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Message started by killsport on 11/15/14 at 09:26:20

Title: Stalling when cold
Post by killsport on 11/15/14 at 09:26:20

Hi all... In sunny south florida, it's about 65 to 70 in the morning (not gloating). Still, when I start my 2011 s40 (5000 miles) it seems to have a very low idle. When I drive it, it accelerates fine, but when I put in the clutch to coast at a stop sign, it stalls. After 5-10 minutes, everything is perfect and the idle is smooth.

If I use the choke for 10-15 seconds at start, it increases idle temporarily but doesn't solve the issue. Is this normal? Should I just warm it up for 10 mins in the driveway? Is there some other adjustment I should make?

Thanks!

Title: Re: Stalling when cold
Post by bobert_FSO on 11/15/14 at 10:01:00

Leave the choke (enrichment) out for the 10 min it apparently needs. Go ahead and ride with the choke out during that time. Half way out should be enough. You won't hurt anything and it will keep the idle up. Don't forget to push the choke in when warmed up.

Those S40's with the ultra-lean idle settings might need that. They can be very cold-blooded. I looked at one that would barely run when cold without a choke, even at 70 degrees outside. I put a larger idle jet (can't remember the size, but it was the next size up) in my 2001 Savage, and it would start and run well without choking all the way down to 50 degrees F. It was probably a little rich under normal operating temps, but it also didn't backfire under deceleration or during shutdown.

Title: Re: Stalling when cold
Post by Kris01 on 11/15/14 at 10:27:15

I haven't rejetted mine yet and it runs at a pretty low idle when cold with no choke. I pull the choke out one notch and just leave it there. It runs pretty good at all temps like this. Probably runs a little bit rich at warmer temps though.

Remember, at colder temperatures your bike will run a little leaner than normal. Without pulling the choke it will run extremely lean. Think lean enough to starve the engine of fuel. That's probably why your engine stalls.

Title: Re: Stalling when cold
Post by raydawg on 11/15/14 at 12:09:42

Yeah, mine will get cold quickly when the ambient temp is low. I choke to start, and run her about a mile on half out choke.
I get to the ferry, a half hour of sitting on its deck in the cold, 50 degrees and lower, and I have to choke her to get her to quickly fire and idle her.
A few minutes into the ride and she is good, choke off.

Title: Re: Stalling when cold
Post by MnSpring on 11/15/14 at 12:49:26

Some Internal Combustion Engines. Need to be, 'totally at Operating temperature'. To function as you want them to. This ICE is one of those. Although you can buy a 2015 one, it is still, the SAME, 30 year old design.

So, in this ICE, Idle speed, when cold, is not the same as idle speed when warm.
You can use the Choke to increase the idle speed, until you have reached the correct operating temperature, even drive it with choke on, until it is up to Temp. (Choke changes the gas/air mix temporarily).

Or, (I am fortunate to have one that adjustments allow it to start right off, with NO Choke, at above 50f). The screw is set to provide a 1050RPM +/- idle, when warm. But it is not high enough when cold.

One solution would be, 'Temporarily', raise the idle speed, until it is warm. By putting a, 'shim', under, the 'idle adjust screw'. (Not by adding more gas). Which is attached somewhere, and then just falls out, (but stays close), when the throttle is turned.

Another is, run it with Choke, full/part, whenever works, until it is up to temp.

I chose the first, because I am already their, (Raptor Petcock, to turn 'on'.) It's a 1 sec thing, to 'turn on/insert shim, all by feel. And I have adjusted things, to make the ICE, run smoothly, the way that works for me. Balancing the, 'Power' that I need, and the 'Economy', I desire.

I, (wrongly thought), that a '06 one, would have refinements like newer ICE's do. And not need the attention, like a 80's 'barn queen. Especially the Oil requirements. But through the knowledge and experience here, about that particular ICE, I have Learned.

Now yours, (as to your post), starts just Fine, with no choke. So here are two suggestions. Read the 'Technical Documents/Reference', posts, and change the oil.

Title: Re: Stalling when cold
Post by killsport on 11/16/14 at 09:23:30

I took her out this morning and used 1/2 choke as recommended by y'all (thanks bobert, kris, raydawg and mnspring). Worked great. Really appreciate the advice from this group. Makes owning my first bike so much better... more calming, and have lots of folks who've "been there, done that." Again, thank you! :)

Title: Re: Stalling when cold
Post by petervt on 10/13/20 at 13:56:07

Afternoon I am a cold weather rider, and reviewed some older posts on 10-3-10 (Bubba) suggested set petcock to prime, I did and did my morning commute 30 degrees for 30 minutes and bike ran perfect just like 70 degrees, my question is am I doing any damage? I set petcock to normal setting and ride home was great. 60 degrees helps thanks for all great info petervt :)

Title: Re: Stalling when cold
Post by justin_o_guy2 on 10/13/20 at 14:30:12

my question is am I doing any damage..
No..
Only downside to running on prime is
No reserve..

Title: Re: Stalling when cold
Post by petervt on 10/14/20 at 02:18:22

Thanks I fill up every 100 miles!

Title: Re: Stalling when cold
Post by bobert_FSO on 10/14/20 at 05:42:40

If you are running the original vacuum fuel petcock, it could be the culprit. Most people seem to experience the petcock leaking gas.

However, in my case, I experienced a stiff diaphragm that would starve fuel in low vacuum conditions, especially in cooler weather. It manifested under two conditions. One was putting around at about 40 mph in 5th gear. It would stall when coming to a stop. The other was sustained high speed, especially into a headwind, where I was really pushing it to maintain speed. In that case, It was just like running our of gas. The engine would stumble a couple of times, then just cut off. Flipping the petcock to prime would bring the engine back to life, usually before I could coast to a stop.

Title: Re: Stalling when cold
Post by Dave on 10/14/20 at 17:11:29

5C515C5B4C4A3E0 wrote:

Yep....this could be your sign that the stock vacuum petcock is failing.

They all will fail eventually - this may be your time.

Either replace the petcock with a manual Yamaha Raptor petcock (buy the original part and not the Chinese copy). Or you can rebuild your petcock if you want to keep the automatic shut off option.