Problem with my Yz 125

[ahorner7]

I have a 2003 yamaha yz 125 and it has recently just seized. I had only rode it for two days after buying it from the owner and before this it ran fine. We took it to Shawmut hills to see how much the repair was going to be and they said we needed a crank and up rebuild. which would cost me $2200 and i bought the bike for $1,600
but then when i go online i can find aftermarket cranks for $200 and pistons for $80 and all the gaskets for $40. Can someone tell me if i put all these new parts on if my bike will run great or will the same problem continue to occur. that would be greatly appreciated
-andrew

 

[zaneyzrex]

they are stupid. i charge 45$ an hour to do rebuilds. got a 91 yz 125 in the garage right now thats got the same problem.
you can go two ways with this............
1. rebuild the crank
2. replace the whole crank
we are gonna rebuild this crank cause a new on is 568$ and i can get the parts to reubild for 130$ or so and my machinist can rebuild it for 75$
that shop is riping you off and screwing you with no lube. i will have about 6hrs labor into it and prob. 400$ in parts total.
to bad your not in the phoenix area .

 

[ahorner7]

hey thanks yeah im taking it to one of my dads friends who is a mechanic and im gonna buy a pro x crank assembly for $200 and a pro x piston kit for $90 and hopefully that wont be too much in labor but do u think once i put this stuff on it will fix the problem or will it happen again

 

[whenfoxforks-ruled]

I would recommend a wiseco top end and hotrod or wiseco crank and or rod kit.

 

[oldguy]

do u think once i put this stuff on it will fix the problem or will it happen again

Probably will happen again if you don't bother to find out why it happened this time
You need to find out the cause before you seize another one

 

[ahorner7]

how do i find out the cause though i took it to a dealer to find out the cause and they just told me a crank up rebuild would fix it

 

[whenfoxforks-ruled]

You need a shop manual,and some tools. Pull up your sleeves and take it apart. Popular bikes can get a complete engine kit for around 300 dollars. You will need a shop to clean and inspect your cylinder and head. Or some more tools!

 

[_JOE_]

It's possible that a leaking crank seal could have caused it. You said it only ran a couple days, what fuel were you running?

 

[ahorner7]

i was running premium 30:1 with a oil named KLOTZ but someone told me that it might be becuase i mixed my gas with old gas that was already in there from who i bought it from who was runnign different oil

 

[oldguy]

There are many possible causes of a seized motor. Your jetting might be way off, you may have had a leaking seal, or many other causes
I wouldn't think it was because you mixed 2 different brands of oil but if you don't find the cause you will be rebuilding again in the future

 

[RM85rider123]

I would recommend a wiseco top end and hotrod or wiseco crank and or rod kit.

I agree too.

 

[ahorner7]

what is the jetting and if i am rebuilding completly from crank and up will that cover the jetting and the seals and whatever else could have caused it

 

[whenfoxforks-ruled]

You rebuild the motor. Check, reeds, silencer packing, rubber boots on the carb, air filter and seal, ignition and timing, sparkplug, clean and inspect the carb. When you have the carb apart, see what jets and needle are in it. Break it in with stock jetting and oil ratio. Keep an eye on the sparkplug, and listen for lean signs. What did the plug look like that was in it?

 

[ahorner7]

the first five that came out of it looked really oily but when u touched them nothing really came off and the last one that came out after my dads friend opened the throttle up for 3 min with out letting up was completly white and thats when it seized..
what are lean signs and i was running 30:1 so i dont think it was lean

 

[oldguy]

30:1 has nothing to do with lean or rich
A white plug means a very lean condition and that was the reason (or at least one of the reasons) your engine seized. Whether the lean is a result of jetting or many other causes is now what you need to find. Look at jetting compared to stock, make sure there are no air leaks in rubber boots, or case gaskets, make sure airfilter is clean and properly oiled, and make sure no passages are plugged in the carb for starters
BTW why in the world was your dads friend holding the throttle wide open for 3 minutes? He is as big a problem as any mechanical issues

 

[ahorner7]

i know i was like wtf why did u do that well anyways its at a mecahnics house right now and for 950 bucks hes doin everything so thanks everyone for ur help

 

[whenfoxforks-ruled]

Why isn't he guy who blew it up paying for it. Can I take your new bike for a little ride?

 

[ahorner7]

idk where u live

 

[whenfoxforks-ruled]

Umm, to the right by the flag, where yours says you do not know where you live, mine says Indiana.