what to do with a roach of a yz426?

12 replies to this topic
  • sonic reducer

Posted May 03, 2014 - 08:53 PM


I just bought a 426 for very very cheap.  clean title signed over to me now. 

it has a locked up motor, PO said it gradually siezed up and didnt go bang or anything.  rusty/dented frame, rusty bolts everywhere, garbage plastics  etc.

I'm weighing various options of what to do with it.  maybe you folks can help.  I'm a intermediate rider about 165lbs and a 426 might be a bit much for me(woods only)


1.  pull motor apart for rebuild,  will likely need a cylinder, piston kit, some head stuff, etc.  to really do it right will start to be like $800 and that's if the bottom end is all gravy(doubtful?).  probably paint the frame, new plastics, some wear items, etc.  could be into it around $1200 at that point but it could get out of hand as well.  and then it's still a crusty old POS with a good motor.  I may pull the top end off for a looksee anyway


2. find good used motor.  whats that run, $700-1000?  would think about trying to get a WR. 


3.  try and put a WR250F or YZ250F into it?  what's that entail?


4.  part out motor/carb/cdi/exhaust/rads and use the roller for an XR200 or 250 swap to build a bombproof tight woods bike(had a wild hair to do this for a while and I do custom fabrication for work)  or maybe KDX200.   the YZF chassis is a worthy platform to go to an effort like this isnt it?  I'd still have to do some bearings, suspension work, repaint the frame, etc.  any other ideas for a candidate for a motor swap?


5.  part it out fully.  how much do you guys think some of the big ticket items like carb, forks, shock, wheels, etc. go for?  do I sell the motor complete or do I part it out piece by piece on ebay?  seems piecing it out would be the way to go because it's current condition is a mystery?  or are there engine builders who would want it whole?



I guess my heart says build the woods bike.  I'm kinda needing a bike like that I can get better at woods riding on.  I'll still recoup a good amount of money from all the stuff I wouldn't use anyway. 

of course, I can't lose any money by going #5

  • yz133rider

Posted May 03, 2014 - 09:08 PM


Really depends on whats really really cheap, how bad the motor is. And then the real important is how is the rest of the bike? Do both ends of the suspension need work, bearings everywhere, levers, clutch, transmission, odds and ends?

Id say your almost always better off finding a bike that is older but barely ridden. I just got a like new 04 cr125 for 1600 and my like new04 cr250 for 3k. Like paint not worn off the clutch covers, or scratches on the frame new.

  • sonic reducer

Posted May 03, 2014 - 11:59 PM


Really depends on whats really really cheap...
Id say your almost always better off finding a bike that is older but barely ridden.


about the value of the carb is what I paid.

agreed, a clean bike is the better basis for most situations but I couldn't resist.

I enjoy seeing bikes and things live on in some way even if they are still junk, rather than getting parted out.

Edited by sonic reducer, May 04, 2014 - 12:01 AM.

  • yz133rider

Posted May 04, 2014 - 06:54 AM


Clean it up take better pictures and try to sell it turning a profit. If its a rescue mission and you'd enjoy bringing it to life budget be damned you cant lose either though. As you'll know the bike in and out and it will be fresh,

Forget swappjng a motor in it. Strap a heavy flywheel weight on it, g2 throttle, lower compression piston when you rebuild it and you can make the big 426 super smooth and easy to ride

Edited by yz133rider, May 04, 2014 - 06:55 AM.

  • ekulb14

Posted May 04, 2014 - 07:05 AM


So just a realist here but, the carb is probley far from ok, forks will need a rebild, shock every bearing top to bottom... ect


is seems to me like a part out is your best bet, im all for running older bikes if you trust them but wht all you described sounds like you will have a better end product if you start with something a little better off.  

  • sonic reducer

Posted May 04, 2014 - 03:06 PM


well Ive been cleaning, examining etc. and managed to get the motor un stuck just with some 5th gear rocking!  and it seems to have good compression.  of course that doesnt mean the cylinder is all good, there was a bit of magnetic, shiny silver stuff in the oil in the sump.  not a ton, but definitely alarming. strangely the filter was not completely full of it.  is nikasil debris magnetic?    or perhaps it was bearing debris?


the oil was not terrible, other than the aforementioned flakes, the coolant looked perfect. 

Edited by sonic reducer, May 04, 2014 - 03:21 PM.

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  • jojo1224

Posted May 04, 2014 - 09:55 PM


Nikasil is non magnetic. It is quite possible it is the big end bearing that is seized.

  • sonic reducer

Posted May 04, 2014 - 10:58 PM


well the motor's on the floor now and I won't be futzing with it anymore.  even though it isn't stuck stuck, with the sparkplug out requires a decent effort to kick.   i didn't figure just bearings could put up such resistance to the kicker, thought it was the rings too but who knows for now. 


I'd like to tear this thing down for shits and giggles but I'd rather sell the motor whole for cheap if a builder can use it.  I know that a lot of builders prefer to do the teardown themselves to get a sense of what's happened.  what do you guys think?  

  • yz133rider

Posted May 04, 2014 - 11:05 PM


Im not sure the market for blown up 426 motors.  Im really unsure what your goal is honestly.  

  • jojo1224

Posted May 05, 2014 - 07:49 AM


Running 426 motors are so cheap it wouldn't be worth selling as is. You could make money parting it out on eBay.

  • peaceofwork

Posted May 05, 2014 - 11:44 AM


I think the most sought after things are wr transmisions,  wr stators, good heads and cylinders every thing else is plentyfull and cheap, carbs are a joke people put in 450 carbs as replacements good luck

  • sonic reducer

Posted May 05, 2014 - 09:12 PM


well I'm unsure too lol.  I guess goal was 1. have some fun  2. come up  3.see if the thing can be got going easily enough.  4. If No, part out motor stuff to break even at the least   5. keep chassis for project??? It's actually a great platform for a wierd project.  big opening in the frame, steel frame, high performance chassis etc.


how much are good used motors going for?  haven't seen one for sale.  if they were cheap enough I'd definitely do that and this bike would stay a thrasher(albeit actually looked after).  seems like these bikes become thrashers, the motor takes a shit and the bike gets parted out.  where are the good used motors?

I will probably start tearing down the motor tomorrow for inspection.  Although I am inexperienced with this particular motor.  done XR, DR, RFS, various street stuff but not these.  I do like the way they are put together so far.  and I don't regret buying it yet.

I know this is a bit of an odd thread.  but I figured it would be nice to have at least a bit of guidance and you guys get to chuckle a bit.

  • yz133rider

Posted May 05, 2014 - 10:44 PM


give us more info post some pics.  Whats the rest of the bike like? Will you have to spend 1000-1500 just to get the rest of the bike up to spec?  Bent wheels, bad bearings, blown suspension, bent bars, smoked chain and sprockets, torn grips etc all adds up.   


Your going to have to open up the motor and see what your working with how will you ever decide if its worth fixing without opening it up? 

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