My bike is 99 VTR1000F. I bought it about 4 months ago, but I couldn't ride on it because of cold weather. At last weekend, I have gone for winding and it gave me great pleasure except breaking . When I was coming back home, my bike became somewhat different. It makes after burnings at every time I return the throttle.

These are something to consider.

1. It is tuned with a full exhaust system, including pipes and silencer. The diameter of silencer is about 65mm and its sound is very very noisy.

2. My buddy ride it about 20km and he is not familiar with big twin engine. Right after he ride my bike, It becomes make after burnings.

So, anybody can advice me?

 

do you mean backfiring? I would guess your fuel mixture is off and you may need to sync the carbs.

 

Is the PAIR system still hooked up? If so, that is what is causing the problem.