Ok, my dirt bike still wont run, what the F?

ive had the bike going on my 4th season, the first 3 seasons i barely ever opened the throttle wide open. the engines in great shape i think.............


when the throttle is wide open the engine boggs down, just changed the spark plug......... the old one had black tar like stuff on the outer rim of the plug, and only 8 rides or so on that one. i assume its over fueling, took the carb apart, all the jets everything is crystal clean, the float appears to be seating the inlet valve correctly, i adjusted the depth of the jet needle both ways, leaned out the pilot screw which supposedly corrects your fuel input similarly to adjusting the jet needle.


i dont know what iam missing here, unless the throttle position sensor is done/ out of adjustment, maybe it doesnt have enough compression for open throttle( top end rebuild), the hot start valve isnt seating?


also my chain put a hole in the crankcase, if backpressure is required in the gearbox i dont know
Ok, my dirt bike still wont run, what the F?
For starters, what type of bike is it?





Are you sure you are putting in the right spark plugs? I dont know how many bikes I have 'repaired' by fitting the right sparkplug.





People try and save money by fitting a $3 sparkplug instead of the correct one.





Have a look on the sparkplug and see if the part number has a 'R' on it. That is Resistor. If it doesnt, change it for a plug with a R.
Ok, my dirt bike still wont run, what the F?
I would have to say in my profession of riding dirtbikes, That it would be that the hole in your crankcase is probably SEVERLY making your dirtbike not run good. and i advise you not to ride it anymore until you get that fixed. That hole can severly damage your engine.
Reply:sounds to me that it is out of time,,,,try taking the cover off the magneto side and adj, the timing,, you may need to remove the magneto itself to do this,, Being I don't know what kind of bike it is I cant give you a sure ans er .Or if it has points then you probably need to replace them
Reply:Back pressure seats the rings to the cylinder walls, especially the oil ring on a 4 stroke. It won't run right until you fix the crankcase.