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A PISTON QUESTION
1 Attachment(s)
HI Guys: I was wondering about this piston I posted a photo of a DLE30 piston(not my engine) below. How may used engines have you found with this (SPS) shiny piston syndrone condition. On same piston seems like some galling or whatever. This is a DLE30cc piston with not very much run time at all. I myself have not found anything quite like it. I did find scratches in bore & on piston from hard carbon and maybe a broken ring. I know some of you guys have seen many pistons since you do engine conversions. let us know what you have seen or come up with. Thanks Capt,n
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RE: A PISTON QUESTION
looks to me like they polished it...
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RE: A PISTON QUESTION
The shininess has to do with a manufacturing process and nothing to do with the engine having been run
I would venture to say that I would think that a rough piston would be better from a oil retention aspect. |
RE: A PISTON QUESTION
I have seen thousands of pistons...I worked at Continental Motors for 34 1/2 years. I want to hear your take on the manufacturing process. Also worked in the engine experimental Lab. In fact as a hobby I worked on about every kind of small engine you can think of, because I like em. Capt,n
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RE: A PISTON QUESTION
It was probably thown into a tumbler with corn cobs,
The old McCoy crankcases used to be as shiney as a new dime when new. They were tumbled. |
RE: A PISTON QUESTION
How to use a cylinder bore gauge 101
OK, you bought this new fancy tool and you want to put it to good use, right?Measure each piston individually to their respective bore perpendicular to the ring bore with your micrometer, you do have a good set of these right? Good. Each piston manufacturer, and each type; cast, hyperutectic, and forged has a specified location where to measure,and how much piston to cylinder wall clearance you should have, however if you cant find it, measure at the widest location. When you mic the piston and feel comfortable with the "feeler gauge "method, lock the micrometer. Now take the dial bore gauge and "rock" it in the mic you have locked to come up with the shortest distance. This is your piston diameter. Zero your gauge with the dial and put the gauge back in the mic to double check your reading. Now put your dial bore gauge in the appropriate cylinder that the piston will live in and rock it again to find the shortest distance. The + side will tell you how much clearance there is between the piston and the cylinder wall, if you have negative clearance -, I suggest you go back to your machinist, this time with a baseball bat! You should be OK. Good luck!! Besides checking piston clearance,you can use a bore guage to check cylinders for out of round and taper from bottom to top.These checks help you determine if a used block is reusable.For example,cylinder walls,excessive out of round may indicate a block with a core shift problem. Capt,n |
RE: A PISTON QUESTION
ORIGINAL: w8ye It was probably thown into a tumbler with corn cobs, The old McCoy crankcases used to be as shiney as a new dime when new. They were tumbled. |
RE: A PISTON QUESTION
Pieces of bambo?
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RE: A PISTON QUESTION
ORIGINAL: captinjohn How to use a cylinder bore gauge 101 OK, you bought this new fancy tool and you want to put it to good use, right?Measure each piston individually to their respective bore perpendicular to the ring bore with your micrometer, you do have a good set of these right? Good. Each piston manufacturer, and each type; cast, hyperutectic, and forged has a specified location where to measure,and how much piston to cylinder wall clearance you should have, however if you cant find it, measure at the widest location. When you mic the piston and feel comfortable with the ''feeler gauge ''method, lock the micrometer. Now take the dial bore gauge and ''rock'' it in the mic you have locked to come up with the shortest distance. This is your piston diameter. Zero your gauge with the dial and put the gauge back in the mic to double check your reading. Now put your dial bore gauge in the appropriate cylinder that the piston will live in and rock it again to find the shortest distance. The + side will tell you how much clearance there is between the piston and the cylinder wall, if you have negative clearance -, I suggest you go back to your machinist, this time with a baseball bat! You should be OK. Good luck!! Besides checking piston clearance,you can use a bore guage to check cylinders for out of round and taper from bottom to top.These checks help you determine if a used block is reusable.For example,cylinder walls,excessive out of round may indicate a block with a core shift problem. Capt,n Looks pretty close to a post written by another car guy in my home state. (Post #2 in the link.) It almost looks like you have signed at the bottom of your post "Capt,n",seemingly indicating these are your original thoughts,or at least forgot to give credit the actual author. http://www.hotrodders.com/forum/how-...uge-71522.html |
RE: A PISTON QUESTION
The machine marks have been worn right off, seen that on a lot of high milage lawn tool engines, not on something that is supposed to be low hours.
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RE: A PISTON QUESTION
ORIGINAL: nitro joe ORIGINAL: captinjohn How to use a cylinder bore gauge 101 OK, you bought this new fancy tool and you want to put it to good use, right?Measure each piston individually to their respective bore perpendicular to the ring bore with your micrometer, you do have a good set of these right? Good. Each piston manufacturer, and each type; cast, hyperutectic, and forged has a specified location where to measure,and how much piston to cylinder wall clearance you should have, however if you cant find it, measure at the widest location. When you mic the piston and feel comfortable with the ''feeler gauge ''method, lock the micrometer. Now take the dial bore gauge and ''rock'' it in the mic you have locked to come up with the shortest distance. This is your piston diameter. Zero your gauge with the dial and put the gauge back in the mic to double check your reading. Now put your dial bore gauge in the appropriate cylinder that the piston will live in and rock it again to find the shortest distance. The + side will tell you how much clearance there is between the piston and the cylinder wall, if you have negative clearance -, I suggest you go back to your machinist, this time with a baseball bat! You should be OK. Good luck!! Besides checking piston clearance,you can use a bore guage to check cylinders for out of round and taper from bottom to top.These checks help you determine if a used block is reusable.For example,cylinder walls,excessive out of round may indicate a block with a core shift problem. Capt,n Looks pretty close to a post written by another car guy in my home state. (Post #2 in the link.) It almost looks like you have signed at the bottom of your post ''Capt,n'',seemingly indicating these are your original thoughts,or at least forgot to give credit the actual author. http://www.hotrodders.com/forum/how-...uge-71522.html |
RE: A PISTON QUESTION
So how did your bore measure out? Measure the piston to see how things look. Is the shiny surface wear or is it a dud forging where the unmachined areas got polished in the deburring tumbler? You'd probably get more response from the Gas forum.
I happen to check a used FS-52 liner last week and it was round within ±.0001" and was about .0003" larger toward the top, but that didn't seem to be wear. |
RE: A PISTON QUESTION
ORIGINAL: gkamysz So how did your bore measure out? Measure the piston to see how things look. Is the shiny surface wear or is it a dud forging where the unmachined areas got polished in the deburring tumbler? You'd probably get more response from the Gas forum. I happen to check a used FS-52 liner last week and it was round within ±.0001'' and was about .0003'' larger toward the top, but that didn't seem to be wear. this is the gas forum.:eek: shiny surface is from too tight clearance, either bore or piston or running in a plain bore thats tight btw glow liners should be tighter at the top than the bottom so your engine is probably shot or your measuring equipment is shot |
RE: A PISTON QUESTION
Awesome! Thanks.
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RE: A PISTON QUESTION
1 Attachment(s)
Here is a photo of a piston from a Homelite 25cc with a lot of running. I was going to post it sooner...but camera battiers went dead. I will Take a better photo with a better camera later...side by side. Capt,n
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RE: A PISTON QUESTION
If I had a digital camera, I could show you some of the pistons I've found.
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RE: A PISTON QUESTION
Hello Capt'n
I was wondering why you took a new engine apart? I believe glass beading the piston would do the trick. It would give a surface that would hold oil. If the piston was too tight in the cylinder you could lightly sand it and then glass bead it. How do the intake passages look? Were they pretty rough? |
RE: A PISTON QUESTION
Hi Ralph. It was not my engine that was took apart. I posted the photo (of another piston) to see if anyone else seen a piston like it. I was tinking of just pulling the jug up a little off the case just to see the total piston. It is running to good, so I decided not to take it apart. Capt,n
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RE: A PISTON QUESTION
With the original piston picture, your assuming that they knew what they were doing in the first place:). To me it looks like the piston was small enough in diameter(bad casting) that the lathe could not clean it up, so they polished out the other imperfections like casting flash.
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RE: A PISTON QUESTION
ORIGINAL: TFF With the original piston picture, your assuming that they knew what they were doing in the first place:). To me it looks like the piston was small enough in diameter(bad casting) that the lathe could not clean it up, so they polished out the other imperfections like casting flash. thats not the case, they wear like like that. |
RE: A PISTON QUESTION
Hey Guys....if you like video, go to RCU community and see the latest photos of engines running. One is my DLE30...the other is my Gas/glow conversion. Thanks Av8tor for getting me to try Gas/glow. He know his stuff on G/G. Capt,n;)
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RE: A PISTON QUESTION
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RE: A PISTON QUESTION
ORIGINAL: captinjohn HI Guys: I was wondering about this piston I posted a photo of a DLE30 piston(not my engine) below. How may used engines have you found with this (SPS) shiny piston syndrone condition. On same piston seems like some galling or whatever. This is a DLE30cc piston with not very much run time at all. I myself have not found anything quite like it. I did find scratches in bore & on piston from hard carbon and maybe a broken ring. I know some of you guys have seen many pistons since you do engine conversions. let us know what you have seen or come up with. Thanks Capt,n |
RE: A PISTON QUESTION
Who knows what really happened with the piston shown without having the entire engine to inspect and measure, but most often times wear (and sometimes seizures) at the four locations such as can be seen in this picture is due to revving an engine before it has had a chance to warm up. Pistons aren't machined round; they get that way after they have reached operating temperature. (Hopefully.) When an engine is revved up and/or loaded before it has warmed up and the clearances have optimized, they experience wear in abnormal ways and locations, and usually fail "before their time"....
AV8TOR |
RE: A PISTON QUESTION
Some pistons are machined round, and some are cam ground & I am sure there are other ways. Basic pistons are turned on a machine just for that size & type.....and round. Pistons for a very tight clearance (ABC Glow engines) are sometimes finished ground. Pistons are sometimes made out of round,so when they warm up the fit in bore will be better. Capt,n
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