1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

TTR 125 Problems

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

  1. DmanSlam

    DmanSlam Well-Known Member

    I don't recall the original poster mentioned a method (?) but his words were strong for his feelings about carburetors. :crackup: Re the screw setting, no loss. Turn the idle screw in until it's seated, then back it out 1-3 turns and tune/adjust from there. Pilot and main jets are the simplest to tune.
     
  2. pscook

    pscook Well-Known Member

    You should have seen my response to yours before I edited it!

    My job requires me to analyze a situation to identify the problem so the team can work on a solution, and my job found me. I love asking open ended questions to find out how we got here. If we know the pathway here, we can find the pathway home.
     
  3. pscook

    pscook Well-Known Member

    When warm, perform the actions above to achieve highest idle. If 2+ turns out, increase the pilot one step (until you achieve highest idle at 1.5-ish turns). If you are less than one turn from seated at highest idle, decrease the pilot size by one step until you get to 1.5 turns.

    After that, we can discuss main jet, needle jet, needle diameter, needle taper, and needle height. But yeah, the pilot is the easiest to tune (when the carb is clean).
     
    DmanSlam likes this.
  4. SuddenBraking

    SuddenBraking The Iron Price

    My "method" as it were is to (most likely) install new carb incorrectly and then bitch about how carburetors are pieces of shit (in my defense, they are). That being said, got a good amount of my yardwork done today so may go back in the garage (after re-reading what you gentlemen wrote) and try to get these bikes running. I think I'm going to start with the KX as that carb was simply rebuilt and (if memory serves) is probably a float height issue. The TTR has the added variable of me putting a new carb on and (almost certainly) putting that new carb on incorrectly :rolleyes:
     
  5. DmanSlam

    DmanSlam Well-Known Member

    Oh c'mon, man. I don't recall the service manual mentioning a "clean carb". Sounds like more work to do when all we're doing here is just trying to help resolve the OP's issue. :D:D
     
    pscook likes this.
  6. SuddenBraking

    SuddenBraking The Iron Price

    Update - was going to buy an RM85 but called a last minute audible and decided I'd be better off getting my TTR 125 running first.

    1) Checked the valves - were tight, but are now within spec.
    2) Replaced spark plug.
    3) Confirmed there's spark.
    4) Got a high compression reading (seems too high, but also seems to rule out low compression).
    5) Spent a few hours yesterday trying to start it, so was surprised when I took out the float bowl that gas didn't come spilling out (that feels like a clue).
    6) Took the intake boot off, and liberally sprayed starter fluid into engine. Tried to kick start it and it sounded like an explosion/bomb, and I can't be sure but it seemed like there was pressure coming out of the head (i.e., going back to the carb vs negative pressure pulling in air from the carb.

    Not sure of what next steps should be.......I tested compression assuming it'd be low and it would need a new top end, but everything seems to point to the fucking carburetor and it being a fueling problem. Unfortunately, I'm on carburetor number 3 at this point.
     

    Attached Files:

  7. Boman Forklift

    Boman Forklift Well-Known Member

    Are the 3 carbs cheap Chinese crap off eBay? That would possibly be a problem although I don’t have any current experience where to get good ones, other than OEM?

    on the original OEM carb, did you remove all the jets and verify that is all clean? Often pilot jets are really hard to clean and you can get a new one for 5-10, I believe.

    If you remove the float bowl, and hook up the gas line, have the carb standing up like it was attached to the head or it can still be attached to the head. Turn on the gas and move the float up and down to make sure it is allowing fuel In and then stopping flow when you push the float up.

    Did you mess with the air screw? Have you blown compressed air through all the orifices? This is where an ultrasonic machine works well for cleaning everything out.

    There are many options and I can’t tell you which one is better but they are pretty reasonably priced now.
    https://www.amazon.com/VEVOR-Commer...ocphy=9031564&hvtargid=pla-524064442053&psc=1
     
    SuddenBraking likes this.
  8. SuddenBraking

    SuddenBraking The Iron Price

    Nah, two carbs are the OEM and the other is the aftermarket Mikuni VM24 - all quality carbs. At this point, I'm at my wit's end so confirmed the spark plug gap is correct (it was).

    The only thing that is notable is the valves were extremely tight when I readjusted them recently, and there's VERY little play (to the point of almost zero) in them when I take the valve covers off even after the adjustment. What is that pointing towards as the likely culprit, and what would my next steps be?

    To recap:

    1) Have gas
    2) Have spark
    3) Have air
    4) Have good compression
    5) Valves were VERY tight before adjustment, and even after getting them in spec there's very little play in them

    BTW, @Boman Forklift in messing around with/researching this project I believe I've diagnosed the issue with the KX65 you've got - methinks it's a stuck float valve.
     
  9. Boman Forklift

    Boman Forklift Well-Known Member

    Yes most likely on the float. Did you ever find the title?

    If your bike was an older Honda CRF250R or X I would tell you the valves are toast and maybe the head is too because it was very common. I don’t think TTR’s usually have that problem.

    Have you checked compression with a gauge? Harbor freight has them for under $30. When valves are tight, they hang open, and this means you get no compression, hence the no start.

    I would recheck and if still tight and you are adjusting them right, loosen them some more. I presume that is a screw and nut setup on a TTR versus shins over the top of the valve under a bucket, which makes you remove the cams to adjust?

    If you did remove the cams, reverify the cam timing.

    I think you have my phone number from before. I’m leaving now to help my buddy pull a motor out of his MG and rebuild it, replace clutch etc. So feel free to call me all day today or tomorrow, I will be wrenching ir at work.
     
  10. SuddenBraking

    SuddenBraking The Iron Price

    Appreciate it, Rob, and unfortunately no on the title - PO confirmed there never was one.

    Regarding the compression, yup - compression is good. Have spark, air, and gas so somewhat at a loss for where to go from here.
     
  11. SuddenBraking

    SuddenBraking The Iron Price

    I guess what I'm asking is, should I just buy a big bore kit and would that almost certainly solve my problems or maybe not so much?
     
  12. Boman Forklift

    Boman Forklift Well-Known Member

    Who am I to stop a man in search of more horsepower?

    Did this run properly and then just stop or did you buy it as a non-running bike?
     
  13. SuddenBraking

    SuddenBraking The Iron Price

    Lol, more horsepower would be good (not sure this bike was designed for 250+) but it was more of a defensive/preemptive measure to just nip this shit in the bud and rebuild the motor so it runs good for a while.

    Was curious if a top end rebuild (either big bore or OEM) kit would be a good solve for the symptoms I've described. I don't know the difference between what symptoms are indicative of a bad top end vs what may be a bad crank.
     
  14. 418

    418 Expert #59

    Have you done a leak down test on it?

    No offense but after 2 years and throwing parts at it, you probably would have had it sorted out if taken to somebody worth a shit. It's probably something stupid simple you are missing.
     
  15. SuddenBraking

    SuddenBraking The Iron Price

    Haven't done a leakdown test so will order a test kit and report back.

    Also, hard to argue that a competent mechanic wouldn't have figured out how to get a TTR 125 running after more than 700 days :D; that being said, I've reduced my stable of bikes from ~10 to ~4, and would like to really understand and know how to wrench on the 4 bikes (as the plan is to keep them for a long time).
     
    Boman Forklift likes this.
  16. TurboBlew

    TurboBlew Registers Abusers

    I would talk with Mr. Nye. https://www.xr100.com/
    I sent him an xr100 engine, in pieces, that I got as part of a deal. A couple weeks later I got a huge smile on my face opening up the crate.
    It fired first kick (after reviewing ALL of his included instructions) and had been suprising unsuspecting riders for a couple of years.
    He does all the single cylinder air cooled stuff including TTRs.
     
    SuddenBraking likes this.
  17. SuddenBraking

    SuddenBraking The Iron Price

    Well, some things happened.

    1) Have been spending some time on it each night, and a couple of nights ago decided "huh, maybe I've got the fuel hose going to wrong part of the carb" (I'd been trying to blow through each orifice of the spare carb - insert joke here - and the overflow valve seemed to have the least resistance so that's what I tried). Once fuel came pouring out on me I realized my error and switched it back.
    2) Reached out to a mobile mechanic on Facebook who's local yesterday. Was about to call him to stop over and then thought "you know what, let me take a look at something"......
    3) Had previously tested spark and had it, but it wasn't super strong. Cross checked my spark plug inventory to what I'd purchased through Amazon and realized I had a NIB NGK (4549) CR7HSA Standard Spark Plug, Pack of 1 (5100.5714).
    4) So figured what the hell, may as well give it a go. Did so and first kick, revving to the moon. Turned bike off, tried again, one kick, revved to the moon. Guessing there's still a ton of fuel left in the float from my routing to the overflow nonsense, but I'm quite confident that now it's going to be good to go once I dial the carb in (AF and idle tuning to come, and methinks I need to change the float height).

    I don't know what the order of operations was of me getting myself fucked up - if I had to diagnose, it'd be this:

    1) valves were steadily tightening, making starting harder and harder
    2) bike sat for a while, carb got me frustrated
    3) bought VM24, changed out spark plug, bike ran but so damn rich that it *kinda* fouled the plug (although plug still sparked when kicked over)
    4) two lost years of futzing with carbs, adjusting valves, and generally driving myself nuts
    5) I've found jesus and have a newfound appreciation for carbs, and I know 10,000X more about how to wrench on my bike than I did before

    Stay tuned for next week's update where I break something else :D
     
  18. Boman Forklift

    Boman Forklift Well-Known Member

    Congratulations!!!!

    If it were me, I would try the stock carb again. Especially if you have cleaned it out and it has a clean or new pilot jet. Trying to find all the proper settings for an aftermarket carb is not easy, IMO.
     
    SuddenBraking likes this.
  19. SuddenBraking

    SuddenBraking The Iron Price

    Hmmm, I might've declared victory a bit prematurely. Bike starts first kick now, but trying to figure out the carb settings is driving me bananas - I actually took off from work today to just get it sorted, and at this point the fight is not over.

    But I learned more about carbs in the past 24 hours than I did in the previous 40 years, so there's that :rolleyes:
     
    Boman Forklift likes this.
  20. britx303

    britx303 Boomstick Butcher…..

    Interested in selling the ttr yet? Im considering another wee bike for riding with my daughter. Our RT has run its course and we like the TTRs.
     

Share This Page