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!

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.

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.

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  

Thanks  I fill up every 100 miles!

bobert_FSO wrote on 10/14/20 at 05:42:40:


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.