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Cox Engine of The Month
August-2024
balogh's
![](https://i.servimg.com/u/f95/15/46/86/41/1_balo14.jpg)
"Cox TD09 R/C Beast of Burden featuring Kamtechnik head and DIY metallic fuel nipple"
![](https://i.servimg.com/u/f95/15/46/86/41/sponso12.png)
PAST WINNERS
balogh's
![](https://i.servimg.com/u/f95/15/46/86/41/1_balo14.jpg)
"Cox TD09 R/C Beast of Burden featuring Kamtechnik head and DIY metallic fuel nipple"
![](https://i.servimg.com/u/f95/15/46/86/41/sponso12.png)
PAST WINNERS
Piston resetting
Page 1 of 1
Piston resetting
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
![Piston resetting Img_2018](https://i.servimg.com/u/f64/20/25/04/02/img_2018.jpg)
![Piston resetting Img_2019](https://i.servimg.com/u/f64/20/25/04/02/img_2019.jpg)
![Piston resetting Img_2018](https://i.servimg.com/u/f64/20/25/04/02/img_2018.jpg)
![Piston resetting Img_2019](https://i.servimg.com/u/f64/20/25/04/02/img_2019.jpg)
Last edited by Gordinir8 on Mon Aug 17, 2020 7:34 am; edited 2 times in total
Gordinir8- Silver Member
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Join date : 2020-08-05
Age : 49
Re: Piston resetting
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
balogh- Top Poster
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Iceberg- Gold Member
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Re: Piston resetting
.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.
I like the apparatus you made to measure.
Cribbs74- Moderator
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Marleysky- Top Poster
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Re: Piston resetting
By paying subscription I guess but I am not willing to do.
Gordinir8- Silver Member
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Age : 49
Re: Piston resetting
Just attach the original image to this forum instead.
Surfer_kris- Diamond Member
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Location : Sweden
Re: Piston resetting
Are you sure? I thought that image has to be host somewhere! Gonna try it thanks.
Gordinir8- Silver Member
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Re: Piston resetting
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.
Surfer_kris- Diamond Member
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Location : Sweden
Re: Piston resetting
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.
Copycat
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.
Happydad
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happydad- Rest In Peace
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Re: Piston resetting
Thanks for info, this is what I have in mind also. Tool is on its way.
Gordinir8- Silver Member
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gasface- Moderate Poster
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Tee Bee- Platinum Member
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Iceberg- Gold Member
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Re: Piston resetting
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 .
getback- Top Poster
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Re: Piston resetting
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.
Re: Piston resetting
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.
![-](https://2img.net/i/empty.gif)
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