Hyosung: engine misses then cuts out when doing 80km+

[not2slow]

Hi, the Hyobag is having a problem.
Bike is a 2008, GT250R, 12,000km, iridium plugs (4,000km old), SD pipe, Battery is 6 months old

Cruising at 80-100km and after a few minutes at this speed the engine starts to miss and cuts out. If i button off and reduce speed it continues to miss and then cuts out. All the electrics (lights and speedo) are still on. I pull the clutch in and pull over. After coming to a stop, it may take 1-2 minutes to get the bike going again. One time I tried to shift down through the gears to “crash start” it in 2nd gear but the engine made a buzzing noise and would not let me go from neutral to 2nd with the clutch still pulled “in”.

Riding on the streets the bike is fine.

• I have disabled the side stand switch...no joy
• Checked the earth lead from battery to engine...seems good
• Changed fuel tap (part under the tank)
• Have not noticed a vacuum lock in the tank (i ran out of fuel a few weeks ago and there was no “hissing” sound when i opened the tank).
• Inspected carb vacuum hoses....seem good

I just went for a blast to double check disabling the side stand switch...still cutting out. I had a look at the fuel filter it was full of fuel and not clogged. Might change it out as i’m due for a 4,000km service
Thinking about cleaning carbs and jets but i think the problem is electrical??
Anyone got any good advice

[AllanB]

Fuel tank breather blocked? A vent hole in the filler usually - open the cap and you should see it.

Or you have reached the speed limiter!





Aw come on I had to have a wee poke at the Hyo

[TOTO]

with 4 authorized workshops in auckland to work on Hysosung, you decided to ask the online mechanics first. My hat off to you sir.

[DMNTD:Me]

Fuel tank breather blocked? A vent hole in the filler usually - open the cap and you should see it.

Yep...but usually the fuel tap/cock thingy that fails on them.
Easy fix

[not2slow]

Yep...but usually the fuel tap/cock thingy that fails on them.
Easy fix

Will have a look at vent holes in tank.
Swapped out the fuel tap/cocky thingy after talking with the hyosung dealer on the Shore
Just looking for adivce from people who may have had the same prob or have experience with Hyo's.

I was expecting some grief about the hyo

[not2slow]

Just an update; bike has been in the shop. Carbs have been cleaned and fuel pump swapped out. Shop tested it before it was given back to me and it was running good.....except when i rode it home... guess what....miss miss and then it stops . Back to the shop we go...

[RideLife]

Our race one had an electrical fault that we thought was coil (and everything else electrical under there), turn out to be in the dash unit.
So if you want to rule out something else - unplug connection into the dash next time bike faults like that.

Racey

[not2slow]

Our race one had an electrical fault that we thought was coil (and everything else electrical under there), turn out to be in the dash unit.
So if you want to rule out something else - unplug connection into the dash next time bike faults like that.

Racey

Do you know if it was a bad earth into or from the dash/speedo or the connection was just loose? cheers

[RideLife]

It seemed to be an electrical fault of unknown discription within the dash.
We now just run the bike without any dash unit.

[Jantar]

.....i ran out of fuel a few weeks ago .....

This is the clue. I suspect you have a dirty fuel filter. The bike will run fine at very low throttle, but as you open it up it will use fuel faster than it can get into the carb, runs lean, then runs out. After a short time fuel will refill the carby bowl and it will run again.

I don't know just where your fuel filters will be on a Hyo, but I would check the one in the tank first. After that see if there is one where the fuel line meets the carb.

[not2slow]

This is the clue. I suspect you have a dirty fuel filter. The bike will run fine at very low throttle, but as you open it up it will use fuel faster than it can get into the carb, runs lean, then runs out. After a short time fuel will refill the carby bowl and it will run again.

I don't know just where your fuel filters will be on a Hyo, but I would check the one in the tank first. After that see if there is one where the fuel line meets the carb.

Hi,
i should have mentioned that this problem was occurring before i ran out of fuel. But the fuel filter is getting changed to eliminate it and the fuel cock/tap has a filter on it and that part is new as well.

[not2slow]

To wrap this thread up...bike has been fixed (well i have ridden it twice and it seems to be running like it use too). The problem was the fuel tap, so the brand new fuel tap I installed was faulty? Made diagnosing the problem a little interesting for the bike shop. But i suppose it helps having spare bikes sitting around where you can swap parts to eliminate possible causes.