Georgia Off Road Visit Highland Park
Home
News
Forums
Calendar
Ladies
Gallery
Track Map
MX Tracks
ORV Trails
Dirt Bike Guide
Reviews
Dealer Guide - our own yellow pages!
Contact GOR Administrators
Georgia Offroad

Create Your Badge


It is currently Tue Jan 23, 2018 6:51 am

All times are UTC - 5 hours




Post new topic Reply to topic  [ 7 posts ] 
Author Message
 Post subject: YZ125 help - blown piston/gouged cylinder
PostPosted: Thu May 19, 2016 3:53 pm 
Offline
B - class
B - class

Joined: Thu Apr 24, 2014 10:59 am
Posts: 54
So, because I'm a wuss, I raced my wife's '01 YZ at a few hare scrambles last year instead of my 250. I ended up burning a hole in the piston and the resulting shrapnel gouged the cylinder. No huge deal, I thought, until I started looking at options.

First, I've bought her another bike, so this one will be sold as soon as I fix it, so I'm trying to keep $$ output at a minimum, but still sell a rideable bike.

I can't figure out what the best route is and could use some advice. Looks like I'm looking at about $550-600 if I buy a new complete cylinder/piston. I see a lot of repair places on the 'net and the back of motocross magazines, but I'm not sure whether to get it repaired, sleeved, etc. I'm not even sure I understand the benefits/cons to doing either.

I'm a good wrench, but mostly with cars. Taking things apart and putting them back together is no problem, just a little lost on what I should do in this situation. Any advice would be appreciated!

James

_________________
'01 YZ125
'09 Husqvarna TE310


Top
 Profile  
 
 Post subject: Re: YZ125 help - blown piston/gouged cylinder
PostPosted: Thu May 19, 2016 4:22 pm 
Offline
GOR Assisted Living
User avatar

Joined: Tue Apr 22, 2008 6:11 pm
Posts: 4302
Location: Stockbridge, Georgia
Send the jug to millenium instead of buying a new one. check the main bearings for play, if good, you'll need to flush the bottom end out or split the cases to clean. Depends on your comfort level and how things look in there.

_________________
I don't FEEL tardy!


Top
 Profile  
 
 Post subject: Re: YZ125 help - blown piston/gouged cylinder
PostPosted: Thu May 19, 2016 4:59 pm 
Offline
GOR Veteran
GOR Veteran
User avatar

Joined: Tue Aug 19, 2003 11:48 am
Posts: 872
Location: Georgia
What mog said and.....

AFTER you have had a reputable company bore and re-plate the cylinder, THEN either have them specify and supply the piston size for you based on the final bore diameters, or take measurements once you get it back and then make sure you buy the correct sized piston for that bore size.

Check the head too, it's probably chewed up. Chewed up areas will lead to hot spots. Don't remove a bunch of material inside the dome or the surrounding areas though as this changes the squish band of the engine, which can change a lot of things about a 2T engine.

Make sure you haven't bent the rod, probably didn't because the piston material is rather soft compared to something like a Ti valve on a fourstroke getting dropped and punching a hole in the piston, but just be sure.

So was it just WAY past service life or did you run the engine lean and melt it down?

Could be both, and probably means the bottom bearings and seals need to be replaced as well.

If you have ANY up and down play in the Big End Rod Bearing, you have to split the cases and then split the crank in order to replace it. Splitting the crank to replace a rod bearing is something you generally need to let a very experienced mechanic do, because getting the crank indexed and aligned so that it runs absolutely true requires special jigs and a press. If you dont, it will have a run out on one side, will eat up the mainbearing and seal and blow up in no time flat. Otherwise, just buy a new crank and install.

All in all, you're probably anywhere from $500 to $1700 to fix this engine depending on your skill and time availability. And a pretty good bit of time since you have never done any of this.

The bike is probably worth $1000-$1200 maybe higher if its mint on the outside. Spending time and money to repair it only to sell it will probably not make sense.

Patching it up so it "Runs" in order to sell it to some dope who doesn't know any better is not the right thing to do and you could end up with someone very unhappy with you.

Better thing to do, would be to leave it put together and sell it as a project bike to someone for $300-400. Then its no worries regarding if it blows up again in 5 hours of riding time and you dont have to invest a bunch of time in order to make the same amount of money off of selling it.

Just my .02


Top
 Profile  
 
 Post subject: Re: YZ125 help - blown piston/gouged cylinder
PostPosted: Thu May 19, 2016 9:06 pm 
Offline
KTM GURU
User avatar

Joined: Mon Jun 27, 2005 8:48 pm
Posts: 15863
Location: Cedartown
All good advice so far. I'll add one more thing. If you don't find the reason it melted the piston and fix that problem (air leak, jetting, ignition timing, wrong plug, etc), chances are near 100% it's going to do it again after you rebuild the motor. ::eek::

_________________
Paul Wright
http://www.KTMWorld.com
http://www.HighlandParkResort.com

A fine is a tax for doing wrong. A tax is a fine for doing well.

If you find yourself going through He11, keep going!


Top
 Profile  
 
 Post subject: Re: YZ125 help - blown piston/gouged cylinder
PostPosted: Fri May 20, 2016 4:41 pm 
Offline
B - class
B - class

Joined: Thu Apr 24, 2014 10:59 am
Posts: 54
Great advice. Thanks all.

The bike supposedly had 6 hours on a top end rebuild when I got it. I ran compression test right after I got it, and it was within specs. I only put another 12 hours on it. The jetting and timing seemed good, as the bike ran like a top until it let go. I was about an hour and a half into a two hour race when it blew, so there's a chance it might have been acting funny and I was just too delirious to notice.

If I decide to replace or have the old cylinder repaired, I will definitely have a matching piston supplied by the company repairing or replacing it. Just gotta decide what I'm gonna do.

_________________
'01 YZ125
'09 Husqvarna TE310


Top
 Profile  
 
 Post subject: Re: YZ125 help - blown piston/gouged cylinder
PostPosted: Fri May 20, 2016 5:35 pm 
Offline
GOR Assisted Living
User avatar

Joined: Tue Apr 22, 2008 6:11 pm
Posts: 4302
Location: Stockbridge, Georgia
If they go to stock size it shouldn't be that big of a deal. Millennium just sent me a stock wiseco piston kit. I've bought them elsewhere ever since for less money.

_________________
I don't FEEL tardy!


Top
 Profile  
 
 Post subject: Re: YZ125 help - blown piston/gouged cylinder
PostPosted: Fri May 20, 2016 5:47 pm 
Offline
GOR Assisted Living
User avatar

Joined: Sun Dec 18, 2005 10:51 am
Posts: 13370
Location: Flowery Branch, GA
Send a piston and cylinder together to Millennium and they will size it together for a perfect fit

- c bob

_________________
KTMWorld & Highland Park - Great staff, Great place to ride
Pro Line - GREAT support!
Fragile Kids Foundation Family Fun Ride - Apr 30, 2017
Thanks to: Mika Metals, Twin Air, Scott, ZeaVision . . . . ><>


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 7 posts ] 

All times are UTC - 5 hours


Who is online

Users browsing this forum: No registered users and 5 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group