2 Stroke WHAT SIZE TOP END!!

Hi, I need to buy a new top end on my ktm 125 and it currently has a "2" 53.95, cyl in good condition...Should I get another 53.95 or 53.96?
Please help asap!!
 

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SRAD97750

Moderator
Staff member
Howdy! What year?
It depends on what part is worn...
Compression low?
Ring end gap clearance?
Piston to cylinder clearance?
Piston out of round?
Piston skirt cracked or scratched?
Cylinder walls scratched?
-BIG DAN:thumb:
 
Howdy! What year?
It depends on what part is worn...
Compression low?
Ring end gap clearance?
Piston to cylinder clearance?
Piston out of round?
Piston skirt cracked or scratched?
Cylinder walls scratched?
-BIG DAN:thumb:
It's a 2006 with low hrs.
Heaps of compression. Haven't checked any clearances - assuming they're all good bike running mint! Cylinder is in good condition with no scratches I can feel as per photos. The black on the piston skirt is worn although not silver just dark grey. Rings look pretty shiny.
 

SRAD97750

Moderator
Staff member
I recommend checking all specs per the manual to find out what needs replacing.
By your description, I am not sure why it's apart in the first place.

If I tear down for hours alone and find nothing out of spec, I replace the wrist pin bearing no matter what.
-BIG DAN:thumb:
 
I recommend checking all specs per the manual to find out what needs replacing.
By your description, I am not sure why it's apart in the first place.

If I tear down for hours alone and find nothing out of spec, I replace the wrist pin bearing no matter what.
-BIG DAN:thumb:
Just doing top end per maintenance...I could run it longer but I don't want to risk anything. I don't have any precise measuring tools to do the bore but I can certainly do the ring end gap. I'm just unsure whether to get the same size piston (53.95) or a "C" size of 53.96...
 
Just doing top end per maintenance...I could run it longer but I don't want to risk anything. I don't have any precise measuring tools to do the bore but I can certainly do the ring end gap. I'm just unsure whether to get the same size piston (53.95) or a "C" size of 53.96...
Measure the clearance between the piston and cylinder with the at several different points including the skirt with a set of feeler gauges.
 
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