NATE- if your carb is less restricted now............July 16 2012 at 1:24 PM
rex (Login thestinkiestbob)
And if it's starving out at higher speeds then surely the answer is just a more tapered needle at the pointy end.
Running too lean at the high end wouldn't necessarily seize or overheat your engine if it's not running lean until right at certain higher speeds where it USED to run richer due to the increased restriction of the air filter at that those higher revs.
It's a bit like what happens if you put some fingers over a carb when it's running- it won't make any difference at low revs but at higher revs it gets very rich. If your bike was designed to do this on purpose then derestricting the air flow will make it starve for fuel at high revs.
If that's the case, the it's not starving until you reach the certain higher revs where it's been needled to to run correctly WITH a restricting airbox that causes the carb to suck more petrol at those revs.
Tthe airbox will cope just fine at lower revs not giving much restriction. The engine runs basically no different at low revs with or without the airbox.
But at higher revs it'll NORMALLY suck more petrol due to the restrictive air flow because the box is only SO big and can only cope with SO much air at a time.
So if you unrestrict the air flow it will probably run fine at lower revs but suck too much air at higher revs and just die off like it's running out of petrol.
It won't necessarily be overheating due to running fine up until that very point because the airbox isn't actually restricting anything at low revs, only at higher ones.
Got an spare needles you can butcher? If so pop one in a drill and use sandpaper to pointy it up a bit more. That's what I used to do for running open CV carbs and no airbox (befor I discovered the perfection and reliability of cable pull carbs).