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I just completed exhaust on my GV125S. I used the muffler from HD sportster 883. Highly recommend! No power loss, nice sound, not too loud. The only drawback I see is that the bike gets up to higher temperature a bit quicker. I’m getting two bars on temp display after 15min on idle while previously it was taking a bit longer. All the rest works very well. Muffler is legal and has Euro4 standard.
I have the same bike and also looking for the muffler. I plan to wrap the exhaust pipes + install better muffler.
Megatone has db killer which you can adjust (3 screws) but overall it’s loud
I was also looking for this one: https://www.silverstonemotor.com/en/silencers/13924-ixrace-hyosung-bobber-125-300-2018-2023-gamme-custom-black-exhaust-silencer-ag4022sb-not-approved.html
It’s matching the bike very well and it’s not that loud…
Oct 13, 2025 at 8:27 PM in reply to: Valves adjustment – too tight? -GV125S 2022 Clearance Adjust #20986I managed to replace the shims. The only problematic rocker arm was the exhaust on front cylinder. All the rest were sliding sideways super easy.
What I did with the problematic one was the following:
I unscrewed and removed this part:

which holds two rollers on which the rocker arms are placed
I wiggled the rocker arm and moved out slightly the camshaft and the roller. It was enough to get some extra space and slide out the rocker arm… after that, all was easy, shims have been replaced and the clearance has been adjusted properly.
Engine fired up immediately. I can hear the valves chattering when engine is cold but at least I know that the clearance is the right one. The idle is smoother and more stable now.
I used 1.85 / 1.90 shims on intake and 2.0 on exhaust so not bad for 5k miles engine
Next step is clutch upgrade and sprockets + new chain when Marcel will send me the parts π
Cheers All
Tomasz
Oct 10, 2025 at 1:57 PM in reply to: Valves adjustment – too tight? -GV125S 2022 Clearance Adjust #20975Hello Marcel, here is the video: https://youtube.com/shorts/5IljoL_IzjI
Oct 9, 2025 at 10:42 PM in reply to: Valves adjustment – too tight? -GV125S 2022 Clearance Adjust #20973Take a quick look at this topic below, as i did post some clearance values:
https://hyoriders.club/forums/topic/gv-125-s-valve-clearance/embed/#?secret=QXbF27h6tQ#?secret=248HWE90L9 Also , report back to this thread when you spin your engine 10x , then recheck clearance, it might change 0.05mm to 0.07mm , although let the bike cool down overnight and do it on a cold morning as heat does affect the clearances. If the markings inside the engine look like pen-markers like the green one, thatβs what Hyosung did during production, as long as nothing looks broken.
Thanks Marcel,
The engine is completely cold. Clearance is way too tight (0.03 on intake and 0.04 on exhaust) so I need to replace the shims.
I was able to move the rocker arm sideways on rear cylinder but I’m not able to move the rocker arm on the front cylinder (exhaust one is stuck, intake can be moved).
What’s the tip to move the rocker arm? I tried TDC and also every other position of the camshaft but it’s not moving sideways π
quick update: I re-adjusted again the clutch cable ensuring that there is 4mm slack
went for the ride, 5th gear goes in without any problem… BUT on the display it doesn’t show. It stays on 4th. Only few times the dash showed 5th and few times 6th for few seconds (although the gearbox has 5 gears only)
Is there any sensor which translates gears to the dash?
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