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  1. #1
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    Broke piston 3.3

    Has anybody else had any piston issues on there 3.3? Mine broke where the pin comes through, and took off some of the skirt. It is a 4 1/2 gallon motor that I keep fairly rich. Any thoughts on what could have caused this?

  2. #2
    RC Turnbuckle Jr. icepick832's Avatar
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    Could be anything really. Even being to rich. 4 1/2 gallons is good. Time to just rebuild.

  3. #3
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    I was happy with the run I got out of it. Everything else was perfect so I built it and I was bashing again Saturday. I build Ford engines for a living and I have that what was the root cause itch.

  4. #4
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    if your running it wide open for long distance this could cause it to lean out. I would have thought you would have split the con-rod before you broke the piston. used to be a guy who built these engines with better rods and did some work to the piston and engine to make them run better, was a couple of years ago. not sure where he is or if he even does it anymore. would like to see pics of the piston though
    NFFN nitros forever, forever nitros

  5. #5
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    I think somewhere I read that after 3 gallons of fuel that the motor needs to be rebuilt. And they even make a kit for it I belive. So if you got 4 1/2 gallons through it then you did good.

  6. #6
    Marshal Double G's Avatar
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    Is this your first nitro engine? 4.5 is good, though with more tuning experience you should be able to get much more than that.
    The Super Derecho

  7. #7
    RC Turnbuckle Jr. Nitronaught's Avatar
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    Quote Originally Posted by ville615 View Post
    Has anybody else had any piston issues on there 3.3? Mine broke where the pin comes through, and took off some of the skirt. It is a 4 1/2 gallon motor that I keep fairly rich. Any thoughts on what could have caused this?
    Your first nitro? If that's the case imagine this.
    You break in your 1st nitro. Now you try tuning. It takes you a little while and during THAT time period the engine is being ran with either not enough lubrication, or having too much fuel in the engine while running.

    Now, after a gallon or so, you've caught on the the acquired skill of tuning. Happy with how your engine is sounding and performing, but wait. For some time it was exposed to poor tuning conditions which will wear out an engine early...

    The piston conrod will split at it's weakest point, usually the wrist pin area (piston side of the conrod).

    I bet there is some dark brownish coloration on the top of the piston in this case. Usually what I have found is the piston skirt being the thinnest part of the piston with the least amount of material around it, when ran too hot for too long (lean), becomes weakened from the extreme heat and friction from not having enough lubrication. Now combine that with the added stress on the internals being ran with not enough fuel/lubrication and the conrod gets strssed at it's weakest points.

    Now you've learned to tune, your temps are good and the weakened piston skirt chips off internally. The bits are banging around at 20,000 - 30,000 rpms and eventually cause more stress on the internals. The conrod fails due to the added stress and there you have it.

    You next engine, or the rebuild of this one done right, will probably last longer as you will not be brutalizing the engine with poor tuning...

    Too lean, not enough lubrication, lots of added friction and heat.

    Too rich, the engine does not expand fully, again too much friction, conrod is swimming in fuel at high rpms causing stress and stretching...

    Those are the 2 main causes, the lean part usually being the culprit. Often happens when the LSN is too lean HSN too rich to compensate....
    Robin Williams
    He will be greatly missed...

  8. #8
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    nitronaught hit the nail on the head. I just blew two engines this morning. Both at the conrod on the piston side. I was using the Losi carb mod and had a good tune and good smoke. However, as Nitronaught put it, The damage was already done and it was a matter of time. Since the carb mod add more power, the conrods couldn't handle the added stress and "POOF" they up and died on the spot. I think I will repair one engine and use the Traxxas replacement plan for the second one. It's always something....
    uh oh.... that didn't sound good

  9. #9
    RC Turnbuckle Jr. Nitronaught's Avatar
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    Quote Originally Posted by guardog View Post
    nitronaught hit the nail on the head. I just blew two engines this morning. Both at the conrod on the piston side. I was using the Losi carb mod and had a good tune and good smoke. However, as Nitronaught put it, The damage was already done and it was a matter of time. Since the carb mod add more power, the conrods couldn't handle the added stress and "POOF" they up and died on the spot. I think I will repair one engine and use the Traxxas replacement plan for the second one. It's always something....
    I just get Avid engine bearings, (I use the ceramics for $35.00. Then pick up a piston sleeve and conrod combo off an ebay chop shop for $60.00.. Now you have a basically new mill with ceramics for under $100.00.. And if you want you can do a nice polishing and porting job.... That's what I do these days.... Still ends up cheaper than the replacement plan IMHO.
    Robin Williams
    He will be greatly missed...

  10. #10
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    Ok on same Topic a follower of mine of Twitter just got a T-maxx 3.3 during break- in Engine stopped and when he thought it was flooded he removed GP turned upside down and rotated flywheel by hand and This fell out.


    He had it set at factory Tuning, Running really rich and spewing lots of fuel, followed break-in procedures to a T even more thorough then I am ( Which is shocking) I am thinking it must be a flaw in piston or something, I cannot figure where else such a large piece of aluminum would come from other then piston.
    He is really bummed now and thinks he messed up and should of stayed electric like his Revo so I am trying to help him as much as I can. I really enjoy Nitro once ya get the twerks etc figured out.
    T-Maxx 3.3 :)

  11. #11
    RC Turnbuckle Jr. Nitronaught's Avatar
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    Looks more like part of the rear inner bearing retainer.... The piston shouldn't be that color..

    NOt every engine is perfect, no matter who makes it... Social media shrinks the world...

    I also don't see many people who say, I have ____ RC and it runs flawlessly..... Usually when people have a problem, the first thing they do on the internet is post about it... Very rare I find those who don't post...

    I bet 90% of our forum members probably came here because they were internet savvy AND needed a little help or advice on a problem. NOt all.

    I confess, I did.... When I couldn't find my tune, I came here.

    Best thing to do have him call Traxxas Customer Support. They probably will ask him to mail the engine in and any pieces,,, often they have replaced engines much to my surprise...

    They are one of the best customer service groups I've ever dealt with on anything...
    Robin Williams
    He will be greatly missed...

  12. #12
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    Thank you, I did and he messaged me just prior to my email stating that was exactly what Traxxas had told him to do.
    I sure hope it gets worked out for him as he just bought the truck and is now thinking he should of stayed electric.

    I am not sure but I think I may have came here either right before I bought my first T-Maxx or RC of any quality or maybe it was just after not positive now since it was almost 2 years ago LOL
    Last edited by Double G; 05-20-2014 at 10:09 PM.
    T-Maxx 3.3 :)

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