Drilling holes in my new piston ????

**HONDA_ATC_FREAK** · 02-25-2011, 03:00 PM

Is this right I'm rebuilding my 83 250r and the weisco piston kit says I need to drill three holes in my piston for lubrication.

**Brockey** · 02-25-2011, 03:09 PM

Wow. I don't doubt it. I never had too do it with my 81R piston kit from weisco and they are the same kits. Maybe they were already there. Can't remember.

**fabiodriven** · 02-25-2011, 03:11 PM

I've never read the directions when installing a piston. Note to self- read the dadgum directions.

**JasonB** · 02-25-2011, 03:35 PM

wow I dont remember that part of rebuilding my 84R 4 times lol maybe thats why it had to be rebuilt 4 times....... Or I just FAIL at jetting

**Dirtcrasher** · 02-25-2011, 03:41 PM

It even came with my 350X piston; Just general instructions for 2 and 4 strokes.......

How many air cooled bikes seize up?? MANY! Is it jetting? clearance? who knows but I certainly know they want .006-.007 clearance on an air cooled cylinder, that exhaust bridge is often dremel'ed back a bit to ensure clearance.

Do what you want, it's all for lubrication but the bore to piston size is most critical.

**HONDA_ATC_FREAK** · 02-25-2011, 03:53 PM

I just called the honda shop where I got it from they said you don't have to it's mainly for modified engines. I'm not going to do it I think it will be fine the way it is. I"m gonna put her together this weekend and have her running.

**bcredneck** · 02-25-2011, 04:04 PM

im about to do a 83R top end thats good to know where do you put the holes

**Dirtcrasher** · 02-25-2011, 04:08 PM

I can try and scan/post pics of there suggestions.

Freak, I hope you have the correct clearance and relieve the exhaust bridge. Ronnie Yamahoondaman told me to do this and he was a wealth of knowledge so I suggest you at least look into it or call Wiseco. As they say "I wanna ride I wanna ride I wanna ride" pertains to all of us, but a few hours of fun to a blown motor aren't worth it. Do whatever you wish but I truly have seen MANY AC trikes blow up quickly upon rebuild.

Just trying to help

**HONDA_ATC_FREAK** · 02-25-2011, 04:13 PM

Yes the exhaust is relived all the way around the edges and the other ports are too for that matter I had it done at the local honda shop. I'm sure they did it right but just to be sure how do you check the clearance?

**NOS_350X** · 02-25-2011, 04:22 PM

Even with the exhaust releaved DRILL THE DANG HOLES. Its an easy security And easy to do. Alot of the enignes i tear appart have some wear on the piston at the bridge with the cooling holes, i would think if no holes where there it would defenlty lock up.

**Dirtcrasher** · 02-25-2011, 04:34 PM

^ Glad someone who's built plenty of motors as well as tested them chimed in! Merely rounding the edges does not relieve the exhaust bridge; Guys may differ on my thoughts on that.

Only way to check clearance is with a 2-3 or 3-4 micrometer and a telescopic inside bore gauge.

Are they an ATV specialy shop? or just a place that bored it for you? Did they ask "How much clearance do you want" or did they just do there thing. A quick call could tell you what they normally use for clearance. .003 on an AC motor is a disaster waiting to happen..............

**HONDA_ATC_FREAK** · 02-25-2011, 05:16 PM

They are a atv specialty shop and dealership. They didn't ask on clearance, they did think it was cool it was a three wheeler one of the guys there used to own the same year. all I have is a flat feeler gauge and a digital caliper so I guess I'm outta luck.

**zmpolaristech** · 02-25-2011, 05:46 PM

yes, drill the holes in the piston at the exhaust bridge. they want them there for a reason.

**mi500** · 02-25-2011, 05:48 PM

for the cr500 it seems mandatory. didn't realize other 2strokes did it to.

**HONDA_ATC_FREAK** · 02-25-2011, 06:08 PM

ok I'm gonna do it but the directions are not very good and I want to make absolutly sure I get it right a new piston isn't cheap, for one what exactly is the exhaust bridge.
these are the directions
1. install the piston and wrist pin on the connection rod using one circlip.
2. slide the cylinder over the piston and align it th its normal postiton on the crankcase.
3. slowly turn the engin over until the bottom ring grooce is at the top of the exhaust bridge.
4. reach through the exhaust port with a pencil, and mark a vertical line on the piston on both sides of the exhaust skirt.
5. remove the cylinder and piston, and dril 2 holes(.060-.090"diameter),.375"apart, starting .300 below the bottom ring, and between teh pincel lines.
6. remove all burrs from the lubrication holes, and clean the piston thoroughly.

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Drilling holes in my new piston ????