♠️ M77
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Thank you an also what’s the gearing to make it have a little more acceleration I know it depends on the front sprocket but is it the more teeth it has or the less teeth it has that makes it have that little extra boost?
Hey,
Depends on the stock that’s ready to go , combinations of 13 / 48 , 15 / 42 are the normally the best ones and the chains max out 100-105 , that’s already the limit of the 250 , sometimes i send 13/46 in some orders – All 3 combinations i said , add some acceleration without affecting gearing too much.I know sometimes even a stock 125 has 14 / 52 . Just dropping to 13 without rear, is too much lol. Fast take off sure, but top speed is sacrificed now.
The GD250 uses a GT250 sprocket carrier , but it’s sprocket is now factory 48T instead of 46 on GT250 , i think that probably helped it take off a bit better lol.
Hope i made sense!
Generally over here in UK we use this kit by many 125 n 250 owners.
Uprated Japanese 520 Chain & Sprocket Kit :: Hyosung GT125R GT250R GT125 GT250
Also the best front sprocket aftermarket would be the UK made RENTHAL ones. They are on the shop page.
I am looking to see if I’ll stock up PBI (US) sprocket, i believe i may have found one but will be sure soon lol.
As for chains. You will want to use a japanese one over cheap aluminium copies.
When you go to the bike;
1. Fuel lines, get bigger braid ones which flow faster to carb. Hint. Exhaust notes are deeper (slightly)
2. Open the carbs. Ensure floats are at correct height which is 7mm ish. While carb is open, 100000% clean the jets (mains & pilots) also remove the black slider tubes and remove any debris clung to them.
Bigger jets help and you may get a little torque boost. Search *Carb* on this site to lean how to remove the carb and also swap jets. Plus there is troubleshooting info on carb starting/idle.
3. Use Platinum Laser plugs. They are that good & you will feel its effects through gears. No plug beats these and hyosungs always respond happier with better electrics.
4. Get a meter. Switch to Ohms (20k). You HT cap & the FRAME (unpainted part) must be 6.2k ohms max. As per manual.
This is your entire coil & HT cap together.
HT Cap *on their own* disconnected will say 7k healthy. Race caps have less (= less means better sparking power). Stock HT caps can misfire sometimes. This is common for all stock hyos n their coils. Their EFI coils arent much better!
5. Fuel filter. It will slow fuel delivery if its clogged also. Bigger filters can hold a nice little reserve until the carb drains fuel again without always waiting for the tap. (Stock hint = bike cuts randomly on a fast sprint, then i have tk crank to start it again or sometimes acceleration jerks a bit = this is your fuel system hint including a potential clogged jet in tandem of a clogged filter)
6. Charging System Test. (Advanced)
Rev the bike to 4k max
Unplug the MAGNETO’s 3 yellow wires (plug) near the rear shock.
Meter out. All 3 wires (in different combinations) = must say 70v+ AC (not DC)
If its less than 70v change magneto. Your coils & electrics depend on a good magneto.
7. Regulator. Bike goes no where without it.
Rev to 2-4k. It must say 14v at your battery te rminals (no 13.xx in any revs). Sadly stock ones never do this even though manual says 14.5-16v is best! Most of us including the 650 folk upgrade the stator and regulator to the kawasaki ones (trust the Japs)
Battery. 12ah is required. (YTX 14BS)
Yuasa / Varta / Unibat are my picks.
Key off = battery will be 12.8v charged or higher (the better)
Once this is sorted. Test ride. Then pay attention again to the engine for any top end tick sounds. Clearances are every 4k normally🤙
Over various bikes i owned i found YUASA (real ones), varta (german made), and UniBat are good. Varta my fav.
80% of other brands have chinese grade components inside. Hence it is a consensus to be careful shopping online for batteries due to fakes or duds.
For the hyosung. The correct size is 12ah for good reason, some garages fit small ones with little research. It says it in the manual but they ignore to cut costs. Lol.
Look for YUASA YTX 14BS at halfords , atv shop , bike shop locally (and ideal over online hunting)
However some folk use Amazon
This is it.
Also, Varta YTX 14BS
14BS batteries generally float at £45-60 range. The top 3 i mentioned are trusted brands 👍
Generally you will want to use Premium oil with ESTER. As the manual generally says premium oil is best.
Ester oils are: Motul 7100, 300v, Silkolene/Fuchs Comp 4 , silkolene Pro 4 Plus. These oils are unbeatable to most cheap crude mineral oils.
Fully synthetic beats any semi-synthetic simply because it has extra properties to help your engine , especially vtwins with a lot of bearings!
Depending on the store you visit , buy any oil that has
*JASO MA2* certification due to our wet clutch system10w40 is the normal grade. On summer or hot days 10w50 is ideal! (Best).
FULLY SYNTHETIC is best. ((Anyone that says Semi is best probably hasnt done enough oil science lol. ))
If the bottle says *ESTER* or DIESTER on it , then even better.
My personal favourites (over many years on various bikes)
Motul 300v , 7100
Silkolene Pro 4 or Comp 4
Rock Oil TRM vTwin race oil.Hope this info helps.
Hey,
Welcome to the site!Usually these things are mostly china aftermarket units found online to some varying styles but this is the most common way i’ve seen them fitted on various brand bikes (not just hyosung)
a. Sensor uses magnets near the shifter area
b. The “Neutral” wire sometimes is used to splice together (both dash & aftermarket gear display share the N sensor near the sprocket front)Typically, they should come with instructions with some diagrams to aid in the install process.
There isn’t a “specific” hyo manual regarding this, so this will be classed as a custom job. You may or may not need to splice in to the electrics depending on the unit.
Also this forum contains Service manuals for your bike, read one of them, you will notice there is a wiring diagram of the entire bike laid out on one of the last pages of the book.
Good luck, let us know how you get on!
Hmmm, i’m afraid to say that you may need to replace the whole dash , i think the regulator did more damage to it , so it is better to replace it entirely.
The manual doesn’t tell us how to repair the dash by changing electronics inside , so there is limited information in regards to GV650 dash units.
Welcome to the site!
Sorry I delayed , I wanted to also say you can meet us on one of the annual hyo meets that we do , check out the “events” section of this forum or more specific conversation also appears in the facebook group “UK Hyosung owners club” (Yes, some are still on social media lol)
Maybe you might see us on one of the future meets , speaking of rides.
The 650s are generally good bikes, and a little more torquey than the SV although, both company have a long shared history with engine R&D work these bikes.
Id caution to keep an eye on the regulator , and stator. These would be the common complaints across all hyosung CC bikes , the koreans did try to improve it , but they still fail. As yours is a new bike , your dealer should replace it accordingly if it acts up.
#1 most annoying problem and sadly may void the warranty , is the side stand switch. Even when while riding , your bike may cut out frequently as the kick stand switch rattles away inside , it’s just a really crap unit but i digress!
We usually cut it off & bypass it by joining wires . Our only caution is that don’t set off without double checking the stand is up!
All in all , good TLC and servicing will keep you riding it for years , i do know some of our members on here have had 1 hyo for 7-12 years.
Ride steady, summer is coming!
Hi, I have 2011 GV Aquila 250 efi with single silencer, would it be ok to swap to twin silencers or would it cause a problem for the efi system?
The trouble with the EFI hyosungs is they don’t take kindly on pipe changes, as a few owners can also atest to that.
The trouble is with the Lambda sensor that’s inside the pipe which senses gases going past it, it will trigger the ecu to either intervene in the fueling process or dash throws an error.
You may get away, with keeping the 2-in-1 stock system (best for performance wise) and then expanding the and can hole (make it bigger at the exit, about 5-10p size max)
The other problem is the end can itself. this would be looking at making sure the end can is as long or little shorter than the stock can and must have a baffle with a hole of a 2p size or less.
I hope this info helps!
Hopefully someone can think of something I haven’t thanks again
Hey,
The pilots are too big. Size 15 front and rear is plenty. (You said you up-jetted, this assumed to be higher than stock. You did not say what size.)
Pilots control IDLE & slow running. Your problem could be this too.
Air mixture screws must not be tampered with by any garage (They are idiots if they did) as the service manual discourages air screw messing , and for good reason.
Main Jets should be 90 & 92.5 = Unless the bike is doing 90-100mph, it won’t need size 95 which is 250cc
Some of the information below is copied from other topics which I replied into. (other topics have pictures & much deeper replies, so have a browse too.)
====================================
Start your bike. Rev to 4k rpm. Your battery “must” say 14.5v at the meter , otherwise change the regulator. All electrics depend on how healthy the regulator and stator is.
Anything 13.xx is not good. So bare minimum is 14.5 up to 15v as specified in manuals.
This is your charging system (& sparking juice)Big sparks come from better electric supply.
======================================
Speaking of sparks. Remove your spark plugs. If they are “RICH BLACK” (Your jets were too big or the diaphragm slide needle may be on the rich setting, if the garage touched this), a healthy bike will show “DARK BROWN” plugs. No sign of ash blacks anywhere.
==============================
Before you start the bike again, grab a multi meter. Switch to 20K OHMS (20,000), then follow this…
1. Red wire of your meter INSIDE the HT CAP
2. Black wire of your meter on the FRAME (NO PAINT) (Find a shiny area!)
3.—>Your meter must say UNDER 7k ohms max!Hyosung says your ignition coils must be 5 – 6.2k ohms max. If its higher, you found your sparking / bogging issues. This is way too common, I digress! – I’d ditch the stock coils at all costs & the bike will be a lot happier (AND less annoyed spark plugs).
Kawasaki units win.
======================================Lastly, Grab yourself some “Platinum Laser” racing plugs. No other plug beats this , period.
You WILL have a better throttle with such instant plugs.The stock plugs foul up too easily & hence the peformance of your bike wanes quickly.
Lasers last 2yrs / 50k whichever comes first, if your fueling system is nice and good too.
Sorry I took ages to reply, let us know how you get on. Good luck!
way to work around this is CDI unit under the seat to cut the green & blue wire & then use some electric tape to secure it.
It works on “GT250-M815″ stamped CDI’s only, and it’s minimal.
Changing the coils will do better on throttle response than a small cdi cheat which helped old 250s to please eurotree huggers (emissions maybe?)
The effect on 125cc means the stock coil gets a little push up in 3-6k rpm (which is the area the bike tends to take off from lights)
M795 or GT”125-M815” are already full power as far as I’ve experienced them on my donors.
Some report placebo effect , like the SV650 coils are the same as the old 650 lol.The original poster may not need to worry about the cdi as there aren’t restricted like an ECU is .
True, the hyo’s biggest let down is its heavy wheels!
If the koreans had mad the wheels lighter instead of heavy cast metal, it would have weighed as much as another similar sized 150
Frame is only 30kgs lol.
The older generations models are generally a little bit beefier from stock than the new shape RC
RC is a bit lighter than old gen, except it was let down by slower parts fitted to it , so we’re talking 88mph vs 82-84 on RC.
You may consider a lithium light battery to cut some weight off, better tyres have less weight , the stock suicidal tyres weigh a tone of bricks! and ofcourse, ditching the stock parts for upgrades seems to do them better justice now.
More torque can be done on the extreme scale such as better custom valve springs, carb needle , jet tuning , ht wire changes , k&n filter, 250 cooler so it runs colder, etc…. but that’s a topic for another day lol , some tuning can be individual based
/Shop/ section at the top of site has the tried & proven bundle kits not found elsewhere.
And ofcourse i can always order genuine parts or your local dealer can do it too. Just email me.
Most sellers online can be fishy, so i dont talk about them or even give them a spotlight! as many people complained on facebook.
Speaking of facebook. Sometimes lads are breaking bikes , you make inbox them too if on budget. Group is called UK Hyosung Owners Club
Hey,
Welcome to the forums! You could also find us on facebook too 👍 (to be honest we all came here via FB lol)
Congrats on the purchase of your bike. As a mechanic / trader dealing with these hyosungs , i wont bore you with a mega long reply but this information below is based on feedback on most owners and my own experiences , so here we go.
Front to back!
– Front Brakes = Goldfren Ceramic Pads. Others are cheap crappy organics
– Headlights = Philips Xtreme Vision H1 and Osram Nightbreaker H3
– It hates stock plugs. Laser Platinums win. IX is boring & overhyped.
– Electrics are very common but fear not, just swap over to the proven japanese upgrades ( REGULATOR × IGNITION COILS × NGK HT Cap × 100v Kwak magneto). Take it from me, stock electrics are like bipolar women!
I would replace these ^^^ electrics before throwing any extra money on it. You will be glad you did!
– good vtwin engine. Following the manual schedule & regular TLC will keep it happy. It loves Motul and Silkolene ESTER oils.
If the bottle doesnt say *ester* dont bother. Enough said 😉
Get fork protectors around your forks. Stops grit from damaging seals then leaking. Also forks are soft. So upgrade to 10w fork oil to make them less bouncy.
Battery must be 12ah/14ah rated. As per manual . Smaller batteries cause too many problems later on; some fake mechanics put wrong ones.
Rear Caliper is known to get muddy. So monthly clean up and greasing protects the brake pistons from seizing up.
The Hyosung doesnt have a rear hugger from factory thats why.
Hyosungs hate bad weather but fear not. Make sure monthly , the old girl has a nice wash down. Protect the wires from weather attacks. Change as many bolts on the bike as you can to STAINLESS STEEL. Trust me.
Buy a bottle of ACF50. Its the best friend for dealing with winter rust. Spray the whole bike (except plastics n brakes!)
Then it will leave a nice film of anti corrossion protection all over it.
Carburetors are from a Yamaha 600 bike and upside down. So it is critical a carb is cleaned from time to time to maintain optimal power.
After all. *foreign micro particles* can clog the jets up. Our salty roads dont help either lol. It is eventual.
Change the chain to a 520 upgrade its not just for power but trust me , the stock 428 WILL snap. The hyo is 180 kgs loaded. You will quickly drain the wallet dealing with crappy 428 chains. Too many people know this. 520 kits are also much safer as they cant let you down in the middle of countryside
Tyres. Strictly Michelins or Bridgestone , Pirelli only. Cheap tyres is asking for a low side in winter. The stock *shinko* and *avon* tyres are just woeful woeful & suicidal!
If you have stainless exhaust or upgrade filter. Its mandatory to change jets!
Hmmmm, this is the common stuff. So i hope this info helps. More deep science is found in the manuals as you browse the forum. Tutorials and Owners book go a long way to keeping the old girl happy.
If i missed anything let me know!
Hey Wellsie,
Only the 250cc , it uses a chain that is off a suzuki , it shouldn’t need replacing unless the bike has had a hard life or its around 50k old ish…
However , the “tensioner” on the bike is automatic, that deals with the tension /& chain stretch as motor spins, the tensioner is usually the “first item” to replace as they do wear out more than a cam chain does.
One way of checking the chain is to listen to it as it spins on the motor.
another way is to remove the top valve cover- inspect cam sprockets for wear (the teeth eventually wear down)
- touch the chain, if it feels saggy , it could be sign the tensioner is worn or the chain may need replacing
the service manual only has this information about timing chains.
if the image doesn’t go full screen when you click on it. Save the image to your PC or Press & Hold on your Phone to download it.
Hope this info helps!
what can I use to clean my exhaust I got black grit dots stuck on it
Some wire brushes, very very fine sand paper, then sponge etc = Use AutoSol paste on the parts that are rusty 👍
Spray ACF50 on the pipes , a little = leaves a nice dry layer when exhaust warms up , should help it stock more salt attacks on it.
Im going to try either tomorrow or sat when its dry is try force to turn it from where it connects to carb with pliers which im hoping this does work as I be out of options
Remove the adjuster off the carb.
Get some wd40 to soak for a bit , then get mole grips
Bit it hard , then turn left to force it to undo itself.
The road salt / muck near the front is what causes them to seize. Not always easy to get on their own.
Also, get some ACF50 or grease –> spray in to it , so that it will keep the area lubricated.
Hey,
I received your email regarding this exact topic – So I’ve replied back to you.
Hope this helps.
Hey!
You may have hit the nail on this one , as indeed *C* without digits doesnt seem to indicate any actual fault.
You may ride as usual but just keep a good eye on all parts to ensure nothing rattled loose under braking?
Dare I say though, what if you checked your brake switches arent loose or attacked by weather?(rusty contacts). Hopefully thats not whats causing them to act funny under a full brake (where bike even shifts its weight to brake force)
If this was a different brand, i would have guessed it was something to do with an ABS system and ECU talking to each other (something’s a bit off but not to panic yet?)
As for Hyosung usually the ECU will tell the exact code (eg. D45) if some device is failing or acting intermittent.
But i hope this bit of reply helps & hopefully its just nothing really👍
But update us if something changes or If i missed something.
You may also disconnect battery for few hours or overnight max. It may or may not force the ECU to reset the C code. (There isnt a lot of research data ive collected yet on GV650 EFi/Ei’s to see how effective this is. So you may try)
Do I start chucking money at it!?
Probably,
The bike still isn’t happy = Look at your own spark plugs , will tell you exactly if its electrical / fueling / or poor air system. (Rich vs Lean vs Poor Electric Sparking)
Bike will not ride perfect unless all 3 work in tandem (air / fuel / sparking electrics)
I would read my replies above ^ on this topic = write down as a list. tick off every single checkpoint.
Fueling Parts & Carb OK & checked over? = then we are done with the carbs.
Then the electrics or plugs would be your enemy , I would go here below …
(GV125/Gt125 = same engine, same carb, same coils = same behavior)
(Follow my replies in those threads, as i go quite deep on electric dramas & HOW to test them yourself)1. https://hyoriders.club/forums/topic/gt125r-no-power-between-4k-8k-revs/
Yes,
Faulty Coils & Regulators happen to all hyosungs. They are just a cheaply made parts that die out eventually. The japanese win when it comes to electrics.
— > Could also explain your plugs not doing their job or otherwise fouled/annoyedRemember this always:
High revs / RPM needle stuck high / very slow to drop revs down = Air Leaks (anything air flows thru) or CV sliders stuck or choke is not off (still on choke)Boggy / Jumpy Revs / Laggy = Electrics (inspect all including plugs , can’t stress spark plugs enough) or Fueling Drama (anything that petrol flows through)
