Need your help please - 950 erratic idle and other questions...

hmmngwy · 09-27-2008, 04:48 PM

Need some help. Bought my 2003 950A a couple of weeks ago. Idle is a bit erratic. Fairly stable above 2000 rpm. If I move it to <1800 rpm, it starts to fluctuate between 1800-1400 rpm. If it falls below 1400 then it dies. Starts ok using the choke when it is cold. When it is hot, I either need to give it choke or gas to get it to start. Acts lean.

Mods -

When I bought it, the PO had removed the canister. The two tank vents were tied together to a tee and then connected to a connection below the snorkle of the airbox.

Q: Is it ok to leave this like this or should I just let the tank vents open to atmosphere and cap off the airbox opening?

What I did...

I removed the EPC valves, capped the connections at the carbs, and plugged the holes to the airbox. Did the flapendectomy

The SAS is still connected because the cats are still in the cans.

I raised the needles in the carbs up one notch and set the air screws to 2.5 turns for both carbs. This really seemed to help the throttle response.

I was pretty careful to check the carb to intake boots and the seal of the air filter and airbox.

Observations...the carb vents are routed outside of the airbox. I didn't check the connections to synch the carbs (sorry I forgot to check when I had it apart). There is an open hose connected to the bottom of the airbox, looks like a drain. The tank vents in the middle of the tanks are vented to open hoses.

Back to my original problem...erratic idle and having to use the choke or throttle when starting the bike hot. What should I check or try?

Any advice is greatly appreciated.

CycleDoc59 · 09-28-2008, 05:19 PM

And old method to find if the bike is running too lean, especially
at idle, is to remove the air box lid/filter and cover most of the
carb inlets. Two small pieces of cardboard work ok. It's best
to have two people; one to operate the bike and keep it running,
the other to move the cardboard pieces to cover more or less of the
carb inlets. If the bike is too lean to idle, movement of the covers should
allow a proper idle after some trials..

You may well find that only one carb needs to be
restricted. The likely problems could be: idle air bleed screws
not turned out enough, pilot (idle jet) plugged, or pilot too small.

If the bike is set up to run well at idle, and is not too lean, there
will be no improvement in running by covering carb inlets.

Dyno operators often use duct tape to partially cover carb inlets while trying to find optimal carb settings...

Carbs on all bikes are usually Very close to optimal from the factory.
But "close" means they can be off just enough to make riding an unpleasant affair. One or two small changes are usually all that are needed.

But shops/owners often make multiple changes to the carbs, exhausts, etc.,and when the bike runs poorly, it can be quite difficult to find what
item or items are wrong.

09-27-2008, 04:48 PM	#1
hmmngwy ^OP Gnarly Adventurer Joined: Sep 2005 Location: Northeast Florida Oddometer: 232	Need your help please - 950 erratic idle and other questions... Need some help. Bought my 2003 950A a couple of weeks ago. Idle is a bit erratic. Fairly stable above 2000 rpm. If I move it to <1800 rpm, it starts to fluctuate between 1800-1400 rpm. If it falls below 1400 then it dies. Starts ok using the choke when it is cold. When it is hot, I either need to give it choke or gas to get it to start. Acts lean. Mods - When I bought it, the PO had removed the canister. The two tank vents were tied together to a tee and then connected to a connection below the snorkle of the airbox. Q: Is it ok to leave this like this or should I just let the tank vents open to atmosphere and cap off the airbox opening? What I did... I removed the EPC valves, capped the connections at the carbs, and plugged the holes to the airbox. Did the flapendectomy The SAS is still connected because the cats are still in the cans. I raised the needles in the carbs up one notch and set the air screws to 2.5 turns for both carbs. This really seemed to help the throttle response. I was pretty careful to check the carb to intake boots and the seal of the air filter and airbox. Observations...the carb vents are routed outside of the airbox. I didn't check the connections to synch the carbs (sorry I forgot to check when I had it apart). There is an open hose connected to the bottom of the airbox, looks like a drain. The tank vents in the middle of the tanks are vented to open hoses. Back to my original problem...erratic idle and having to use the choke or throttle when starting the bike hot. What should I check or try? Any advice is greatly appreciated.

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09-28-2008, 05:19 PM	#2
CycleDoc59 Wrench Rider Joined: May 2006 Location: East Virginia Oddometer: 712	And old method to find if the bike is running too lean, especially at idle, is to remove the air box lid/filter and cover most of the carb inlets. Two small pieces of cardboard work ok. It's best to have two people; one to operate the bike and keep it running, the other to move the cardboard pieces to cover more or less of the carb inlets. If the bike is too lean to idle, movement of the covers should allow a proper idle after some trials.. You may well find that only one carb needs to be restricted. The likely problems could be: idle air bleed screws not turned out enough, pilot (idle jet) plugged, or pilot too small. If the bike is set up to run well at idle, and is not too lean, there will be no improvement in running by covering carb inlets. Dyno operators often use duct tape to partially cover carb inlets while trying to find optimal carb settings... Carbs on all bikes are usually Very close to optimal from the factory. But "close" means they can be off just enough to make riding an unpleasant affair. One or two small changes are usually all that are needed. But shops/owners often make multiple changes to the carbs, exhausts, etc.,and when the bike runs poorly, it can be quite difficult to find what item or items are wrong.