Hi guys please help. I will put as much info as I can as I am really stuck now.
so I have a cbr125 2008 fuel injection.
started bike and after about a mile just cut out.
Replaced coil with HTC lead, fuel injected body with injector and sensors and cdi unit.
then took it to a bike shop to be told it had low compression.
So replaced with a second hand engine that was running (or so I am told but from breakers with warranty).
now when you try to start the bike it back fires though both the injection unit and big bangs from the exhaust pipe.
And of course it will not start.
So have had a general look over the wiring as much as possible. Checked the earth.
checked the valve clearances and seems to have good compression we have replaced so much not in the engine then the engine itself that I really dont know where to turn so am looking for some help.
thanks in advance

 

I'm not all that familiar with the 125, but it sounds like it's firing on the wrong stroke.