♠️ M77
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I can’t edit the previous post, so I’m writing another one.
I have done my homework properly and know that valve lash affects piston compression.
I have checked them and they are:
FRONT – 6,73kg/cm2
REAR – 7,65kg/cm2
It should be 8kg cm2 minimum, so i suspect you have gone over the “safe limit” , as per service manual but the bike is still operational.
Next time you do this ===> Pour a tiny bit of oil inside the RUBBER intake pipes , so that oil will go inside the cylinders
Then see if the compression improves?this will help determine if we have to look at piston rings or a possibly scratched cylinder (A cylinder is easier to replace)#
Keep in mind also, if you or previous owner ever removed the cylinders or changed cylinders (they did, i can see you have mixed size cam tensioners) , then it is possible some compression loss is due to bad gaskets ? It is just a thought . Very common on cars , but you are lucky that if a gasket has problem, your engine is not burning blue smoke (water radiator coolant has mixed with oil!) – Your GT125 only uses oil, so the worst is burning oil (plugs will be oily and very sooty) and loosing compression overtime. It is advised to check ebay for a cheap piston and cheap cylinder as emergency back up. Korea is not making any more cylinders for carby 125cc bikes , so they only make parts for Fuel Injected GV125 now (it wont fit GT)
Also it will be advised 100% to buy spare cam tensioners , it looks like we cannot trust the ones you have. So buy a backup on ebay that’s cheap.
Also don’t forget to get tensioner gaskets! (I have loads), if you re-use tensioner gasket, you will burst oil there, the chains spin a lot of oil!
Also, if you ever get time, remove clutch cover ===> look at the rear cam chain crank, hopefully the right side of the crank does not have damaged teeth causing chains to dance and skip around and knock#
The left side is tricky as you will need to remove the flywheel and magneto, then look at the crank teeth there too
If you go this far, you might aswell replace the cam chains
Another chance with the gap on valve;
Front
0,03 (IN) 0,12
0,24 (EX) 0,26
Rear
0,11 (IN) 0,11
0,25 (EX) 0,16
I’m crying right now…
Front intake is too tight. Try to aim for 0.13-0.15 as perfect mark.
Rear = It will need re-doing as both EX & IN are on the tight side , if the engine gets hot, you will get problems and possibly cylinder head damage as hot heat reduces the clearances even more, so it is like we are “chocking” the bike’s neck and it can’t breath like it used to.
I’ve uploaded them here for you. Just click the “Add media” button when reply, so it uploads directly to the site. Google Drive is a good backup! (⭐)
That regulator is very big! :-O , where did you even mount it ?
I hate doing Forks , so good luck , as sometimes it is a stressful job doing USD forks, when your forks are apart , get “FORK GAITERS” to protect the chrome & seals from bursting!
10W fork oil is good. 15W is too stiff , factory is 5w but its too bouncy!
This may sound stupid, but i trust you already did that but can you tell us what compression is on each cylinder?
As you follow the service manual , i won’t need to explain how to do it but if you get stuck , just reply here again.
Also, when the noise comes from engine –> Get a screw driver and poke the tensioner –> put your ear on the other end of the screwdriver — > ask someone to rev the bike a little bit, so see if you hear any abnormal/weird tensioner noises and cam chain slapping hard ?
Did also check each camshaft is correct ? and checked cam-shaft bearings are OK? – Sometimes previous owner puts a “Rear EX” camshaft in to Front Cylinder and problems start
Check compression as mentioned before and let us know the results.
Compression test?
Bike needs to be warmed up 1st => then get both spark plugs out ==> crank the bike for 5 seconds ==> get compression readings and let us know ?
I can see the ECU plug has gone funny, so try to clean it with contact cleaner but NO LIQUIDS on the ECU itself. It would be miraculous if you found a brand daewoo ECU again. Daewoo for 650 & 250 have historically been sensetive ECU’s and most difficult to acquire.
While its apart, you would also want to go over the harness like a fine tooth comb.
Regards
If it fits , why not but…. if its too long, you will bent it eventually , also the swingarm has a very narrow space to work with , so if the springs are fat, it will hit the swingarm 100%
As found out by another member on a GT650R , was having suspension issues because someone else fitted a 250R shock! – So he got a 650R shock for his 650 and all was better and solved
Also you may run in to the issue that the “Y” bone under the swingarm will 100% hit the frame if the shock is too long and it may not slot the bolt (too long/too far out)
You will be wise to measure your old shock first (bolt hole to bolt hole) and dimensions of the fittings etc to try make sure you get another 1-to-1 copy (or close to it) , also hyosung is a nearly 200 wet kg bike (especially the GTR) , you want the shock to handle it.
I have spent days dredging the dark corners of the interwebs and found nothing but cloned websites of cloned websites. I was concerned about the stainless piston rebuild kit as there is a warning sign next to the GV650. Something about it only working on the silver and not the black calipers. I have the black rear calipers on my 2008 GV650 efi
Yes because Hyosung even changed the rear calipers of the GT650 sister to a “dual opposing” piston caliper and it doesn’t say “TCTC” anymore.
So if in doubt, attach a picture here of the calipers or just email me regarding the brake lines we discussed privately.
But i did had to add warnings for 650cc , they did change calipers all round even the front later on.
As you have a 2008, we should be OK!
2010 EFi – I assume Daewoo ECU but does it have a /_\ triangle logo on it? Then it could be mitsubishi.
Are you able to click “Add Media” on your next reply and attach a picture of the ECU? I could pull up some instructions on how to get error codes from the ECU based on the ECU
(If picture uploads are an issue with your device, tell me if its Android or iPhone , what error message it says if forum fails to grab the image off your phone or tablet etc)Check resistance primary and secondary of the coils? what values are they?
Also check HT Cap isnt cracked or damage but be suspicious of them not sending sparks , it does happen and we usually switch to NGK caps. If coil actually gets power to them, then sparks must come out.
Check Stator Pickup coil resistance and their plugs (or check stator isn’t fried inside but drain oil 1st)
You want to be sure every connector on the bike is thoroughly cleaned and all contacts work , so there is no dead signal on the wire that the ECU is waiting to recieve or send down the line. (Damaged internal/ Shorting wire?)
let us know!
I can’t get an image or link it won’t allow me, the electric start won’t work now either
What was the error message ? I want to fix it as some one else seems to upload pictures OK. So i’m not sure what to look for unless i know what error it says on your end or what it is doing.
If not, upload a picture to “www.imgur.com” and copy the “BB-CODE” and paste it here.
I’m going to overhaul this site this year, believe me so its more fluid to use.
Electrics = explain more?
Answered your other topic. Email me if still needing me otherwise i gave you alternative bikes you could try and also caliper , consider SS pistons sold here, they will get to you faster.
I have GT master cylinders for the shop in stock, they will fit the GV650 but the “clevis” may need adjusting , so i’m 90% sure on fitment.
If not, i can still get you OEM stuff.Simon is correct on the coils too, early Hyosung EFi’s had identical coils to SV650 early models (because Mitsubishi Japan supplied both companies, Hyosung just put their own logo and part number)
TCTC brakes used on Hyosung were made specifically for Hyosung as far as i am aware and the Koreans used their own in-house brackets to make the mounts for them.
Also newer GV650 models had updated front calipers made by Hyosung and Kayaba made the forks with Hyosung mounts.
So “some” of the SV650 early models already robbed parts from the Hyosung but Hyosung was a “parts maker” for Suzuki at their R&D place in Japan. Hence engine similarities but not 100% the same. Ie. I could use the valves but you cant use the same air filters.
As simon said, rear masters are a case of mounting points for the GV650 itself. If you grab an older GSX bike, get their NISSIN Japan rear master cylinder and be prepared to drill a bigger hole to fit your foot-mount where the master cylinder sits.
Caliper – No need to replace it ,if you can just get stainless pistons for it ? Unless the caliper shell is beyond saving ?
There were times where Hyosung and Suzuki had the same SKU’s for a part but it did not mean they fitted the same. ie. front forks off the SV and GV are both Kayaba Japan but caliper mounting points are different. Suzuki had their own rim designs and brake discs (which influences a bit on how far up or apart the caliper can be away from the disc) (280 vs 330mm rotors etc)
Tokico is OEM to Kawasaki bikes.
You can use an EARLY ZX9 rear caliper on to the GV650 back caliper on if you drill and thread 1 extra bolt to the ZX9 mount. Been done before on some german forum , i can’t remember now but i saw that years ago.
Don’t use those Hyosung websites that scammed you, they all clones of 1 guy running it (yes “few people” do get lucky to even have orders delivered) !
If in doubt, email me!Hey Leo,
Got your service filter delivered?And are you able to connect a spark plug (MUST BE “CR8E” only , dont use other plugs like CR7 , CRB-EX9 etc.. like some twats do)
Then make sure battery is charged
Connect the spark plug to the HT cap (front engine)Disconnect the rear ignition cap too
Place the front spark plug to the “BOLT” on top of the valve covers ==> Do sparks come out when you try ?
Also do the same for the rear engine ?
Also , swap coils around
Here is the safest way to remove the airbox below to access the rear coil , take absolute care not to stress down the rubber intake pipes as they are more difficult to get and they split easy! (can’t stress it enough)
[Tutorial] How to swap Carb Main Jets – Hyosung GV & GT 125/250
Stop at step 5 on that link.
Let us know!
if anything looks suspicious under the hood, click “ADD MEDIA” on this forum reply box as you write and click “upload picture” to show us
If you get trouble uploading, just post it to “OneDrive/GoogleDrive/DropBox” and get a public share link so we can view this image.
Hyosung uses the same EFi clutch covers for all EFi models, but they come grey or black.
But the GV650 is “chrome” , and is thicker but should not affect anything as Hyosung did not change O-rings since 2006.
There is some guy from ukraine on ebay making GV650 gaskets , ask him to do just the “clutch only” , he may post one for you to try, since ukraine is a little closer to you than South Korea.
But yes it is a good idea to have the original o-ring gasket as future backup.
Good news, all fixed. Fitted new headlight relay and Switch assembly on RH handlebar, lights work and park light also working. Thanks for all your help, great to have it all sorted. Cheers Paul
Yay! ⭐
Stay safe now
Welcome 🙂
Share a picture of her and do you have any plans for it ?
30,00 miles is very good! Keep going 😉
The Europeans get all the lastest Hyosung models , so i am jealous!
Here in UK, we only have 2020 GV125-Bobber and GV300-S
I am still waiting for Hyosung to import GV650PC 2025 and GV250-DRA model 🙁
Hyosung left Australia (according to multiple reports on the forum) , I hope they did not leave the UK market lol – USA/Canada does not get any new models since 2018 which is crazy (USA/Canada did get RX125 / RT125D Hyosung but in very very small numbers)
I wish i could comment experience on GV125-X but we don’t have it yet in UK
For temp sensor , check the “brown wire” under the dash = use a meter to make sure the wire is not broken along the harness.
For Speed = Signal comes directly from speed sensor on the fork leg, so put your front wheel in the air , spin the wheel fast and see if it comes on?
Or
Remove the plug for speed sensor , check connections and clean contacts. Check the wire colour for speed sensor going to dashboard blue socket, use a meter to verify there is no breaks along the harness (signal loss?) or try another speed sensor.Fuel Gauge = If you have fuel , the bars will go up yes.
Does “Turn Left, Turn Right, Neutral , High-Beam” work ?
Describe loose?
Are you comfortable opening the right throttle switch first ? and see if there is any breaks or move the cable up a second notch inside the grip and try that?
Also the cable has an adjuster , adjust it with 2 spanners until you feel there is about 1-4mm pull before it bites the carb ?
Not unless previous owner fitted a cable that was too long for the bike. (Click “Add media” button when replying and insert a photo to this forum, so we can see it
or upload photo to a place like DropBox/OneDrive/Google Drive and post the “share link” to this forum)
