520 Upgrade Chain & Sprocket Set (Full Conversion Kit) – Hyosung GV125 Carby Aquila
The only complete conversion kit strictly for CARBY GV125 Aquilas. Stop fighting for top speed and constantly adjusting a stretching 428 chain. This kit is guaranteed to improve your acceleration and cruising speed from the first ride. #Guaranteed.
- ✅ Accelerate Faster: Better 1st gear pull and faster 0-70mph times #Guaranteed.
- 🛣️ Touring Reliability: 520-spec hardware outlives all stock 428 setups.
- ⚙️ Much Lower Revs: Comfortable cruising at 70mph+ without engine screaming. #Guaranteed.
- 🏃Go Faster: This kit can do MORE than 75-80mph! #Guaranteed.
- 📦 Full Bundle Kit: Chain, Custom Sprockets, Washer, & Stainless Bolts.
❌ It WILL NOT fit EFi GV125-S 2019+ Injected models.
Description
The Hyosung GV125 Aquila is widely regarded as one of the best 125cc v-twins ever made, but factory cost-cutting left it with a major bottleneck: the 428-pitch drivetrain. In its stock form, the GV125 often feels “under-geared,” screaming at high RPMs just to maintain 60mph. Our #HyoRiders Exclusive 520 Conversion Kit is the definitive performance overhaul, replacing thin, high-maintenance hardware with a heavy-duty setup that finally allows the v-twin to breathe.
💎 Touring Performance with the Daily Reliability!
This isn’t just a maintenance swap; it’s an engineering upgrade. By moving to a 520 pitch, the chain surface area is significantly increased, distributing the load more evenly and virtually eliminating the “stretch” issues that plague 428 kits. Real-world testing by seasoned GV125 owners has shown that this conversion transforms the bike’s character: top speed is increased to a potential 85mph+, and 5th gear finally feels like a true cruising gear rather than a desperate struggle for revs.
| Optimised Gearing Accelerate to 70mph faster than stock. |
85mph+ Potential Unlock the true top-end of the v-twin. |
| High-Carbon Steel Custom 520 sprockets for maximum life. |
Japanese Gold Chain RK/DID/EK Quality for zero-drama touring. |
📜 Confirmed Fitment Guide (Carburettor Only)
The results speak for themselves. We have sold hundreds of these kits to riders who want a “Fit and Forget” solution. This is a 100% direct “Swap & Go” for the carburettor years. Forgo the 428 skinny chains and trust the heavy duty 520 versions with more meat for those long distance touring , and you can trust them to keep you going if you also carry heavy luggage.
❌ NO EFi: Does not fit 2019-2026 EFi Bobbers (Different engine/chassis).
Reference OEM Part Numbers: 27510H41732 | 27510H41721 | 27600HG5150
To reach the full speed potential of this gearing, your engine needs to be crisp. Pair this kit with our [High-Performance EBC HD Clutch] for the ultimate gearbox GV125 setup.
🔧 Expert Installation & Gearing Notes
This kit is supplied as a complete bundle. You don’t need to source anything else to complete the conversion:
- Premium Components: We include a custom rear sprocket (Silver or Black), a Yamaha-spec front sprocket, and a high-tensile Gold 520 chain.
- Hardware Included: Includes a genuine Hyosung Front locking washer, plus 4x stainless rear sprocket bolts to replace your rusty originals.
- The Gearing Win: By moving to 520, we provide a more stable rotating mass that handles v-twin pulses significantly better than the flimsy 428 standard.
📧 FITMENT QUESTIONS? Email us directly. For technical tutorials on chain tensioning and real-world owner reviews, visit the HyoRiders Forums.
Additional information
| Weight | 3 kg |
|---|---|
| Dimensions | 30 × 30 × 4 cm |
8 reviews for 520 Upgrade Chain & Sprocket Set (Full Conversion Kit) – Hyosung GV125 Carby Aquila
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GARAGE PICKS // ADD TO BUILD
-
NGK LASER Iridium Spark Plugs x2 – Hyosung GT/GV 125 250 650 Models
£29.99 -
Uprated Ignition Coil – Carby Hyosung GV125 GT125 GV250 GT125R GT250
£29.99 -
Oil Filter Service Kit & O-Rings – Hyosung GV125 GT125R GT125 GV250 GT250
£9.99 -
NGK Uprated HT Coil Spark Plug Cap/Covers [x2] – Hyosung GTR GT GV (Various Models)
£34.99
EXPLORE // RELATED PRODUCTS
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Rubber Damper (Rear Cush Drive Absorber/Sprocket Hub) – Hyosung GV125 RX125 GA125
£24.99 -
Front Engine Sprocket Nut – Hyosung GV125-S EFi [Bobber 125 S]
£15.99 -
Sale!
Renthal Racing Front Engine Sprocket (for 520 Chain Kit) – Hyosung GT125R GT250R GT250
Original price was: £35.00.£33.00Current price is: £33.00. -
Premium Front & Rear Wheel & Sprocket Bearing Kit – Hyosung GV125-S Bobber EFi
£30.99
Your Hyosung parts hub genuine & aftermarket parts + upgrades with UK & worldwide shipping.
David (verified owner) –
Just had this fitted big difference good deleviery aswel
Luke –
This was my major upgrade on my GV125. I can’t recommend this enough. Has greatly improved the performance, especially up hills.
Moustache Man (verified owner) –
Took out the 125 for a test spin and wow i am absolutely amazed.
I’m amazed at the rev range that it now provides, i can cruise at 2500rpm doing 30mph in gear 5, it actually hits 60mph in gear 3 which is crazy! I can cruise at 70mph at 8000-8500 revs, whilst beforehand I would only be able to just hit 70 at max revs, around 10500 to 11,000rpm. This means i can safely commute to work with the bike running at 7000rpm doing about 60 to 65mph which is fast and means the engine is under a lot less stress!!
Those gains are insane, however, the top speed is even more impressive. I was under the impression that the sprocket kit wouldn’t add power, but just shift the power band instead. Which is actually kinda correct. With the stock bike, I only managed to hit 70, barely 71mph.
With the new kit installed, I managed to hit 80mph today on a motorway. That’s insane! So fast for a 125cc!
Thanks for your amazing customer service, keeping me updated throughout my delivery
And thank you for the sprocket kit, it has sure made me happy this christmas. The bike is wonderful, and the acceleration too omg! It’s crazy! It gets to 0-60 in no time
Absolutely wonderful, would highly recommend this modification, so cheap and the chain is a lovely golden colour. Plus the chain seems a lot thicker than the stock one, so it’ll definitely take a couple thousand more miles than the stock one. I love it!
Joe Banks (verified owner) –
Upgraded the chain and sprockets on my GV 125 c, to the 520 chain, and what a difference it makes. From pulling away for the first time after fitting the differene was clear. Smoother and faster transference of power to the back wheel through the gears and fourth really does feel like fifth.
Really happy with this feels like a new bike. Cheers Marcel 😛
Joe Banks (verified owner) –
I have to agree to pretty much all Moustache Man has to say. Not had the chance to hit the motorway yet but was running up hill at 55 in fourth. Previously would have been struggling to sit on 50 uphill, I am bigger than average so it is to the bikes credit that it manages this :p.
Oliver (verified owner) –
After reading the reviews and speaking to Marcel I decided on getting this kit and I’m glad I did. Great quality parts and I have noticed a change in performance. I can now get 90mph out of it, which is crazy for a 125 cruser! It will comfortably ride at 70 all day and acceleration has improved to for safely getting away from idiot drivers haha! Would highly recommend
roy (verified owner) –
the 520 kit does actually work it changes your gear shifting altogether 5th is more like a 6th gear
i have had 70mph out of my aquila gv125 2008 reg and im around 18.5 stone.
of course i in my last review did not think much of the kit but i was in the wrong ( FOR THAT IM TRULY SORRY)
MY CARBS WERE AT FAULT
standard main jets are supposed to be both 87.5 ……………………….MINE WERE 82.5 BOTH
standard pilot jets are supposed to be both 15…………………………..MINE WERE 17.5 BOTH
so after doing the upgrade mentioned on here main jets front 90 and rear 92.5 MAIN JETS
and PILOT JETS 15 and 2 1/2 turns out with the mixture screws PLUS balancing the carbs .
fitting irridium plugs
fitting upgraded ngk plug caps found on here
my bike has gone from doing 55-60 at a push slowly………….TO A VERY FAST PICK UP AND 70MPH AND BELIEVE ME WHEN I SAY ITS FAST ENOUGH….
LASTS WORD GOES OUT TO MARCEL FOREST HE IS TRULY A GOOD GUY .
Balazs Wittman –
I just installed the kit and it’s amazing!
Feels smoother
And I gotta do more upgrades by roys review!
I feel like slowly making this bike better and better
Customer help is also 5*
You guys really helped me out with all! Thank you!