Rebuild time * need input*

[Cr250rider04]

I just bought a 04 cr250. I love it. I bought it from the original owner. he claimed he never rebuilt it. So im rebuilding it this weekend. I got a wiseco pro lite piston kit. cometic gaskets and wiseco needle bearing. my question is our cylinders arent ment to be honed so can i just clean it with soap and water and a scotch pad? the cylinder is very clean no scratches or anything like that. also It says you have to drill holes for the exhaust bridge for lubrication. how big do the holes have to be and how many do you drill? the instructions dont say anything specific. any other tips would be great. Its my first topend rebuild but im very mechanically inclined. and i have all the tools needed. just want to do it right. let me know. thanks

[mrcribbs]

WD40 and the maroon color scotch brite pad

[MXtras]

You seem to have a good grip on things so far. Just clean the jug really well and yes - you can use ScotchBrite lightly on the bore to break the glaze a little. I use Brake Cleaner on the jugs - it removes splooge easily.

As far as the holes - drill two 1.5MM holes in the piston just below the ring right at the exhaust bridge. The first hole was 4MM from the ring, the second was 10MM from the ring - further down on the skirt, in line with the first. I would heavily chamfer both sides of these holes. This mod made a pretty substantial impact on ring wear in that area."

(copied from this thread: 2000 Yamaha YZ125 questions.)

Scott

[nutty]

I had to drill holes in my piston also. I used a drill press with a 1/16'' bit and clamped two 2x4 blocks to the platform of my drillpress to cradle the piston and it was very easy. Just lay it out like Mxtras describes and you will be fine.

[Cr250rider04]

I already did the rebuild at work today. it was very easy. I went along with what the service manual said. I took my power valve apart and got it spotless and in the exhaust port also. Cleaned the cylinder good and the ports also measured it. Measured the ring end gap at .018" the range in the service manual says (0.016- 0.022) so I measured and it was 0.018" is assume thats perfect? Also one question I checked the crank movement. it has no play up and down but has a fair amount of side to side. is that normal? should I be worried? I havent started it yet so well see monday.

[mrcribbs]

Side to side is normal. I believe there is a spec for rod to crank web side clearance... .030 or .032" sticks in my head but don't quote me on it.

Up and down = junk.

[Cr250rider04]

thanks for the input guys. i just wanted to go throught this thing and make it perfectly sound. I love this thing I wouldnt want it to grenade. thanks again

[mxman107]

the holes in piston would it be a good thing to do to my 97 cr250r