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  1. #1
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    3.3 runs like crap

    I have a 3.3 and i will start it let it idle for a min and as the engine warms up the idle starts picking up high and higher till its wide open, pulled off backplate and sealed that up with gasket sealer, removed carb and sealed that also. As idle is picking up I spray down the engine with brake cleaner to see if there is a air leak and there is isn't. Any ideas on what it could be? Engine may have 2-3 gallons of nitro thru it.

  2. #2
    Marshal Double G's Avatar
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    How's the tune? Start at factory? Does the idle gap stay around 0.7-1.0mm open during this whole time?
    The Super Derecho

  3. #3
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    Yes, I put carb back to factory settings, no change

  4. #4
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    sounds like you may have an air leak in the carb housing. i had one that I couldnt turn for the life of me. when I tried to rebuild the carb, I found a tiny crack in between the high side needle and the plug on the end of the carb!

  5. #5
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    2 to 3 gallons? The engine may be past its best, traxxas engines have never lasted very long compared to picco or other brands.
    Sent from my lumia 920. woot.
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  6. #6
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    Quote Originally Posted by revomikey View Post
    2 to 3 gallons? The engine may be past its best, traxxas engines have never lasted very long compared to picco or other brands.
    Sent from my lumia 920. woot.
    That wouldn't make the idle keep rising, it would make it not want to idle from no compression. The only reasons I can think of are a bad tune, idle gap (tune), air leak and throttle linkage. Engine longevity can be "Luck of the Draw". But really, it's all about the tune. If you use a quality fuel and have safe tuning practices, then you should be able to get well over ten gallons thru one.

  7. #7
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    It ran mint up to this issue, best part about this whole deal was I was going across a field and she stuck wide open into a tree and busted up the a-arms and bulkheadd, this is my 3rd 3.3 in this truck, I keep breaking conne ting rods and traxxas keeps warranting them, I'm ready to call it quits with traxxas.

  8. #8
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    The only reason I've ever broke a rod, was running it a little rich trying to tame the power down for a small track. Between the over rich tune and not being able to hit wot very much, it overloaded with fuel and broke the rod. I admit, the rods are a little weak on the top side, but if you keep it tuned right they'll do the job. If it doesn't still rev with the brake applied, adjust the linkage. If it does, you probably have an air leak. An air leak causes a lean condition, it could be too much air or not enough fuel.

  9. #9
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    Rods broke with 1 gallon of nitro ran thru engine, tune was perfect. I think the 3.3 is just a very poor design. I have a savage xl that has 8-9 hard gallons of nitro ran thru it and haven't had a single issue with the 5.9 or the chassis. I just wanted to try something different and the revo can't stand the abuse I throw at it

  10. #10
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    Quote Originally Posted by NSR View Post
    Rods broke with 1 gallon of nitro ran thru engine, tune was perfect. I think the 3.3 is just a very poor design. I have a savage xl that has 8-9 hard gallons of nitro ran thru it and haven't had a single issue with the 5.9 or the chassis. I just wanted to try something different and the revo can't stand the abuse I throw at it
    I put 15 gallons thru my last 3.3. And I have a lot bad things to say about HPI. But, to each his own.

  11. #11
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    I broke a rod too on my last 3.3, unbelievably its the same rod as a 2.5 so i fitted an old spare, i think its a poor design too, its almost as if they couldn't be bothered so used the tonnes of old rods they had laying around. It holds a tune well though and is a nice engine to use, its classic traxxas though, they design something fantastic but build it from crap materials.
    Sent from my lumia 920. woot.
    Signature removed due to excess awesomeness.

  12. #12
    Marshal Double G's Avatar
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    Given the large amount of 3.3s out there yeah it could happen but the ratio is pretty small. And yes, everyone knows that the 2.5 rod was used in the 3.3...that is not new news.
    There are quite a few of us that have run 3.3s for many gallons--some even modified--with no issues at all. I'm still running my first rod in my second engine which has a mismatched piston and sleeve and a sleeve re-pinched by Ray A. That means two break-ins and with my first engine it experienced high temps due to my learning how to tune.
    If the OP is having issues breaking rods, then the problem is not Traxxas but rather the one running the engine and turning the tuning screwdriver. In addition there are numerous people that have many gallons on their engine.
    The Super Derecho

  13. #13
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    I build 200+HP 2-stroke snowmobile engines for a living, I know a few things about how to tune a 2-stroke, I have a .15 rustler and 2.5 t-maxx that have been great. You pay a lot of money for a rc and you have nothing but issues with it sucks. But it's the name of the game with nitros I guess

  14. #14
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    I live in south Florida where the out door temps are a running between 85 - 90 during the day. I broke in my revo 3.3 by the
    book but have had several problems. After wot, my engine stuttering so I richened my hsn but by doing so I spit a lot of fuel out the exhaust. To stop the stuttering I'm about 4 1/4 turns out on hsn and my lsn is at 1 3/4 out. Also my idle is set to the ideal gap but no matter what I try my engine has a high idle for 3-5 seconds after releasing the throttle. I'm running 30% sidewinder fuel with a medium traxxas plug. Any help would be greatly appreciated, I want to head to the track but can not get this engine
    To run properly for two weeks now.

  15. #15
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    Does anyone have any advise?

  16. #16
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    Traxxas engineers have determined that 4 turns out on the hsn and 1 3/4 on the lsn are safe settings to break in their engines in most whether conditions, except freezing cold. Engines need to be a little rich during break in. Which means, even for break in your hsn is to rich. The hotter it is the leaner your tune needs to be, because hot air has less oxygen in it than cold and is less dense. After you lean your tune you'll find that a 1mm idle gap is a bit to much. With 90 degree whether and using 20% nitro my hsn is 3 1/2 and the lsn is 1 3/4, idle gap just under .7mm. But I'm about 1500ft above sea level, so my tune should be a little leaner than yours down there next to the ocean. And if you use a higher % nitro you need to be a little richer for that. But the differences aren't that much. If your spitting raw fuel out of the exhaust your 1/2 turn to rich on your hsn.

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