Rebuild a 2stroke 125

Related:
Create New Tag

9/19/2019 11:13 PM

Just got back into mx, what’s the best kit to use when replacing the piston and rings on a 2008 RM 125?

|



9/20/2019 1:28 AM
Edited Date/Time: 9/20/2019 1:29 AM

I like OEM stuff personally for KTM. Unsure for that bike specifically .

|

9/20/2019 1:51 AM

Vertex 👍

|

9/20/2019 3:15 AM

X2 Vertex. Stay away from wiseco.

|

9/20/2019 3:21 AM

A 144 kit from Eric Gorr.

|

9/20/2019 3:44 AM

I use Woosner in my RM's.

|

9/20/2019 3:48 AM

LumpDog841 wrote:

X2 Vertex. Stay away from wiseco.

I've used Wiseco for over 20 years. Never had an issue. Matter of fact, they've been great on top ends, and clutch baskets, and clutch kits.
I'd go Wiseco

|

9/20/2019 3:53 AM

LumpDog841 wrote:

X2 Vertex. Stay away from wiseco.

kawasa84 wrote:

I've used Wiseco for over 20 years. Never had an issue. Matter of fact, they've been great on top ends, and clutch baskets, and clutch kits.
I'd go Wiseco

Well having actually used both Wiseco is complete garbage compared to Vertex. There is a reason why they are an OEM supplier and Wiseco isn't

|

9/20/2019 4:19 AM

LumpDog841 wrote:

X2 Vertex. Stay away from wiseco.

kawasa84 wrote:

I've used Wiseco for over 20 years. Never had an issue. Matter of fact, they've been great on top ends, and clutch baskets, and clutch kits.
I'd go Wiseco

LumpDog841 wrote:

Well having actually used both Wiseco is complete garbage compared to Vertex. There is a reason why they are an OEM supplier and Wiseco isn't

Two posts, and you have failed to give data on why Wiseco isn't a good product. I gave you reasons why Wiseco is good. ( 20 plus years of use)
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

|

9/20/2019 4:25 AM

kawasa84 wrote:

Two posts, and you have failed to give data on why Wiseco isn't a good product. I gave you reasons why Wiseco is good. ( 20 plus years of use)
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

Great job on the ring. Think proof in the fact that Wiseco isn't an OEM supplier while Vertex is. And you know my own personal experience (as seen below), not "my buddies"

.....



|

9/20/2019 4:30 AM

I'm at work so I cant post pics of his shredded vertex.

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

|

9/20/2019 4:48 AM

Oem.

|

9/20/2019 4:59 AM
Edited Date/Time: 9/20/2019 5:00 AM

When I worked at a local shop we used Pro X pistons and rods almost exclusively and never had issues. Basically an OEM replacement.

|

9/20/2019 5:46 AM

I'll throw in my 2 cents worth. I'd go Vertex. I've had 2 failures with Wiseco pistons (not on an RM125, on other bikes, but still). T

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.

|

Only dead fish go with the flow

9/20/2019 5:55 AM

I've got probably close to 1000 hours on various stock and ported/modified 125 and 250 two strokes over the years using wiseco. Never once had a problem.

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.

|

9/20/2019 6:02 AM

Used wiseco in my CR125. Haven’t had an issue yet.

|

why does Kermit's fingers always smell like pork?

9/20/2019 6:17 AM

kawasa84 wrote:

I'm at work so I cant post pics of his shredded vertex.

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

Me thinks you like to make broad baseless assumptions without knowing a single thing about myself. So please continue to make dumbass assumptions for your defense of Wiseco I have never had or paid someone to do mechanical work for me. That bike had 86 total hours on it, with 82 being on 4 vertex pistons without issue, all of them being changed by me. The last 4 were on that garbage Wiseco.

Once again this is from personal experience and not "my buddies."

Premix was Maxima K2.

|

9/20/2019 6:52 AM

cp pistons used to make a piston for 04-06 rm125, wossnër is a great choice

|

9/20/2019 7:14 AM

It's not the piston, it's the mechanic

|

9/20/2019 7:23 AM
Edited Date/Time: 9/21/2019 12:16 PM

LumpDog841 wrote:

Well having actually used both Wiseco is complete garbage compared to Vertex. There is a reason why they are an OEM supplier and Wiseco isn't

kawasa84 wrote:

Two posts, and you have failed to give data on why Wiseco isn't a good product. I gave you reasons why Wiseco is good. ( 20 plus years of use)
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

LumpDog841 wrote:

Great job on the ring. Think proof in the fact that Wiseco isn't an OEM supplier while Vertex is. And you know my own personal experience (as seen below), not "my buddies"

.....



Not calling you out. Just asking. Did you measure the piston or ring gap?Looks like a ring got snagged on a port. I've had good luck with Wiseco. I've only seized one piston over 32 years. I was a 13 year old kid. Started it then immediately rung it out. My fault. I do however believe firmly in using OEM gaskets. I break the bike in using non synthetic pre mix. Then after a few hours, or a tank of gas, I'll switch to Pro Honda HP2 pre mix. Once again. This is what works for me.
Edit: Forged pistons require a few extra heat cycles.
AND HAPPY FRIDAY EVERYONE!!!!

|

9/20/2019 8:56 AM

Chance1216 wrote:

Not calling you out. Just asking. Did you measure the piston or ring gap?Looks like a ring got snagged on a port. I've had good luck with Wiseco. I've only seized one piston over 32 years. I was a 13 year old kid. Started it then immediately rung it out. My fault. I do however believe firmly in using OEM gaskets. I break the bike in using non synthetic pre mix. Then after a few hours, or a tank of gas, I'll switch to Pro Honda HP2 pre mix. Once again. This is what works for me.
Edit: Forged pistons require a few extra heat cycles.
AND HAPPY FRIDAY EVERYONE!!!!

In the thread I started concerning the piston, I took responsibility for not measuring ring gap. That's on me. By the same token, I've never measured ring gap once on a Vertex, and never had a problem. And like most of us here have changed a lot of pistons over the decades. I've used both a lot also, but all things considered, with Vertex being an OEM supplier and such I'll personally stick with Vertex. My opinion is that Wisecos tolerances aren't what Vertexs is. In the incident above I gave the bike numerous gently heat cycles as I was coming off a shoulder surgery.


Oh yeah oem gaskets all the way.

|

9/20/2019 9:04 AM

I don't know anything about any other Wiseco products but have heard stories. I've used Wiseco pistons for years and never had any trouble with them. Not once. That's all I can say - besides like others above have noted - you really need to warm up a forged piston before running it hard. Other than that, use whatever you can find and suits your fancy. OEM is always best - if you can get it.

|

I have nothing more to say.

9/20/2019 10:12 AM

Bruce372 wrote:

It's not the piston, it's the mechanic

Ding ding din! We have a winner. 99% of piston failures are mechanical related (unless it's a Namura they are crap).

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...........

|

9/20/2019 11:31 AM

Bruce372 wrote:

It's not the piston, it's the mechanic

Tracktor wrote:

Ding ding din! We have a winner. 99% of piston failures are mechanical related (unless it's a Namura they are crap).

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...........

Spot on post Tracktor!

|

9/20/2019 2:27 PM

Bruce372 wrote:

It's not the piston, it's the mechanic

Tracktor wrote:

Ding ding din! We have a winner. 99% of piston failures are mechanical related (unless it's a Namura they are crap).

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...........

Right on the money. With modern CNC machining and manufacturing tolerances there are plenty of good brands and parts to choose from. I have been running a lot of Wiseco pistons in my Yamahas, but the only brand I wouldn't run is Namura. Most people don't own a set of mics, snap gauges and feeler gauges to measure their stuff pre-assembly and that's a mistake.


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.

|

9/21/2019 8:56 AM

I've never had an issue with Wiseco pistons.

|

9/21/2019 9:05 AM

Pro-x. OEM.

|

9/21/2019 9:18 AM

I have never had problems with wiseco pistons but the 98 cr250 cranks they sell are junk.

|

9/21/2019 9:32 AM

Almost as good as an oil thread...

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.

|

James

9/21/2019 9:42 AM

SoCalMX70 wrote:

Almost as good as an oil thread...

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.

I 2nd that Wiseco cranks are good now, never had an issue with 2 stroke Wiseco piston either.

|

recmx.com

REC MX, JE Pistons, Wiseco, Rusk Racing, Yoshimura, Enzo Racing, Dubya Wheels, Asterisk, Rocket Performance, CCR Sport, & MMR