Forums 🚦#HYOCULTURE 😃 General Chat no disrespect ment at all just curious Reply To: no disrespect ment at all just curious

  • Topics: 38
  • Replies: 545
Nov 30, 2017
North UK

Sorry I’ve been away at inlaws this weekend, so i stand corrected that you did not fit it yourself the original 428s.  As i will quote your exact reply:

the 13 front and 49 rear was on from when i bought it…..theres nothing in the side panniers the chain was a gold one the type with rubber seals…. its had a engine swap done by oiley bikers top speed before was 62mph using gps at aound 1100rpm the bike has done 19.488 km its had new ngk spark plugs new ngk uprated caps new ht leads new CG125 coils carbs are standard i use castrol power one 10w 40 oil plus run orangey brown. v power fuel
to be honest with you i dident think it had adjustable valve clearences the bikes speedo has indicated 70 before but in reality using a gps app it was doing 65mph


Using the gearing commander  (it’s on google) so you can play with the settings if you like) it’s a decent source as it is on par.  I played with various 428 sprocket settings on a GV125, the 13T and 49T defo drops the mph for sure, it’s not factory set up.

I do own aquilas and GTs , i know the speedos are out, so the speeds i mention when selling chain sets are what it says on the dash, i can’t try just one bike , i need several donors with varying engine mileages , some modded bikes, some stock and i have people who are test dummies to help me and i send the kits before i go retail, i can’t take back what i say online, i’ve way too many witnesses now (which is a good thing), 10% has to be removed when GPS is used. No speedo made by hyo i’ve known so far is ever the same as GPS.  Even most cars are like this,  sometimes 10-15% is removed from any speed to actually slow down people  (even though they think they are truly driving 70 in motorways) but no they drive at 80mph on the dash so it’s 72ish on GPS, are they taking a risk with smart-camera motorways ever increasing, yes they are but its what i see everyday.

Don’t worry too much about the chain set for now, we’re going back to the engine internals (cams, clearances, clutch basket, compression, etc)  &&  (plus whatever else is attached to it, be it fueling or electrical things to make it come to life)

If one has a digital hyosung dash, and it says 33, going down the estate, the light poles in the street will have a matrix display saying “Your Speed xxxx”  –  33 on dash is always 30 by the matrix display in the street  =  that’s 10% removed from the dash.  44indicated is 40.  I can see why  80 will drop to 70 gps as any speed is always factored in around 10%.  Common figure , some dashes are less out  (5%) , some will be 15% out.

The revs is the main concern on a small cc bike, we want it screaming less at the “same” speed it did before a change of modification  (ie. chain set) ,  the valves on hyosungs don’t like staying at 13k revs for long. The valves start floating at 12k revs.  All GV125 engines peak their power at 10-11.5k revs.

Please take a look at the service manual below which another member has kindly posted on social media, as you’re on it already,  if it helps.  I know trawling through the forum has all kinds of books, but i’ll organize that much sooner with another site design change.

Link to manual here

it is specifically for your bike, so it has so much detail.  The troubleshooting section at the end will back up the “clearances” being mentioned multiple times (even if engine idles fine),  the challenge now is to beat everything the engineers have said in the book.  Trust them than any of us here , they made the motors 🙂 . You’re a mechanic yourself fella so the book’s instructions will be familar to you in some pages read,  if not, a local garage can do what the book says and don’t pay them until it is so.  (Some garages are just cowboys, sorry to say, they really are, so i’d watch them!)

If the manual has something missing, tell me i’ll upload it again directly to this site.

Have a great weekend ❤



PS. I really do need to start making more tutorials of engine jobs unless Korea’s english is perfectly fine ,  I can try to break things down to layman terms.

Like this tutorial here on clutch ( i do need to update it anyway)


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

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