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  1. #1
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    New 3.3 stripping spur gears

    I broke in a new 3.3 yesterday, I ran a total of 8 tanks. It was running ok except it was trying to creep forward when stopped. I messed with the idle speed needle but I also had to turn the throttle trim some to apply the brakes alittle. I had a 15/36 gear combo and today the creeping got worse. I messed with the needles and finally it went WOT and stripped the spur. I put on a 38t and I thought I meshed it right but the same thing happened again. I was adjusting the idle speed needle and it went WOT and I lost the second spur gear.

    Tomorrow when I get more gears I'm going to tighten the slipper some and tighten the mesh alittle bit. I looked at a drawing and noticed I put the bearing washers on wrong. I'm going to fix that then set the needles back to factory and try again. When I tighten the slipper nut I read that u tighten it all the way then back off half a turn. Is that a good starting point?

    Could those bearing washers on wrong and a loose slipper be my problem? Or I just had it meshed wrong? Any input for me, thanks
    Revo 3.3

  2. #2
    RC Turnbuckle Jr. Wildman4910's Avatar
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    Make sure the slippers spring washers are like this ( ) , not like this )(.

    Also check the engine clutch spring for breakage & check the clutch bell bearings for roughness.

    If all is well then you need to get the idle down if it's idling too high.

    Where you adjusting the LSN for the idle or were you messing with the Idle Gap screw?

    Idle Gap screw


    For setting the Idle Gap(needs to be about 1mm, use a #61 drill bit shank to set)
    Look out for the tree/crunch!

    LiPo? Naw NITRO!!

  3. #3
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    Yes I guess I was adjusting the wrong screw. I guess I opened the idle gap. Let me ask this, in the pic above is that the correct ? How to I achieve it?? I never could get it that close on my 2.5 either. I am also going to recenter my servo.
    And for max low end should I get a 38 or 40 tooth spur?
    Revo 3.3

  4. #4
    RC Turnbuckle Jr. Wildman4910's Avatar
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    Get a #60 or #61 size drill bit, use the smooth end that goes in the drill chuck and put that down in between the carb body and the slide.

    Pop the linkage arm off the slide to be sure it has no effect.

    Then turn the the Idle Gap screw till the slide just releases the bit and your set.

    Then put the arm back on and readjust the throttle linkage if needed to be sure the linkage doesn't hold the slide open and allows it to close like it is supposed to, then retune the engine from there, tuning both the HSN & LSN at opperating temp and at half tank of fuel.

    Larger spur gives you more bottom end and less speed.
    Smaller spur gives you more speed but less bottom end grunt.

    A 38 or 40 toothed spur should give more bottom end.
    Look out for the tree/crunch!

    LiPo? Naw NITRO!!

  5. #5
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    I'll give it a try today. I got a 38t spur, I read somewhere that a 40t is too low, is that true??
    Revo 3.3

  6. #6
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    I figured it out. I left out one thing, to adjust the linkage going to the carb. I'm ready to run it now.

    Will the 3.3 wheelie a revo short chassis on demand with a 38t spur?
    Revo 3.3

  7. #7
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    i got the idle gap set and set all needles back to factory and it was hard to start. i got it to run a few times, but as soon as it started it took off like wildfire. i tried leaning the lsn but it did it again, then it quit starting. i did the flood clearing process in case i flooded it. i tried 3 glow plugs (all of which lite up bright when i tested them) and i can see nitro flowing through the lines. however today, it really banged my hand up pulling the pull start. i don't know how to describe it but i could feel it in my hand unlike in the past. i removed the pull start and checked the owb, and it seemed ok. with the glow plug out (or loose) it pulls easy but it's a pain when it's sealed, i guess all the compression. what else can i do????
    Revo 3.3

  8. #8
    RC Turnbuckle Jr. Wildman4910's Avatar
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    Warm up block with a hair drier, or loosen the GP slightly, & tighten the GP up once started.
    Look out for the tree/crunch!

    LiPo? Naw NITRO!!

  9. #9
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    I guess it's safe to say my problem is due to new engine and high compression? I also have a new tank (150cc) and new lines coming so once that's swapped it will rule out any fuel problems for sure.

    I also checked the owb and it was okay.
    Revo 3.3

  10. #10
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    put the new fuel tank and lines in and nothing. i busted my knuckles again today. i have all needles at factory and i believe my carb is set right. the next thing i'm doing is buying a few glow plugs tomorrow. if that don't work then i don't know what to do. it did start up for a few seconds today, but once again i was WOT. what causes that??? here is a pic of my carb, is it too open or closed? i've got fuel going i can see it moving thru the hose. so it's either no air or no spark. tomorrow will be new spark, so all that's left is air. if my carb is a little too open, i had it more closed but nothing, so i opened it just a hair.

    Revo 3.3

  11. #11
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    I had the same issue with a 3.3 that had just been broken in and it really ran good but I know I has the mesh set perfect and idle was great but I kept killing the plastic spurs so I upgraded and alls good now!

  12. #12
    Marshal Double G's Avatar
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    With a properly set mesh and you still are stripping gears then there is another issue. I assume you have a Revo based upon the gearing and photos and sometimes the issue is the chassis is bent under the engine.
    As pointed out earlier, you need to find something that will gauge the carb opening 0.7-1.0mm open.
    The Super Derecho

  13. #13
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    The 2 I stripped I assumed they were meshed right. The new one I got I took extra time lining it up. And I got 2 new glow plugs to try. Hopefully today will be a good run.
    Revo 3.3

  14. #14
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    After reading some other threads I pulled the engine and found the clutch spring is broke. Back to the hobby shop lol
    Revo 3.3

  15. #15
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    for anyone interested, i got the truck running. starts pretty good right now. this evening or tomorrow ill take it out and play with the needles and see what the 3.3 can do in the short chassis revo.
    Revo 3.3

  16. #16
    RC Turnbuckle Jr. Nitronaught's Avatar
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    Quote Originally Posted by ericg2000 View Post
    for anyone interested, i got the truck running. starts pretty good right now. this evening or tomorrow ill take it out and play with the needles and see what the 3.3 can do in the short chassis revo.
    Sorry I didn't chime in earlier,,,, job has been keeping me offline for a bt...

    Glad to hear it's running...

    1st, let's address stripping spurs. This happens for the following reasons...
    1. Incorrect mesh, usually happens not from setting the mesh, but from other reasons.
    2. Transmission mount loose causing the mesh to change under load.
    3. Loose motor mount screw, or damaged threads allowing the screw to back out.
    4. Chassis flexing from heavy bashing and/or hard landings. This causes the mesh to change under load. Fix is aluminum chassis braces or upgrading upgrading the chassis.
    5. Engine not accruately aligned with the transmission, meaning the engine shaft is scewed compared to the tranny input shaft as far as alignment.. (rare but happens).

    Now as far as tuning,,, The factory settings are to get you running, beak in. It usually leaves you with a lean LSN... You must address the LSN when tuning, if it is not set right the HSN will never be right...
    This write up will help with your tuning..
    http://traxxas.com/forums/showthread...ul-Tuning-tips.
    Founder of H.U.A.
    Hop Ups Anonymous

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