Inconsistent idle/off throttle surging

[Robby45]

Looking for help on two (maybe related, maybe not) issues with an '11 300 ec.

First issue is the engine is stalling (while throttle is shut off) during hard riding especially on uphills/downhills. The idle works fine at rest although I have had to turn the idle screw in nearly all the way. My first thought was float height, but it looks to be ok. I have had this issue since the bike was new.

The second issue just started last weekend: the bike surges while the throttle is shut. Just quick short blips that while coasting with the throttle closed cause the bike to accelerate every so slightly. This started (I think)after I backed the the air screw out to 2 turns to try and get a higher idle to fix problem #1. I have enough slack in the throttle cable so I can't figure out what's happening here.

Carb set up:
175 Main
38 pilot
stock needle ???
air screw 2 turns out
not sure which model carb, but the bike is an e-start with ohlins/marz.

 

[Krieg]

Looking for help on two (maybe related, maybe not) issues with an '11 300 ec.

First issue is the engine is stalling (while throttle is shut off) during hard riding especially on uphills/downhills. The idle works fine at rest although I have had to turn the idle screw in nearly all the way. My first thought was float height, but it looks to be ok. I have had this issue since the bike was new.

The second issue just started last weekend: the bike surges while the throttle is shut. Just quick short blips that while coasting with the throttle closed cause the bike to accelerate every so slightly. This started (I think)after I backed the the air screw out to 2 turns to try and get a higher idle to fix problem #1. I have enough slack in the throttle cable so I can't figure out what's happening here.
Carb set up:
175 Main
38 pilot
stock needle ???
air screw 2 turns out
not sure which model carb, but the bike is an e-start with ohlins/marz.

That sounds like a lean surge issue. Since I like a really crisp off-idle acceleration, I tried going as low as a 35 on the pilot and got similar symptoms. I tried a 40 pilot with as many as 2.5 turns out and the bike got blubbery off-idle. I ended up going to a 38 pilot at 1 3/4 turns and bumped the idle up a tad. I also swapped the 48 tooth rear with a 50 which enables me to ride a gear high in most situations and lug around in 2nd. This keeps you into the throttle a bit more and avoids the worst of the gurgling/blubbery part just off-idle. I'm using a JD blue needle (GasGas kit) in #3 clip, 175 main. Typical elevation is 500 ft and temps are anywhere from 45 to 65 degrees F. I think the 38 pilot is probably marginally lean and I still get a minor surge every now and then, but my plug tip is fine and anything bigger on the pilot will cause the off-idle to blubber too much for my liking.

 

[Robby45]

That sounds like a lean surge issue. Since I like a really crisp off-idle acceleration, I tried going as low as a 35 on the pilot and got similar symptoms. I tried a 40 pilot with as many as 2.5 turns out and the bike got blubbery off-idle. I ended up going to a 38 pilot at 1 3/4 turns and bumped the idle up a tad. I also swapped the 48 tooth rear with a 50 which enables me to ride a gear high in most situations and lug around in 2nd. This keeps you into the throttle a bit more and avoids the worst of the gurgling/blubbery part just off-idle. I'm using a JD blue needle (GasGas kit) in #3 clip, 175 main. Typical elevation is 500 ft and temps are anywhere from 45 to 65 degrees F. I think the 38 pilot is probably marginally lean and I still get a minor surge every now and then, but my plug tip is fine and anything bigger on the pilot will cause the off-idle to blubber too much for my liking.

Thanks for the info. I forgot to mention the bike ran pretty close to spot on back when temps were in the 40's, but now that its been in the sixties here lately, these issues have come up. That makes me think it may be running too rich at the higher temps, but I'm just speculating. Need to do a plug chop to verify the main, but my seat of the pants check says it's real close.

 

[eff]

My bike started surging when I stopped during a ride once. When I got home I removed the carb and cleaned it out. The problem went away. Never hurts to start with a simple solution.

 

[Robby45]

Update - surging is gone, but the stalling issue is worse. Anytime I come to a hard stop, the bike quits running. You can keep it running by holding the throttle open. When you do that, it seems to be loaded up, like somehow the sudden stop caused the carb to go rich.

I'm bumfuzzled. It's nearly unridable. I've cleaned the carb and tried all kinds of jetting combinations but the bike still stalls just the same.

I don't know why, but I have to have the idle screw turned nearly all the way in to get the bike to idle (with a 35/38/or 40 pilot, doesn't matter -air screw position either). Is is possible that the slide is raised enough for fuel to dump into the intake on a closed throttle on hard decel?

I'm bolting on a 38mm AS1 tomorrow as a last resort.

 

[WTEC]

If you're running the stock needle and position, try moving the clip higher. The stock needles seem to be way too rich right off idle, I think mines in the top groove now on my ASII with a 38 pilot and somewhere around 175 main. It runs good, no blubbering or hesitations and idles nice, but I think it could be made crisper with a different needle. I'm going to pick up a YZ250 needle to try, seems to be a lot of guys who like them.

Wes.

 

[Robby45]

I've tried stock and JD red & blue needles in variuos positions.

This isn't a blubbering issue - this is the bike shutting off at every corner.

 

[mrkartoom]

Just a guess, have you checked the float height? I'm wondering if you have a fuel level issue.

 

[jeffs2200]

Not sure if it will help but try safety wiring the throttle cable where it enters the carb. The GasGas cable is different than other bikes the way the cable end is made. On mine I could not get the idle set consistently and this was the problem.

 

[thumperrider1]

Do the reeds look ok?

 

[Tlineman]

Clutch dragging, what weight of oil are you running. My dealer tells me to run 0-40W Amsoil or the clutch will drag.

 

[Jakobi]

Maaate,

I had the same issue with the stock needle. Would idle nice when cold and stall out when up to temp. Idle Screw was almost wound right in. Could work around it by then backing out the Air Screw, but then would get the Symptoms you describe.

I still get this happening occassionally as the N3EG is still a bit fat on the lower end. I have just been a bit slack to change it for the N3CH.

Try lifting the needle one clip, and then resetting the air screw.

Like others here I have ended up with good results using the N3xx range of needles, a 38 main, and 175 pilot. I run my clip position a bit higher than most, but being in Australia we've been experiencing 80%+ humidity and tempts in the 30C, elevations to around 1000m.

 

[Jakobi]

I don't know why, but I have to have the idle screw turned nearly all the way in to get the bike to idle (with a 35/38/or 40 pilot, doesn't matter -air screw position either). Is is possible that the slide is raised enough for fuel to dump into the intake on a closed throttle on hard decel?

Just a bit more. Typical condition (called pulling over)

- Needle diameter is too small. Bike is too rich 0-1/8th throttle.
- To compensate for the richness, you wind the idle in, which lifts the slide, allowing more air in.

This is why the pilot and air screw are making hardly any difference. You are effectively holding the throttle open and bypassing the idle circuit.

Resolution -> Leaner diameter on needle.
Stock Needle is N1EF. The F is the diameter.
From Rich to lean
N1EF
N1EG
N1EH
N1EJ

The N3 range has a different taper. The last letter still applies. The E and C are a half a clip different (c being leaner)

What needle do you have?

 

[Bailey28]

Jakobi,

IF you ever get the chance, try a neat combo I did the other day in my 300... I had a:

40 pilot
BGL clip 5
180 main
air screw out 2 turns.

whoa!

What a smoooooooth set up. The taper starts a bit sooner on the B needle however it is leaner past 1/2 throttle than the N1ex taper.

I like it, the bike won't load up and is really smooth getting on the pipe. It just barks in the sunny mode too. I will try clip 4 and re evaluate. My temps were upper 70's, very humid at sea level.

I'm still playing a bit, I was at CCK-3 which was good all around. I'm always tinkering..

 

[Jakobi]

Jakobi,

IF you ever get the chance, try a neat combo I did the other day in my 300... I had a:

40 pilot
BGL clip 5
180 main
air screw out 2 turns.

whoa!

What a smoooooooth set up. The taper starts a bit sooner on the B needle however it is leaner past 1/2 throttle than the N1ex taper.

I like it, the bike won't load up and is really smooth getting on the pipe. It just barks in the sunny mode too. I will try clip 4 and re evaluate. My temps were upper 70's, very humid at sea level.

I'm still playing a bit, I was at CCK-3 which was good all around. I'm always tinkering..

Cheers Bailey.

Will give it a go if I ever get around to it. I still have a N3CH and an N3EJ here to try. I just haven't got around to it as the bike is running well enough as it is, and all my spare time seems to be getting sucked up with riding or other house hold chores

In all honesty I kind of like the N3 transfer onto the pipe. It reminds me that I'm riding the bike!

http://www.youtube.com/watch?v=EwXC1LZRIvw

 

[Klausen]

I got a also problem with the idle.
Yesterday I ride a little bit.
Carb specs:

#7
CCK needle #3
178
38
500ft
20?C
mixture screw 1,5 turns open

The bike has no idle and a stalling issue from 1/8 to 1/2
I think the CCK needle is to lean and the 38 idle jet to rich.

today I changed

DDK needle #2
175 main
35 idle

The idle screw is 2 turns open from full in.
Is this OK?
I got only a idle when I open the mixture screw 3,5 turns or more.
But after 1 minute the engine die off.
This means normally a to rich idle jet .
But I don't have a 32 jet at the moment.

 

[Jakobi]

I got a also problem with the idle.
Yesterday I ride a little bit.
Carb specs:

#7
CCK needle #3
178
38
500ft
20?C
mixture screw 1,5 turns open

The bike has no idle and a stalling issue from 1/8 to 1/2
I think the CCK needle is to lean and the 38 idle jet to rich.

today I changed

DDK needle #2
175 main
35 idle

The idle screw is 2 turns open from full in.
Is this OK?
I got only a idle when I open the mixture screw 3,5 turns or more.
But after 1 minute the engine die off.
This means normally a to rich idle jet .
But I don't have a 32 jet at the moment.

36mm or 38mm PWK?

2 turns open is fine.. Where is your idle screw set? If its all the way in, its a good indication that your needles diameter is too rich.

If the idle is wound right in, you're fuelling your bike by lifting the carb, which is what happens when you open the throttle. Lift it enough and you transition from the pilot onto too much combo of needle and pilot. Thus you end up chasing a smaller pilot jet as a bandaid.

Does this make any sense?

 

[Klausen]

38mm PWK

the idle adjuster screw is 2 turn open from full close

the air adjust srew is 3 turns open

I use the DDK needle diameter is 2,695mm.
Do anyone know the diameter of N1EF, N1EG, N1EH.

 

[Jakobi]

38mm PWK

the idle adjuster screw is 2 turn open from full close

the air adjust srew is 3 turns open

I use the DDK needle diameter is 2,695mm.
Do anyone know the diameter of N1EF, N1EG, N1EH.

Stolen from elswhere

SIZE: P/NO Dia.
NOZF 13383-37EB0 2.705mm
N1EF 13383-37E60 2.705mm
N0ZE 13383-37EA0 2.695mm
N1EE 13383-37E50 2.695mm
NOZD 13383-37E90 2.685mm
N1ED STOCK NEEDLE 13383-37E40 2.685mm
N0ZC 13383-37E80 2.675mm
N1EC 13383-37E30 2.675mm
N0ZB 13383-37E70 2.665mm
N1EB 13383-37E20 2.665mm

seems to indicate f=2.705mm E=2.695mm D=2.685mm and so on...

..so
G= 2.715
H= 2.725
J= 2.735

 

[Robby45]

Well, I finally got it dialed in for the most part. The bike now runs and idles fine, but is still real lean at 0-1/4 throttle. But that is only jetting combination I have found that allows it run well across the range.

I fiddled with everything, so I can't tell you what finally made the difference. Two things that I think are the most likely:

1. When I first got the bike, the airbox was not fully seated on the carb. It was hard to see, because it was on the right side of the bike. Because my problem got worse over time, I think it may have allowed enough dust and debris into the carb that clogged the air screw. While cleaning the carb (twice) I noticed residue in the pilot screw hole.

2. Even after checking my choke cable free play and things looking okay, I noticed the cable can bind at either the handlebar or the carb. I adjusted the routing to keep slack on both ends.

After the main problem was solved I tried all kinds of needle/main/pilot combinations to dial it in and settled on what JD recommends: 180 main/38 pilot/red needle in 4th clip position. My final issue is that lean 0-1/4 throttle. This bike is extremely sensitive to needle taper and clip position. One clip change on the red needle changes a ton, so I think I will keep it on the 4th clip and add a shim under the clip.