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Welcome to the site and indeed the biking world, may the Hyosung add many miles under your belt!
I will try to guide you the best i can so the bike runs better, it definitely sounds common the issues you’re experiencing especially as we approach the cold season.
Pretty bikes, but Korea could learn a thing or two from the japanese when it comes to electrics, but i digress, let’s get the 1st thing out the way.
1 – Under your kickstand, see if you can spot a “switch” ?
or maybe the previous owner removed the switch and “JOINED” (brown wire and black wire) to fool the bike thinking its still there (Bypassed)
If you said you saw 2 electric wires under the frame, perharps they could be the sidestand wires? = Cut the rusty part of it –> then peel off some fresh wire – > join both wires -> waterproof tape or good tape (lots of it). Voila kickstand is bypassed.
The reason for getting rid / bypassing the kickstand switch is because it does 2 things very annoyingly
– Rattles and causes the bike to cut out while riding
– Makes it hard to shift in to 1st as it then cuts engine off immediately.
For that reason again many of us bin in it and protect the remaining joined wire away from weather attacks (water and electrics dont like to mix)
2. Spark Plugs
You can take one out? If it looks ash black (plug is fouled or the sparking system has gone weak making it prone to cuts and hard starting in the cold)
If the plug says “CR8EIX” – I would advise to get rid of them and use a standard plug “CR8E” or the better “laser” plugs (You can see what they look like at the /shop/ section on the top menu of this site) – Hyosungs dont like the “IX” branded plugs. Stock or Laser wins.
If we can get the plugs right, then our next check is the sparking system so its doing as it says
3. Sparking System (very common on most hyosungs)
Like i said, Koreans could have used Jap electrics but costs had to be cut somewhere i guess!
When you unhook the spark plugs , the “HT CAP” (the long tube that attaches to spark plugs)
That “HT CAP” we call , is another cause of intermittent / random behavior when throttling up or throttling down, when the bike is at hot temps , the HT Cap if worn down/old will start to wane and make the bike move SLOWER (weaker sparking=prone to misfires/pops?)
For that reason , i wouldn’t advise to buy the original Hyosung “Golden” branded HT Caps again, as they will just fail again (lifespan is too wild to measure) and cause problems for the “ignition coil” (more of that below)
Using an “NGK” branded HT CAP will generally make the bike rev a lot better and ofcourse a trusted brand, it rarely fails even under hot temps so you know the plugs will always get the spark signals transmitted to them.
Your garage may not know this but will most likely attempt to dismiss it without testing it on his meters or use the standard again (rather than switching to a more reliable NGK branded one)
It is number 10 on the picture below: (Spark plug “HT CAP”)
So in short, HT Cap = responsible for sending spark signals to the spark plug coming from #7 which i will explain below
4. The same picture above ^ , at #7 these 2 circular shaped coils are attached on the frame 1 behind the oil cooler and 1 under the airbox of the bike. This item is more crucial than the #10 HT CAP
The coils are probably #3 on the list of parts many owners change to use better coils on their bikes, I too also suggest better coils.
The ignition coils are responsible for sparking your plugs. The bike won’t move anywhere or be rideable if either is dead. Signs of a failing coil are always these
— Hard starting in the cold / takes ages to warm up
— When engine is up to hot temps = it is prone to cutting off while riding
— Throttle feels sluggish or heavy (ie. as if on a leash)
In conclusion, a healthy hyosung will benefit from the NGK HT caps and better coils, winter mornings will be better for you and it also.
5. Regulator (see #5 on pic above) – Probably the #2nd item that causes electric woes once it starts to wane. General consensus in the community is to change for a better one
I think you can check this yourself and change it as it is located on the LEFT side of the rear bike, that giant square block item with 3 yellow wires + 2 red/black coming out of it.
The regulator is what charges your battery and supplies running electricity to the whole bike, so its crucial this object works optimal , otherwise just like number 4 ^ (coils)
– Starting will be harder (as if battery wasn’t charged?) (slower cranking is a hint)
– The lights will be more yellow n duller until you rev up
IF LIGHTS GO BRIGHT if you increase revs, its time to change it.
– If the “DASH” spazzes out or gets very dimm while trying to crank start (battery hint)
If you have a multi meter at home, I can easily explain how to test your coils , HT cap, regulator voltage – You might save some mechanic bills if you’re confident to do some self diagnosis and also some mechanics don’t always check everything (always rushing / taking shortcuts)
Back to the regulator, if you start your bike and rev up to 3000 revs, your battery should say 14v on the multi meter switch to V20 (20 volts)
if there is any “12.x – 13.x” readings = regulator is toast or dying away so bike will generally perform poorer and these things always blow up when they die. It’s very cheaply made sadly.
if its beyond 15v in any revs = change right away. Once it hits beyond 15v the battery will cook and blow. Hyosung has been through various regulator designs on their bikes, they are all rubbish if i am brutally honest. When i service customer hyos, i check electrics starting with the regulator & battery so i know the electricity supply is right, before attacking other parts of bike.
These things i mentioned so far , you can see them at /shop/ section then click the “pictures” in full view , those bikes you see are when the customers fitted the parts by themselves , they were a literal “swap and go” kind of job, so no business about chopping up things / botch jobs lol etc…
Ofcourse the mechanic can always fit them too. It is better you had the replacements in your hands and tell him to fit these , than him trying to use whatever he finds in the shop that may not always be suitable (then problems resume again)
Okay, so lets move on to fueling. = Any form of bogging / cuts / poor riding up hill can be a sign of a clogged fuel system. Let’s try the 1st trick.
—–Fill 3 bars of fuel max (maybe £2-3 in the tank) or your display should show 1/4 or 2/4 of fuel.
—–Go to Halfords / Asda / Poundland = Get 2 bottles of RED “REDEX”. (each bottle is called 1 shot)
—–Fill 2 shots (2 whole small bottles) of it in to the tank , ride hard until bike is goes in to the “RED” (if speedo is mechanical) or “1 bar” if dash is digital display, then put fuel normally.
The bike “should” be a tad bit better than it was before. It is sort of like a “mini soft fix” to unclog the fuel pipes , and your carburretors (huge silver thing under airbox). the redex will burn away as you ride.
To improve fueling , hoses are changed to colder braided ones (hot engine thats why) and stock pipes must be changed after 2-4yrs or they rot inside (hence clogging debris flowing down the lines to the carb!) – On top of that , the filter is quite tiny , we change to the large ones almost 3x the size, such huge filter best trap a lot of particles for a long time even as far as 10,000 miles that way you will have a less clogged fuel system feeding your carbs (carburettors)
The carbs ==> then feed clean fuel to your spark plugs! – So we are attacking “fuel” and “electrics” at the same time because they are as good as each other (air / fuel / spark)
If the situation improves when the fuel +vacuum pipes and filter was beefed up (tutorial here) …. (and also here…) , the bike should start better and feel a little bit throatier at top gear (less excuse to starve of fuel with bigger lines)
Looking at those 2 links, would you be familar with the process ? if not , a mech can change the lines and filter if you supply them to him. We wouldn’t want cheap lines just to change in 2yrs again, the braided lines will last you 10 years, so you will pretty much forget em once fitted, should i say!
Okay lines done, let’s make sure the carbs are the last resort. If what i say above ^ has been done, the last thing would be your carburettors needing a clean (from old particles clogging it)
At the same time you can upgrade its jets so it improves its fueling (tutorial here…..)
At least that way if a carb needs cleaning , it can be beefed up a bit at the same time just to improve general cruising or top gear riding. A mech can do this if you supply jets, but i must stress HE MUST NOT “change the hidden mixture screws” whatsoever unless he is a professional carb tuner (not just some amateur) – Koreans don’t even tell in the service books to touch the hidden mixture screws (they are fine for the 125s almost spot on tuned at the factory)
Only “Main Jets” change. “Mixture screws” are hidden away usually , so you won’t even to worry about them anyway.
Now, we should have a bike that splutters less as if trying to misfire or bogging out of fuel after a fast long sprint etc..
Fuel out the way now!
This one should be a little easy and a fast checkup, – Lift your tank up and place a long fat object under the tank bolt hole and “yellow frame” plate that it sits on or someone to help hold it up for a moment.
—Disconnect the “2 pipes” under the tank and “sensor wire” (yellow n black plug)
(see one of the tutorial above which has pics of tank removal)
(use the same 2 links i shared if unsure which hole the pipes fit back on , under the tank)
The tank sits away somewhere safely, now next , unscrew the 4 screws on top of the airbox that mount the air filter. Take it out.
If its DARK yellow towards a brown ish tint = it’s likely dirty (remember we want no particles escaping in to the engine) – you can change it now . They last about 6-10k and discarded for a new one. = Bike responds a LOT better simply.
A clogged/stuffed up filter will just make it hard to accelarate sometimes and makes throtte action problematic (its either bogging low down then it surges forward like a rocket at high revs etc..) A fresh filter generally makes the engine run a bit cooler (more air is back to normal) and your spark plugs will be less sooty as they need good air to burn the mix fuel too.
Less air = more unburnt fuel likely escaping = pops/gurgling/ etc.. in some senarios.
If the filter looks like WHITE GAUZE material inside , it’s trickly to clean it because it has a snorkel-plastic inside (also a restrictor,but i digress) – Air Filter Cleaners for bikes generally clean the foam and gauze material filters and they also get some oiling spray afterwards – the gauze material of the filter traps fine dust better when its sprayed on after a clean , but filter has to dry first. then oil it a bit afterwards.
K&N is also gauze material, its red because of its oiling too (done at the factory) however K&N filters are also classed as “high flow” or uprated meaning they flow way more air than a stock filter does —– this requires the carbs ^ to be upjetted (see carb talk above ^)
A clean standard filter is better by far over an old uncleaned one or badly clogged.
“YELLOW” filters can’t be cleaned as they are made of paper = Hyosung switched to GAUZE material filters since 2010 i believe (and they flow better than the old style yellow ones)
Right then!….. now have done “spark / fuel / air ” related stuff to the bike , i should expect it to behave way better than you say initially and definitely suggest the good TLC before winter comes – No fun doing stuff in the freezing cold lol. Autumn is still warm i guess!
Last shout…… If a battery is 2yrs old or more – A garage must test it that it CAN hold charge and doesn’t DRAIN so soon (makes it annoying to run = hint , lights flicker at idle speed)
Battery size is 12AH – Brand to use is YUASA YTX-14BS or Varta 14BS (german) or good 3rd “UniBat 14BS” – Any other brand, walk away, most have rubbish cells that cant handle 2 winters even. (Smaller eg. 7ah are not ideal but some have fitted them to save money purely)
When daylight comes back, maybe you can show us better picture of the pipes / wires you speak of – but i was guessing they would be on the left side of the bike frame one of them being a brown color wire going towards kick stand. (switch removed maybe last owner forgot to bypass it properly) either way the switch is annoying so bypassing it is a good idea.
Speaking of bypass = Ensure the cable from your “CLUTCH LEVER” going in to the frame isn’t frayed or kinked etc…
Inside the handlebar lever = the CDI will sense that you pulled in the clutch before starting/or bike is in gear.
The clutch “switch” is inside the hand lever itself with a wire sticking out going to inside the frame, if the switch is faulty , it will for sure cut the bike out while riding or instant in to 1st gear
I think i have covered as much as i could ? for you to check yourself – I could go on , but if there is something i said not making sense let me know! – Excuse any grammatical errors, typing away as my thoughts flow out lol.
Lets see how you get on , keep us updated.
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