Gn250 running problems

[JebJU]

Hey guys new on here,

Just bought a gn250 for some day to day transport, first road bike. I have taken it for a few rides and noticed when cruising at consistent speeds it doesn't run smooth. I keep the throttle consistent and it has like a chugging action. It seems like it may not be getting fuel smoothly? But my knowledge is pretty limited.
Not sure if its related but it doesn't idle particularly well. It won't cut out but sounds like its going to.

Has anyone had any experience with this? Or any indications what it might be?
Any help much appreciated

Cheers

[Rhys]

My guess, I would lift the back wheel of the ground and slowly turn the wheel, you will probably find a stiff link also check how tight the chain is (when siting on the bike should be about 20-30mm of play

The idling, is it idling very low? I would think a small single cylinder should be about 1200 -1400 rpm

[MSTRS]

Gns tend not to be maintained all that fastidiously. Yours may be no exception...
I would clean the fuel tap and put a fuel filter in the hose (or replace the one that's there). Fit a new air filter. Fit a new spark plug. Check and sort the chain as above.
After that, if no improvement, then it's time to strip and clean the carby, do tappets etc...

[JebJU]

Current chain does seem to be shot so I will replace that and see how it goes. And I will also clean the tap etc and let you know.

As for the idling, just went and ran it before and it was idling at around 1000, ever so slightly over, but seemed to be idling okay this time.

Cheers for the help
much appreciated!

[Grashopper]

I don't think my GN ever idled as low as 1000, but I can't check it anymore as the needle has fallen off my rev counter...

If it sounds like idle is not running smoothly try adjusting the idle screw a bit. That's what I did to make my GN run smoother at slow speeds. It might not like the cold either at the moment so might run smoother when it is warm. Also count the teeth on your sprockets. My bike had surging issues that felt like the fuel supply or something was not working smoothly. Turned out my front sprocket had two teeth less than usual. Changed to only one tooth less and suddenly the bike was running much smoother.

A loose chain could be the problem, too, as I've noticed lately.

If you need a GN manual search through the threads on this site, there is definitely one, just can't remember in which thread the linkyding was.

Actually, I'm not sure how mech savvy you are, but if you just got the bike and don't know what kind of issues it has it might be a good idea to have a bike shop have a look at it and do a thorough check/service.