Two Stroke Motocross

Two Stroke Motocross Forum => Technical => Topic started by: Dirt Addict on April 10, 2012, 02:59:08 AM

Title: yZ125 piston life?
Post by: Dirt Addict on April 10, 2012, 02:59:08 AM

I'm running a vertex piston in my yz. I ride it aggressively , solely track riding.  How long can I go between top ends? I'm trying to be conservative so Idon't blow the thing up.  I know I should do a compression test, but my gauge is junk.  i have about 5 - 6 hours on it now....
It's a 05 yz125....

Title: yZ125 piston life?
Post by: VintageBlueSmoke on April 10, 2012, 10:37:57 AM

I've never used Vertex but my Wiscos were good for about 15 hours per ring and 30 hours per piston from '96 to '02. After that, there was a noticable performance drop.

Title: yZ125 piston life?
Post by: MetalMike1982 on April 11, 2012, 05:31:55 PM

 IMHO you should just get a new compression gauge . Its pretty cheap to do topends on your bike so do em every 25-30 hrs with ring changes at 15 hrs and you should be safe given your running good oil at a decent mixture ratio and you keep your filter/air box spotless . I also run wiseco pistons so I'm not familiar with vertex .

Title: yZ125 piston life?
Post by: Dirt Addict on April 11, 2012, 08:25:50 PM

ok thanks gents.  i know I need a new comp gauge. just being lazy.  re-ring @ 15.  I guess I need to order some up.
Vertex makes most jap oem pistons. They make ktm oem pistons, at least on their 2t's. great quality in my experience...

Title: yZ125 piston life?
Post by: MetalMike1982 on April 11, 2012, 08:36:54 PM

wiseco' has always worked good for me but my next rebuild I may try vertex .

Title: yZ125 piston life?
Post by: eprovenzano on April 11, 2012, 08:51:53 PM

When I redid my top end in my KTM, I used a Vertex.

Title: yZ125 piston life?
Post by: MetalMike1982 on April 12, 2012, 01:15:08 PM

Quote from: eprovenzano on April 12, 2012, 03:51:53 AM

When I redid my top end in my KTM, I used a Vertex.

Are they cast or forged?

Title: yZ125 piston life?
Post by: Dirt Addict on April 13, 2012, 05:38:36 AM

pretty sure they're cast. The manufactures use cast pistons for reliability during break in. Something about how cast pistons expand differently than forged. I saw a lengthy explanation once but don't remember the particulars.

Title: yZ125 piston life?
Post by: Stusmoke on May 04, 2012, 08:45:22 AM

To save clogging up this beloved forum with an extra unneeded topic, I'm gonna ask, whats the expected piston lifetime on a 2001 YZ 250? Its got an absolute shit ton of mid and great bottom (for a smoker) but remarkable still has heaps up top, but I hardly ever use it. The bike gets ridden hard, but I rarely overrev it. I'm trying to make my engine last as long as possible and I usually keep it low-mid. Also, where would my bike Redline do you think? Cheers guys

Title: yZ125 piston life?
Post by: TMKIWI on May 04, 2012, 09:27:32 AM

250's rev to about 9k rpm then drop of power.
Piston life? How long is a piece of string.?

Too many variables Stu.
30-50Hrs if you are joy riding.

Title: yZ125 piston life?
Post by: Stusmoke on May 04, 2012, 10:48:16 AM

I'm definitely not easy going on the throttle, it gets a sort of mid range thrashing lol. 30-50 hours is sweet Thanks mate

Title: yZ125 piston life?
Post by: cnrcpla on May 04, 2012, 03:59:36 PM

My YZ250 lasted two years of trail rides and races, that was at least 100 hours + on the same piston and rings. It would have even gone further if it wasn't for the damn coolant pump gear blowing my top end and stuff.

Title: yZ125 piston life?
Post by: Shawn36 on May 04, 2012, 05:54:32 PM

Your service manual is usually a pretty good answer.  A fast and aggressive rider will want to replace pistons pretty often, my manual suggests every 8 hours.  Some people run them until the piston gets loose or the bike actually loses power.  Not a good situation to put your bike in if you want to ward off problems. 

Vertex is cast, it's basically an OEM piston in another box.  Their quality is solid.