Forums 🚥 PIT STOP 🔧 Hyosung Technical Help Jetting a GT125R – 2017 ..?

Viewing 10 reply threads
  • Author
    Posts
    • #8230
      Cobra2
      Member
      • Topics: 2
      • Replies: 15
      Joined:
      Sep 30, 2020
      @cobra2
      Norway
      GT125R

      I have the GT125R-2017, bought new a year ago, as new overlayer(3+ years!!) Went thru the run-in-process last summer, then fitted :

      BlackWidow system; pipes & muffler,(loud, even with largest can); https://www.blackwidowexhausts.co.uk/hyosung-gt125r-gt125-comet-full-exhaust-system-400mm-round-silencer-1295-p.asp
      K&N air-filter
      + re-jetted with 6SigmaJet kit; https://www.6sigmajetkit.com/hyosung-gt-125-r-s-comet-jet-kit.html
      – now with the largest jets: F-95/R-97,5. (Bowl-Level checked ok, dry, and wet). Still running lean…????
      Sparkplugs are still as white as new.

      I can get a GPS controlled 70+mph (with ”520-upgrade” DID-VX3 & JT-13/46t) = good enough, but there are no power/torque at top-end, (feels lean), drops speed (and rpm) as soon as you can see the road rise upphill, or god forbid, I meet wind…
      Bike is ”almost new”, just round 500 miles total, (have changed oil/filter 4 times, (more than needed), but the almost black oil I emptied out after the first 50 miles scared me…been better thereafter).
      Shinko-Tires swapped to Bridgestone T32 front & Michelin Road 5 rear.(stock size).
      (Tried NGK Iridium Spark Plugs; DCR8EIX – no change)

      Back to question: Lean? Not enough fuel supply? Or should I just try even larger jets?

      Suggestions, please.

      regards
      Arne
      -any/all spelling-mistakes are dedicated to my teachers…I’m Norwegian…

      BTW, had a 2014 Honda Varadero XL125V -3 years ago, similar weight, had more power, (watercooled & injected), but no stability compared to the Hyo…

      Old and grumpy, have fairly wide engine & tuning experience, "restoring" cars & mc, worked as electronic tech.

    • #8237
      ♠️ MARCEL
      Admin
      • Topics: 39
      • Replies: 763
      Joined:
      Sep 30, 2020
      @mf448kxn6
      North UK
      GTR

      Before we get to the parts, it is still under 1000 miles old, so its very much in the “running in” stages

      Around 600 miles , it is mandated for dealers to;
      – check valve clearances (must be checked otherwise tight valves or loose ones will have a domino effect on peformance to the engine, carbs, etc..)

      – Compression Test (very easy) – must be sure the pistons are putting out correct PSI after it has warmed up,
      — Warm up engine -> then remove plugs (both of them) –> crank bike for 5 seconds max –> read compression.
      Repeat again for rear cylinder too

      Let us know the PSi it is doing

      // Meditation doesn't mean you have to sit still....

    • #8268
      Cobra2
      Member
      • Topics: 2
      • Replies: 15
      Joined:
      Sep 30, 2020
      @cobra2
      Norway
      GT125R

      Compression-test: 12,5 Bar (F & R)  = 175 psi

      Old and grumpy, have fairly wide engine & tuning experience, "restoring" cars & mc, worked as electronic tech.

    • #8284
      ♠️ MARCEL
      Admin
      • Topics: 39
      • Replies: 763
      Joined:
      Sep 30, 2020
      @mf448kxn6
      North UK
      GTR

      Compression-test: 12,5 Bar (F & R) = 175 psi

      That’s very very good!
      Is this when engine was hot? and both spark plugs were out?

      Can you wait overnight, wake up in the morning and get service manual, open top valve covers.
      Get feeler gauge that is in “.mm” (0.05mm to 0.40mm)

      And let us know clearances for each valve? Dont do this when engine is warm, it must be overnight cold.

      // Meditation doesn't mean you have to sit still....

    • #8292
      Cobra2
      Member
      • Topics: 2
      • Replies: 15
      Joined:
      Sep 30, 2020
      @cobra2
      Norway
      GT125R

      It was not hot…but warmish…(they should have made a hinge on tank and oil-cooler, & quick-connects….)

      BTW, compression was checked with 2 different meters (read identical). -both plugs out, and 1/2 throttle. (Had a long screwdriver stuck in the carb to keep it open)

      Will do valves as soon as time permit.

      Old and grumpy, have fairly wide engine & tuning experience, "restoring" cars & mc, worked as electronic tech.

    • #8298
      Cobra2
      Member
      • Topics: 2
      • Replies: 15
      Joined:
      Sep 30, 2020
      @cobra2
      Norway
      GT125R

      Todays conspiracy: How-come even japanese-made feeler-gauges are made of recirculated British steel from early 70’s?

       

       

      Old and grumpy, have fairly wide engine & tuning experience, "restoring" cars & mc, worked as electronic tech.

    • #8301
      ♠️ MARCEL
      Admin
      • Topics: 39
      • Replies: 763
      Joined:
      Sep 30, 2020
      @mf448kxn6
      North UK
      GTR

      Todays conspiracy: How-come even japanese-made feeler-gauges are made of recirculated British steel from early 70’s?

      The Japs & the brits got a little cosy during war days and they both fought wars (to each other and to their enemies) expect them to know how to both work the steel/metals for whatever instruments they made. But ofcouse im going off-track on a bike forum , history is wishy washy so i dare not digress haha

      // Meditation doesn't mean you have to sit still....

    • #8312
      Cobra2
      Member
      • Topics: 2
      • Replies: 15
      Joined:
      Sep 30, 2020
      @cobra2
      Norway
      GT125R

      Clearances are spot on; on both cyl, intakes, a .010 slides in, a .020 dont. and ex: 020 slides, 030 dont.

      However… the plot thickens …

      Seeing the camshafts, I noted a strange difference… and checked with the manual. Alignment is off! On rear cyl, both index-markers points straight up, and not to each side… (see pictures !!!)  Front:

      Old and grumpy, have fairly wide engine & tuning experience, "restoring" cars & mc, worked as electronic tech.

    • #8314
      Cobra2
      Member
      • Topics: 2
      • Replies: 15
      Joined:
      Sep 30, 2020
      @cobra2
      Norway
      GT125R

      Rear:  (with the magic of mirrors, I could just see the lines pionting up)

      The way the cams pointed up/inwards, alarmed me to check…

      No wonder there is a lack of power…actually a wonder that it did as well as it did.

      This seems like a factory-error?

      Old and grumpy, have fairly wide engine & tuning experience, "restoring" cars & mc, worked as electronic tech.

    • #8320
      ♠️ MARCEL
      Admin
      • Topics: 39
      • Replies: 763
      Joined:
      Sep 30, 2020
      @mf448kxn6
      North UK
      GTR

      The cams on the rear face up but torwards each other.

      But look at the edge of the cam shaft bars and make sure the dark black _________ line is on the same level as the surface of the cylinder head (where rubber gaskets sit)

      Both cams must be equal ________ marked to match the surface of the engine gasket area.

      Also if i remember correctly (it’s 10pm, so my brain is a little funny!) , the #2 on the sprocket is 100% facing straight up | ^ to match the cam cover holder bolt thread.

      #3 on the sprocket for the intake is facing UP but it will be like this / than | straight up

      Spin the crank 10x to be accurate and recheck feeler gauge for clearances.

      // Meditation doesn't mean you have to sit still....

    • #8325
      Cobra2
      Member
      • Topics: 2
      • Replies: 15
      Joined:
      Sep 30, 2020
      @cobra2
      Norway
      GT125R

      The index-lines I refer to are the (faint) line at cam itself (not the sprocket). Should be like circled in green, mine are close to the red line… The sprockets align (blue circles).

      Cams are correct placed, IN/EX marking between lobes. Cams are bolted in similar to picture…

      Will maybe bolt on a degree-wheel to crank and check timing figures tomorrow. Front & rear should however be the same… -and they are not.

      Old and grumpy, have fairly wide engine & tuning experience, "restoring" cars & mc, worked as electronic tech.

Viewing 10 reply threads
  • You must be logged in to reply to this topic.