Motorcycle Repair: 79 yamaha DT 175 hard to start when cold, yamaha dt 175, mikuni carb

Question
Gary,
I have been restoring this old bike. Finally got it running last week after rebuilding the carb, and cleaning the carbon build up in the tail pipe. it has good compression, the reeds are good. and seals appear to be OK too. Now I face the issue of it being very hard to start when cold. The choke appears to work just fine, and it only starts when this is on, so I know it works. Here is a link to a video I took of it trying to get it to start.

http://s913.photobucket.com/albums/ac333/davidscott59/yamaha%20carb/?action=view...

Eventually, after about a couple minutes of kicking, it will start and stay running. It idles and runs just fine once I do get it running.
A neighbor told me of a trick he was taught that he does with his dirt bikes. Tip the bike on its side just long enough to allow fuel to flow out of the carb over flow line. Then try to kick start it. I humored him and tried this. To my surprise it started on the 3rd kick and stayed running! Does this give you any clues? I have the idle screw set at factory which is 1.5 turns out. There is no other low idle adjustments on this Mikuni carb.
I know a fair amount about bikes and am a pretty good mechanic, but this one has me puzzled!

Answer
It sounds like you are not getting enough gas into the carb to draft up into the choke circuit. Take the carb off and pull the bowl and check the float level it may be to low. Tipping the bike tricks the float and fills the bowl with fuel so it can start. Hold the carb side ways with the intake up and the float pivot point on the upper side and slightly tilt the carb back untill the float touches the needle and puts  a slight amount of pressure. This will give you a pretty close start at the float level it should be parallel with the base on the carb. The mixture screw may need to be out about 2 turns. Also a little trick to try install the carb and take an old battery vent hose thats clear and put it on the drain tube on the base of the carb bowl. The hose only needs to be about 6" long. Bend tube up along side of the carb without kinking it. Open the drain screw and let the gas flow into the tube and you should see where the gas level is in the bowl.It should be about 1/8" below the seam where the upper part of the carb and the bowl meet.