Backfire on inlet

[Veemanzero]

Guys I've put this in engine and gearbox section , however its unlikely that its to do with it. However I'm not ruling it out completely. The engine has been completely rebuit and im sure i have done a good job.I have what i would describe as a intermittent inlet backfire but only when trying to hold the throttle at certain revs (say 3000). The bike idles perfect and revs stationary cleanly and quickly. Problem only occurs when trying to hold the revs, it didn't like it at all. I'm thinking a vac pipe leak or a sensor. Any help especially from some one who has had this problem would be appreciated. I should point out that I have not ridden it yet

[T 24]

Sounds that your engine is running lean@3000 rpm. Check at first vacuum lines(all of them), map sensor( you can change it with one in air box) and fuel pressure, it should be about 3 bars. Fuel pressure will tell you the condition of the pump, regulator and fuel filter.
Check also if you have air leaks in your throttle bodies etc.

[Veemanzero]

Bike runs much better with atmospheric pressure sensor unplugged. No backfire, but its not the sensor as i have swapped them around ?

[grog]

backfiring thru inlet is def. weak mixture. why , no idea. spray around inlet bits with carby cleaner, if it runs better, you have a leak. first place to start im thinking. keep us informed.

[Veemanzero]

Done yesterday Grog. No leaks ?

[Veemanzero]

Sorted cleaned crank position sensor plug. Set throttle position sensor. And ballaced the TB'S. all sweet