Rough running GN250 when cold

[Micks3]

Hi all, just making my first steps into the biking world, My GN gives me grief first thing in the morning starts fine into gear and away up the drive bit of a slope more throttle then it sort of hesitates and nearly throws me into next doors hedge! I have to gun the throttle a bit to get it to keep going this happens at most intersections/stops until its good and hot. I have changed the spark plug, and removed carb and given it a clean didnt seem that dirty.
I also fitted an inline fuel filter as there didnt appear to be one even in the pet stop valve, the bikes a 2007 with about 7000 kms any advice would be great Thanks Mick..............

[quickbuck]

Firstly, welcome to Kiwibiker.

Secondly, DO NOT ride your bike until it is warm.

You have an air cooled motor, and the fins should be too warm to touch before riding off.
It is not a cage that warms up a little bit of water in the jackets under a closed thermostat....
It is a little engine, that has a lot of metal to warm up before all the bits get to the correct dimensions through thermal expansion, before it works properly.

[Cayman911]

What i usually do, is start my bike, then enter the process of putting my riding gear on.
by the time i do that the bike is warm and good for riding, (even on warm days)

then again you shouldnt leave the bike just sitting there on for more than 5 mins, its aircooled, you want it to warm up. but it'll warm up a bit too much sitting there too long.

but the gear process works fine. get in the habit, try that. :)

[quickbuck]

Some Say.... That you shouldn't actually leave your bike unattended while it is idling away.
Only ever start your bike with all your gear on, and sitting on it with the Side Stand UP.

However, yes, the age old procedure of start bike on Choke, and walk back inside and start getting gear on, walk back outside, then close (or is that open) the choke and let run while putting on the rest of your gear.....
A good 5 minutes first thing in the morning.....

[Cayman911]

Eh i just turn on on choke, put gear on and by that time its ready,

just gotta remember to put the choke to normal....that catches you out when you're in a hurry haha, although you wont get far without realising it....

[Cayman911]

Sorry for double post. dunno why it happened... *delete*

[Robert Taylor]

Hi all, just making my first steps into the biking world, My GN gives me grief first thing in the morning starts fine into gear and away up the drive bit of a slope more throttle then it sort of hesitates and nearly throws me into next doors hedge! I have to gun the throttle a bit to get it to keep going this happens at most intersections/stops until its good and hot. I have changed the spark plug, and removed carb and given it a clean didnt seem that dirty.
I also fitted an inline fuel filter as there didnt appear to be one even in the pet stop valve, the bikes a 2007 with about 7000 kms any advice would be great Thanks Mick..............

Is it one of those atrocious Chinese made GN250s? If so has the carburation been set up properly? Out of the box the calibration is usually so lean they will only run properly in the thin air at the summit of Mt Everest.
Attention is required to the fuel volume screw setting, perhaps also the fuel level, pilot jet size and maybe the needle setting. This needs to be done by a highly experienced motorcycle mecahnic known to be very good with carburetors.

[Slyer]

Yeah I recall hearing that the carb mixture screws on all GN250's were meant to be adjusted when imported into NZ but none ever were...
You should be able to adjust this yourself, take it out for a decent ride so it's warmed up, leave the bike running and then start turning the mixture screw slowly inwards till the cylinder starts to miss and then turn it 1/4 to 1/2 of a turn outwards.
I'm not sure exactly where it would be on the GN but here are some example pics:
<img src=http://www.ratwell.com/technical/DualCarbs/14-MixtureScrew.jpg>
<img src=http://i27.photobucket.com/albums/c163/earlwb/Scooter%20Carb/Carb_Low_Speed_Air_Mixture_Screw.jpg>



When cold you should just be able use the choke a bit, start the bike then adjust the choke till it's idling nicely, give it ten seconds of gently giving it throttle to make sure it's running right and then ride away.
Just take it easy on the throttle till it warms up and then flick off the choke while riding.

Also, check the air filter. Give it a cleanout.

[rogson]

As mentioned above, the stock carburation set-up on the GN250s is too lean.

A simple first step/no cost adjustment is to set the mixture screw (on top of the carb in a recess with a rubber plug over it - take the tank off to access it) to 4 turns out. This will improve the starting, warm-up, idling and pulling away from a stop.

Beyond this, to get the best performance out the bike you need to reset the jetting with a bigger pilot jet and a raised needle. This should be done in conjunction with checking/setting the float height.

[gsx katana]

welcome to kiwi biker

[Micks3]

Wow this site Rocks ,Thanks for taking the time to reply will give it a go, and Forum whore Honest I couldn't help it
it was shiny and cheap!! lol
cheers
Mick..............

[Micks3]

WOW! This site rocks Big thankyou to you all for taking time to help will take your advice onboard. And Forum whore
Honest I couldn't help it was shiny & cheap!! lol
cheers Mick................