What piston size would i need for a 65.72 bore?

[niftylittleguy]

I picked up a 1984 200x and the bike had a loud piston knock noise and it smoked a lot. When i opened up the top end I found that the piston was 64.5mm and the bore of the cylinder was 65.72 or so. The piston is a brand new wiseco. Would a new piston that is 65.5mm work in that 65.72 bore?

[arlaunch]

I like to send jugs away to professionals who bore the cylinder to match the exact piston that they supply.

Pistons can measure differently in different locations due to the anticipated exhaust side being hotter blah blah blah

How this particular situation exists in real life is shocking to me.

What else did the previous owner fix?

[DohcBikes]

That's peculiar since a stock piston is 65mm. This is why we can't have nice things.

[niftylittleguy]

I hope nothing else is wrong with the engine. Im looking to get rid of this bike once im done putting it back together. So im thinking of picking up a 65.5mm piston and throwing it in.

[DohcBikes]

im thinking of picking up a 65.5mm piston and throwing it in.If you stand far enough back, and get a video of it, maybe dudeperfect will make you youtube famous.

[niftylittleguy]

Well i'll have .2mm of play so i think i might make the shot. LoL

[El Camexican]

What did you use to measure the bore?

[arlaunch]

I hope nothing else is wrong with the engine. Im looking to get rid of this bike once im done putting it back together. So im thinking of picking up a 65.5mm piston and throwing it in.

I strongly advise against that option.

Remember at the very minimum you need to get the bore honed to set the new rings.

Let the pro's bore it with the correct forged or cast piston clearance.

Do everything else correctly and survive with a good running, reliable engine.

[niftylittleguy]

I strongly advise against that option.

Remember at the very minimum you need to get the bore honed to set the new rings.

Let the pro's bore it with the correct forged or cast piston clearance.

Do everything else correctly and survive with a good running, reliable engine.

The cylinder has been honed previously. I dont think it needs to be honed again.

[niftylittleguy]

Micrometer i got off amazon.

[tripledog]

This looks like a job for loganm, AKA "the piston whisperer".

[John Tice]

Howdy mate; your numbers are going all over the place
64.5mm = 2.53937”
65.5mm = 2.5787”
65.72mm = 2.5874”
A Wiesco piston for a 65mm bore would be .002”. Too many decimal points to work with, you’ll turn your brain in knots trying to work the numbers.
A 65.72mm piston fits a 65.75mm bore, the difference .03mm is the new skirt clearance, .00118” don’t believe it. This is why the skirt clearance is printed on the Box; mostly, Wiesco pistons increase in 1/2mm or .020” steps.


John Tice
503-593-2908 Alternate 541-508-3944
www.smallenginemachineworks.com & www.nwsleeve.com
Turning Custom Cylinder Sleeves Since 1971
http://forums.everything2stroke.com/threads/49513-How-It-s-Done-Projects-around-the-Shop.com

[El Camexican]

This looks like a job for loganm, AKA "the piston whisperer".

LOL!!! Hell yea!!! He'd get a 66mm piston in that hole faster than you can scream "Put down that hammer!"

[tripledog]

LOL!!! Hell yea!!! He'd get a 66mm piston in that hole faster than you can scream "Put down that hammer!"

Why must you leak down upon people that ask questions but don't listen to answers?

[niftylittleguy]

The bore i have is 65.72mm. The closest piston to the bore i can get is 65.5mm. So there would be a .22mm difference.

[Velislide]

Instead of wrecking a 100$ piston, why not get a 40$ bore and do it right? Trying to save a dime will cost you in the end.

[DohcBikes]

The bore i have is 65.72mm. A properly measured bore uses a minimum of six values to "draw a picture" of the cylinder. I don't know what you used, or where you measured to get your 65.72mm, but you need to put the tools down and let a pro handle this.

[86T3]

You're here asking for advice, please accept it. Take the cylinder to a machine shop, let them measure it, bore it and get the appropriate piston.

[Mackus84]

Micrometer i got off amazon.

Like a regular micrometer? Or a bore gauge? Cant trust the micrometer measurement because you have to measure different points throughout the bore. And a standard micrometer isnt going to "get down in there" like you need it to. I would take the advice of the guys here, a get a new piston and have the bore matched to it. They know what theyre talking about.

[Scootertrash]

M
This looks like a job for loganm, AKA "the piston whisperer".

SCORE!!!!!

I knew you'd seize the opportunity!

[oscarmayer]

wiseco no longer sells pistons in the .25mm sizes. it is only .5 now Honda did offer stock pistons in the .25 range and I think it was probably a stock piston at that size. that means you will want a wiseco 66mm and have it bored/honed to the piston once you have it.

[DohcBikes]

wiseco no longer sells pistons in the .25mm sizes. it is only .5 now Honda did offer stock pistons in the .25 range and I think it was probably a stock piston at that size. that means you will want a wiseco 66mm and have it bored/honed to the piston once you have it.You're full of shlt oscar. I don't care how nice a guy people here are fooled into thinking you are, your mechanical advice is often wrong. Don't say unless you know. Nothing personal, of course.

Where's your friend Milner? He's scamming members here for thousands of dollars.

[RIDE-RED 250r]

Add me to the list of those advising to get the next size overbore piston, then send that new piston and cylinder to a reputable machine shop and have the cylinder bored to match the piston per the piston manufacturers specs. Don't just stuff "whatever fits" in there....

Do it right, do it once.

This isn't quantum physics.....