Engine tuning?

[Blackhauk90]

Alright i got something i've been having trouble with on my bike and i was wondering if anyones gotta idea what the problem is. Heres the setup-

YSR50 swapped out with a dt175 engine.
The engine has some minor port work and a older style rd350 carb (stock jetting). The pipe on it is a high revving one that is suppose to stop pulling at around 12ish.. The electronics are stock and it has a 5" uni foam filter..

The problem i'm having is with the tuning of it all. It idles at around 2-3ish but i have to constantly play with the throttle and i can't just let the handle go and have it idle on its own. The idle screw is in all the way too so i figure it's probably at about half throttle when i gradually roll on it for it to idle right.. Also when im running it up i can get it upto about 11k max and when i let off the throttle to shift it like bogs for like 2 seconds then then power kicks back in a little..? I was guessing it could possibly be the airfilter.. just the fact that there is no airbox on it and it's a strait foam filter..? I know some engines require airboxes to run proper but im not sure if the problems i'm having are one of the signs for no airbox or not..? Anyone got any ideas on whats up with it?

[flotek]

sounds lean on the main .sounds s like a real macgyverism bike too . that shitty carb is probably shot too(worn slide) and casues erratic jetting . wh y do yo uthink your hitting these high rpm numbers ? theres no way your hitting 11 grand on that engine .. i really doubt your even getting 9k out of it .

[fletchman919]

Pull the plug and tell us what it looks like. You don't need an airbox to get it to run perfectly. In fact, it'll be peppier without one with the propper jetting and an opened up exhaust. I agree with eviltwin that the old carb may be junk. I'm not familiar with that particular carb, but I have rebuilt carbs and they still don't perform well. I like how your mixmatching parts though. I do that on old street bikes sometime when it's hard or expensive to replace with an original.