Post by: ACMX on April 15, 2012, 11:13:56 PM
~10 hours on this rebuild and she seized. Small water leak. It overheated. Suspect it was one of the the o-ring head gaskets. I could just rebuild it but I suspect I may need a new cylinder. Or just need it re-sleeved?
I checked the crank... It has no up/down play.
What do you guys recommend?
If I get a new cylinder, should I get OEM ($335) And if I take this option would I need new cyl. head too? or an Athena big bore (entire kit ~ $700)..?
Or just resleeve it?
As for the piston I have 3 options... Wiseco, Pro-X, or OEM (I get discount on Wiseco and Pro-X)
Bike is a 2003
Skip to close to the end of the video...
Post by: xandyx on April 16, 2012, 12:42:14 AM
if you need a new barrel, i'd go for the athena, a few more quid, but it will feel like a new bike.
get a wiseco piston and drill 2 small holes on it to help lubricate the cylinder a bit better!
Post by: ford832 on April 16, 2012, 12:50:36 AM
Post by: cnrcpla on April 16, 2012, 02:00:15 AM
Post by: xandyx on April 16, 2012, 03:40:14 AM
Post by: factoryX on April 16, 2012, 04:47:38 AM
Post by: ACMX on April 16, 2012, 06:55:49 AM
it seems that the bike was bogging in the last minute of the video before it staled. is it my impression, or were you feeling it loosing power?!It had lost a TON of power on that last lap. Zero compression.
Post by: 2T Institute on April 16, 2012, 08:16:40 AM
I don't know why you kept wringing it's neck when there was clearly something wrong.
Your piston looks a bit lean which is why I would say it's over heated. A good pic of the piston will tell.
Post by: SachsGS on April 17, 2012, 12:00:07 AM
Post by: ACMX on April 17, 2012, 08:55:25 AM
I would have had a new piston or untrapped the ring , sanded the piston down, hit the cylinder with acid and been racing it again in an hour or so after that.When the top end is going out in this fashion, if you don't keep rpm up it dies out. I was trying to find a safe place to exit the track as soon as I realized something was wrong. I didn't want to get stuck in the middle of the track with bike going all around me.
I don't know why you kept wringing it's neck when there was clearly something wrong.
Your piston looks a bit lean which is why I would say it's over heated. A good pic of the piston will tell.
Post by: 2T Institute on April 17, 2012, 09:50:06 AM
Post by: scotty dog on April 17, 2012, 12:07:31 PM
Post by: juliend on April 17, 2012, 11:11:39 PM
Post by: Super Trucker on April 18, 2012, 05:45:52 AM
Post by: cnrcpla on April 18, 2012, 05:48:13 AM
Quote
I would just hone it.I don't think you can hone it. Aren't the yz125's nikasil platted?
Post by: ACMX on April 18, 2012, 11:26:48 PM
Ring traps at about 7.50min in the video and at 8.50 you pull of the track. There was more than ample opportunity to pull safely off the track. As I said if you would have stopped the bike pushed it back to the pits and untrapped the ring sanded the piston you would have been out for the next race. The pick up on the cylinder is from running hard with a partialy trapped ring.I didn't notice anything really wrong until 8:08 in the video. I pulled off at the first safe place to pull off after that point. What is a trapped ring?
Post by: ACMX on April 18, 2012, 11:29:31 PM
Post by: 2T Institute on April 19, 2012, 12:09:27 AM
Ring traps at about 7.50min in the video and at 8.50 you pull of the track. There was more than ample opportunity to pull safely off the track. As I said if you would have stopped the bike pushed it back to the pits and untrapped the ring sanded the piston you would have been out for the next race. The pick up on the cylinder is from running hard with a partialy trapped ring.I didn't notice anything really wrong until 8:08 in the video. I pulled off at the first safe place to pull off after that point. What is a trapped ring?
At 7.45 a comment is on the screen saying how bad the bike is going ? What's a trapped ring ..................have a look at the piston and what do you notice?
About 5 seconds after you noticed the engine going off, anywhere on the left was a good spot to safely pull off the circuit or at the end of the corner had a large run off area/carpark. You were not going fast at the time either.
Ruuning the bike after something is obviously wrong is what costs you big $$ not only in repairs, the money you spent to do the race meeting is also wasted.
Post by: ACMX on April 19, 2012, 08:07:13 AM
Does a trapped piston ring just mean it's compressed? Because mine it compressed. Didn't know you could fix that.
Post by: cnrcpla on April 19, 2012, 04:03:31 PM
Post by: Coop on April 27, 2012, 11:44:39 AM
QuoteI would just hone it.I don't think you can hone it. Aren't the yz125's nikasil platted?
You are confusing hone with bore. A hone just cleans up the cylinder wall but boring actually removes enough material to make the bore larger. You can hone that cylinder, but not bore it unless you get it re-plated after.