GN250 idle question

[want-a-harley]

Hello, have found some topics relating to this but has not answered my question completely.

Have had the GN250 for about a year, when cold, coming into winter if I came to a complete stop when still cold the engine would cut out, got over this by revving slightly for the first km or 2 if I had to stop. No problem I thought.

Since getting it serviced recently, the cutting out has been more common, when stopped at traffic lights, revs will drop and cut out or idle but feel like it's about to stall and then stall. Won't happen every time bit enough to be annoying, get around it by revving the bike slightly when stopped (around 2000).

At idle it was about 1400, I've increased the idle now to 1800 and it seems to have solved the problem but as it doesn't always happen will need to ride a bit longer to be sure.

My question is, as the manual says it should idle at 1250-1350rpm, will idling at the higher rpms have any adverse effect?

[CookMySock]

Thats what the choke is for. Leave it partly on until the engine can idle properly without it.

Steve

[want-a-harley]

It cuts out even when it's properly warmed up

[gwigs]

Check for vacuum leaks around carb....maybe carb needs stripping and cleaning.

[Laava]

I had a GN that had a very erratic idle and it was spark plug cap, it was sparking erratically through cracked insulating material. Worth checking for, in fact I found I could hear mine arcing. I put heat shrink around it and it ran like a charm!

[molex]

Vacuum leak test spraying wd-40 on carbs join intake between engine (plastic)
check engine can idle properly?

[SS90]

I see you have a 2007 GN250

The later models (like yours) are made to international (e4) pollution standards, and as such are considered "lean burn" (no cat. converter)

Basically, the engines are set up to pass rather tough emmissions standards by having (among other small mods) small pilot jets (the jet that controls how much fuel you get at idle, as well as contributes to how much fuel your engine gets up to about 1/2 throttle.

That is why it is called a "pilot jet", not an "idle jet"

The pilot jet your carb comes with (I really can't remember the size exactly) is simply too small for the colder climate NZ has.

Central Asia it's no problem.

From what you write, it seems that your bike it "cold blooded" i.e it takes a while to "warm up", and when it is warm, it functions ok.

The solution for most of these problems is simply to put a larger pilot jet in (I can't remember if they are a Mikuni or Kiehien carb), but the pilot jets are easily available for either.

I suggest that you simply need to put a larger pilot jet in (say 10% bigger than you currently have) and all will be well.

[CeeBee]

Hi
I had the same prob on my GN250 not long after aquiring it, with a good service (Done by myself) and altering the pilot jet to ever so slightly rich,fixed that. Now I also had lean out backfiring upon deceleration and narrowed this down to the incorrect main jet needle height....obviously set up for European standards. Once I had lowered the jet "one click" even the idle problem dissappeared. It took quite a few carby dismantles to get the jet set right as you do not want it rich or too lean.