TTR 125 Problems

Discussion in 'Mini Racing' started by SuddenBraking, Jan 4, 2020.

  1. SuddenBraking

    SuddenBraking Well-Known Member

    Long story short, hadn't ridden it in a while and let the carb get gunky; no worries, rebuilt the carb and tried to start it.

    Bike tried to turn over more, but still didn't start.

    Checked spark plug, carbon buildup like a motherfucker - replaced.

    Tried to start bike, and would idle extremely weak and then die - any throttle the engine would die.

    Said eff it and bought a new carb (Mikuni off of ebay). Finally got it installed (wasn't a direct bolt on) and kickstarted the bike - voila, it turned on. Let it idle for a bit and then gave it some gas and there's steady while smoke coming out (similar to how a carb'd engine is when it first starts). After a minute or two of idling rough-ish, it died. Restarted it and it died thirty seconds later. Went to kickstart it again and the compression seems comically low (I don't have a tester).

    I guess all of the above is a longwinded way of asking - is there anything else I should trouble shoot before getting the engine rebuilt?
  2. joec

    joec brace yourself

    Valve seals. Mine smoked worse than a 2 stroke.
  3. TurboBlew

    TurboBlew Registers Abusers

    Id investigate why the mixture was so rich?? Collapsed filter? Pest nest in box/manifold??
  4. joec

    joec brace yourself

    I'd check the pipe for oil first.
  5. SuddenBraking

    SuddenBraking Well-Known Member

    My guess was that the bike was running too lean, but I'm an idiot so that's almost definitely not the right thought.

    For an update, went and started it and rode it around my cul-de-sac two or three times - bike was dangerously snatchy (like throttle was so on/off that I was lifting the front wheel like I was clutching up). Also oodles and oodles of smoke coming from the pipe - drained the oil to see if there was anything amiss but it all looked good to my eye. Didn't refill as I'm almost 100% certain there's engine issues at this point and assume I'll be rebuilding some amount of the engine.

    On the plus side, got a new to me KX65 delivered on Friday so it'll hold me over while I figure this bike out.
  6. SuddenBraking

    SuddenBraking Well-Known Member

    Anybody know where the fuck to get an engine rebuild kit from? Googled it and none of the dirt bike kits seem to fit a TTR 125.

    None of these kits fit....


    [EDIT: is it most likely that I just need a top end and not a full rebuild? If so, can find top end kits but coming up empty on finding bottom end kits.]
  7. Kurlon

    Kurlon Well-Known Member

    I don't believe you will find anything beyond a full gasket kit aftermarket for the TT-R 125, crank/etc are going to have to be OEM if you think you need them.
    SuddenBraking likes this.
  8. TurboBlew

    TurboBlew Registers Abusers

    I got an XR engine from this guy a few years ago... was suprised how well it ran.
    Im positive he does TTRs as well because I was about to send him one.

    I did the flywheel service from on my old ttr. It woke the bike up noticeably.
    I kind of got carried away before the 150r came out. :D
    SuddenBraking likes this.
  9. SuddenBraking

    SuddenBraking Well-Known Member

    Yeah, I'm just going to tear the fucker apart today down to the frame. I'm planning on doing a full top end rebuild (but to be honest, not really sure what that entails). It seems like a no-brainer once I've got it torn down to do the bottom end as well for preventative maintenance if nothing else.

    I'm debating doing this myself or sending it over to a local expert on minis. It's balancing out my time vs knowing how to do it in the future. The issue with me doing it is I'm sure I'll run down a few rabbit holes and waste time, but as long as I learn something each time I guess that's acceptable.
  10. Spang308

    Spang308 Well-Known Member

    Service Pavilion likely has or can get anything you need for a TTR.
    Didn't he build your bike?
  11. SuddenBraking

    SuddenBraking Well-Known Member

    He did - he's the "local expert" I referenced in the post above yours. On a related idiotic note, I'm going for the dumbest question on the interwebz today - how the fuck do most people put air into TTR50 tires? I had to use a grinder to cut the little latch thingy off of one of my pumps to be able to fit it onto the stem but that can't be what most people do.

    Is there a 90* stem conversion that happen without removing the tubes currently in the tires? Feel free to end any post responding to this with ", you idiot."
  12. TurboBlew

    TurboBlew Registers Abusers

    like this??

    There are extenders you can put on but the above chuck should get you perpendicular to the stem.
  13. SuddenBraking

    SuddenBraking Well-Known Member

    I bought these - I think they should do what I need (assuming they work).
  14. SuddenBraking

    SuddenBraking Well-Known Member

    Forgot the link above:

    Anyhow, here's where I'm at. There's a couple of pics that I hoped to embed so that my questions around them would be more obvious, but here goes anyhow:

    1) You see me pointing to the battery harness - I'm getting rid of the battery and everything associated with it (starter), so that pic is me asking where I can cut.
    2) How do I open those two openings on the left of the bottom end (my big fat pointer finger is pointing at them in the pic)? Need to get them open to check the valves and I assume there's a yamaha tool I need.
    3) What is that light grey cylinder that the oil fill cap is safety wired to? There's a wire running there from the battery so can I get rid of that whole assembly?

    Thanks for your help, guys - it's much appreciated. If you're ever in the Philly area I'll gladly buy you a couple of beers.

    Attached Files:

  15. pscook

    pscook Well-Known Member

    1. I can't say what you can and can't cut. Wait for an obvious expert on this as any wrong moves and you have to do lots more to fix than you want.
    2. Find a piece of flat steel, aluminum, or a quarter and use pliers. It's plastic, so if you use a flat blade screwdriver it can (and likely will) end up gouged and possibly unusable. You can buy aftermarket hex ("allen") drive plugs (example) to replace tem when you do mess them up, or over tighten them and they collapse (Ask me how I know...)
    3. That big gray cylinder is the starter, the thing that you want to remove.
    SuddenBraking likes this.
  16. damiankelly

    damiankelly Well-Known Member

    I would send it over to Rob at TSP get it fixed properly and then you can mess with it in the future..
    This helps get them open..

    But why take off the nice push button -how much weight would you save for stock class?

    Just takeoff the kickstand the chain guard the front sprocket cover and run less gas in sprints —put a lithium battery in and that should make up the difference right there..
    Last edited: Jan 5, 2020
    SuddenBraking likes this.
  17. SuddenBraking

    SuddenBraking Well-Known Member

    Yeah, I was leaning that way and then I realized I need to figure out how to work on this machine a little bit so figured I'd turn this into a science project and hopefully get it fixed while learning a thing or two.

    Regarding the push button - that's never worked (and is a common problem with those starters). I've left it planning on fixing it one day but decided I never will and kick or bump starting it is easy enough.
  18. britx303

    britx303 Struggling stoic.......

    For what its worth that bucking and jerking and excessive exhaust smoke scenario could be just the needle valve not seated properly or installed in the wrong order, not being held down by the spring,and its bouncing up and down loose in the carb. Ive seen that a few times on a bike or 3 and we even did the ebay carb thing,and found them to be assembled wrong brand new.
    SuddenBraking and TurboBlew like this.
  19. britx303

    britx303 Struggling stoic.......

    And the bike that got the ebay carb is our TTR125 by coincidence.It did all what yours is doing,even feeling like low compression,which i think is just the nature of the ttr. I disassembled the entire throttle assembly and put it together in the right order to where it held the needle in place properly.......... My daughter got 3rd place in her hare scramble yesterday on it. I'd take a step back and go back through the carbs settings,jetting and needle condition/situation etc .
    SuddenBraking likes this.
  20. damiankelly

    damiankelly Well-Known Member

    No better way to learn about how a bike engine works!
    Plus you get to buy some more tools...
    Took my first bike apart at age twelve with vise grips and a screw driver...put it back together and it actually RAN...

Share This Page