Posts
3
Joined
9/19/2019
Location
GB
Edited Date/Time
9/22/2019 2:39am
Just got back into mx, what’s the best kit to use when replacing the piston and rings on a 2008 RM 125?
The Shop
I'd go Wiseco
If you have reasons, maybe you could state them in your THIRD post.
I have a reason not to use Vertex. A riding buddy of mine had about 10 hrs on a Vertex in his 08' YZ 250 smoker years ago, when it blew up. He ended up purchasing a new head and jug, costing him around $1000
.....
Me thinks you should probably pay someone to do your mechanical work. Looks like a mistake on your part, not a product failure on Wiseco.
Maybe I need to find out what brand premix you're using as well
he first one the locating pin for the ring came loose, worked it's way out until it scored a groove up and down the cylinder. I talked to Wiseco and they said to send the piston and cylinder in and they would look at it. Well they gave me a new piston and fixed the cylinder - HOWEVER when I got it back and put the bike back together it wouldn't stop leaking coolant around the cylinder head. Turns out they didn't machine the top of the cylinder very well and so the head gasket wouldn't seal and it kept leaking coolant into and outside of the cylinder. Had to take the cylinder back off and have it machined flat locally to fix the issue.
Second problem I had with Wiseco was the piston developed a crack on the top of it that caused a loss of compression. This was after about 3 to 4 hours of riding time on it. Luckily that one didn't grenade and wreck the engine. Ever since then, I'm done with Wiseco.
I had a 2006 RM 125 and used Vertex pistons without any issues. They always looked good when I pulled them out to change them, no issues like the Wiseco ones. YMMV.
Warm the bike up properly and check ring end gap. The three different engine builders i've worked with over the years have all utilized wiseco for what its worth.
I've recently installed an entire clutch assembly from them from basket all the way to the cover in a ported yz250, feels the same as a hinson, but warrantied for life.
Once again this is from personal experience and not "my buddies."
Premix was Maxima K2.
Pit Row
Edit: Forged pistons require a few extra heat cycles.
AND HAPPY FRIDAY EVERYONE!!!!
Oh yeah oem gaskets all the way.
I rebuild a couple bikes a month on average for either my boys or other people. I've used every name brand piston made and haven't had a part related failure in as long as I can remember.
Every top end -
Check piston clearance
Check squish
Check ring gap
Disassemble and clean powervalves
Brush hone cylinder then clean clean clean.
Replace wrist pin bearing
Obviously make sure the rest of engine is in good running shape
One warm up then they are ridden like they are raced. When pulled pistons look great with very little blow-by. And our bikes run strong.
Most just slap a piston in and then wonder why something breaks. Easiest choice is blame the part.
I've mostly used Vertex because we have quite a few KTM/Husky 65-125's over the years. Second would be Wiseco. ProX makes a good budget piston also. For thumpers Vertex/CP/JE have all been great.
I wouldn't use a Wiseco or a Hotrods crank. OEM or OEM with ProX rod is best choice unless going high end for a thumper...........
The quality of the OEM crank cheeks, crank stuffers and especially the rod forgings is superior to the aftermarket stuff. This is true for Kawasaki, Honda and Yamaha in my experience (I haven't worked on Suzuki in many years).
I'm not a break in guy either (on two strokes)... Heat cycle that sucker and go straight to the track to wring it's neck up that hill. I've never had any issues when I've done all those things you listed.
I will say one thing, since I saw wiseco cranks mentioned a few times. They have a bad rap from having a few issues, years ago. They FULLY ADMIT their QA was bad. I would not let some still disgruntled customers perpetuating an old issue steer anyone away from considering their cranks today. Read this:
https://www.wiseco.com/Powersports/CrankshaftQuality.aspx
Anyway, run whatever piston.... Just do it right. I run vertex, and have for years, but I don't just dismiss everyone else. All the big names and OEM are fine.
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