Gt125r NO POWER between 4k-8k revs

[Harvey]

Hi guys, im new to owning a Hyosung and have got a 2016 gt125r that has a lack of power between 4,000 and 8,000 revs. Anybody got any ideas or tips on how to solve this, bike only has 340 miles on the clock and its a bit annoying with having a lack of power. Thanks guys. ☺

[♠️ MARCEL]

Hey ,

Welcome to the forum. Someone asked a similar question on facebook not too long ago, so this is what i said (which therein applies to you too)

Here it is:

“”bogging” / Cuts At Stops / Spark Cap being damp ? / not above 40

1. Start the bike – Use a multi meter -> Switch to Volts -> At the battery get a reading of 14v around 3-4k revs
14.2v at idle (if its any less, it won’t have high speed juice.)
Looking at the data says these bikes should be 14 – 15v norminal.

2. Switch off the engine , put all the lights on inc high beam. Switch on the left or right indicator – If the dash dims badly – > Investigate battery.
A Garage will just check it for you (they will tell you if it DOES need replacing due to age)
Some Old batteries run worse in the freezing cold.
An Oximizer helps in some cases to pro-long the life an old battery

3. COILS = Get that meter out again , switch to K ohms
– > Bike look -> Look for wire going to coils.
-> Put “RED” wire of the test meter on the “spade” terminal of the coil
-> Put “black wire on the BOLT that is attached to the coil”
Get 5K ohms reading (Within that figure)

4. COILS = Remove them, scrap the frame off rust, until you see a shiny element – reconnect coils – Spray “tiny” drop of ACF50 (Anti Rust) in to the exposed elements of the coil (frame, fins, wire)

5. Coils = One tiny drop of acf50 inside the “insulator” cap shround helps maintain electrical connection to the plugs , god forbid should water get there.

6. Spark Plugs = Dark Coffee cream colour = Jetting is OK. (not rich)
Must be almost identical to both engines.

If there isn’t ACF50 to use or similar product – Clean the areas of rust near the coils & bike harness (wires) especially when they attach themselves to the frame

7. Spark Plugs = Take em out, clean the tips –
The only plugs i can verify & few others is that now “CR8E IA” lasers plugs do better job at maintaining throttle response (its easier for the engine to burn off fuel in chambers)
“IX” is good too, but IMO waste of cash now as it’s not as dramatic as switching to IA ones.

YOU WILL be less likely to use the choke!

8. Can get to 40 plus?
– Valve Issues (Tappets/Cam Chain/Tensioner/Valve Springs) – Believe it not, you won’t ever see 70 plus if the valves system hasn’t been service – Get the service history & find out when it was done compared to your current mileage now. A clear running video helps , if you ever post it.
– Carburetors (will explain below) – Bike can’t run good without it 100% right.
– Coils (^ as above ^ ^ ^ )

9. Air Leaks = Investigate these areas:
Airbox (unsecured air filter?) / Carbs (check rubber manifolds are tight) / All hoses.

10. Boggyness = Too much fuel or weak electrics.
Other hand, if it runs better on choke (enriching) – Sort the jets.
Choke for 5mins is enough. They get hot quick if they stay above 3K revs.

High revs = Too much or leaking somewhere.
Boggy low revs = Electrics or Fueling system. / Weather.

Set idle speed to 1650 rpm when its normal (running fine)
Next time it starts from cold, it will idle a bit higher than 1300 rpm which for some reason is way too weak , fine on bigger cc machines. A CBR 125 2018 idles at 1700 from cold. We have 2 pistons to spin.

11. Carbs = This whole operations means carbs stay on the bike & you’re on the left side.
Drain the fuel (1 screw INSIDE each bowl) (x2)
Fuel drains on the small lines. Get a bowl.
Take off the bowls.
Inspect your carbs.
You will see 4x jets (2x main =above20mph they take over)(2x Pilot Jets.)
Stock sizes 87.5 at the front + 15 Pilot then 90 Rear (+15 Pilot)

If unsure, remove the carbs entirely and have a local mech blast it clean. in & out.

12. Cuts Off = Sidestand switch &/Or – Fuel delivery issues (inspect whole fuel system from the tank to the carb)

Sometimes your bike electrics may be fine , but the carbs may not be cooperating…. A lot can be done these motors run better but let’s get them to standard running 1st (y)

Kill the list ^ one by one

If you ignore all i said ^ and are in a rush – Kill the rust, check contacts , hear for sounds near the top end ; touch the clutch basket to feel for any low-end knocking , or loud basket clatter (clutch plates) , ensure the bike is dry
Failing that – Time to inspect in detail ^

A naked comet much easier to get to that a GTR. As with naked bikes, inspect their exposed elements (y)

All GV125/250 engines have “shroud” cover that is supposed to seal the entire spark plug hole (old age can detoriate them , so check) its separate – You can actually take it off.

Listen to both cylinders and inspect their heat consumption during warm up – If the rear is cold – the coil is dead or there is no juice going to plug or its too fouled , etc..

A bike running 1 one cyl must feel like its taking twice the time to take off at lights & WILL stuggle on hill climbs above 40.”

—————————-
End of quote.

So take some time, i think you may laugh later, could just something silly that has gone amiss while you are busy investigating it.

Since it is a new bike, it should be under warranty, the dealer has a responsibility to make sure it is at optimal running. Also it is less than 1,000 miles old, so you could give it more chance to “run it in” (engine wise) so that after 600 miles, a full major service can be carried out , this includes valve clearances , timings check (these can affect top end power) , flushing the oil with fresh one , checking the whole bike basically. If something was amiss, they must replace it or supply you the part free as under warranty.

Hope this info helps, but update us all on your progress!

// Meditation doesn't mean you have to sit still....

[shane]

well I had similar issue when I brought my bike a week ago i thought I brought a lemon and he said he not hardly used it but since

I put premium fuel and ragged it under the red for a few days it ran without issue now I don’t need to rev the crap to make it stay in speed I want

but depends how long the bike you got as been stood as fuel does go off

my advice is get in garage for a carb check and clean wont be much get quotes from a few garages

 

my bike due a clearance check next month as mine nearly done 10 thousand miles

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