Valves adjustment – too tight? -GV125S 2022 Clearance Adjust
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Bike Model = : GV125S 2022
Hey Guys,
I need your advice regarding valves. I just bought the bike and I’m checking the valve clearance. I think it’s way too tight as I can push barely 0.05mm 🙁
They way how I check it is the following:
I turn the engine until TDC (ex Rear):
I ensure it’s really on TDC (vertical line):
and then I check the lash. I can barely put 0.05mm only, through exhaust valve (intake is even tighter):
it’s like this on both cylinders. In the service book, there was a first dealer service at 1000km (so they probably set the valves)
I’m very surprised and confused as the bike runs just fine, starts like a charm, has acceleration and doesn’t overheat. Am I doing something wrong?
One thing I noticed is a strange color on the tips of the rocker arms… what could that mean…?
Please let me know what do you think. I’m ready to change the valve shims to make the proper clearance but wanted to double check with you first
Thanks
Tomasz
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Take a quick look at this topic below, as i did post some clearance values:
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, that’s what Hyosung did during production, as long as nothing looks broken.
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Take 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, that’s 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 🙁
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Does the shim come out if the engine can be spin until the rocker arm is at its highest point ? (This is just checking if the arm is not bent or anything)
If not , show me a video (upload to youtube => mark as “unlisted” , so it’s only found on this forum , get the share link) or a picture upload here.
If the engine you say sounds fine when it is running with no issues , i suspect there should be nothing stuck.
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Hello Marcel, here is the video: https://youtube.com/shorts/5IljoL_IzjI
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If you see the metal unthreaded part , it should be stopping the exhaust arm from moving too far away from the spiral thread (and not touching the intake arms). In the older models , we still had to remove the cam shafts. In fact hyosung has made 2 versions of the engine one that uses a screw-top to adjust and yours is classic shim style
Like this one https://hyoriders.club/forums/topic/tutorial-hyosung-gv300-valve-clearance-check-correction-guide/
I will double check later if there is another way to get to the shims without taking apart the cams away , i envy some newer engines that have a newer screw top , makes life so much easier.
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I 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 🙂
Cheers All
Tomasz
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