I've had the s4rs for 2 years now and this is new.  It has gotten to 100+ degrees here and the other day I was riding in traffic - fans cycling etc.  I stopped at a store and came back out 15 minutes later and the bike didn't want to start/idle.  The auto starter kept running trying to keep the engine going.  I gave it a little gas and the engine started running.  I rolled off the throttle and it died.  After riding a bit without letting the throttle completely close it began idling properly again.  It has happened a couple of times since then always when it is hot outside and the engine is hot.  If the engine is cold it always starts, if the air temp is 80-90 degrees it always starts.  Could this be vapor lock?  Has anyone else had this happen?

Could be, though FI with an in tank pump tends to prevent this.  Probably about all you can do is cycle the fuel pump on and off a couple of times before starting and or try a different brand of gas. 

I have the same problem with my ’06 Sport1000 since day one, I bought the bike new in May ’08 and this problem usually occurs after a hard/long ride and I leave it alone for a coffee break and go back to ride it the bike refuses to start, and once it did it idles high at around 2,000-2,500rpm for a while and returns to normal after a few minutes. Originally I thought they added this feature in to make it actmore vintage you know; part of its Italian heritage  .

I brought it to the dealer just this Tuesday and the mechanic said it could be the emission canister dumping excess fuel/vapor into the cylinder and with the combination of the heated environment a vapor lock is very likely. I removed the emission canister yesterday and haven’t been able to reproduce the problem.

I hope this helps  

Quote from: howie on July 24, 2008, 01:43:35 PM
Could be, though FI with an in tank pump tends to prevent this.  Probably about all you can do is cycle the fuel pump on and off a couple of times before starting and or try a different brand of gas. 

Oh yh, I discovered this happens more using Shell gas then any other brand...
Dont know why/how but thats just my observation lol

Good point about the canister.  If the tank is filled to the top and temperatures get hot expansion can send liquid into the canister.  Easy enough to figure out if this is the problem.  Either do a canisterectomy or disconnect the lines to the manifolds.  Covering the vacuum nipples with 5/16 rubber caps is an easy way to do it.

I will try a different brand of gas.  I did fill up at a station I don't normally use before this started happening. 

edit:  my carbon canister is long gone - I have the DP ECU and a full exhaust so I think cycling the key and different gas is the first thing I'll try Thanks!

sounds like the bike is loading up (too rich).
every time the bike starts no matter how warmed up the bikes are the ECU goes into cold start mode and richens the mixture weather the bike needs it or not. with very hot temps it does not need the extra fuel and loads up.
If the DP ecu or efi set-up is too rich at idle then this will be compounded.

Good call.  I've recently switched from ethanol blend to straight gas since they started requiring the pumps to be marked July 1st.  This could have pushed the mixture too rich - it was most likely rich to begin with.  I'll trim it down a bit and see what happens.

Quote from: ducvet on July 24, 2008, 05:37:30 PM
sounds like the bike is loading up (too rich).
every time the bike starts no matter how warmed up the bikes are the ECU goes into cold start mode and richens the mixture weather the bike needs it or not. with very hot temps it does not need the extra fuel and loads up.
If the DP ecu or efi set-up is too rich at idle then this will be compounded.

Same thing was happening with my supercharged Cobra...would piss me off.  Spent several hours on the dyno and worked all the bugs out.  Too rich, too much fuel