CR 500 piston lubrication holes

[Dogger]

I read somewhere that when you install oversize piston in CR 500 you should bore two holes for lubrication of the exhaust port bridge. I checked my piston (91 mm) and there were no holes in it. I also noticed some sign of seizing in cylinder above the exhaust port bridge :(
Now, could somebody provide the instructions:
- where should I bore those holes (for ex. measured from top of piston)
- what size (diameter) should them be ?

 

[MikeT]

Follow Wiseco's Instructions
To locate the holes correctly:
1. Install the piston without rings.
2. Install the cylider. No gaskets required.
3. Reach in through the exhaut port, and scribe a line on both sides of the exhaust bridge.
4. Remove the cylinder
5. Remove the piston
6. Use the scribed lines to center the lube holes on the exhaust bridge (radially)
7. Use your ruler to locate the lube holes as specified in the Wiseco instructions (axially)
8. Drill and debur the holes
9. Assemble top end.

 

[Dogger]

Thanks MikeT. Now, since I don't have the Wiseco instructions I would also like to know the location from top of the piston and diameter of these holes.

 

[MikeT]

Hmm, That one I really can't say. I would give Eric a call. I mean actually pick up the phone, because if you are doing your top end now, he will give you an immediate answer. He is very easy to talk to and won't laugh at the simpleist of questions although you have a serious question. Most people don't even read the directions on the piston so I think Eric would be happy to see you taking the time to do the job right. :D

 

[morph]

dont stress.if you are replacing the top end with a wiseco piston the instructions to drill the holes come with it .i use to use wiseco untill i found out PRO X piston come in increments of .25mm instead of wiseco's .5mm giving you twice as many bores if you dont score it deep.while it's apart check the exaust bridge wether it has been reccesed.if it is not your piston wont last long.those specs are also in the wiseco instructions.

 

[TravisCR500R]

Don't scribe!~!!

Dont "scribe" the piston! It will scratch the side of the piston and wear out the cylinder quicker! Instead:
use stuff called "dykem" its a machinists blue...you can get the spray stuff or use the paste...or take a black marker and "color" the area on the piston...the area inbetween the "color" or dykem (if you choose to use that) will be the area you should drill your holes.
Would you run sandpaper on the side of a new piston before putting it in your cylinder? I think not!
Do be sure to deburr the holes...they will create a hot spot if you dont.
Travis R.

 

[MikeT]

You don't really scratch the piston, you just use a lead pencil to draw on it. It won't harm the piston in any way.

 

[TravisCR500R]

Okay but...

Okay, the lead pencil is fine. I have come to the realization that it is hard to see and can wipe off easily. Being a machinist, a scribe is exactly that. A compass with two metal points (or a single one put in the shirt pocket. There are geek machinists you know! But it pokes the boobies!) So when I heard "scribe" I immediately thought of the Middle Eastern people in Jesus' time...no wait...wrong story I think of an actual scribe.
Just remember dude, whatever you use, dykem, pencil, hammer (DOH!) take your time, and be patient. It pays off in the end!!
Travis R.