My GV developed a sputter

[Spwoody]

Recently my 2009 Grand Vista 250 (2100 miles) has developed a sputter at idle. It sounds as though it is going to stall, but does not quite stall. I have tried adjusting the idle speed and either it idles to high or to low and stalls. Can't seem to get it right. It was time for oil change so I did that and changed the spark plug. Neither of these helped. The bike also revs really high when started from cold and seems to take a while to come down to a "normal" idle. It has not sat much during our mild winter months; rode a few times a month during winter months, so gas should be fine. If anyone has any suggestions, I am willing to try just about anything.

[zombie]

Bad gas! Add a double dose of Sea Foam, and adjust the Idle MIX screw to get the best idle. After running the tank out you may need to adjust again. Fuel containing Ethanol spoils within 2 months of sitting. Even quicker in Humid or damp conditions.

[Doug9678]

When its cold my GV takes a couple of minutes to idle down. I use only premium gas with no ethanol in it.

[zombie]

I would check EVERYWHERE for a vacuum leak. It sounds like it is leaking air somewhere. Most likely the intake coupler.

[Spwoody]

Thanks for all of the replies. I did end up finding an air tube that I must have knocked off when removing the seat to change the spark plug. Reattached the tube and everything works fine now.

[zombie]

Super cool.

[Rudolf]

Mine sputters at acceleration because of the diaphragm has holes in it, and can't lift the needle quick enough as i accelerate. I have to wiggle the throttle to run smooth.

[mrbios]

f the diaphragm has holes in it,...

Have you thought about replacing or repairing the diaphragm with silicone?

[Rudolf]

I've repaired it with a thin film of silicone rubber, also noticed that the air filter that I've never checked it was fouled with a mix of dust, gas, and some moisture. Changed the air filter and accelerates nicely but now i have small interruptions in the idling of the engine. The idle is not as smooth as it should be. Only at idle i get these interruptions, accelerating seem to go smoothly. When i leave the engine running at idle, runs at around 2000 RPM but goes up to 4000 RPM without throttling than comes back again. When i stop the engine, the exhaust puffs.

[mrbios]

I've repaired it with a thin film of silicone rubber,.... goes up to 4000 RPM without throttling than comes back again. When i stop the engine, the exhaust puffs.

I would spend $50? and order a new diaphragm.  Also I sounds like the pilot jet and pilot passage need to be cleaned.  Restriction in the pilot passage will cause low idle and dying when coming to a stop (especially once the engine is warmed up fully and the automatic choke aka autobystarter enricher is off).  The idle going up to 4000 rpms is a classic sign of a vacuum leak which causes an excessively lean condition and can cause popping in the exhaust.  Check the color of your spark plug for signs of a lean burn (white tip).

[zombie]

I've repaired it with a thin film of silicone rubber, also noticed that the air filter that I've never checked it was fouled with a mix of dust, gas, and some moisture. Changed the air filter and accelerates nicely but now i have small interruptions in the idling of the engine. The idle is not as smooth as it should be. Only at idle i get these interruptions, accelerating seem to go smoothly. When i leave the engine running at idle, runs at around 2000 RPM but goes up to 4000 RPM without throttling than comes back again. When i stop the engine, the exhaust puffs.

That is a vacuum leak somewhere. 100% guaranteed.

[Rudolf]

Forgot to mention that i have a hard start when the engine is cold, or i leave it out this time of the year for 8 hours. The battery is brand new. I have to push the starter button two or three times to start up. Sometimes soon after startup it cuts out, because it's low RPM.

[mrbios]

Forgot to mention that i have a hard start when the engine is cold...

It sounds like the Autobystarter aka Electric choke's wire is disconnected. You can check that through the hatch under the seat.  As a test try this next time you do a cold start overnight: Twist the throttle all the way 3 times.  Then let go of the throttle and see if it starts better and report results. 

[Rudolf]

The electric choke is connected and it is getting hot so it works. The engine still has short interruptions in the idling especially when is warmed up.

[mrbios]

The electric choke is connected and it is getting hot so it works. The engine still has short interruptions in the idling especially when is warmed up.

Good info.  However, if either the input or output passage that feeds or is fed by the electric choke is clogged then the electric choke - even though it works will not supply extra gas when cold. 

1. Try the throttle twist at start up test and report results.
2. Check the spark plug color - lean?  Fowled = rich?
3. Try adjusting the pilot screw for the idle mixture by carefully turning it in in until it gently seats 1/2 turn at a time and count / record / post how many turns it was set at.  If it is open more than the standard 2? turns it tells us that either you or Previous Owner (PO) adjusted it.  Assuming it is open less than 3.5 turns - increase it to 3.5 turns out. and report results.  Like the electric choke - if the tiny pilot jet passage / circuit is clogged then will have no effect from 0 to 3.5 turns will run / idle the same. Report results.  TIP: To make it easier to access the screw - loosen the boot clamp and rotate the carburetor clockwise 1/4 turn.