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Post  Gordinir8 Sat Aug 15, 2020 6:12 am

One of my engines has a play and I need to buy a reset tool to make it true again it but I noticed that if you want to speak with numbers it's not very easy to hold this tiny piston and measure it. Things can be very easy with a piece of fuel silicone tube and a toothpic! This way you can keep the Conrod against the piston while at the same time you can compress it with the caliper or with the micrometer. In this case play is 055mm or .021in


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Last edited by Gordinir8 on Mon Aug 17, 2020 7:34 am; edited 2 times in total
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Post  balogh Sat Aug 15, 2020 7:42 am

A smart setup! I cannot measure the play though just keep knocking until there remains a hardly tangible one when you pull on the rod. I also spin the rod around to make sure it doesn't stick to the edge of the cup
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Post  Iceberg Sat Aug 15, 2020 9:46 am

Interesting setup!
Please humor me. What is the perfect piston play?

Thanks
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Post  Cribbs74 Sat Aug 15, 2020 10:21 am

.002 is the number that is usually thrown around. Enough for the oil to creep into. To be honest though it isn’t super critical. At least not in my experience. I do resets mostly for longevity and not for performance. I measure play by feel. Some are tight and some are probably just right. After being run they settle out pretty even with each other.

I like the apparatus you made to measure.
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Post  Marleysky Sun Aug 16, 2020 11:50 am

How do you eliminate that Photobucket Black Stripe across your pictures?? [url=https://servimg.com/view/19103929/1131]Piston resetting  Acd45910[/url

Kinda ruins the view.
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Post  Gordinir8 Sun Aug 16, 2020 12:24 pm

By paying subscription I guess but I am not willing to do.
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Post  Surfer_kris Mon Aug 17, 2020 3:57 am

Just attach the original image to this forum instead.
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Post  Gordinir8 Mon Aug 17, 2020 4:22 am

Are you sure? I thought that image has to be host somewhere! Gonna try it thanks.
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Post  Surfer_kris Mon Aug 17, 2020 5:05 am

It will technically be hosted on the forum (or another service "servim"?), and everyone will be able to se it here. Just use the "Host"-button with a tiny floppy drive disc on it.
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Post  Gordinir8 Mon Aug 17, 2020 5:35 am

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Post  roddie Mon Aug 17, 2020 9:33 pm


Hi, I saved your photo and it previews fine for me with Windows Photo Viewer.

I have the Cox .049 reset tool. When I use it, I place the "cup" on a very solid surface. An anvil usually. I like to use a small hammer and tap very lightly on the tool; checking the ball/socket clearance after each tap. Being careful NOT to get heavy-handed; I rotate the tool approx. 120 degrees after each tap.. until the rod will not drop by gravity.. but will move if shaken. If your "setting" feels a little tight.. it might be fine. Some people here have mentioned that they set theirs' on the snug-side.

I'm led to understand that the ball-socket joint need only be reset "once".. as part of a break-in measure. Under normal operation, it shouldn't need resetting again and should hold it's setting due to work-hardening.
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Post  happydad Tue Aug 18, 2020 1:48 am

@roddie wrote:

Hi, I saved your photo and it previews fine for me with Windows Photo Viewer.

I have the Cox .049 reset tool. When I use it, I place the "cup" on a very solid surface. An anvil usually. I like to use a small hammer and tap very lightly on the tool; checking the ball/socket clearance after each tap. Being careful NOT to get heavy-handed; I rotate the tool approx. 120 degrees after each tap.. until the rod will not drop by gravity.. but will move if shaken.  If your "setting" feels a little tight.. it might be fine. Some people here have mentioned that they set theirs' on the snug-side.  

I'm led to understand that the ball-socket joint need only be reset "once".. as part of a break-in measure. Under normal operation, it shouldn't need resetting again and should hold it's setting due to work-hardening.

roddie: That is exactly how I do my piston resetting. Always being sure to rotate the tool, and light to medium hits with a ball peen hammer. Anyone remember those??  My dad used those when putting rivets into sheet metal. WW2.  He was a single parent before he met my mom.

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Post  Gordinir8 Tue Aug 18, 2020 4:05 am

Thanks for info, this is what I have in mind also. Tool is on its way.
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Post  gasface Sat Sep 05, 2020 4:15 pm

Some really great info thanks. Very Happy
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Post  Tee Bee Mon Sep 07, 2020 7:12 am

That’s a neat measuring technique! Thanks for sharing.
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Post  Iceberg Sat Feb 13, 2021 8:09 am

I just tap carefully on 90 degree rotations until play is reduced acceptably. I didn't have the tool to do it yesterday so made one in the lathe it is working very well.
I made the crimping end very snug on the tool and very easily shaped the piston socket.

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Post  getback Sat Feb 13, 2021 9:09 am

Nice looking tool , cool you can just make up one like that , see you have a piston with the oiler hole in the rod boss 3 piece .
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Post  Mark Boesen Sat Feb 13, 2021 10:13 am

I've found (based on others) that a smooth hard surface (glass) makes an idea anvil, also lots of light taps. set socket to rotate freely, but no real play. I'd also give it a drop of car oil prior to assembly, once its running the gap will open a little.
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Post  Mark Boesen Sat Feb 13, 2021 10:16 am

@Cribbs74 wrote:.002 is the number that is usually thrown around. Enough for the oil to creep into. To be honest though it isn’t super critical. At least not in my experience. I do resets mostly for longevity and not for performance. I measure play by feel. Some are tight and some are probably just right. After being run they settle out pretty even with each other.

I like the apparatus you made to measure.

yep, about the only time it becomes an issue is high RPM and/or tight piston fit.
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