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Pop sound from radiator area

487 views 14 replies 5 participants last post by  naster  
#1 ·
My V Strom 650 XT has occasional pop sound or kinda backfire type sound near the fuel tank area below the ignition key hole area.

Unable to ascertain whether it's from Radiator or from air filter box or anything else.

This sound comes while deceleration after revving up while coming down a hill or revving up till 5-6 k rpm and slowing down.

Its not always either.only some times during hard accelerations and then decelerating.

I can't record it since i will be riding at that time
 
#9 ·
@manufagf, any chance that the backfire may be coming through the airbox? I wonder if the air mixture might be too lean? Check the vacuum hoses and even the exhaust for any leaks.

@2metermatt, I'm inclined to suspect the TPS. Have a look if the following discussion to see if it covers the same symtoms as you currently have, https://www.vstrom.info/Smf/index.php/topic,6564.0.html Also check that the hot (engine coolant temp showing at least 2 bars) idle speed is not perhaps set below 1,200 rpm. If all these are correct, have a look at at TBS sync as discussed in https://www.stromtrooper.com/threads/02-12-1000-tb-synch-with-pics-and-write-up-thanks-yarz1.409330/.
 
#12 ·
@manufagf, your profile shows that you have a 650, while 2meterman has a Vee. My reply #9 is in two parts, giving advice to two different members.

Your comment wrt "This sound comes while deceleration after revving up while coming down a hill or revving up till 5-6 k rpm and slowing down." leads me to think that either unburnt fuel or an excessively lean mixture. The air intake sensor sends info to the ECU which in turn will regulate the fuel mixture. A vacuum leak or an exhaust leak could cause a lean mixture. Dispite your ride being a 2023, perhaps also check the airbox breather, for the condition of the Positive Crankcase Ventilation airbox breather sponge. If too much oil vapour being passed into the throttle bodies, could add to the already lean mixture.
 
#15 ·
Contrary to common wisdom, I think installing a K&N without a modified exhaust/decat could add more latency and disbalance in the feedback of the whole chain - electronic throttle body -> injectors -> O2 sensor -> exhaust flow debit. I also hear a pop when decelerating/downshift but in the exhaust and I quite like it tbh. Could it be the K&N makes it more pronounced when rapidly turning the throttle when idling? I noticed a partial stall with stock exhaust and air filter, not so much after I let her breathe. But there is some latency in the electronic throttle body which could be to reduce abruptness in throttle response in everyday riding.