Drilling holes in piston for the exhaust bridge.

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3/17/2018 3:25 PM

Does anyone ever do this to get lubrication to the exhaust bridge on two stroke pistons from wiseco? I do pretty regular 20-25 hour intervals but have never done it. Then I stumbled across an article wiseco had posted about doing it.

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3/17/2018 3:26 PM

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3/17/2018 4:04 PM

The instructions are included in all Wiseco kits. They are in a green paper. At least the ones that I have used.

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3/17/2018 4:13 PM
Edited Date/Time: 3/17/2018 4:13 PM

Yep, did it on my 02 CR, especially since they like to crack exhaust bridges from what I understand.
It was a little disconcerting to drill into a new piston, but was a piece of cake.

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3/17/2018 4:15 PM

Forgot to add, my dad’s 78 CR already had them drilled from Wiseco. Not sure why some come with it and some don’t, unless some pistons are used in models with and without a bridge.

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3/17/2018 4:40 PM

I have always done the holes in engines with an exhaust bridge. It does aid in cooling that bridge and is a must if you are running a forged piston.

Paw Paw

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3/17/2018 5:52 PM

Yes, I do drill them as well.

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3/17/2018 6:10 PM

Pictures please

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3/17/2018 10:55 PM

beamer wrote:

Pictures please

Here’s Wiseco’s instructions. In the piston pictured it’s the two vertically centered holes.

https://www.wiseco.com/PDFs/Manuals/MSeries.pdf

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3/18/2018 9:37 PM

Just got a wiseco piston kit for my 06 yz125 on Friday. I also was wondering if it would have holes drilled in the piston for the exhaust bridge, and the holes were already there.

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3/19/2018 7:43 AM

Rohr144 wrote:

Just got a wiseco piston kit for my 06 yz125 on Friday. I also was wondering if it would have holes drilled in the piston for the exhaust bridge, and the holes were already there.

They are not pre-drilled, you would have to drill them.

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3/19/2018 8:01 AM

Rohr144 wrote:

Just got a wiseco piston kit for my 06 yz125 on Friday. I also was wondering if it would have holes drilled in the piston for the exhaust bridge, and the holes were already there.

easydoesit wrote:

They are not pre-drilled, you would have to drill them.

I'll take a pic later and post it on here. I was surprised when I saw that they were drilled.

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3/19/2018 8:06 AM

easydoesit wrote:

They are not pre-drilled, you would have to drill them.

Some do come pre-drilled. Depending on what model bike the piston was designed for. If the piston was designed to be used in different model applications than it doesn't come pre-drilled. It will be up to the consumer to drill them if the cyl. has an exhaust bridge.

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Speak softly and carry a big stick.

3/19/2018 8:33 AM

Rohr144 wrote:

Just got a wiseco piston kit for my 06 yz125 on Friday. I also was wondering if it would have holes drilled in the piston for the exhaust bridge, and the holes were already there.

easydoesit wrote:

They are not pre-drilled, you would have to drill them.

Rohr144 wrote:

I'll take a pic later and post it on here. I was surprised when I saw that they were drilled.

Wow! Please also post the part number.

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3/19/2018 6:20 PM

easydoesit wrote:

They are not pre-drilled, you would have to drill them.

Rohr144 wrote:

I'll take a pic later and post it on here. I was surprised when I saw that they were drilled.

easydoesit wrote:

Wow! Please also post the part number.

Here ya go! Part number is PK1571

Photo



Photo

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3/19/2018 6:35 PM

Thanks!

Question:
Are those burrs on the back sides of the drilled holes?
And there aluminum filings on the piston?

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3/19/2018 6:51 PM

easydoesit wrote:

Thanks!

Question:
Are those burrs on the back sides of the drilled holes?
And there aluminum filings on the piston?

The backside of the holes do have slight burrs. I'm not at all worried about that though. I don't see any aluminum filings. Just stuff from me touching it with my hands.

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3/19/2018 8:02 PM

Wouldn't drilling the hole to lube the exhaust bridge result in a loss of compression? You are after all, blowing out bottom end compression, oil and fuel in doing so.

Besides, with a properly relieved exhaust bridge(something I've found to be extremely important In old Elsinores) like they came with from the factory, they never had holes in OEM pistons. Forged pistons always call for a looser tolerance, so why the need for holes? And I've stuck plenty of Wiseco's with and without holes, tight, loose, you name it. laughing

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3/19/2018 10:38 PM
Edited Date/Time: 3/19/2018 10:39 PM

easydoesit wrote:

Thanks!

Question:
Are those burrs on the back sides of the drilled holes?
And there aluminum filings on the piston?

Rohr144 wrote:

The backside of the holes do have slight burrs. I'm not at all worried about that though. I don't see any aluminum filings. Just stuff from me touching it with my hands.

I would deburr the holes. Just remove the thin aluminum flash.
Do it by hand with a cone-type carbide bit...it's quick work.

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