Speed bursts while accelerating. – GV125-S (EFi)

[Chris]

This might be a silly question but I have had alot of issues with my 2019 gv125s since I’ve had it which is just over a month now. What I am noticing is when I am accelerating is it seems a bit slow after gear change to gain speed then out of nowhere I feel a sudden burst of speed until I try to change into 5th gear at around 45mph then the bike seems to lose power slowly and doesn’t regain speed meaning I have to change back down to 4th gear. I can get upto 57mph in 4th gear then again when I change to 5th gear power loss again. I have already checked the air filter and sprayed the carbs with cleaner. Ive also had 3 fouled spark plugs, both went around 4 days after having the bike then now only 1 has fouled. Ive ordered the ngk leads and plugs from the store here. Would the fouled spark plug be causing the issue or is it more likely and air/fuel ratio issue?

[Simon]

It seems very likely that it’s a carb / fueling issue, I doubt it will be worn parts it’s most likely sticking choke combined with debris in the carbs also a vacuum leak could cause similar problems, just check on thing at a time it’s a process of elimination.

[♠️ M77]

Simon makes good points in regards to “process of elimination” ,  since you have a naked bike its much easier to get to it than a full faired bike in this freezing winter lol

 

Because you have a GV-S (EFi) model 125cc , go to halfords and buy this:

• WYNNS FORMULA GOLD PETROL CLEANER BOTTLE

Make sure your bike has half a tank (max!) ,   or 1/4 fuel left.
Then pour all of the formula gold in the tank.
Ride safely on a dry day , slow ride down the streets, then race it up to 60 on the dualcarriage ways, then slow down again,

You want the formula gold to be running through the internal tank pump, internal tank fuel filter,  down the lines, then making its way to the injectors.

It will do its best to “soft clean” any debris clogging the fuel system.

I use it all the time and works wonders.   Do NOT use Redex or any other ones you see in Halfords.  it must say “Wynns Formula Gold Petrol Cleaner”

Failing that,  EuroCarParts should have a store in your city and go to them for it also.     It’s a popular item for EFI cars.

(S) in your bike model means it has Injectors than carbs   (older GV125’s pre-2018 are named GV125C = C means Classic/Carby)

Use E5 fuel only because even if the bike is designed for E10,  the bikes and cars in general run better on E5 .  There is nothing positive about the extra ethanol in the E10 pumps.  If anything it will make certain bikes run weird.

Also Keep us posted since the caps and plugs were sent to 2 addresses , i had a feeling it was you anyway! –

Remember as good as the Lasers and NGK Caps are,  you need good coils 🙂

If your coils are failing,  the  new plugs will foul up as the NGK caps aren’t getting enough spark energy from the coils.  The coils will probably be the last electrical item to worry about.

Test your battery at idle and 5k revs rev-up ===> make sure meter says 14V constant.  If less than 13.5V,  (in any revs) , replace regulator as per service notice by Koreans

Next conversation , (after above ^ is done first)  , is exhaust system , air leak tests , etc … i will explain it all in due time.

[Author]

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