Luckily, the top end is al still really nice, and the cylinder wall isnt scored at all.

  • Ga426owner

Posted November 24, 2006 - 08:25 AM

#7

Guys when you say "lots of hours" how many are we talking about? 100/200/300? more .....any hour meters that have a real answer to this?
also did the camchain and CCT get changed at some point? At multiple points?
I am just curious how many hrs a 426/450 yami will last before it blows up. I am also curious what must be maintained motorwise (what parts must be replaced) at 200-300+ hrs to keep this from happening.
I usually sell my bikes before this many hrs...but my 03 470...rebuilt is a bike I plan on keeping for a long time. Other than crank and valves all other parts are under 20hrs...before it had approx 100hrs on it

  • ONLY4STROKES

Posted November 24, 2006 - 09:54 AM

#8

Kyle, look here for replacement connecting rods and crankshafts, as that sounds like all that is needed, thankfully. This is normal for an engine with a lot of hours on it...and since you bought the bike used that's one thing that's hard to know the exact details of...hours on the engine. Once you get this build done though she will be like new again.

The authoritive source on aftermarket rods and cranks:

http://www.hotrodspr...Controller.home

Also, look at Falicon:

http://www.faliconcr....com/index.html

  • yz426em

Posted November 24, 2006 - 10:29 AM

#9

My 426 had well over one hundered hours, and i did re-build the top end about 40 hours before the connecting rod bearing let go. In that rebuild i put in hot cams, new piston, rings, and cam chain. I put that bike through alot and i have no complaints on it breaking, it had alot of hard hours on it and I got my use out of it so i was happy.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • Kyle Prior

Posted November 24, 2006 - 02:22 PM

#10

Kyle, look here for replacement connecting rods and crankshafts, as that sounds like all that is needed, thankfully. This is normal for an engine with a lot of hours on it...and since you bought the bike used that's one thing that's hard to know the exact details of...hours on the engine. Once you get this build done though she will be like new again.

The authoritive source on aftermarket rods and cranks:

http://www.hotrodspr...Controller.home

Also, look at Falicon:

http://www.faliconcr....com/index.html


Thanks for the links, but niether site seems to have any parts listed for the 426.

  • Kyle Prior

Posted November 24, 2006 - 02:26 PM

#11

Also, how can I get the swing arm pivot shaft out? its the only thing left holding the motor in the fram, and it won't come out. Is there any trick to this?

  • yz426em

Posted November 24, 2006 - 02:43 PM

#12

Maybe try a piece of doll rod just smaller than the hole to hit against it so you don't do any damage to the threads on the end, i know when i took mine out it was in their fairly good.

  • Kyle Prior

Posted November 24, 2006 - 03:56 PM

#13

I got it out, just kept shooting lube in there, and it eventually broke free. There was a small section of rust holding it in, but its now out in one piece. Time for the motor to come out....

  • Matt96xr6

Posted November 24, 2006 - 08:36 PM

#14

I got it out, just kept shooting lube in there, and it eventually broke free. There was a small section of rust holding it in, but its now out in one piece. Time for the motor to come out....


time to replace that swingarm bolt and the bearings. There is a slight lip on the bolt. That is what makes it hard to remove

  • ONLY4STROKES

Posted November 24, 2006 - 10:50 PM

#15

Thanks for the links, but niether site seems to have any parts listed for the 426.


I'm going to give them a call tomorrow first thing, because I'm sure they have them in stock, just not listed online.

  • sirthumpalot

Posted November 25, 2006 - 12:50 PM

#16

Do you often hold it wide open for long periods of time (more than a few seconds)? You said you were going 75mpg which has got to be close to max speed. Anyway, from reading here I seem to remember a few guys complaining of seized cranks, usually after long wide open runs, and I think a few complaints were from cart guys. Carts run high rpm's for long periods of time. My point is, I'm wondering if the YZF motors just don't like to run sustained near-redline RPM's? Just food for thought, search here and I think you'll see most of the seized crank complaints were from people who ran sustained high RPM's.

  • Kyle Prior

Posted November 25, 2006 - 05:08 PM

#17

I had been going flat out for a good 2 minutes or so at that point, which im sure was partly to blame...

  • whyzee426F

Posted November 26, 2006 - 09:15 AM

#18

I had been going flat out for a good 2 minutes or so at that point, which im sure was partly to blame...


crazynova,

I went thru similar issues last year. I had to have a new crank center section pressed on because hotrods don't make parts for 426 anymore, and nobody else seemed to carry a ready made crank kit.

Recommend doing all the usual with the rebuild and the oil pump too...they have a tedancy of picking up trash and getting galled and/or worn...why risk an expensive rebuild on a $100 part.

Have come to the conclusion that my rod bearing seized due to cheap oil filters...sounds like you change oil regurlarly, as did I, but the filter was the weak spot in my motor. I'm now 100% sold on the Scott's micronic filter, and I continue to change oil frequently.

As for wide open riding...I'm in the desert too, on Edwards, and frequently push the bike for long periods. It shouldn't let go/lock up if working properly.

  • Kyle Prior

Posted November 26, 2006 - 09:38 AM

#19

crazynova,

I went thru similar issues last year. I had to have a new crank center section pressed on because hotrods don't make parts for 426 anymore, and nobody else seemed to carry a ready made crank kit.

Recommend doing all the usual with the rebuild and the oil pump too...they have a tedancy of picking up trash and getting galled and/or worn...why risk an expensive rebuild on a $100 part.

Have come to the conclusion that my rod bearing seized due to cheap oil filters...sounds like you change oil regurlarly, as did I, but the filter was the weak spot in my motor. I'm now 100% sold on the Scott's micronic filter, and I continue to change oil frequently.

As for wide open riding...I'm in the desert too, on Edwards, and frequently push the bike for long periods. It shouldn't let go/lock up if working properly.


Thanks for the info, and I figured that it shouldnt lock up like that for being run at near red-line RPM for a few minutes. I might just end up looking into an OEM crank from the TT store if I can't find anyone who carries them...





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