VTEC 800 Engine whoose noise and stalls

[hornetgr]

Hi , to all

I have a small problem with my 2004 VTEC VFR800, but in some cases tends to be annoying or a little dangerous:

 

When i ride and i stop at a junction ,sometimes i hear a whoose noise like a rapid release of air from a balloon lets say, then the engine quits and smoke comes from under the tank near the handle bar.

When i am starting again engine starts, a little bit difficult  but starts,  and there is no problem after that until the next time it happens (in a ride of lets say 12 hours with stops maybe it will happen 2 - 3 times).

I came to a  post with the same problem to another forum, that a rider had the same problem but no solution has been posted. Some guys there said about backfires and smoke is exhaust gases that released from intake valves. Many theories about starter valves, spark plugs and valve clearances .

 

Well my bike has 82000 Km in the clock and i never check valve clearances (i know shame on me, but ok)

spark plugs are about 30000 km old

After the issue i did with no luck the following:

 

did the pair mod, flapper and snorkel mods

raised idle speed to 1400 +-50 rpms

 

Any help or previous experience and maybe a solution with the above issue will be much appreciated.

 

Thanks

Stathis

 

[Bikermike1]

Hi Stathis

I’m probably the other poster from another forum you are talking about. The problem you describe is exactly what was happening to me and a solution wasn’t posted because I never found one. The problem stopped as suddenly as it started, I’ve done over a 1000 miles since the last event and everything has been good. In the end I put it down to dirt or crap getting into the system.

[GreginDenver]

Something that occasionally happens with cars is having a catalytic converter that is falling apart internally, which causes a partial blockage of the exhaust, which causes an increase in back-pressure.  This situation can result in engine stalling when the revs drop to idle at stop signs or traffic lights.  A car (or motorcycle) with a partial internal collapse of the catalytic converter would feel "down on power".  But if the partial blockage develops gradually over a long time the driver/rider might not recognize there's a problem.

[Havagan]

I never got smoke from near the right handlebar, but when my bike (65,000 miles at the time) had an issue with stalling and then hard starting it was due to a failing pressure regulator.

 

Fuel Pressure Regulator explained: 

 

 

 

[Urbanengineer]

Thanks for the vid, that’s nice to see. I’d like a PC5 with auto tune to tune my own bike and diagnose issues. 

[Rogue_Biker]

Smoke coming from under the tank is NOT GOOD.  

 

I don't know what's wrong with your bike.  But if I were in your situation, first order of business for me would be to lift the tank up and inspect all hoses.  Check all wiring and connections to the tank and air box.  Remove the whole air box and inspect everything down there, including connections to the airbox.  Whatever is wrong won't be easy to diagnose and you will have to be methodical as you try to trace the source.  I would start with the obvious and work from there one at a time.  Check wiring connections.  Check continuity of wires.  Check fuel lines.  Check, vacuum lines, fuel vent lines, etc.  Check fluid levels (coolant especially).  You have to act like a detective and eliminate all possibilities until you find the truth.