Posts
305
Joined
11/18/2014
Location
Nacogdoches, TX, USA
Edited Date/Time
12/13/2014 9:01pm
2002 CR125. Airstriker carb, JD blue needle on #3, 185 main, 45 pilot, 2 turns. Airfilter stays fresh.
Cylinder replated 7 hours ago. Fresh piston kit was sent with cylinder so replater could check everything out for me.
Here is what happened over the weekend @ around 7 hours total time on replate and piston.
Pictures 6,7,8 show that the powervalve does not seat against the stop pin, but rather the ex port. Notice the mark inside the port on #8. Not sure if this is relevant to the failure, but it does not seem right?
#1
#2
#3 Bottom of piston head...I had to take the picture though the intake window because of the lighting.
#4
#5
#6
#7
#8
The head was cleaned off by me for inspection.
#9
Cylinder replated 7 hours ago. Fresh piston kit was sent with cylinder so replater could check everything out for me.
Here is what happened over the weekend @ around 7 hours total time on replate and piston.
Pictures 6,7,8 show that the powervalve does not seat against the stop pin, but rather the ex port. Notice the mark inside the port on #8. Not sure if this is relevant to the failure, but it does not seem right?
#1
#2
#3 Bottom of piston head...I had to take the picture though the intake window because of the lighting.
#4
#5
#6
#7
#8
The head was cleaned off by me for inspection.
#9
Paw Paw
I do know the piston was installed correctly....180 would put the intake window on the ex port.
Just went and looked at my used cr125 piston collection....they all (Wiseco, OEM, proX) have the locating pin in the exact same spot as this piston....which I think is a pro X.
WTF is going on
Here is a modified photo that I think shows the locating pin location in the cylinder. It's highlighted in yellow between the red lines.
Maybe the plate company sent me the wrong cylinder back? Seems like a bad spot for the ring end gap.
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Was going to try and use a KTM 250X piston on my YZ so that we had a little more room to widen the transfers. Solid idea but the KTM piston was just a little different that the difference in port timing would have negated what we were trying to do with the transfers.
But having ring end or gaps near ports is bad juju.
My #1 concern right now is building a reliable engine. If the HPP cylinders have a more inherently reliable port to ring end gap relationship, I would get excited. Does any one know?
Right now I am confused as hell as to why Honda would put the ring end gap nearly inside a port.
- A 92-99 cylinder will work. 95 seems to be the desired year (because of slight PV and porting differences I believe)
- A governor and link arm is needed to adapt the 02 bottom end to the HPP PV. I believe that 03+ cases will not work.
- You'll need the corresponding exhaust flange and head for the old cylinder you choose. Not sure about head stays from my 92 head to the 02 frame, haven't crossed that bridge yet.
In the pictures you can see the scoring on the cylinder matches where the ring folded over....which is right where the intake window on the piston is....if I had the piston in backwards, the scoring would be next to the ex port. See?
Kind of looks like the ring end may have jumped up over the locating pin, and rotated ever so slightly, allowing the ring to hang out into the port area.
Pit Row
Paw Paw
Plate co asked me to send cylinder in. They saw my pictures and said that the ring end gap locating pin should not be where it was....happy to be making progress. My tools to split the cases come in tomorrow. Going to spend the weekend tearing down the bottom end. Should be a fun project if it all goes smooth.
They are going to widen that bridge (where the end gap is) just a bit to give it some more support.
I almost said screw it and bought a new cylinder....I am so glad I took the time to send them an email!!
Thank you to all who posted.
Wondering if the end gap alignment pin in the piston was seated to deeply from the factory in the ring channel allowing the same thing to happen.
or the port was beveled too far out.
Post a reply to: Give me an opinion on this top end failure.