engine dies

Posts: 39

my roketa gk-06 cn 250 dies when running on idle, but especially when i hit the throttle.

Cold or warm does make a difference.

It has the mikuni round carb just like in the GY6

110 main jet and standar air filter.

Problem is that the symptons are not regulary

Sometimes it just idles for 10 seconds and then dies.
then it idles fine until i hit the gas and it dies.
Most of the times i just start it back up the first time, but sometimes it takes multiple attempts.

Then i can run it up slowly without a problem, but when hitting the gas fast it dies.

at times i can put it in drive but mostly it dies right away.

I did this with and without an air filter.
I opened the carb and checked the jets.
there was plenty of fuell in tha carb.
I changed the fuell lines to 3/8" for the most part.
fuell is clean
I checked the sparkplug, it is black dry and tan at the top.

when it dies when i hit the throttle, it spotters and sometimes backfires.

I checked all electrical connections and only had to improve a few.

is my carb the problem? should i go with a pump carb?

I apprecaiet any help.

Posts: 1869

If it revs up when on blocks, you probably have a broken clutch spring or stuck variator that is causing the engine to stall out when the clutch engages.

Posts: 68

See if turning off or on your light changes anything. If it does you have a bad ignition switch. The lights might be sucking power from your coil. Easy fix if thats the problem.

Posts: 39

I checked for a spark this morning and thats fine.
I also adjusted the valves, they didn't need much adjustment, maybee one mark

lights are staying the same when running the engine or not.
lights stay on after engine dies.
This morning, it starts and dies almost right away.

if it stays running for a minute, hitting the gas kills it.
but it dies on idlle mostly.

when i removed the sparkplug after a few starting attempts, it was slightly wet and black.

after the sparkplug test, i got the engine to run for a minute and was even able to hit the throttle.
but the engine died shortly thereafter.

Posts: 68

Unplug your light so they "will not" go on at all. That would be a sure way to make sure your not sucking power from the coil. The wattage to your lights is constant while your coil is not. If the ignition is bad you would still get spark but it would be weak and out of timing and would get worse with acceleration. You would not see any change in the lights. But it really sounds like the engine is flooding. Either your jet is to large or the float in your carb is sticking. I would do the light test first. Then go from there. The rod that holds the float may have slid to one side. This can happen with a really bumby road or being tilted on its side. Let me know.

Posts: 68

The more I think about the more I am thinking this is an ignition problem. If you have never changed the jets or air filter ETC. then its the ignition. If your spark is weak or out of timing then you are not getting a clean burn and not all your fuel is getting burned. It would run until the fuel built up then flood.

Posts: 1009

Are you sure your intake ( rubber ) isn't cracked or leaking, sound to me like its loosing vaccume through
the intake, if you can get it to idle for a bit, spray
starting fluid around the intake area, if it revs up, you
have a leak around the intake.

Posts: 39

in regards to the lights.
I got a switch for those and tryed with it on and off.

in regards to the spark.
I can not compare it with another one, but it might be weak.
I got a new sparkplug on its way..see what that does.

the gap is set to 0.6mm should be right.

anyway, after i made the previous post, i went back to my buggy.
I started it and it kept running.
so i hit the throtlle and it kept running.

I was able to ride this thing.
When i hit the gas up to 1/4 fast the engine wants to choke and spotters and even dies.

if i take it slow on the gas and push past the 1/4 it runs great.
i played with it like this for 30 minutes and checked the sparkplug.
it is dry and tan/grey.

looks like a lack of fuel
i have 110 main jet now but have 130 and up on its way.
will also install the rednech intake at that time.
I probaly will order a new high performance coil also, just to make sure.

Posts: 68

Did you try spraying starter fluid around the intake manifold. If that doest give you anything I am afraid I am at a lost. FYI: 110 to 130 his huge

Posts: 39

No, i got to go and get some first.
tomorrow is autozone shopping day anyway lol

I did double check and retightened the clamp between the carb
and the cylinder.

110 to 130 is because of also installing the redneck intake and gutting the exhaust.

The 110 was too small from the getgo, since my sparkplug indicated too lean since day one.

i eventually will look in to a new slow jet also, as soon as i can figure out what i need.

I did read somewhere that it is the slow jet that refers to the first 1/4 of the throtlle.