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Roached my motor - Any ideas?

By tdamore,
in YZ400F/426F/450F/450FX

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tdamore

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I was riding most of the morning with no signs of trouble. I was cruising along in fourth gear on a long wide road (road to randsburg for those of you in so Cal) when all of a sudden it just died. Went to kick it and the kick starter is locked hard.

Bike just had a fresh oil change before the ride and the coolant level was fine. It may have been running a little lean as I was getting quite a bit of popping on deceleration but it wasn't running hot or boiling over. I drained the oil when I got home, and you can see fine metal particles in the oil. I am hoping that the piston just seized, but I have a feeling it's going to be one of the rod end bearings. Any ideas as to why a motor would just go like that? One thing to note, is that it was blowing a bit of oil out the valve cover breather tube most of the day. I usually change my oil before every ride, so I just figured it was a little overflow.

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tdamore

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If the abrupt halt was not accompanied by a brief loud clattering, it's probably the big end bearing.

No noise, and I am pretty sure you are correct. Now I just need to decide if I want to tackle this myself or take it to a shop. There seems to be quite a bit of money to be saved by getting the parts online from TT oem vs. the dealer or a shop, but I have not split cases since I did my 1980 yz80 back in 1987 :lame:

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tdamore

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Only the top end is more complicated. The bottom is just bigger. Download a manual if you don't have one, and go for it.

I think I will, every penny counts these days. Anything to look out for or any tips? special tools needed etc? I am going to start pulling things apart tonight and plan on using zip lock baggies and labels to group assemblies etc.. I am most curious about making sure that I know what to look for so I can make sure it does not happen again.

I really appreciate the help!

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matt4x4

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If you're not 100% sure - take LOTS of pics - use paint pens to mark timing gears/chain, gears etc - although once you have a manual - it won't be needed since every gear has a mark that lines up with something.

It's easy - like grey said.

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tdamore

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You were right on the money Gray. Seized big end bearing. I also noticed my intake cam looks like the journals got real hot. There is some wear and scorching on them so I will probably need a new head as well :lame:

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00WR400F

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The head can be repaired, believe it or not. Send it to EDCo

Also, critically examine the entire oiling system.

exactly, sounds like the oil tube is clogged or the oil pump is to weak to pump oil to the cams.... run clearances on the pump

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yz480doinwork

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what ever you do REMEMBER how to put it back together. working at a dealer ship we see a lot of guys that forget how it goes back together so the box it up and bring there mess to us. its a horrible mess for us because every year things change the most of the time goes unknowtised. you sould be fine. im trying to decide if i should do mine myslef or have our michanic do it when i put my stroker in.

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tdamore

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I packed up the head today and shipped it off to Mike @ Edco. I am going to wait to see what he says before I make my next move. This is what I am planning:

New piston and rings. Probably do a Wiseco OE replacement.

Cylinder hone.

Hot Rods crank and rod.

New main bearings.

Flush all oil passages\lines and check clearances on pump.

Assuming the only thing wrong with the head is the bearing surface and all the valves are still in spec, I'll probably try to reuse them to keep costs down. I think i can clean up the intake cam and remove the deposited aluminum from the journals.

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tdamore

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That may not work out so well. If the cam has seized, or tried to, it may have caused the sprocket to slip, throwing the whole thing out of time.

Yeah, I thought about that. I sent the whole head to Mike, cams included. I figured I'll just let him sort it out. This way I can be confident it's done right.

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tdamore

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I was reminded today of two very important things when working on engines:

1. Wear gloves.

2. Engine cases are sharp.

Unfortunately it took 9 stiches and an afternoon wasted at Urgent Care to remind me :lame:

I lanced the top off of the first knuckle on my middle finger while pulling the right side cover to get at the oil pump. I was sitting there looking at my knuckle bone thinking "Thats gonna leave a scar". Guess I'll be leaving things alone for a few days....

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tdamore

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hahahahahaha sorry for laughing, but I have been there and done that, and was picturing myself sitting in my garage doing the exact same thing. Then I was picturing myself trying to talk my wife out of making me go to the ER

LOL - I was actually considering just using crazy glue to close it up but my wife made me go to urgent care.

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