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Old 01-18-2010, 03:42 PM   #1
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What happened to this mill?







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Old 01-18-2010, 03:55 PM   #2
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did u try to take the backplate of when piston was at BDC ?
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Old 01-18-2010, 04:46 PM   #3
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I don't know, but that was one of the things I suggested.

I'm posting this for a friend, The engine has about 1 gallons on it. Never over 220, run on 30% nitro juice.

Just wondering if anything can be determined from the pics
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Old 01-18-2010, 04:54 PM   #4
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blew out the bottom of the pioston, happens to all motors at any time, ususlly only 1 side goes though. manufacturing flaw really, send it back. 1.5 gallons and it looks like that?, remind me never to run nitro juice, yuk. i've seen motors 5 gallons old that didn't look that bad, what temp gun? she looks like she's been over 300.
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Old 01-18-2010, 05:04 PM   #5
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sh!t happens!
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Old 01-18-2010, 05:05 PM   #6
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Looks to me like is a traxxas 3.3 and thats your problem i had nothing but problems with them. and that looks as it ran a little lean and got hot

I installed a brand new rod and piston in one and it didnt last 1 tank of fuel and the inside of piston around the wrist pin broke just like that one is

Switched to an os motor and havent had an issue

Last edited by MontanaMaxx; 01-18-2010 at 05:08 PM. Reason: Added more
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Old 01-18-2010, 05:08 PM   #7
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Do you have a pic of the top of the piston? Would like to see it.
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Old 01-18-2010, 05:24 PM   #8
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Interesting. Here are the things I can see:

Starting with the head... there is some pitting... not much, but a little bit. That could be detonation, (not shimmed properly, or running too lean) or it could have either ingested something or the coil could have come out of the glow plug. It is hard to tell after it has been cleaned up like that. It would be interesting to see the top of the piston too.

There is also a bit of scoring on the piston skirt. (I'm not talking about the broken parts, I mean the vertical "scratches" in the skirt that show distinctly in the carbon deposits.) Again this indicates that SOMETHING went through there. Obviously that could possibly be parts of the piston itself, given the damage... for that matter, so could the pitting on the head.

Given the deposits on the broken parts it is also obvious that it was run that way (with bits broken off) for a while. Otherwise the broken parts would simply look like metal.

The piston has a single groove (which acts like a ring) and is very rough in appearance- not a very well finished casting. I suspect this isn't exactly a top-quality engine.

It also doesn't look like what I remember my engines to look like when I ran Nitro Juice- the deposits were much more distinctly red in color, not dark brown approaching black.

Based on the darker carbon coloration on the piston skirt, the signs of pitting on the cylinder head, and the damage to the piston pin area... I would suspect it was ran a bit too lean (despite what was said about never being over 220 degrees- temperature truly is not the only factor.) The skirt doesn't look to be broken by pulling the backplate- unless it was reinstalled and ran after it was broken. It looks like a failure in use.

I'd suspect the cause is a combination of being too lean (and hence not enough lubricant) and a poor quality piston casting, and MAYBE over-revving it.

Again, that is just my thought on this... there are MUCH more experienced folks on here who may disagree.
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Old 01-18-2010, 07:13 PM   #9
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+1


Saved me some typing DOMIT!

Thanks, .



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Old 01-19-2010, 06:45 AM   #10
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IMO it looks like it threw a bearing...
Trust me, this engine was in GOOD hands. And Nitro Juice is made by Mike B himself, suppose to be awesome fuel.
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Old 01-19-2010, 07:22 AM   #11
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Quote:
Originally Posted by quadracer111 View Post
IMO it looks like it threw a bearing...
Trust me, this engine was in GOOD hands. And Nitro Juice is made by Mike B himself, suppose to be awesome fuel.
Hmmm... VERY good point! I've seen a broken piston from a sloppy rear bearing before... piston hit the backplate and pretty much shattered.

But the yucky dark brown/black deposits look like it was run too hot.

I know many, MANY local racers, both sportsman and pro, running Nitro Juice, and I know Mike Battaile personally. He makes it, and he runs it. I've never seen anything like that (color of deposits on the piston skirt.)

I ran it for over a year, and never had a single problem... the ONLY reason I'm running another type of fuel now is that all of my "crew" is running O'Donnell. If one of us runs out, one of the other guys always has some handy, no retuning needed for different fuel. Nitro Juice is good stuff!
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Old 01-19-2010, 07:33 AM   #12
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Quote:
Originally Posted by j_blaze14 View Post
blew out the bottom of the pioston, happens to all motors at any time, ususlly only 1 side goes though. manufacturing flaw really, send it back. 1.5 gallons and it looks like that?, remind me never to run nitro juice, yuk. i've seen motors 5 gallons old that didn't look that bad, what temp gun? she looks like she's been over 300.
J_blaze i have been running Nitro Juice for over a year in 3 or 4 motors now and have never seen anything like that from nitro juice. That motor looks like its been well over 300 more then once for sure. Its not the fuel that made it look like that i can tell you that.
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Old 01-19-2010, 07:58 AM   #13
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Quote:
Originally Posted by shane oc View Post
did u try to take the backplate of when piston was at BDC ?
Being the mill is a 3.3, the piston skit does not extend down into the crankcase at BDC far enough for the back plate to interfere.
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Old 01-19-2010, 08:08 AM   #14
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Its obviously been very hot... carbon built up on the BOTTOM of the piston is never a good thing once its that hot all bets are off on the piston remaining in one piece. Looks like its seen alot of RPMs

1 1/2 gallons? Not buying that a bit.... thats a ton of color on the rod for that short of a life. I have engines that I put 6 gallons on that dont look anything like these parts
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Old 01-19-2010, 05:14 PM   #15
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Every piston I have seen has the brown colour on the piston skirt...
I still say it had a bad rear bearing.
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