03 KX125 Rebuild.... Athena Cylinder & Head Questions.....

WileCyot
Posts
459
Joined
9/23/2014
Location
Katy, TX US
4/26/2016 6:22pm Edited Date/Time 4/28/2016 9:18am
Guys,

Picked up an 03 KX125 to rebuild and I'm not very familiar with these engines. I understand engines in general so I'll be fine with that but the queston I have is in regards to the Athena Cylinder and Head combo.

The bike currently has a damaged Athena Cylinder. I'm looking to send it off and have it replated. Would it be worthwile to have it ported while it's gone or even opened up to a 144? I prefer to leave it stock bore but it's worth having the knowledge.

Also, the piston that came out was an Athena. Looks like the piston melted and the ring snagged a port and drug itself up and down the cylinder. The piston is a flat top and it's my understanding that the OEM is a domed unit. Should I purchase a domed piston or go with a flat top? I'm a wiseco forged nutswinger as I've had great luck with them in my CR500 and an old KX250 I built so I was planning on ordering an 822M05400 which is specific to 2003 but noticed there are 2 other options. 788M05400 which is 03-08, a Racers Choice, ElectraCoated, No Intake Window, & Pinned on Centerline. There is also 755M05400 which is for years 1995-2008. It's a Flat Top Conversion, No Intake Window, and Pinned on Centerline.

What do I do?
|
slipdog
Posts
10043
Joined
7/25/2009
Location
Nor Cal, CA US
4/26/2016 6:42pm
You get the Athena piston as that cylinder and head is set up for the flat top. you can't run a domed piston in it. As for the porting, the Athena 125 cylinders have much more aggressive port timing than a stock cylinder so they run better. Their problem is the casting isn't as good so a good porting blueprint job(meaning clean up ports without changing port timing) will make it run really well.

If you want to go to 144 then you will need a full porting job with the port heights reset after it is over bored. I can't remember if the Athena's have a 2 piece head or not so modifying the head to accept the 58mm piston may present a problem. My reccolection is that the Athena parts are not interchangeable with OEM.
WileCyot
Posts
459
Joined
9/23/2014
Location
Katy, TX US
4/26/2016 6:48pm
slipdog wrote:
You get the Athena piston as that cylinder and head is set up for the flat top. you can't run a domed piston in it. As...
You get the Athena piston as that cylinder and head is set up for the flat top. you can't run a domed piston in it. As for the porting, the Athena 125 cylinders have much more aggressive port timing than a stock cylinder so they run better. Their problem is the casting isn't as good so a good porting blueprint job(meaning clean up ports without changing port timing) will make it run really well.

If you want to go to 144 then you will need a full porting job with the port heights reset after it is over bored. I can't remember if the Athena's have a 2 piece head or not so modifying the head to accept the 58mm piston may present a problem. My reccolection is that the Athena parts are not interchangeable with OEM.
It is the 2-piece head but trying to find further information regarding it is the problem. So, the flat top Wiseco should be fine I assume? Trying to avoid using the Athena junk....
CrGuy2T
Posts
4177
Joined
3/11/2015
Location
Santa Fe, TX US
Fantasy
3665th
4/26/2016 8:02pm Edited Date/Time 4/26/2016 8:05pm
How much is it gonna cost to have the cylinder bored and re plated along with a re-port and piston. Seems like a no bore Athena kit would be about the same if not cheaper.
Bruce372
Posts
6341
Joined
4/1/2008
Location
US
4/26/2016 11:06pm
You might also have to trim the crankcase to clear the piston on the big bore? I know you do on the RM

The Shop

HenryA
Posts
3789
Joined
12/29/2011
Location
Stockholm SE
4/27/2016 3:46am
Did it also come with the stock cylinder? If it did, ditch the Athena and send the stock one away for 144 modification.

Is the exhaust port that is damaged on the Athena?
jsmx97
Posts
206
Joined
12/28/2011
Location
NH US
4/27/2016 6:18am
KX125 needs cases clearanced on the front side for the 58mm piston. The athena 144 kit works pretty good although I will say I think the quality is not up to par with oem. All athena cylinder kits I have installed could benefit from additional port work.
4/27/2016 10:39am
We have a complete 144cc kit we can base around a stock cylinder/head that includes head mods, porting, strip, bore, NSC plating, diamond hone, power valve mod/service, piston, bearing and gasket for $514.95

http://www.mt-llc.com/serviceInfo.php?id=19

We can also service your Athena cylinder as well:

http://www.mt-llc.com/serviceInfo.php?id=7
jsmx97
Posts
206
Joined
12/28/2011
Location
NH US
4/27/2016 11:21am
We have a complete 144cc kit we can base around a stock cylinder/head that includes head mods, porting, strip, bore, NSC plating, diamond hone, power valve...
We have a complete 144cc kit we can base around a stock cylinder/head that includes head mods, porting, strip, bore, NSC plating, diamond hone, power valve mod/service, piston, bearing and gasket for $514.95

http://www.mt-llc.com/serviceInfo.php?id=19

We can also service your Athena cylinder as well:

http://www.mt-llc.com/serviceInfo.php?id=7
And he will still need to split the cases and have the cases machined for piston clearance... you may want to include that info!
4/27/2016 11:29am
We have a complete 144cc kit we can base around a stock cylinder/head that includes head mods, porting, strip, bore, NSC plating, diamond hone, power valve...
We have a complete 144cc kit we can base around a stock cylinder/head that includes head mods, porting, strip, bore, NSC plating, diamond hone, power valve mod/service, piston, bearing and gasket for $514.95

http://www.mt-llc.com/serviceInfo.php?id=19

We can also service your Athena cylinder as well:

http://www.mt-llc.com/serviceInfo.php?id=7
jsmx97 wrote:
And he will still need to split the cases and have the cases machined for piston clearance... you may want to include that info!
Yes he will!
WileCyot
Posts
459
Joined
9/23/2014
Location
Katy, TX US
4/27/2016 12:45pm
We have a complete 144cc kit we can base around a stock cylinder/head that includes head mods, porting, strip, bore, NSC plating, diamond hone, power valve...
We have a complete 144cc kit we can base around a stock cylinder/head that includes head mods, porting, strip, bore, NSC plating, diamond hone, power valve mod/service, piston, bearing and gasket for $514.95

http://www.mt-llc.com/serviceInfo.php?id=19

We can also service your Athena cylinder as well:

http://www.mt-llc.com/serviceInfo.php?id=7
144 kit is off the table. I'm looking to have this cylinder replated and will more than likely send to you guys. I still need to know, however, what piston I should be using. Will the flat top wiseco work?
4/28/2016 5:33am
We have a complete 144cc kit we can base around a stock cylinder/head that includes head mods, porting, strip, bore, NSC plating, diamond hone, power valve...
We have a complete 144cc kit we can base around a stock cylinder/head that includes head mods, porting, strip, bore, NSC plating, diamond hone, power valve mod/service, piston, bearing and gasket for $514.95

http://www.mt-llc.com/serviceInfo.php?id=19

We can also service your Athena cylinder as well:

http://www.mt-llc.com/serviceInfo.php?id=7
jsmx97 wrote:
And he will still need to split the cases and have the cases machined for piston clearance... you may want to include that info!
Yes he will!
You should be careful using millennium tech. Despite what their website says they will not warranty their work. They passed the blame onto weisco in my case after 2 local mechanics told me my engine failures were from the cylinder work MT performed. Most people on here praise them and I'm sure they do good work. It just wasn't the case for me.
4/28/2016 9:13am Edited Date/Time 4/28/2016 9:18am
WileCyot wrote:
Anyone?
WileCyot

- Send me an email at chip@mt-llc.com with the details of which Athena kit you have, which piston you are currently using and I will get you some information. If the Athena piston is no longer available, I am sure we can find a suitable replacement, but we will need some specific measurements.
4/28/2016 9:18am
jsmx97 wrote:
And he will still need to split the cases and have the cases machined for piston clearance... you may want to include that info!
Yes he will!
You should be careful using millennium tech. Despite what their website says they will not warranty their work. They passed the blame onto weisco in my...
You should be careful using millennium tech. Despite what their website says they will not warranty their work. They passed the blame onto weisco in my case after 2 local mechanics told me my engine failures were from the cylinder work MT performed. Most people on here praise them and I'm sure they do good work. It just wasn't the case for me.
DirtJumper936 - Sorry to hear you had an issue with a piston and/or a cylinder. No idea what transpired, but we work very closely with Wiseco on a daily basis. Typically, if we determine the piston was the issue, Wiseco will stand behind that piston.

If there is anything I can do to help, let me know.

Post a reply to: 03 KX125 Rebuild.... Athena Cylinder & Head Questions.....

The Latest