Dirt Bike Modifications Forum

im about to get a new jug cause my old cylinder sleeve was eatin on the top rim just about where the piston rings stopped so being i'm going to buy a new jug i went ahead and bought a new wizeco piston the first piston i will have replaced since i've got the bike (really good being its a 2001 and it still has pretty good compression !) anyways the directions say to drill three lubercation holes into the piston for the exaust bridge.. now i've replaced pistons on my fourstroke (timing chain slipped and banged up the insides..long story and headache) but i've never heard of drilling these holes in the piston any advice ? its a wizeco M series .054 oversize with .020 clearance and its a 2001 rm 125  
when it rains pull it apart

Yes, on some Wiseco pistons they recommend this (my question is why don't THEY (WISECO)do it in advance?).  I haven't used WISECO (I use OEM Yamaha pistons) so I can't offer any suggestions on best way to do this.  
Dave H 2006 YZ250
(2008 YZ 125 son)

1990 the holes are need because suzuki uses an exhaust bridge in the cylinder at the exhaust port.

because there are no cooling ports in this area the cylinder needs lubrication and gets it from the fuel mix through the piston wall.

The first thing u need to du is installl the piston and wrist pin (u dont need to put in the circlips now)
Then slide the jug over the piston and seat it onto the cases.  now use the kick or crank end to get the piston @ TDC. Then through the exhaust hole  use a pencil or marker to outline the exhaust bridge.

Its between these two marks were u will drill your holes.

just make sure that u de-burr ur holes and then hit them with some light Emory or scothbrite to keep it smooth.  

DLHamblin:
Yes, on some Wiseco pistons they recommend this (my question is why don't THEY (WISECO)do it in advance?).  I haven't used WISECO (I use OEM Yamaha pistons) so I can't offer any suggestions on best way to do this.

DL my only guess would be that if u've had any porting done in this area, Factory predrilled holes may become exposed.

By making u do it they will now b inside the lines regardless of bridge size.  

DLHamblin:
Yes, on some Wiseco pistons they recommend this (my question is why don't THEY (WISECO)do it in advance?).  I haven't used WISECO (I use OEM Yamaha pistons) so I can't offer any suggestions on best way to do this.

masterlink:
DL my only guess would be that if u've had any porting done in this area, Factory predrilled holes may become exposed.

By making u do it they will now b inside the lines regardless of bridge size.

Yes, good point.  
Dave H 2006 YZ250
(2008 YZ 125 son)

thanks masterlink this that answer resolves my question plus a tip how to do it! very much appreciated  
when it rains pull it apart

another question masterlink the directions didnt specify if the holes are straight threw the wall or slightly recessed into the wall  
when it rains pull it apart

amatthews1990:
another question masterlink the directions didnt specify if the holes are straight threw the wall or slightly recessed into the wall

drill right through at their dimensions and deburr both sides. Its also best to use a punch to mark out the holes. U wouldn't want the drill bit to walk across the piston surface   . take ur time and all should be good.

the object of the holes are to lubricate the exhaust bridge.

Also bikes with an exhaust bridge like Suzukis require more warm up time. When ever you ride be patient and give ur bike an extra few minutes to warm up before u open er up.

it gives the cylinder wall time to catch up with quickly expanding piston.  

i was just thinkin about using a drill press to drill because the whole zig zag dril bit scratches arent that appealing :/  
when it rains pull it apart