no disrespect ment at all just curious

[Anonymous]

anyone on here purchased a 520 sprocket and chain kit for there gv 125 that lives close to greater manchester that will let me test there bike has im curious to see and feel the change…..

has i say no disrespect to anyone im just curious

[Kernow]

Hi, unfortunately I am in Cornwall so you cannot try mine unless you travel a long way.  Everything is miles away from Cornwall.

The 520 kit gives you the stated better wearing and stronger 520 setup. But most importantly it changes the gear ratio from 3.692:1 to 3.167:1.

The engine can easily handle the change in ratio so you get higher top speed and longer distance between the gears.  Bike remains very pokey, I would also say faster accleration due to gear length. If you go for it and do the 520 upgrade you will not regret it. The upgrade will turn the 125 into a near as damit proper cruiser.  Eats hills and you can hit 80+ mph which means better rpm when at 60 – 70 mph (70mph at about 8500 rpm instead of flat out). All the gears and rpm suit traffic better whether in town, main road or on dual carriageway.

It is worth doing, the difference is very noticable.  I did not get mine through Marcel but bought the sprockets and chain after doing a little math. I won’t post the sprocket sizes and chain length due to respect for Marcel.

The advantage of buying from Marcel is all the math is done, the sprockets and chain are top notch and you get the front sprocket lock washer (which it is important to replace).

[Anonymous]

just ordered tom  😀

[Peter]

I’ve considered doing this myself and as I need new sprocks and chain I’ll have to go for it me thinks

[♠️ M77]

Peter wrote:

I’ve considered doing this myself and as I need new sprocks and chain I’ll have to go for it me thinks

Quote

Go for it!
Send me an email of your riding style please and what kind of roads you use so i can customize the gearing if need be  , otherwise i will send the kit as optimal as i can be for both accel and top end  (balanced but better than stock 😉 )

 

[Anonymous]

honestly i wish id not bothered spending £95

im sorry if this offends but the truth is my bike still does 62-65 indicated but instead of 10,000-11,000rpm its now at 9,000rpm …….no 70,80,90mph  like the reviews

my honest opinion is try using a gps speedo to get the true speed

you will be shocked on how far out the speedo is on the aquila gv125

[Carter]

If your bike I’d doing that speed at a lower rpm that also means it will go faster at 11,000rpm I agree it may not be alot but you can’t expect alot from chain and sprockets in term of top speed because your engine is still the same power ect if you are expecting noticeable changes in speed you should think about losing any unnecessary weight from the bike and put performance ait intake and bigger jets in the carbs and maybe even an exhaust so you have alot better acceleration and then alter the gearing(sprockets) further towards top speed…. The chain is the money as that is the crucial thing that has to be strong enough to handle more power than that bike can put out they are often priced on strength as that is their purpose

[Anonymous]

Carter wrote:

If your bike I’d doing that speed at a lower rpm that also means it will go faster at 11,000rpm I agree it may not be alot but you can’t expect alot from chain and sprockets in term of top speed because your engine is still the same power ect if you are expecting noticeable changes in speed you should think about losing any unnecessary weight from the bike and put performance ait intake and bigger jets in the carbs and maybe even an exhaust so you have alot better acceleration and then alter the gearing(sprockets) further towards top speed…. The chain is the money as that is the crucial thing that has to be strong enough to handle more power than that bike can put out they are often priced on strength as that is their purpose

Quote

go look at the claims on the review of this kit

[♠️ M77]

I have tried to advise the customer in a few occassions that it will be easier if the bike had clearances done and a deep clutch inspection.  I wanted to know every nook and cranny of the bike including seeing the plugs “with my own eyes” , so i can see any potentioal bottlenecks , and i would have advised some mods to do free.

He has already done 1 carb mod which is altering his slide needle to improve the 4-7k range. (mid range,) that’s well and good.  he would pass a stock GV, just a little bit side to side.

He said it’s had an engine swap and mileage is beyond 10k miles.  It needs clearances doing.  I’ve advised the valves really do matter when it comes to top end performance.

I’ve advised it doesn’t always need to be modifications but it can help sometimes on the “lower end”  so it has a bit more oomph to start off before it runs out of puff at the top gear

He has not told me what the maximum speed was in 5th gear and what rev range it was on, this is with a 520.

<hr />

See the screenshot of another customer below ::

This aquila is brand new and he is the only owner and he was my test dummy when helping me choose the correct sprockets during the time i was doing 520 kits for GV125 aquilas. No one was doing 520s for the GV’s years ago after all, the UK isn’t the only country i send chains to.  There is many GV owners on here from spain and other eu countries where the 125cc exist, they seem to ride a lot more than we do! I hope they prove me wrong!

Make of this image below of what you will , my other client has not done any mods , he is an elder man with full bike license rides a pan big cc tourer. He kept the Aquila as a winter hack.  The only mod so far was the chain from this shop.

is his speedo out?  GPS either way is in the 70’s and he is in 4th gear trying to get past a car that was moving too slow on a 70mph road.

This is a dual carriage way, look at the horizon, the road is FLAT (mostly) , there is not much downhill here, if anything, the road inclines up a little bit.

 

Moving on, i advised that if the clearances get sorted out, she will be happier.

I would not send Roy a 35T sprocket because his engine isnt ready for that,  I can go as low as 30T  (which 30T is unachievable on a 125cc no matter how tuned, 30T has a theotrical max speed of 100 mph, it just won’t happen)

So i customized his gearing to peak at 90 and while that is well and good, it dropped his revs down to about 1,000 rpm less which is intended, as the aquila should scream less.
If i drop the revs too much, it won’t accelerate as good, i had to make a balance, the UK has hills and what not, i do not know which rides he uses.

I would gladly send him a 30T sprocket, he will still moan the bike is not doing 90mph. Will it be the 520’s fault?

No, he hasn’t even maxxed out the chain kit I have sent him yet, which suggests a garage must check his clutch and clearances. He says it’s good.  Korea will say the plates should be a certain thickness and a spring should be this way and that way , from the service manual to suggest if the clutch is “good” or “wanning , but rideable” , mind you the engine is 10k+ old.  It will not be the same as a bike that’s 1,000 miles run in.

Clearances matter. We could spend £400 trying to go fast with mods, but clearances will draw the motor back if its hot and valves close/open too soon, hence clearances to be done.  In the same time, his mechanic will do a COMPRESSION test.
150 psi is awesome (example)  , 120 is OK but at the limit.   150 psi with engine that’s got clearances of 0.10 & 0.20 dead on will be faster in general  (modded or not)

Then henceforward, it’s much easier for the 520 chain set to do justice.

Now then, the GV 520 kits are meant for 2 things  (longevity) as i know aquila riders like to go on long stretches and carry things (panniers!)  . A skinny 428 will wear out much sooner.  I can attest to the fact the hyosung bikes i fix in my own workshop i always change to stronger chains , & 2 clients have had issues that almost caused them an accident.   Is it Korea’s fault ? No , they ship with Oring chains standard, but after that cheaper 428 chains are fitted by garages once the bike comes of age.

Next, KRMotors and any owner that’s bought a brand new aquila will quickly realize the top speed is 70 ish screaming at 13k revs.  Is that healthy? No.
It’s all well and good to drop teeth on a 428, but you loose either top end or acceleration as dropping teeth is more dramatic than a 520  (520 cog teeth are more spaced out, if you want to be scientic,   a 14T 520 will have a circumferance of 10cm and a 428 14T will be 7cm  (this is an example). Rotation size and spinning size mass matters if we are to get scientific, not just the “teeth” count. Gear ratio matters in this case.

He said he has already put a 49T on the 428 which the aquila uses 46 or 48T factory. I was wondering why it won’t hit 70 in the first place. It’s got a 49T, he needed to get lower, which i did on the 520.

Now henceforward he hasn’t maxed out 5th gear at 13k revs to tell us what speed it was on 520. He already knows the bike screams less.

GV = To scream less, and more durability when carrying panniers or going extended tours (hence “Cruiser”) , it’s never going to be a drag racer.  80 is possible because the engine is “designed to do so”

GTR = uses the same GV engine and its factory “82-88mph” =  GT520 kits  (more accel in general, just a little bit, no point me focusing on top end as it already does 80+ factory and ofcourse chain longevity over a skinny 428)

GT= Same engine as the GV = 80+, though its naked so it will have some wind drag slighly.

GTR is the fastest of them all ,  GV was purposefully dropped to 70 by Koreans by means of certain restrictions and weird gearing , so bike is already screaming.

80+ is not impossible ,  you want less revs = happier valves,  you ain’t racing on a drag strip but you want to be able to go 70 in 4th gear and 5th gear now becomes your overdrive.

Whereas on a stock GV you’re already on 5th trying to scream to 70.

I say all this with love please ❤ , but had i known more in depth of the motor , i would have advised a little overhaul job with your mechanics professionally and they will follow the “service” manual. I will then talk to them what the bike needs to meet the client’s desires, i can get super technical with them. Once its in spec, then pimps happen after.

If in any doubt, please ignore this website,  research the top end speed , and watch youtube videos of riders attempting the national speed on a “stock” GV and look at their rev counters.

If in any doubt again, please trust the Korean engineers when they mention what to do when bike has speed issues in troubleshooting section of their service manual.  Also follow what they say to the T including clearances, carb, fueling,  their service manual has a lot of detail and a LOT of checks happen for every part inside the bike including measuring things to see if they are at their limits or not, and beat their limits.

You will be much happier, don’t spend on any more mods, just do what the service manual says every page, she is past 10k after all and so will she show her mood after wards, even if its a little bit better, it’s better than nothing or can leave her alone and enjoy for her what she is & allow the mechanics to sort it themselves , just don’t use cowboy garages or you will waste money again ❤

[Carter]

So the issue you have here is you’re trying to get a worn out engine to run better/faster than standard in that case I would fully agree with Marcel valve tuning is the heartbeat of a 125cc engine it is the most crucial part of keeping your engine at its best therefore you should be doing your mods and gearing when you have your engine 100% otherwise no matter what you do you will never know how fast it should be or how much difference your mods have made

[Anonymous]

hey marcel i think we need a chat on the phone.

i never said that id fitted a 49t rear sprocket or a 13t front sprocket

i said that is what was on before NOT fitted by me

how do you adjust non adjustable valve clearences

bike did 62-65 indicated before at 10,000 rpm   (gps speed app around 56mph) so speedo is out

now still 62-65 at 9,000 rpm (no faster ) lower revs

if you wanna come look at it marcel be my guest

i even offered to ride to you.

[♠️ M77]

Sorry I’ve been away at inlaws this weekend, so i stand corrected that you did not fit it yourself the original 428s.  As i will quote your exact reply:

the 13 front and 49 rear was on from when i bought it…..theres nothing in the side panniers the chain was a gold one the type with rubber seals…. its had a engine swap done by oiley bikers top speed before was 62mph using gps at aound 1100rpm the bike has done 19.488 km its had new ngk spark plugs new ngk uprated caps new ht leads new CG125 coils carbs are standard i use castrol power one 10w 40 oil plus run orangey brown. v power fuel

 

to be honest with you i dident think it had adjustable valve clearences the bikes speedo has indicated 70 before but in reality using a gps app it was doing 65mph

 

Using the gearing commander  (it’s on google) so you can play with the settings if you like) it’s a decent source as it is on par.  I played with various 428 sprocket settings on a GV125, the 13T and 49T defo drops the mph for sure, it’s not factory set up.

I do own aquilas and GTs , i know the speedos are out, so the speeds i mention when selling chain sets are what it says on the dash, i can’t try just one bike , i need several donors with varying engine mileages , some modded bikes, some stock and i have people who are test dummies to help me and i send the kits before i go retail, i can’t take back what i say online, i’ve way too many witnesses now (which is a good thing), 10% has to be removed when GPS is used. No speedo made by hyo i’ve known so far is ever the same as GPS.  Even most cars are like this,  sometimes 10-15% is removed from any speed to actually slow down people  (even though they think they are truly driving 70 in motorways) but no they drive at 80mph on the dash so it’s 72ish on GPS, are they taking a risk with smart-camera motorways ever increasing, yes they are but its what i see everyday.

Don’t worry too much about the chain set for now, we’re going back to the engine internals (cams, clearances, clutch basket, compression, etc)  &&  (plus whatever else is attached to it, be it fueling or electrical things to make it come to life)

If one has a digital hyosung dash, and it says 33, going down the estate, the light poles in the street will have a matrix display saying “Your Speed xxxx”  –  33 on dash is always 30 by the matrix display in the street  =  that’s 10% removed from the dash.  44indicated is 40.  I can see why  80 will drop to 70 gps as any speed is always factored in around 10%.  Common figure , some dashes are less out  (5%) , some will be 15% out.

The revs is the main concern on a small cc bike, we want it screaming less at the “same” speed it did before a change of modification  (ie. chain set) ,  the valves on hyosungs don’t like staying at 13k revs for long. The valves start floating at 12k revs.  All GV125 engines peak their power at 10-11.5k revs.

Please take a look at the service manual below which another member has kindly posted on social media, as you’re on it already,  if it helps.  I know trawling through the forum has all kinds of books, but i’ll organize that much sooner with another site design change.

Link to manual here
https://www.facebook.com/groups/345623961212/permalink/10156911795301213

it is specifically for your bike, so it has so much detail.  The troubleshooting section at the end will back up the “clearances” being mentioned multiple times (even if engine idles fine),  the challenge now is to beat everything the engineers have said in the book.  Trust them than any of us here , they made the motors 🙂 . You’re a mechanic yourself fella so the book’s instructions will be familar to you in some pages read,  if not, a local garage can do what the book says and don’t pay them until it is so.  (Some garages are just cowboys, sorry to say, they really are, so i’d watch them!)

If the manual has something missing, tell me i’ll upload it again directly to this site.

Have a great weekend ❤

 

 

PS. I really do need to start making more tutorials of engine jobs unless Korea’s english is perfectly fine ,  I can try to break things down to layman terms.

Like this tutorial here on clutch ( i do need to update it anyway)
https://hyoriders.club/forums/topic/tutorial-hyosung-gv-gt-125-250-clutch-plates-replacement

 

[Author]

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