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  1. #1
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    Question Jato 3.3 keeps blowing plugs

    Hello,
    After if changed nitro percentage (from 16% to 25%) my engine kept blowing plugs.
    The first 2 plugs where just burned out (wire still intact), but the 2 after that were completely blown out (the glow-wire was gone) or the glow-wire just snapped. What is I haven't done is cleaning the engine after the first glowplug. That was my fault.

    After i switched the nitro i've put on a bigger shim, because i already had pitting with the 16% and i retuned the engine.

    But still I keep blowing plugs.

    I can get the engine running great and tuned great, but when i shut the engine off with the pinch method, the glowplug just gives out.
    When I pinched it did took like 5 seconds for it to shut off. But when I ride it, it still left a nice trail of smoke.

    Today I've taken off the head and found a couple of very small pieces of metal. Smaller then a grain of sand.
    Also i've taken of the clutch and I can feel a little movement on my input shaft? And I have noticed a lot of nitro/oil around the block of my engine. My one-way bearing also keeps slipping even after I have cleaned it. So it looks like there is also nitro leaking out of there. I have already changed the bearings 1 gallon ago. But maybe I have thrown another one? Because it looks like it is coming from the bearing, but it can also be coming from the carb. I'll just replace the o-ring on the carb and on the fuel tank to write those problems off.

    Maybe I have stretched my connecting rod?

    I just don't know anymore what could be the problem, because before I changed the nitro it ran great to 60mph and no problems.

  2. #2
    RC Turnbuckle Jr. olds97_lss's Avatar
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    Could try getting the lower % nitro and see if it still runs ok with that.

    Might want to check your crank case for cracks near/under the mounting flanges. I had issues with that on my jato before I converted it to electric. I jump mine a lot and the impact from landings were causing the crank case to crack.
    https://www.youtube.com/c/olds97lss

  3. #3
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    Is it maybe possible that I need to add another shim?
    Because I already had pitting with the 16%

  4. #4
    RC Turnbuckle Jr. olds97_lss's Avatar
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    I'm not sure. I ran 25% byrons in my 3.3's without messing with shims. I just ran a OS LC4 (medium) plug with it.
    https://www.youtube.com/c/olds97lss

  5. #5
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    Alright, I’ll try a colder plug then too.

  6. #6
    RC Champion grizzly03's Avatar
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    Quote Originally Posted by olds97_lss View Post
    I'm not sure. I ran 25% byrons in my 3.3's without messing with shims. I just ran a OS LC4 (medium) plug with it.
    Same. I run the medium plugs with 30%. I never had good luck running a hot plug on anything higher than 20%.

    Burning up plugs like you are could also be a sign of being lean. Have you tried going back to factory settings and re-tune?

  7. #7
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    I just use the traxxas plugs. Are those hot or medium?

    And if retuned the engine 3 times now, each time putting it back at the factory settings. Or those are too lean? And when I shut the engine off the last time with the pinch method it ran for 5 seconds instead of 3. So it is not the low end. It may be the high end tho
    Last edited by partypinguin376; 04-14-2021 at 01:39 PM.

  8. #8
    RC Champion grizzly03's Avatar
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    Quote Originally Posted by partypinguin376 View Post
    I just use the traxxas plugs. Are those hot or medium?

    And if retuned the engine 3 times now, each time putting it back at the factory settings. Or those are too lean? And when I shut the engine off the last time with the pinch method it ran for 5 seconds instead of 3. So it is not the low end. It may be the high end tho
    Traxxas plugs are Medium.

    Also check out your exhaust. A rip or hole in the exhaust coupler can cause issues.

  9. #9
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    Alright, just checked the needle settings. High is 4,2 turns out and low is just a bit out of the first ring.
    I’ll check and try the Rossi r3 and r4 plugs. I can’t get McCoy or OS plugs in my country.
    And the exhaust has no visible damage. But i have one sitting in a different jato, so I’ll try that.
    But I never had problems with the exhaust before the nitro change

    Edit: there is some build up around the exhaust exit at the motor, so I’ll change that o-ring too

  10. #10
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    And I guess it’s also not good to have small pitting on the starter shaft?

  11. #11
    Marshal Double G's Avatar
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    You mentioned that there was some material in the cylinder. I would tear the engine down for an entire clean and possible partial rebuild.
    The Super Derecho

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    With tear down you mean taking the sleeve and everything out? Even the bearings?
    Because when I looked at the starter shaft i've blowed it out with some brake cleaner and compressed air. (with the cilinder and sleeve still installed).
    And the small pitting on the starter shaft is normal?

  13. #13
    RC Champion grizzly03's Avatar
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    Double G's post is good advice.

    It would be a very good idea to totally disassemble to clean it all out. Small pieces from the broken glow plugs can be all over inside the engine. Those small pieces do damage and can also be the cause of the next glow plugs getting damaged. Once apart it's super easy to clean out the engine case, parts and bearings.

  14. #14
    RC Turnbuckle Jr. olds97_lss's Avatar
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    After cleaning, just make sure to put a few drops of ARO on each bearing, conrod journals and the sleeve before pushing the piston in. Don't want things to be dry on your first startup after a clean out.
    https://www.youtube.com/c/olds97lss

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    Okay, tomorrow I’ll do a full clean. With disassembling everything. Even the bearings.
    Thanks for the tips guys! And the quick reply’s.

    When I’ve cleaned and reinstalled it I’ll come back to this thread to tell if it worked

  16. #16
    RC Champion grizzly03's Avatar
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    This article by Traxxas should help:https://traxxas.com/support/TRX-Engi...Instructions-0


    ps. Make sure the piston cut-out side is towards the carb when you put it back together. A simple double check will save you grief if accidentally installed the wrong way.

  17. #17
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    Thanks for the tip!

    But still, is it okay to have little pitting on the inside of the starter shaft? The part that is attached to the crankshaft. (the plate).
    And I still find it weird that the engine runs great, but when I turn it off the plug dies. Do I need to change my way of turning it off? By pushing something on the flywheel or something?

  18. #18
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    I've found the problem.

    https://www.dropbox.com/s/f89trh6ozg..._3185.jpg?dl=0

    When I disassembled the engine I found out that the rear bearing has quit a bit of movement too each side, so I guess that needs replacement. But I've also found a chunk missing of my piston.
    It still has amazing compression but I don't think it can be good too keep running the engine with that side piece missing.

    So what do you guys recommend to do now? I can't use the power up program.
    And I dont't know what would be more usefull.
    Spending over 200 dollars for parts to try to save this engine or spending 270 dollars for a new engine.
    The parts that I think I will need are: Bearings, connecting rod, cooling head (it has damage from pitting/material in the engine), startershaft, cilinder/sleeve and a crankshaft.
    The only thing I think I can keep is the case, but that needs replacement too I think. Because of the material I found in the engine.
    The carb is still good, but that is the only thing.

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  20. #20
    Marshal Double G's Avatar
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    I've never had an issue with pinching the fuel line. Others have plugged the exhaust or stalled the flywheel.

    I would like to see a pic of the pitting you say is on the starter shaft. Is is on the outside of the back plate or where it spins inside the brass bushing?

    Edit: (was taken away on a medical for the past half hour)...there are other options to get a replacement 3.3 - maybe talk with an importer to see if the Power-Up Program exists. In any case, you found your problem as the skirt broke off and the pieces had a rave party in the cylinder.

    I would go with a piston, sleeve, rod and bearings. Make sure the crank is good and if you can smooth out the pitting from the head that would help.
    Last edited by Double G; 04-15-2021 at 09:16 AM.
    The Super Derecho

  21. #21
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    These are the parts I'm considering replacing:
    The startershaft:

    https://www.dropbox.com/s/wrgd3tli34..._3190.jpg?dl=0

    The piston/sleeve:
    https://www.dropbox.com/s/07vm06nk7s..._3193.jpg?dl=0
    https://www.dropbox.com/s/0kecccogbw..._3195.jpg?dl=0

    The coolinghead:
    https://www.dropbox.com/s/mctne57odt..._3186.jpg?dl=0

    And the conrod, since I don't know if it needs to be changed. So I am better off replacing it.

    Edit: I just read you're edit.
    I can't use the power up program since I live in the Netherlands, and it is only possible in the USA.

    How can I check if my crank is still good? And how can I smooth the pittig?
    Last edited by partypinguin376; 04-15-2021 at 09:23 AM.

  22. #22
    RC Turnbuckle Jr. olds97_lss's Avatar
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    If your getting a starter shaft, you should also get a new one way bearing as running a new shaft on old bearing will likely just cause it to wear the shaft prematurely. And if your replacing the starter shaft due to wear, odds are the bushing in the backplate is worn and that should be replaced as well.

    Might be better off just getting a new engine if your replacing all of that.
    Last edited by olds97_lss; 04-15-2021 at 01:10 PM.
    https://www.youtube.com/c/olds97lss

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