Wiseco piston help.

I'm replacing the top end on my bike and I pretty much have everything figured out except this one thing I'm a little unsure about. The directions for the new Wiseco piston say if the cylinder has an exhaust bridge you have to drill holes in the piston skirt. I'm a little nervous about drilling into my brand new piston and I'm unsure if I need to because the OEM piston did not have these holes. I assume the exhaust bridge is the narrow piece in the center of the port right? Advice would be appreciated as this is my first time and I REALLY don't want to mess this up!

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It's an 04 Honda CR250 by the way.

Yes that is an exhaust bridge. Are you sure that was an OEM piston? You need to drill these holes for the wiseco piston. Just use a small punch and tap the punch with a hammer where the holes needs to be, then get your drill bit out and drill it. Start slow till you know for sure that your in your hole.

The OEM piston is cast and doesn't need holes in it. Only goofy forged pistons need to be drilled on.

Ain't even my post but i learned something. THanks CamP

Yeah it was an OEM piston. Judging by how dirty the power valve was (the 3 grooves in each flap were completely filled up with carbon buildup!) I don't think the bike has ever had a new top end put in it. The guy also told me it had a hinson clutch in it, it was a stocker:banghead:. Oh well I guess that's what you get sometimes when you buy used from an individual.

Anyway I'm in the process of going through the entire engine so it should be running top notch when I'm done. Only thing I wish I would of done is tore this thing down in the middle of winter when I couldn't ride instead of right now when my first 2 races are almost a month away!:smirk:

you really dont need to put in a circlip but otherwise just follow the instructions.

if he said there was hinson but its only stock you should give him a drop kick to the face or nutzz just for being a dooosh :smirk:

Lol! I'll throw him a bone for all the extra "brand new" parts he threw in!

Only reason I'm rebuilding is because it started fouling plugs bad. I'm replacing the crank seal and putting in the new top end for safe measure. It ran good but would load up a little on the bottom end and foul out the plugs at slow speed. I'm guessing that it's gonna run alot better without all the crud gunked up on the power valve and the leaking crank seal replaced!

Anyone else happen to notice those instructions say to drill "TWO" holes, but the illustration shows "THREE" holes?

I'm calling FOUL!

:smirk:

when you are finished and crank it, go ahead and pull the power valve inspection plug on the left side of the cylinder to see if it operates right because it is tricky to set it up right even if you go by the manual.

when you are finished and crank it, go ahead and pull the power valve inspection plug on the left side of the cylinder to see if it operates right because it is tricky to set it up right even if you go by the manual.

Will do! I had to order a new front

cable on the power valve anyway because it was frayed and almost broke.

Anyone else happen to notice those instructions say to drill "TWO" holes, but the illustration shows "THREE" holes?

I'm calling FOUL!

:smirk:

ya i noticed. some big motors with long stroke you can put 3 holes. seems like i put 4 on mine. 250 should be fine with 2 or you could put 3 i suppose.

Will do! I had to order a new front

cable on the power valve anyway because it was frayed and almost broke.

Oh sorry, the rc valve will propably be ok. For some reason i thought was doing a 2000 or 2001.

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