2012 S40 that I bought last November with 850 miles.  Stock exhaust.  I've only put a couple hundred miles on it after reconditioning it for the road.  I've posted about the hot odor before, but nobody could identify it.  It's not burning brakes or oil, and I only smell it after shutdown while the bike is hot.  Nothing is leaking.  It's like a cross between burning brakes and a lean carburetor odor.  Can the wet clutches smell?  I've adjusted the clutch at the handlebar.  The book says 3mm of slop at the lever, and mine is about 2-3mm.  I read somewhere on here the clutch arm at the engine case needs to be between the 2 marks.  Mine is more like ON the top mark.  The clutch seems to operate right, and there is no slipping.  I'm just wondering if I need to back off the adjuster by the engine case a bit to place the arm between the marks.  If a wet clutch can't produce an odor, then maybe I'm on the wrong track.  Thank you.

J Mac wrote on 10/21/23 at 11:47:26:

All you would smell is burning oil
Top mark only adjustment limit indicator.
To get it lower you need to change the throw out rod of which there are 3 sizes. And to get to them you need to remove the cover.

Thanks to everybody.  I'm going to give this one a shot first.  It didn't seem like brake odor exactly, but I've been known to be wrong.  Just ask my wife.

Gary_in_NJ wrote on 10/21/23 at 12:06:44:

I backed off the rear adjuster some to give more free play in the foot pedal.  I jacked the bike up, and front and rear wheels spun freely.  I rode it, and the disk and drum were cool afterwards.  It's not the brakes.  When I shut it down, I immediately got down on all fours and smelled the bike all over like a dog (be kind).  That acrid odor was perhaps present slightly by the fins on one side of the cylinder, but not the other.  It was present at the muffler opening and most pungent where the muffler heat shield is.  Maybe it's something with the stock exhaust baking off.  My 2003 didn't have the stock exhaust on long enough for me to remember.  I don't know if the muffler is carboned up or if the bike is still running lean, but I'm not going to worry about it for a while.  I hear Dave and others in regard to the head oil leak, but this odor is NOTHING like oil.  My problem is that I smell everything, often things that nobody else notices.  I can tell what kind of laundry detergent people at work used 3 weeks ago .

Gary_in_NJ wrote on 10/21/23 at 12:06:44:

I was reading on StackExchange that a sharp odor in the exhaust can be NOx due to lean conditions.  I might try another 1/2 turn of the screw, but then I'll be at the limit of 3 I think.  Idling is fine; no backfires.  I'm close to sea level.  I have the stock muffler and airbox and did the spacer mod.  Should I try the next size pilot jet only or the next pilot jet AND the next main jet?

If your throttle response is good, I wouldn't touch the jetting. If your mixture was lean enough to cause an odor, you would have a lean bog off idle (pilot jet) or upon roll-on (needle).

People tend to focus way too much on the pilot circuit. Beyond the first few degrees of motion at the throttle, it's all but inconsequential. We ride 90% of the time on the needle.

Dave wrote on 10/21/23 at 13:50:33:
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It sounds like the leaking head plug.  It smells like burnt paint in the beginning because the oil is burning off completely.  Over time, the leak will worsen, oil will start accumulating and the smell won't be as strong.  

I've gone through this twice now and would look there first.

As for jetting, what Gary said.   If it ain't broke, don't mess with it.  

Thanks, Paul and everybody.  I just looked for good measure, and that area is as clean as the day it was made.  This bike is a 2012 with a little over 1000 miles on it.  The odor I have smells NOTHING at all like burning oil.  It's sort of like when you first turn on your furnace after not using it for months but not exactly.  I think it's something gunky with the stock muffler.  Maybe it's a symptom of the bike mostly sitting for 7 years from 2015-2022.  I apologize for the false flag here.


ThumperPaul wrote on 10/24/23 at 10:58:01: