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Oil Field Engines & Related Equipment

Pitted piston opinions?


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  #1  
Old 10-24-2016, 09:24:50 PM
con-rad con-rad is offline
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Default Pitted piston opinions?

Hey all,

I just picked up a very nice 15HP Pattin two stroke, however there is one bad spot on the piston where i believe it laid on a garage floor for quite some time. See the attached photos to see what the damage looks like. the entire piston looks excellent except for this spot.

Also, this spot is almost exactly on the top side of the piston, so there would be no wear or weight on this area. The rings are a concern though. the top one is nice, but the others are iffy. What do you think?

Thanks,

connor
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  #2  
Old 10-24-2016, 09:52:26 PM
J.B. Castagnos J.B. Castagnos is offline
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Default Re: pitted piston opinions?

Rings need to go, try the piston, a two stroke uses the skirt for crankcase compression, may cause some problems.
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Old 10-24-2016, 10:31:19 PM
sunshineman sunshineman is offline
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Default Re: pitted piston opinions?

Hi .
I have used pistons that bad not a problem with new rings (in a 2 stroke with 5 inch bore) .most of the piston is okay that you have it will still support the rings , etc
Regards sunshineman
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Old 10-24-2016, 11:29:39 PM
Rob Charles Rob Charles is offline
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Default Re: pitted piston opinions?

New rings and run it. I'll bet there's a lot of pistons like that running right now. Rob
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Old 10-25-2016, 12:10:55 AM
K-Tron K-Tron is offline
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Default Re: pitted piston opinions?

Have you looked into what it might cost to have it spray welded and machined back to proper spec? That might be the best solution if you plan on running it alot.

Chris
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Old 10-25-2016, 08:08:15 AM
Martin Reed Martin Reed is offline
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Default Re: pitted piston opinions?

I would recommend running it as is. There will be no problem with performance.
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Old 10-25-2016, 07:42:50 PM
Andrew Mackey Andrew Mackey is offline
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Exclamation Re: Pitted piston opinions?

Re-ring and run as is. Look carefully near the bottom of the skirt. On your second photo, it looks like there is a ring near the bottom. If so, then the pitting should not be an issue. Clean and smooth the rough area with some 300 grit emory, and use the piston as is. The pistons on oilfield engines usually use SAE 50 oil. This should supply enough seal and also help fill in the pitting. After a while, the pitting will fill in with carbon, especially if you use propane for fuel, and set the oil flow on the rich side for a while. Your oiler should be set for 2 drops per inch of bore per minute to start. you can increase to 3 for a while to get you started.
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Old 10-25-2016, 09:51:22 PM
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John Tice John Tice is offline
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Default Re: Pitted piston opinions?

As indicated above; free up & replace the rings. A light hone with a new cross hatch in the bore to aid in the new ring break in. As long as youíve got it torn down this far; measure the cylinder to see that itís round & straight. A dial bore gauge should be slid around the cylinder where ever itís possible.



Quality bore gauges are available for less than $50; any good mechanic should have one in their tool chest
It would be a good idea to spray soapy water around the gasket areas to check for air leaks. (Soap Bubbles) Some place there may be some information on what the cranking compression should be.
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Old 10-25-2016, 11:19:16 PM
con-rad con-rad is offline
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Default Re: Pitted piston opinions?

Thanks for all the input guys. Are there many options as far as where to get rings from, or should i just go to Niagara for replacements? (unless someone reading this has rings for a 15HP pattin!)

Good idea on the bore gauge. I actually have one but have never used it... time to take it out and see how it works!

connor
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Old 10-26-2016, 08:11:45 AM
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John Tice John Tice is offline
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Default Re: Pitted piston opinions?

Custom rings? Find any std rings to fit your bore dia. Either stack them or machine spacers; I can supply iron blanks to machine spacers from. This may take a little experimentation but would work.
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Old 10-26-2016, 08:47:28 AM
Gasenginegangster Gasenginegangster is offline
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Default Re: Pitted piston opinions?

I agree with Rob C. Install new rings and run it.
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Old 10-26-2016, 11:28:59 AM
Andrew Mackey Andrew Mackey is offline
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Default Re: Pitted piston opinions?

Niagra is good, so is Otto Engine works. Not sure if H&M Enterprises has them that big, but you never know. You might even check with Starbolt! Have a look in the sponsors pages here on the Stak, for ring suppliers and manufacturers. I'm quite sure someone has what you need!

You will need piston diameter, ring groove depth and ring width measurements. if the bore is also pitted a bit, I would stick with the full width rings if possible. less tendency to bind in the rough spots.
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Old 10-26-2016, 12:33:54 PM
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Reed Engine Reed Engine is offline
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Default Re: Pitted piston opinions?

If the piston mics good the pits will only be a place to carry a little oil. Ring it and run it. The bore on the other hand is another issue. If it's pitted you will loose compression.
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Old 11-05-2016, 07:40:05 PM
con-rad con-rad is offline
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Default Re: Pitted piston opinions?

I took off the old rings and saved them for spares, and a helpful Stakker emailed me because he thinks him friend might have a set of new ones! Looks like we're all set in the piston department for this engine.

connor
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