| Volksdraggin |
Sun Jun 05, 2011 9:33 am |
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I pulled a head off a motor today and noticed each piston had a small little hole in the middle. Is this normal?
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| Max Welton |
Sun Jun 05, 2011 9:58 am |
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| No |
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| Volksdraggin |
Sun Jun 05, 2011 10:16 am |
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| can anybody help me theorize why each of these pistons have a small little hole in the middle of each of them? |
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| supaninja |
Sun Jun 05, 2011 10:32 am |
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| lean or too much timing |
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| Volksdraggin |
Sun Jun 05, 2011 10:37 am |
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| womp womp :( |
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| Volksdraggin |
Sun Jun 05, 2011 11:42 am |
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| So if I run the motor with the pistons like this, its likely going to burn through the piston? |
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| Max Welton |
Sun Jun 05, 2011 12:10 pm |
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Not only that, but if you replace these pistons and don't find and fix the problem, it will happen again.
Max |
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| KTPhil |
Sun Jun 05, 2011 12:55 pm |
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| So you are saying that all four have this pinhole in exactly the same spot? |
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| Volksdraggin |
Sun Jun 05, 2011 1:09 pm |
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| yes, they all have them and all in the same spot. |
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| kevhum |
Sun Jun 05, 2011 1:18 pm |
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| I have seen pistons like that before.It looks to be centered,like to use for turning in A lathe.I really see no problem with it.It came new like that and it hasn't started burning threw in all the miles it has on it.Do the other ones have the same hole and are they A matched set? |
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| Max Welton |
Sun Jun 05, 2011 1:20 pm |
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It doesn't look centered to me. :?
And I've never seen new pistons with a hole in the middle.
Max |
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| Volksdraggin |
Sun Jun 05, 2011 1:38 pm |
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yes, the others are centered too and the set is a matched set. I've never seen pistons with a center hole short of a 2 cycle piston on a scooter. The holes are different depth, 2 are just a small hole, 2 are a bit deeper.
I'm not going to chance it and just replace them. |
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| DHanna |
Sun Jun 05, 2011 2:41 pm |
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kevhum wrote: I have seen pistons like that before.It looks to be centered,like to use for turning in A lathe.I really see no problem with it.It came new like that and it hasn't started burning threw in all the miles it has on it.Do the other ones have the same hole and are they A matched set?
Yes, it is a centre hole used for support in the lathe whilst the piston is being turned to size. Some maybe smaller than others due to setup at the time of manufacture.
DH |
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| toddgsanford |
Sun Jun 05, 2011 2:55 pm |
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| thought that was why they are called air cooled engines? he air goes through the piston? |
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| Volksdraggin |
Sun Jun 05, 2011 8:35 pm |
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DHanna wrote: kevhum wrote: I have seen pistons like that before.It looks to be centered,like to use for turning in A lathe.I really see no problem with it.It came new like that and it hasn't started burning threw in all the miles it has on it.Do the other ones have the same hole and are they A matched set?
Yes, it is a centre hole used for support in the lathe whilst the piston is being turned to size. Some maybe smaller than others due to setup at the time of manufacture.
DH
So these pistons are able to be used? |
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| FastyinaField |
Sun Jun 05, 2011 11:13 pm |
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Well, is it a hole or a dimple? A hole goes through the crown of the piston, and is the result of running lean. A dimple is a divot in the surface, that doesn't go through. Those look like dimples. Dimples are fine, and part of the manufacturing process.
If there was a lot of detonation, the surface of the pistons start looking like a golf ball. Running lean, there would be an irregular hole through it that looks like someone took a torch to the piston crown.
A matching single dimple on each piston is too regular to be any other cause than a manufacturing step. |
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| Root_Werks |
Mon Jun 06, 2011 7:27 am |
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FastyinaField wrote: Well, is it a hole or a dimple? A hole goes through the crown of the piston, and is the result of running lean. A dimple is a divot in the surface, that doesn't go through. Those look like dimples. Dimples are fine, and part of the manufacturing process.
If there was a lot of detonation, the surface of the pistons start looking like a golf ball. Running lean, there would be an irregular hole through it that looks like someone took a torch to the piston crown.
A matching single dimple on each piston is too regular to be any other cause than a manufacturing step.
That's what I was thinking, is it an actual hole or just a dimple? If it doesn't go through the piston, probably fine. If it's an actual hole that passes through the material, toss them in the recycle bin. |
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| supaninja |
Mon Jun 06, 2011 8:09 am |
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| Must be chinese pistons. I have played with many many pairs of german and brazilian pistons and never seen machined dimples. It would seem to like a possible weak spot on the piston face, I would recycle them anyways. Good pistons aren't expensive. |
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| hazetguy |
Mon Jun 06, 2011 1:12 pm |
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here's a pic of a piston with the centering hole in the center of the VW stamp. go figure.
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