Old gt250 Comet 2006, Perth W.A.
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I have just recently joined this forum, I have purchased a Hyosung as in the title for my son to finally get his bike license. It came very cheaply in purchase, though by now owes me more than double what I paid for it, new brake pads front and rear, new front tire ( was down to the canvas ) and air filter ( was missing ). And while tuning the carby’s has been fun and continues to be, the cam chain tensioners definitely need replacing, and or set the gap in the upper cams both cylinders.
I have removed and cleaned the C.C.Tensioners a couple of times on the bike, takes ages with 1/8 of a turn each screw because of access, and still the bike at idle ticks like a bomb about to explode, it goes away mostly with a twist of the right hand, though damage is being done internally I am sure
It uses the older C.C.Tensioners with the rounded tip, and I saw that these should be ok on this forum, about an upgrade or recall of the CCT.
My bike has possibly done 60,000 + klms as the speedo cable was also broken when I got it.
I am tomorrow going to throw another $100+ into two new cam chain tensioners, I hope this stops the tick tick then latter boom.
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Well damn! I hope it gets sorted out. A new tensioner is always a good call! – Also new cam chains if they have worn down that much considering the mileage , it is almost time to rebuild the bike little by little.
Welcome to the forum, be sure to post a picture of it 😉
Carbs = 2.5 full turns out on each pot and leave them there forever , it lets you focus on other areas on the carb to fine tune it well 🙂 (also compression on the cylinder pistons or valves is very crucial )
Or watch for the rubber valve seals may drop the odd oil in to the pistons and making the spark plugs extra sooty or oily , so look at your spark plugs
You got this!
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The first pic is of the old girl, with added brake fluid burns on the tank, add that to my list.
2nd pic is of the fuel mixture screws, I just readjusted them to 2 1/2 turns out, talk about that latter
3rd pic is mostly irrelevant, though shows the easier cct to get at.
4th is the old plugs which I have already replaced, and I failed to order valve stem seals, so my bad.
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Marcel when tuning the carby’s, what is the process in basic ?
I have tried to bench sync the carby’s the best I could, but the bike really bogs down while riding at 7+ RPM in any gear above 2nd on acceleration. I adjusted the fuel screw while stopping the bike on a ride. But this what I thought was over fueling on acceleration and screwed in to about 1 full turn from seated in, it ran a bit better, better rev’s higher and smoother. It must have been very lean. Its still not rev’ing right up.
I have just made the fuel mixture screw 2 1/2 turns out for now,
What other adjustments can I make?
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Try this mod ?
[Tutorial] How to adjust Carb Slide Needle (Tuning) – Hyosung GV & GT 125/250
Also,
- What size Pilot Jets are on the bike?
- What size Main Jets is it using?
- Is the airbox intact ? (put the airbox on the carb first…… then drop the airbox and carb together in to the intake pipes very carefully as those rubber necks are very difficult to get nowdays.
- Standard air filter used ?
Consider O-Rings below?
Intake Pipe O-RING (Inlet Boot Seals) x2 – GV125 GT125 RX125 GV250 GT250 Hyosung
If you can’t wait for them, try to ask a local hyosung dealer ? = Don’t buy any parts from Hyosung pages that are “Blue/White” as they have a lot of bad reputation, we don’t promote them here either. Too many people got scammed online.
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Thanks for the reply Marcel, I have had the carby’s apart but did not have a magnifier to see the numbers on the jets, I think your on the right track it may have been jetted for the stainless exhaust. I know I will have to remove and check, post the numbers and see why it bogs acceleration under load.
I bought a genuine air filter and installed as there was none, I have today seated the airbox properly onto the carby’s first then the intake to the motor. I needed to have some help doing it as yes its tricky to do properly.
The mod you suggested was done already, I thought of reversing it or going the middle 2nd notch on the slide needle top.
Have not ridden today and am having to deal with other things for a week or two, so have to put this project on hold.
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Hello everyone, back again after a big trip, eventually have gotten some time to work on the Hyosung.
Had to double check the main jets as they look oversized for my bike, might explain why it splutters in top gears on the throttle.
Went down the path of electrics today as high beam was not working, found out I may need a lh handle switches, I am about to heat up the soldering iron and give it another bash so its road worthy.
Rear brake I forgot about the lower nut off the caliper just spins, no tighter no looser, does not remove, cannot remember how I changed the brake pads like this, though they were changed but the brakes
are not working to spec. -
Hmmm, if that nut is running loose, weld it shut there. As i don’t think you need to worry about it UNLESS the “rod” snaps inside where it slides the silver caliper in and out (hence floating caliper)
Yeah those jets are overkill yikes. Even a 250cc is perfect on 95 to 97.5 max , otherwise extra jetting is just making the bike too rich , which isn’t good long term either.
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