Gt125 naked 2016

[Stu]

Hi all,

first post and new rider. Went for hyo gt125 unfaired and love it! Total noob with bikes though so couple of questions if anyone can help

Bike seems to take a age to warm up. Is this normal or is there anything I can do to improve things?

Thinking of updating a few things. Getting 520 chain kit conversion done, maybe filter and jets. Anyone know if chain conversion is straight forward (will be taking to a mechanic!).

Any other basic modding advice?

tia

[♠️ M77]

Welcome Stu!

Post a picture of your ride here -> https://hyoriders.club/forums/topic/owners-photography-thread-new-rider-show-off-your-ride/

To answer the 520 part,  yes what you see on this website’s store is generally self-fitting  (meaning yourself, some correct tools and skill level depends on your confidence to take certain things off and put them back exactly the same way back)  but a garage can definitely do it. However, i would caution and watch what they are doing, it has come to my attention via private communications my clients have had mechs take silly shortcuts or can’t be arsed to work on hyo cause its Chinese (really ?) and they half-arse the job ,  thus meaning what ever mods they fitted became quickly pointless if the bike behaves worse than it did before.

Speaking of behavior,   let’s assume you are a brand new owner and bike is total blind buy  (no history whatsoever or last owners lied etc), so to make it a good “standard” bike ,  can these be done at your end   (trust me, the hyosung will really appreciate you for it)
– Full tank flush and put e5 , cause e10 is from hell.

• Carb = Ultrasonic clean ,  Rebuild it (with this kit) ,  do the slide mod (click here),  check jets are okay  (here)
  Standard Jets are OK, if there is no air intake mods or exhaust mods.    I am assuming this bike has zero modifications?
• Do not mess with the mixtures.  Only thing you have to do is allow the carb to someone ultrasonic clean it, because sometimes rattle cans don’t always get the job done or be ready to go through at least 4L of rattle cans just to really assure the carb is cleaned, remember it has many holes inside , not just jets.
  When i deal with customer carbs , i use air compressor  (as korea advises) and liquid cleaning ofcourse in a bath.  Neither a garage should not mess with the mixtures UNLESS they have experience with a BDS26 carb and a Hyosung GT125.  Just because they know other 125s doesn’t mean the hyosung will behave the same way inregards to them messing with the mixtures
• Go (here)  and look for the picture of float height, make sure it is certain.   Also,  read that topic i just linked in this sentence as it has some back and forth chatter which can help you diagnose other potential running issues.   The lad in that topic may have a 2003 Naked 125 but they have the same carbs and same engines.
• Before opening a carb, make sure to get  “JIS” screwdrivers. I can’t stress it.   Normal UK Made or Chinese made philips (+) drivers WILL ALWAYS ROUND IT OFF.   Sorry for the caps ,  it can get frustrating later so JIS screwdriver set is a good must. I use a set fron USPRO ,  they are great!
• Head over to the shop of this website and get yourself some stainless bolts! For both top and bottom. You won’t regret it.
• Just looking around the hyosung it is almost a consensus for everyone now to use stainless fasteners or titanium all over the bike.  Pricy? Yes.  But its not just for looks ,  the maintanenance of the bike will be a lot better in general.
  The only thing that can stay standard is the axles for the wheels and mono shock linkage parts.  It is not a good idea to go stainless on axles. I dare not digress.
• Putoline race grease  (apply it on ANYTHING that moves)   –> except Wires! & brake discs!
• Wires = Every single plug that exists on the bike  –> use a little drop of acf50 on them.   This every biker’s “must” do list,  UK is salty and weather likes to rust exposed things  given the chance!
• Copper Grease = back of pads ,  on the fork bolts near the bottom of the bike, mudguard bolts,  things that look like they will seized under constant water attacks  which is usually the areas where wheels are.
  The is NO need to apply copper slip on the AXLE BAR NUT on the rear wheel. No need
  Apply copper grease on ALL fairing bolts or Go Stainless.

Moving on…..

• Clutch = Overhaul it  (especially if its beyond 4k miles from new, it tends to be forgotten about.  HP passes through the clutch before spinning the back wheel, so you want the clutch to stay punchy)
• Gearbox and many parts inside the motor = Use Motul 7100 or Silkolene Comp 4 forever. These 2 brands forever. No matter what sales man tells you in his bike shop, they are not that slick to sell crappy Castrols  (no pun intended). The service manual says use costly oil if you can (premium) if bike has a harder life which the 125 generally does compared to a 650.
• Compression Test = A garage can do this within 5 mins  , please get it done and tell us the figures.
• Clearances check  = A garage must only do this below….
  – – Open the valve tops of each engine.
  – – Open the “Timing Viewer” hole , he spins to “F” mark  = Front Engine
  – – Spin 10 times the crank.
  – – Put a feeler gauge and write clearance values for front engine. Dont pay him if he can’t provide this info.Repeat for rear engine.Come back to this forum and let us know the clearances

  Believe it or not, clearances are almost 50%  (if not the main cause) of poor starts, hard to tune the carbs due tight valves,  slower top speed if valves are too loose, engine is generally louder if valves are loose in terms of clearances under heavy load,  and it goes on.    Good news if the clearances are good, then you don’t have to worry about costly garage bill to do it!

I could go on ,  but you have only just joined so sorry if this overwhelmed you,   knock off what i said above ^   , one by one , and if she is a super well behaved standard bike,  then  pimping her “mod wise” will be easier to advise on what benefits what and to save you some cash where possible.    Some silly mods on in the internet are placebo effect (like the infamous CDI cheat on Hyo 125s which is silly but a stronger electric system will be noticeable instead, the CDI isn’t restricted whatsoever, so this is just an example)

[Stu]

Thanks Marcell! Definitely some things for me to get on with! Been reading a load of posts here and on Facebook and glad you replied! Will take your advice and work through your points

Bike has some history, and bought off a copper so all legit and everything seems to be working (but noob so what do I really know!). Does have black widow end can and what looks to be stainless pipes through to manifold.

Will get some decent pics on soon and get the upgrades bought.

There is a mobile bike mechanic in my area so gonna give him a try, and I’ll be staying with him while he works (for my benefit mainly but also to keep an eye out). Spoken to a few places about servicing and swapping bits out and so far only one taker for servicing. Any Merseyside shops that you’d recommend?

Will definitely be posting updates on this!

Thanks again Marcell!

[Stu]

Back spark (old)

Well, I’ve now compression tested and changed sparks. Back cylinder is 4bar/55psi and front is 3.5bar/50psi (approx, and on the basis the tester isn’t screwed). Hoping this isn’t too bad? Oil filter and oil changed. Pics of used sparks attached. Unsure if anything can be determined from them? Running normal/rich/lean? (Back spark has bike in the background).

Sump bolt seemed to have a lot of debris on the magnet (normal?), and oil was very dark.

Had a look at taking the air box off, but aside from being well fiddly to get at, the front jubilee is properly rusted up, presuming because unfaired. Any advice on getting this off without damaging the inlet manifolds?

Taken her out for a short spin and happy with improvements so far 😁

Engine bolt swap out tomorrow. Quick question, can I just swap these out 1 at a time?

Going to have to wait on chain and sprockets change, but can’t wait to get it on. Need bobbins and paddock stands as my workaround bike stand won’t work as my exhaust fouls the frame. Another order on the way soon to the shop as well as updates.

[♠️ M77]

Hey,
Hope you had a good easter.

Back to business! , i’ll try to answer your queries in a drink shot style, if it helps.

• Spark Plugs = Basic CR8E or Laser suggested.  You have CR7E, there has never been a real need for them on our climate to be fair. Also hyos love the 8 grade spark plugs.   Threads OK, engine isn’t overheating.   Center Cone is brownish, mixture ok in 5th gear, what mods are on this bike ? exhaust and intake?
  Black ring, suggests slightly sooty idling (rich mix) or plug isn’t best or electric system is a tiny bit held back (common on stock sparking parts of carby bikes)
• Show us the compression tester ? is it a proper brand or unknown ?
• Oil Drain Plug normal,  its catching flying metalic shavings by the clutch and likely general engine behavior (not much), but proper quality oil will stave off this need to have much debris.  The coloured plugs on the site catch whatever is thrown at the clutch side on the oil filler cap.
  And coloured plug for the bottom has a stronger magnet too and less prone to seizures or rounding off.
  Its not uncommon to replace worn drain plugs eventually. its good insurance.
• Take a pic of the stuck intake clamp?
• Engine bolts i sent you = Max torque is 7lbs please. They are steel but engine is aluminium. Take 1 by 1 because if you take them out all at once , gaskets will give way and oil leaks out.
• What kind of exhaust do you have that prevents you using paddock stands or show us ?

[Stu]

Good Easter thanks. Hope you had a good one too. Was definitely biking weather. Went out after the little service and love that other bikers give a little nod when you pass them on the road!

Anyhow, to business. Only mod I’m aware of is the full black widow stainless steel system straight through from cylinders. Air filter looks OEM (no branding visible) and not ventured to look at the jets yet. Bike was bought in Portsmouth and the exhaust at the same time so perhaps other mods from the outset but nothing i can find in the paperwork and last owner didn’t think so. I did think it was maybe running a little rich when starting as strong smell of petrol, half choke needed together with a twist of throttle (keeping revs low) to start,  but didn’t know if that was normal?CR8’s from you have definitely made an improvement, although not any significant power increase the rideability has improved. Seems to be a little snappier on the throttle and its now idling a little lower when warm. Cold start also slightly improved, but need to turn her over a good few times before she fires. Really want to get the carb off and cleaned, but worried about the clamp. Will get some decent photos posted of the offending rusted clamps tomorrow if it helps. Any advice on removal would be greatly appreciated. Totally don’t want to end up breaking a part that’s hard to replace like the intake manifolds.

I dropped her flat on the right side today (left the disks lock off when pulling out of a parking space and she’s heavy girl, Felt shame!). Nothing major and managed to hold it so it wasn’t a big whack. Bent the brake lever a little, but still well usable. There was a pool of petrol where she landed. Presuming from carbs as it was around that area and it did take much longer to start, after I‘d left it standing for 10 mins. Few questions about this. Would this petrol be from the carb? If it is should it be holding petrol once the engine’s killed? If its running rich is this overfuelling the carb and the reason why its holding petrol? Is it not the carb at all but from somewhere else (the tank as the petrol was sloshing when I dropped it)? Any idea where i can get a second hand lever (only)?

Was going to fudge together a bodged stand with a thick piece of wood and two axle stands under the frame, but the exhaust fouls up that idea, ands probably wasn’t a good idea from the start. Don’t have paddock stands at the moment, so will be investing in a set together with some bobbins from the shop when I get paid at the end of the month. Probably the oil plugs and filler bolts as well.

Compression tester is made by Roadster (?) and was £20 on line, with an additional bike adaptor i had to buy separate as photo. Might be able to speak with a car mechanic (friend of a friend) see if he can compression test or lend me his tester. What would be good/expected compression front and back? Are my readings way off?

Thanks for the advice on bolts. Thought it would leak fluids in some places if I took them all off at the same time, but didn‘t know if I needed to drain oil again. 1 in 1 out approach is great and much easier. Smaller torque wrench on the shopping list now as the one I’ve bought is min 20nm.

 

[Stu]

There may be one other mod. Pretty sure the EGR has been blanked but will check and take photos and post tomorrow.

[Stu]

Got pics of the rusted intake clamp, but can’t upload? Option to add photo from my phone disappeared.
marcel – will do you them.

[Stu]

Well. Update time after a productive weekend!

• 520 kit fitted. Front and rear sprocket and 520 chain. Little more top speed, but significantly better gearing. Fun and games fitting though. Son lifted the rear (the gym membership I pay for came in useful at last!) and axles stands on either side of the swing arm. Sturdy enough to take the wheel off. Rear sprocket removed and replaced with uprated one from kit. Bolts tightened to torque specs. Few questions. Does this impact speedo reading at all seeing as both sprockets are now larger? From other posts the original speedo readings are a little off, so perhaps makes the reading more accurate now? Also noticed there was no rubber donut thing in the rear wheel behind sprocket. Should there be one and if so anyone have any idea where I can get one from?
• Engine casing bolts swapped out and torqued to as per Marcel’s guidance. Small bit of bling, but also more reliable (a bunch of the original bolts had rusty heads, some with pitted shafts and not in great condition so better to be safe than sorry).

Been out for a 60 min ride and the 520 kit makes it much more rideable, and together with NGK’s (from Hyoriders shop) a noticeable improvement from when I bought it. All in all well worth it. Never going to be a super speed monster with only 125cc, but going to look at ways to increase low and mid range torque. Think clutch plates are on the hit list in a short while which should help overall.

Waiting on bobbins (from the hyoriders shop), and new paddock stands front and back (motorcycle parts warehouse). Both will hopefully make things easier for maintenance.

Loving the big little bike still, even more now I’ve gotten oil under my nails! Have tools, will use them!!

Check out the photos, including my axle stand workaround!

[♠️ M77]

Thanks for sharing the pics, just seen them now. Will feature bike in shop galleries 🙂

Hope you get your cush rubbers soon!  Drop a review here if you like the chain set!

Uprated Japanese 520 Chain & Sprocket Kit :: Hyosung GT125R GT250R GT125 GT250

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