♠️ M77

[♠️ M77]

Ucvmn wrote:

I ended up using my power tool; I don’t like those noisy things, but I had no choice.

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We use a tool called “ROTOR” locking tool , as i don’t trust “power guns” near motorcycle engines  (too much torque on some of them and a crank is expensive part) ,

 

it works with clutch baskets too.

 

 

[♠️ M77]

I assume you have read the 2 tutorials on carby removal ?

Unfortunately it looks like we’re headed that way because we can’t be riding on white plugs , it is way too lean to make economical sense to ride it, if something happens , the damage will be worse for your wallet unless you have a backup engine to swap! 😬😬😬

While it is off , it will be a chance to give one full overhaul before the bitter winter sets in. and replace parts , i’d get the parts it needs first so you’re prepared.

[♠️ M77]

Welcome ❤

If you need help, you can always post in the Technical section anytime

you can show off your new ride here or make your own journal!

Owner's Photography Thread (New Rider? Show off your ride…)

Working on your motorcycle is a good learning experience , and your hands are essentially free labour 😉

[♠️ M77]

Based on your reply

• Both coils are GOOD, but almost at service limit.  Keep them.  Saved a bit of money for now there…. Upgrade whenever you feel like it it or if it goes beyond 16.1K with its OEM cap attached.
• Upgrade to NGK caps at your own leisure, that should help even more and your resistance goes down a lot (easier to light up them plugs)

I hope you learned something, you will be your own wizard soon!

[♠️ M77]

See this picture below from the service manual

• Your carb uses OEM 125 size and 122.5 jets
• Check your “Slide Needle” is on Rich mode instead of Lean  (click here for example on 125/250cc)
• Check your “Mixture Screw” , screw all of them slowly to zero (clockwise) , then undo them counterclockwise 2.5 full turns each.
• Get new spark plugs again  (Use only CR8E)
• Check carb float height is 7mm (click here for 125/250cc example)
• Clean the carb hard
• Test Ride and let us know.

Also do not forget to upload pictures of your spark plug colours.

 

[♠️ M77]

Well done!! 👏👏
Glad you shared your fixes , this will also help anyone else that stumbles on this thread 🙂

[♠️ M77]

Well done ,  you’re getting there. 👍

So i will break down the plugs in simplest terms so you know what to expect   (Get a fresh set of CR8E x 4 of them) part of this process is unfortunately called “Plug Chopping” , gotta go through a set of plugs until she is happy, as old plugs wane fast and dont behave the same if they dont work well  (“Fouled up”) .

Your plugs:

• “Dark Black Ring” = Rich Idling / Low air / Dodgy mixture (i hope not) / Pilot Jets too big / Ignition Coil + HT Cap (easy fix) / Choke used during startup or while riding etc… (choke enriches the carb)
  _________
  Ideal colour = English brown tree trunk / Milk Chocolate / Brown Leather Boots = I know, but best way i can describe a ideal shades of brown or “Tanned Grey with Brown Tinge”  ==> Means starts should generally be easy in icy days or not even needing a choke.
  _________
• “White Pure Center” =  Main Jets Blocked / Slide Needle is wrongly put to the lean setting / Air Leak at high revs / Low fuel flow at high revs / Main Jets too smll /
  ______
  Ideal Colour = As above ^ . White is never a good sign because it would mean there is very little fuel at while riding and bike is going to overheat faster , the oil in the bike breaks down hard (sooty black oil much sooner) , plug breaks down , holes in piston may burn one day , compression loss due to piston rings cooking in extra heat, and so on, i believe you will get the gist of where we are going with this.  We would rather a dark center than a white one , at least “slightly” rich MAIN JETS or SLIDES means high speeds help the bike cool a tiny bit on each intake cycle , as petrol has a tiny cooling effect (tiny) (Another reason GTR bikes for Hyosungs have bigger jets at rear than the front due to the fact, it gets less air flow to it hiding under the plastics , plus the front engine is in the way , just how v-twins are.)

I hope this made any sense ?

Let us know your test for electronic sparking coils later on, take your time, it’s a stormy week anyways.

 

[♠️ M77]

Have you looked under the bike to see if the weather has possibly gone inside the cylinder (bad location but i digress, they were trying to make the bike pretty, i hope i am wrong and the designers knew what they were doing)

You can see if the cylinder is moving properly with brake pedal press

Next step, if you have your calipers out  (both front and rear) , clean them out with brake cleaner hard

Then press down each piston gently until you hear some kind of “woooossshh” sound at the rear cylinder pot (with the lid open) , and if you see bubbles, it means air was in the system

Then do the same with rear caliper, clean it and press down the piston until its flat inside the caliper , so you can hear any wooshing sounds and bubbles apearing at the top of the resevoir pot.

Call this “soft bleeding” , if you will but without taking the brake assemblies off etc, it is not fool proof though,  grease the moving parts of the brakes with PUTOLINE RACE GREASE
– Piston lips
– Back of pads
– Axle Bolts for pads to slide easier & less weather rot (temp fix) (Stainless bolts are better)
– Plunger & Lever  (Rear)
– Hand Lever  (Front)

Hope this helps ?

[♠️ M77]

Hey , glad you got the order!

In regards to the carb,  jesus! – I am amazed.   Honestly?

This is probably the strangest reply you will ever get from but needs must , as a brand new carb is about £600 retail (yes, it’s a japanese carb) & rare now due to EFI laws these days making carb makers switch to EFi , and most used carbs from untrusted ebay sources always have hidden problems , i literally have 6x carbs i have to rebuild for everyone else due to owners and garages messing around but i digress….

Follow me….

1. Go to the “middle of the choke rod bar”  outside the carb
2. Unscrew the  “HOOK” that is connecting the rear choke
3.  See if you can the “thinnest wall” spanner to undo the choke plunger out of the carb
   —–
   if it got out ?  Good…moving on
4. Find a local screw shop or any garage , ask them to find a very very short stubby bolt that is the same thread size & pitch as your old choke plunger
5. You will order “MANNOL THREAD TAPE”
6. Apply a bit of thread tape on the actual bolt (to create a seal)
7. Essentially the rear choke is forever cut off.

This will force you now to meticulously take care of the carb, inlet manifolds, inlet o-rings,  cleaned out carb (and also, apply grease to exterior parts of the carb that move and are prone to rusting due to front tyre chucking water at them or road mess)

How to always start in winter without choke?

• Laser Plugs , Uprated coils, NGK Caps & Good regulator
• Engine clearances done  (get proof of it, it will have figures of all 8 valves and their shim numbers) , every 4k is valve “check or adjust”
• Carb + Air + fuel parts all spot on.
• No mixtures on the carb messed with
• Always give the bike 7-10 mins (minimum) & max 15mins before you can ride off, this will keep your engine healthy
• Engine Compression in check (relies on the above statements i said) ,  ie. bad timings , valves or excessively overheating motor can burn a hole in the piston.
• Use Motul or Silkolene oil  (must say ESTER on the bottle)
• Fuel = Always e5. No matter what
• Fuel Lines & Filter Clean.
• If bike is going to be stood for a while, trickle charge battery indoors and drain fuel.   (e5 still has ethanol, it can rot things if not handled for ages , and winter moisture = water in the air, bad mixtures you don’t want in carb or tank)

I think i said a lot but ….

In regards to the choke plunger again,   plan b would be to leave it disconnected inside the carb if you can’t get it out , it should essentially be its own bung, then for extra measure apply a tiny bit of metal based JB welded on that crack, and KNOW THAT IT CANT EVER MOVE AGAIN! 😬

 

In all cases, to preserve the carb, the front of the carb will be taken care of more than the rear as it essentially has one lung to to speak to cough her alive in dead of icy winters!

I will have a carb body listed soon on ebay in about a week or 2   (Just the shell, since owners can just re-use the guts of their old carbs)

[♠️ M77]

Don’t worry about Stockport, we collect bikes all over but lets save that for last, let see what you can do as your hands are free labour , she might want you first.

i will try not to overwhelm you today, so go for a ride with CR8E plugs,  come back and show us the plug colours for front and rear cylinders , then i can fully understand with a trained eye where your “mixture” situation is and if the bike is overheating or not.

In regards to electronics;

• If the reg says 14.3V , that is good.  What numbers do you get at idle and what numbers do you get at 5k revs ?
• We will test the stator soon, (it also is responsible for sparking believe it or not, as the CDI reads the stator’s “coil” to tell when plugs shoud fire up etc, if the stator “coil” wanes, you get dark plugs you see but ….speaking of coil….

Sparking Plug Coil test. (Too easy).

• Remove the left side cover hiding the coils.
• Remove HT cap from the spark plugs.
• Turn on your multi meter.
• Switch your meter to 20,000 (thousand) OHMS
• Put the “RED PROBE” inside the  HT Cap
• Put the “Black PROBE” on the “engine valve cover bolt”  (or any unpainted area of the frame that isn’t rusty)
• ===== Tell us how much ohms you get front and rear.

Part 2 = Try get a picture of the coils and caps.   I have a suspicion about it , if the owner put CR7 (totally wrong plugs), he probably put wrong coils which emphasizes your cold starting woes (probably!)

Part 3 =  Sparking Coil Test (Primary vs Secondary resistance)

• Keep your “BLACK PROBE” of the meter on the frame
• Disconnect the “Signal Wire” That is SPADE Shape   (Front is yellow/black and rear is white/blue)
• Put the RED PROBE on the “Terminal Connector” of the coil itself.
• Reduce the meter down to 10  (Ten) Ohms  (As low as you can get)
• Tell us the ohms for each coil.  I will asdvise them if they within factory spec as per korea’s service limit rules or replace with upgraded ones

In all cases , I would recommend “NGK” caps you saw at this store & Laser Plugs & Ignition Coils = Now you will literally never have to accuse the sparking electronics for letting you down this winter, plus you can do it yourself without needing a garage.  I will provide a tutorial on how to fit caps if need be.   Do not ever buy “CR8EIX (Blue Box IX Plugs)” as Hyosung 125’s generally do not like them and they tend to wanne fast after 5k miles. If want NGK’s best plugs for the street use, it would be their Laser type.
NGK Caps rarely fail, too trusted of a japanese brand at this rate.
OEM Coils = Common, we upgrade them all the time to ones that “resist” less, so bike makes use of them right away.   Can’t blame Hyosung for it as they didn’t make the coils, just outsourced part with their logo stamped on it that’s all. Much like 90% of owners upgrade the stators and regulators and call it a day.

 

That will finally leave us with the carb and airbox and intake being a special delicate event!

Liqui Moly is good! – Don’t use redex though, if you want to try “prolong” the idea of taking off the airbox and carb cleaning (ie, you need the bike for work during the week i guess) , go to Halfords and get this  only

 

 

Regardless if you have half tank or full tank,  pour the entire bottle in.   (Aggressive method perharps? but follow me here…)
Your bike’s mood should improve slightly or more as it drinks down its fuel , the cleaner will collect stuff long the lines, pump, tap, carb unit, and it burns away from exhaust.  This is the product i use on all my bikes, usually once every few months  (well some pumps at the stations are not all perfect) , good thing we also have fuel filters, so keep an eye on that fuel filter for gunk build up.   Remember we want to fix the easy parts of the bike because the “carb & airbox” will be one of the most “patience” testing things you could do but boy you will learn a lot and it will thank you ten fold.  (Even if we have to remove them to access the intake manifold orings under the cylinder heads)

 

[♠️ M77]

Darius wrote:

Hi everyone, I have just bought 2016 hyosung GV125 Classic 2016 , I have done full service, new oil , filters , plugs etc , and what issue I have is basically difficulty to start up when cold , it will take up to 30seconds before it will start , as soon bike is warm it starts straight away, have you got any suggestions what else I could check or adjust?

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Welcome and to your friend on here too lol.

Okay, how about this?

• When was the last time the carb even had an ultrasonic clean? (a very big deal)
• Valve Clearances?   (Loose valves make it hard to start cold, heat tends to narrow gaps , hence easier starts, but power will be lacking in general , so either, get some proof the valves were done in the last 4,000 miles as per Korea’s rules, it is a lot of valves for a 125 after all 😬
• What fuel do you use ? E10 , E5 Super ? which stations ?
• Have you ever had the airbox off ? (We have 2x tutorials for that in the tutorial section)
  (Bad “o-rings” under the manifolds , make it quite annoying to start , however engine can reach 100c degrees, eventually the orings will cake and need replacing, since it will allow particles and dirt to mess up the air system and the carb since they are upside down sending air down the engine with atomized fuel for plugs to spark properly)
• Owner messed with the jetting or carb mixtures?
• Replaced the plugs ? – Be ready to replace them again with another set of normnal CR8E (only that size please) – If the air system or carb system ain’t right, the plugs foul easily
  (you’re welcome to post plug colours on here to see how well it is doing)

It’s a lot to ask I know, but don’t rush, i will have a proper answer based on data you gave us.  Assumptions could mean false diagnosis (i said this, when it was actually something else etc) , so I want to be as accurate as i can 😉 , considering i fix these bikes all the time.

[♠️ M77]

You will need to report back the voltages you get from the stator unit @5k revs in AC , all 3 wires must have identical readings  (hence it’s called a 3-Phase stator)

A stator that is about to give up the ghost tends to slowly fry electronics (anything that is attached to the harness, has an upper limit of how much “current” it can tolerate vs amps)

Regulator = Common, it if its Hyosung branded, don’t buy another one , they always fail since Hyosung doesn’t make them , it is an outsourced part , hence you probably won’t find OEM regs sold on this site.  ebay is fully of fakes , especially those made in China/Taiwan are no better.

 

Also , when the bike is running, or battery is connected

• 3 Pin Plug for headlight must have 12v when you operate light controls
• fuse box will say 12v (without a fuse)
• Regulator connector will say 12v on the red & black wires (it is permanentely on , regardless if bike is OFF or ON)
  (If bike sounds better with regulator and 3-Pin stator plug disconnected, you will need to consider replacing those 2 things, however it can’t run on battery , since even the lights want 55 watts from the stator unit alone)
• pressing the Horn should have 12v , (horn removed)

Hope these tid bits help, keep us posted

[♠️ M77]

It is M7 x 1.00 Bleed Nipple 🙂  , Car Shops will have it too.  It is a common size for older cars also

[♠️ M77]

Hey , use this topic

[Tutorial] How to swap Carb Main Jets – Hyosung GV & GT 125/250

If it is a bike that is currently running, don’t touch the mixture screws, absolutely not required 🙂

Pilot Jets are sold at the shop section   (Send email if needing mains, since they typically go with custom order filters we sell)

While you are in this forum portal, go to “tutorials” section of this forum to find fuelng diagrams.

 

[♠️ M77]

I can hear the exhaust more than the bike 😉

Sounds like few things you could check below

• Air box isn’t sitting on the carb properly (CV vacuum loss to maintain idle)
• Mixtures messed with and Pilots are clogged again. (it sounds like its hunting for fuel to maintain a stable idle)
• Intake Manifolds (more rare than the bike itself!) may have a split from the shop that may have stress fitted the parts instead of being gentle
• Please make sure they did not use stupid things like “silicone” to seal the inlets to the engine heads instead of using proper orings like we have on the shop.
• While the bike is running ==> Look at the ignition coils for sparks flying out of it.  If yes = switch off and replace HT wire immediately replace the CAP , COIL,  SPARK PLUG all three at once , if it is still using standard parts from Korea.
• If it has “IX Blue” plugs = Bin them and use CR8E or NGK Laser only.
• If it has NGK caps , check the HT wires so no sparks is coming out of the cap or coil or loose wiring.  (screw HT wire slowly clockwise until it stops for a tight fit so it doesn’t vibrate out)

If it is “loud metalic” ticks , then

• Cam Tensioner is wanning,  see this topic also below
  https://hyoriders.club/forums/topic/how-to-check-if-you-have-updated-cam-tensioner-on-older-125250-twins/
• Valve Clearances   (if it hasn’t been done in the last 5,000 miles)  Service manual says “Check or Adjust” every 4k to keep the 8 valves happy. Its a lot of valves for a 125!

[♠️ M77]

William wrote:

Winter haha not here in California there’s no such thing! We ride our bikes year round!

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Very jealous!
I do know they have it hard up in Michigan , as i do have some relatives over there lol

[♠️ M77]

Glad to hear your parts are helping you , if you need anything , just let us know!

You got this , do what you can beforte winter sets in 🙂  & keep us posted.

[♠️ M77]

Replace the stator of EFi to Carby Stator , so use your old carby stator
And also use your CARBY flywheel
This is because the EFi flywheel does not work with Carby CDi’s

Next thing, use Size 20 pilot jets and 92.5 + 95 main jets

See full tutorial of jetting here

[Tutorial] How to swap Carb Main Jets – Hyosung GV & GT 125/250

Don’t throw away the old 250 engine, you will NEED IT for spare parts in future 🙂

[♠️ M77]

Personally i have not done this , as i tend to like the OEM setup sometimes.

I know full well the mudguard for the rear is all single piece that allows modifications to the second picture , you can always use existing “locking” mechanism from the OLD main seat, to affix to the new custom spring seat.  As for the “springs” if its a bobber spring style you’re going for, the mudguard gets drilled to support the base.

The other question is that if you ride in the rain, how creative will you get in protecting the electronics under the harness, fuel pump , relays , battery and the like, as the OEM seat with its side panels seems to do enough of a job to keep most rain showers away .

[♠️ M77]

You can take exhausts from either ST7 or GV650 = But your struggle would be “how to i mount it ?”   = Pipes yes , but mufflers will need some creative mounting , if cross-breeding between two bikes.

Aftermarkets = Same thing.  If you can mount it creatively there should be no issues.     ST7 has lambda sensors , so an old carby GV650 pipes would not work due to missing LAMBDA ports , unless you weld one inside.

Electronics = Hyosung uses 7 ECU’s across their EFi bikes from 250 to 650cc.  Very complicated area that needs specific parts you want to change ?  Ie. Even igntion coils are different across the years , even their OHM ratings, there is a lot of sensors too that respond to specific ECU’s
Sentec, Edgetek , Mitsubishi, Daewoo, Delphi Malaysia, Delphi USA,  Motion, etc.   They also sometimes use “certain specific years” of GV650 to use  GT250 igniton coils and its lambda sensor but not the ECU ,  also sometimes they change harness … Ie. a delphi bike , expects delphi sensors on most places with connectors that are not backwards compatible with  Sentec Hyosung models. etc.  It is complicated, it is best to narrow things down to a very specific part you need.

Don’t always rely on part numbers, they do change parts for the same part number for “updated/revised” versions.

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