KTM 125 Piston Kit

CarlinoJoeVideo
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CarlinoJoeVideo
Hey guys, I was looking at the KTM parts list for a full piston kit to fit my 2016 SX and they list 125 size 1 and a 125 size 2. Any idea what the difference is?

Also do you buy OEM kits or Other brands?
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colintrax
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colintrax 2/27/2017 10:32pm
2/27/2017 10:32pm
Size 1 and size 2 is like A and B size.
I've only ran OEM however I wouldn't hesitate to run pro x or other quality aftermarket pistons.
FWYT
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FWYT 2/27/2017 11:05pm
2/27/2017 11:05pm
OEM. I swear I get unholy hours out of my KTM pistons. Re-ring and let it rip.
1
HenryA
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HenryA 2/27/2017 11:36pm
2/27/2017 11:36pm
Size 1 is 53.94mm(A), size 2 is 53.95mm(b). And then it goes on and on like that, C 53.96, D 53.97, E 53.98.
F1 Moto
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F1 Moto 2/28/2017 3:03am
2/28/2017 3:03am
Hi Joe,
As already stated 0.01mm between letter or number grades to also for slight tolerances in manufacturing or wear.
If it's performance your chasing then take a look at these.

http://www.f1moto.com.au/buy/ktm125-sx-billet-performance-piston-kit-12…

http://www.f1moto.com.au/buy/ktm125-sx-vhm-cylinder-head-2016-2017/E06K…

It's what the quick kids here & in Europe are using.

Let me know if this is of interest ?

Regards
Steve.

The Shop

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CarlinoJoeVideo
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CarlinoJoeVideo 2/28/2017 6:44am
2/28/2017 6:44am
Thanks guys, do I need to measure my cylinder before ordering a new OEM one or do I look on the old piston to see which size was run previously between 1,2,3 etc?
CarlinoJoeVideo
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CarlinoJoeVideo 2/28/2017 6:45am
2/28/2017 6:45am
F1 Moto wrote:
Hi Joe, As already stated 0.01mm between letter or number grades to also for slight tolerances in manufacturing or wear. If it's performance your chasing then...
Hi Joe,
As already stated 0.01mm between letter or number grades to also for slight tolerances in manufacturing or wear.
If it's performance your chasing then take a look at these.

http://www.f1moto.com.au/buy/ktm125-sx-billet-performance-piston-kit-12…

http://www.f1moto.com.au/buy/ktm125-sx-vhm-cylinder-head-2016-2017/E06K…

It's what the quick kids here & in Europe are using.

Let me know if this is of interest ?

Regards
Steve.
Are these direct replacement? Same some compression and everything? What type of advantage to they offer?
CarlinoJoeVideo
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CarlinoJoeVideo 2/28/2017 6:46am
2/28/2017 6:46am
FWYT wrote:
OEM. I swear I get unholy hours out of my KTM pistons. Re-ring and let it rip.
Hey chip, what type of hours are you doing on your piston vs rings? My KTM guy said no problem for 40 hours per Piston.
FWYT
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FWYT 2/28/2017 7:35am
2/28/2017 7:35am Edited Date/Time 2/28/2017 7:38am
FWYT wrote:
OEM. I swear I get unholy hours out of my KTM pistons. Re-ring and let it rip.
CarlinoJoeVideo wrote:
Hey chip, what type of hours are you doing on your piston vs rings? My KTM guy said no problem for 40 hours per Piston.
I have a 200, so not quite the same, but it still is pinned most of the time.
I did a ring at 45hrs. (!) and the piston still looked great. It's at about 65 hours now
and haven't bothered to look.

Before this I had a 125 SX which unfortunately I didn't have an hour meter on but
it seemed like everytime I looked at the piston, I just went "looks good!" and did
a ring only.
mxtech1
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mxtech1 2/28/2017 8:32am
2/28/2017 8:32am
You should be measuring both the piston and cylinder every time you do a rebuild.

Theoretically, as the bore wears, you order a corresponding oversize piston to keep the piston to bore tolerance as close to nominal as possible. This spec will be listed in your owner's manual.

Eventually, the cylinder bore will wear to the point that is outside of the acceptable spec range. This will drive you to either recondition or replace the cylinder.

I cannot express enough how imperative it is to take these measurements to get proper fitment of parts. Especially on a small bore 2 stroke like a 125.

If you need more help, ask. There are plenty of people on here who can help walk you through the measuring process.
DS20
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DS20 2/28/2017 8:44am
2/28/2017 8:44am
CarlinoJoeVideo wrote:
Thanks guys, do I need to measure my cylinder before ordering a new OEM one or do I look on the old piston to see which...
Thanks guys, do I need to measure my cylinder before ordering a new OEM one or do I look on the old piston to see which size was run previously between 1,2,3 etc?
Just look on the top of the piston. It is marked. Here is my 2016 125.

braaap707
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braaap707 2/28/2017 9:06am
2/28/2017 9:06am
If I had my pick I would use the OEM KTM piston. You should measure the cylinder to figure out if u need size 1 or 2. Agreeing with chip, I have gotten incredible durability up to 60 hours on my 2012 150sx top end and piston still looked great !!! Ringed it and put it back together. I also run synthetic motorex crosspower 2t motor oil and bel ray synthetic 80w 90 gear oil in my transmission and it fixed my 2016 tc125's slight shifting issues under load.
F1 Moto
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F1 Moto 3/1/2017 1:00am
3/1/2017 1:00am
Here's a video I did of measuring piston to bore clearance.

https://www.youtube.com/watch?v=r7KaxX1lC78

Pistons often look ok & it's not wear that finally kills them it's fatigue failure.
I personally would always advise adhere to the recommended service intervals .
If possible check the clearances ring gap & squish clearance on rebuild.

Hope this helps ?

Regards
Steve
F1 Moto
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F1 Moto 3/1/2017 1:21am
3/1/2017 1:21am
F1 Moto wrote:
Hi Joe, As already stated 0.01mm between letter or number grades to also for slight tolerances in manufacturing or wear. If it's performance your chasing then...
Hi Joe,
As already stated 0.01mm between letter or number grades to also for slight tolerances in manufacturing or wear.
If it's performance your chasing then take a look at these.

http://www.f1moto.com.au/buy/ktm125-sx-billet-performance-piston-kit-12…

http://www.f1moto.com.au/buy/ktm125-sx-vhm-cylinder-head-2016-2017/E06K…

It's what the quick kids here & in Europe are using.

Let me know if this is of interest ?

Regards
Steve.
CarlinoJoeVideo wrote:
Are these direct replacement? Same some compression and everything? What type of advantage to they offer?
Flat top piston with a chamfered edge uses a VHM cylinder head with a custom insert.
Compression is the same.
Different crown height so slightly different port timing & different Insert profile.
It's what the quick kids here & in Europe are using,
Here's a link to some interesting 125 parts.

http://www.f1moto.com.au/10/ktm/125/2016/

CarlinoJoeVideo
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CarlinoJoeVideo 3/1/2017 2:46am
3/1/2017 2:46am
Thanks for the advice guys! You rule!
drumheller34 3/2/2017 9:41am
3/2/2017 9:41am
Vertex makes KTM's pistons still or am I wrong
brocsdad
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brocsdad 3/2/2017 11:36am
3/2/2017 11:36am
drumheller34 wrote:
Vertex makes KTM's pistons still or am I wrong
Yes,

I just installed the Vertex single ring in my 16 125.

I went with size B at 10 hours.

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