♠️ M77
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This has been a suspicion as whenever i open the tank after riding you can hear the pressure escaping so my dad thinks there is a vaccum being created which is causing it to cut out.
Try the hot fixes i mentioned above and see if the situation improves before its time to replace the unit
Hey, I replied to your son’s topic , check it out below
Worst case ? Replacement time for it!
my dad wants to know how to do the fuel cap vent fix, any suggestions?
Inside remove the fuel cap off the tank (unscrew it)
Then look for a hole thats near the bolt holes. That is overflow/breather and drains away to the long pipe under the tank that dangles near the shock.
Keep that clear or spray air compressor. You will hear air hiss out of the super long overflow pipe.
Check the fuel cap unit by pressing its springs down and see if they come up smoothly. There is no rebuild kit for them. So if its suspicious or packed it. A replacement is advised.
That is also a good question from him 👍
i went on the bypass and got up to sixth gear and was sitting at around 10k rpm for about 3 minutes then i felt a loss of power then i couldn’t get the revs up and came to a complete stop
Thats the one!
Assuming you have upgraded all electrics (due to heat failure / common) (coils, caps, laser plugs not IX junk ones, stator, reg rec)
Then your war is slow fuel delivery issues vs high speed runs. In other words my previous comment says the bike is asking for fuel faster than the entire wanning fuel system can keep up.
As such. You might want to look at ur plugs or show us.
Also take a look at the other thread on homepage that says *MOT & Running Issues* there is recent replies which could help you in regards to your thread also.
Let us know if in doubt or have questions on this topic.
Its not dead. Just a little moody as it wants off the leash 😉
We ship worldwide everyday. Send us an email (Tap contact the bottom of this site) The checkout was locked to UK/ireland for free shipping. Overseas = we use multiple shipping companies to find the cheapest quote or fastest delivery & we ask overseas customers to give us accurate addresses properly (in a style we explain them) thats why we have not had any international delivery failures for years now due to wrong addresses or customer spelling errors. 🚚
Or you can buy them on our ebay shop (@evocrest) – ebay will use their GSP shipping and you pay them shipping costs not us. 🙂
So my original comments still apply before.your video replies.
I will add a few notes though thanks to your Youtube Shorts & Plug pics.
- Both Plugs = Slightly overheating… (((With oily deposits on threads????)))
- Front = leaning out at high throttle
- Rear = leaning out too but seems to do better than front.
- Both Plugs = idling OK. (Assumes mixture is 2.5 front and 2.75 rear using size 15 Pilot Jets) but see next bullet point….
- The carb needs to have its jet needle at a richer setting as the white cones need to be brown after full throttle runs.
- Mixture screw will have less effect once the carb slides & main jets take over at past 4k revs. BUT it does have an effect during gear changes as bike momentarily lowers revs or coasting while rider carefully disengages/engages clutch to change gears. The carb slides then lift off again.
Fuel Pump = It looks young. I think you could check your fuel tank. Take care not to let fuel eat paint. And clean the tap of any debris as switching between ON/OFF/RES seems to have an effect now.
If a bike cuts out… Tap is usually the 1st thing i get rid off & replace. Work my way to the pump & filter. Then carb (dreaded airbox removal but needs must!)
Im sure you will follow my tutorial on airbox removal. If you get pics and do better than me ; people will love you for it!
I do a lot but never seem to get round to taking pictures to make new tutorials.
I need a kick up the arse for it! Ill get it done lol.
If the cam chain is making noise……does it go after its hot or get worse?
Does holding clutch reduce it?
Does high revs make it worse or quieter?
Same questions again for the Top Engine Heads (Valve Heads = valves chitty chatting)
You will want to find a way to have youe ear behind each engine cam tensioner behind their heads.
hiya marcel i’m sorry to bother again, the bikes been in at the garage for over 2 weeks and have just got it back today, they fixed a few things- fixed an over pressurising fuel tank changed plugs/ coils valve clearance/ carb balance i rode it when i got it back, seemed fine until i did a top speed run where it cut out at high speed, im so stuck with it and any suggestions will do
Fuel Tap wanning (common)
Fuel Pump wanning or needs a minor clean
Fuel Filter clogged or facing wrong way
Carb Needs *optimizing*
2 weeks just to do clearances and optimize a carb (apparantly). They are taking the piss as i would have had it done much sooner.
Also explain a bit more about this top speed run?
We do not see a video link?
Mixture is 2.5 full turns from closed. Do not adjust this ever again because it is very difficult to optimize if bike has other issues.
So if bike has issues after 2.5 turns. Dont turn it again. Replace jets and have the carb ultrasonic cleaned. Then look for cracks in intake rubber manifolds.
- Sometimes it helps to replace intake manifold O-RINGS (like the ones you see at our shop)
Regarding airbox fitting….
1. Attach carbs to airbox
2. Tighten clamps holding carb to airbox
3. Airbox & Carb together will slowly (slowly!) Go inside intake rubber manifolds
4. Make sure manifolds do not get stressed. Be very gentle with that as they are very difficult rubber parts to buy. Korea stopped making them.
Some previous owners are very stupid aren’t they , that’s why this brand gets a bad name lol.
The hyosung doesn’t like pod filters, many of us worldwide have tried to use pods but the bike becomes unstable and its a very frustrating war of messing with the carbs everyday.
Trust me, the airbox wins.
As Jim said above ^ , why not a metal/plastic sheet there and use “JB WELD EPOXY HIGH TEMP” for plastic. This could be the cheapest and easiest solution.
No screws. Otherwise it may rattle and end up inside the engine and it explodes , very good advise from Jim
Also check your ignition caps (they are known to crack off under heat), you will want NGK ones tbh.
And ignition coil (common) but check primary & secondary resistance values and let us know
Can you show us a picture if possible to see what kind of damage the last owners did to it ?
We have airboxes on ebay and happy to ship worldwide.
Maybe there is a way to fix yours if possible ? but try attach a picture here if you can 🙂
Sorry if i digress or not making any sense at 10pm but ask away if missed something
Well explained , now i fully get the picture, so if you want a tequila shot answers , ill shoot em below:
- Fuel Pump wanning (happens, carb cleaner sorts it when you take it apart CAREFULLY) or as pre-caution, replace with a new one if you want us to get it.
- Fuel Filter Clogging or not flowing fast enough (if its OEM)
- Fuel Float Level low (repeated in service manual too) (check floats are on a good height, as fuel goes low, then the jets won’t reach , due to pump & tap not replacing the fuel fast enough = high revs . high speed , more demand)
- Carb Slides wanning.
- Carb Slide needle may be on the lean setting (sent 1x needle for free, just incase one of yours is bent too)
- TANK TAP , wanning = Common.
Since its naked, after a ride , check carefully that both cylinder heads are hot or get an oven thermometer against each head, mark their temps, then check plug colours.
Plug checks will be a very good way to tell me how your “spark” “air” and “fuel” system is doing , not a full picture but enough hints to show me.
Side view of the plug threads (heat check)
Top down view of plugs (to see the white cones inthe middle)I could advise further after your next comments.
Normally , when a hyosung that is all OEM and negelected (either by garage or last keeper) , the carby 125 ones at least , they usually spend their lives in the city with a max of 40mph runs , then owners use crap service parts on them to keep em going, but never touch the carbs , or do engine clearances (valve clearances do eventually get too tight , being a hot engine doesnt help) , never changing air filter….
Fast forward , the next owner buys it 100 miles away from his house.
He decides to pay the neglectful seller, goes on A1 even to ride home 100 miles, 40 miles are okay but last 60miles involve dual carriage ways of 70mph , he breaks down as soon as he goes from 40mph to 70mph and races it for 2 mins straight, the bike stops sparking , but all the owner can do is coast it to the side of road , electrics are still on!
What happened?
Negelected Fuel System!!! (& some times heat damage to coils, stator & the reg rec = also common)
He starts the bike again after letting it sit for 6mins ….
How?
The cranking & cranking was sending fuel back to the carbs so that the floats can raise and the jets can finally reach the fuel level needed to start.
Now he must ride 40mph max so that the “wanning” fuel system (all of it) can still keep “trickling” down more fuel to maitain fuel level to get him home
Or
His electrics are kinda calm under 5-7k revs …..but the bike rides better at 8-10k revs (catch 22 for him!) UNLESS he is in fifth gear above 60mph, then lower revs is fine but his fuel system already forced him off road if he goes beyond 40mph on dual carriage ways.
He is now forced to ride away from big roads until then.
Seen it. Witnessed it myself.
Hmm, can i just ask , how many tries did it take to start it back up again?
Also if you managed to get home that’s good, but on the 2nd ride, if you tried to exceed 60mph, what does the rev counter do ? does the engine still feel smooth or just it start jerking forth and back ?
hey you are very welcome, please excuse my “crazy/psycho” packing skills, i just had to be OCD to make sure international packages don’t get transit damage whatsoever 🙂
I hope the weather is calmer up there, here in UK we are in spring also . so go have a ride!
Welcome 🙂
Hope the bike life return means you don’t sign off again 😉 Hope you’re doing well with the hyosung, keep an eye on the 250 or 650 versions when you pass Mod tests , and stick around 😉 Hell if you end up with an SV650, it’s okay, they shared the same bed with Hyosung Korea at one point hence their engines have similarities (not the same iniside though!) , hell our GT125s robbed the suzuki GS frames for it.
OEM is 15T , so having 14T , might take 10-15mph off the top speed , but bike will rev much higher as it gets through gears quicker.
I am guessing the accelaration needs mean the engine will have a better coolant (you want the piston heads to stay cool and radiator fans not on all the time) and good grade oil to keep that gearbox happy to go through gears faster ?
But do keep an eye on the engine temp bars from sprocket changes.
It really depends how far you go aswell, if you travel places more than 50miles away , you want the revs to be lower in cruising mode 🙂
Change the slides and do the “slide mod” tutorial on this forum to help with the higher rev range, try using LASER plugs too (if not already but get a 2nd set just incase) , usually a good carb tune goes through a few plugs first 😉 , you got this.
Congrats on the MOT too! Happy days to have another hyo stay on the road. It upsets me when they got sorned off and rot in gardens
Ok thanks I did that, I took it out for a short ride afterwards and when I parked there was light smoke coming off the engine from the heat. I think it could be running lean since I got higher end air filter or could possibly be smthn else?
i would also look to change the jets as “more air” = lean mixture , engine overheats , could burn oil as piston rings can only tolerate so much. There is a jet tutorial on forum if you have seen it ?
As for crank smoke , go with Simon’s comments
