Today I did the 1/2 spacer and 1-1/2 turn of air mix screw mods, still running stock airbox, jets, and pipe.
The bike runs much better, before I had to run on 1 notch of choke all the time. Before the bike would frequently backfire on decel and when turned off. Now it only backfires when I sharply decel.
Much improved but still not perfect.
Some hints I borrowed from this forum:
1. Remove the carb from bike and put it in a vise with wood and duct taped faced jaws.
2. Get the $5 harbor freight mini impact screwdriver, those screws on the diaphragm end of the carb are tight. This tool has a Phillips tip that fits nicely all the screws on the carb without stripping. And yes, impact in the form of repeated light but firm taps was needed to remove the ones on the diaphragm cover.
http://www.harborfreight.com/7-piece-reversible-impact-driver-set-93481.html3. I replaced the diaphragm screws with Metric no 5 screws and used some anti seize when putting it all back together.
4. Inside the diaphragm are 2 Metric no 3 screws that I also replaced as I nearly stripped the Phillips head on one before I again used the HF impact tool-no need for impact, just needed a well fitting Phillips bit.
5. I followed the forum advice and went to Ace where I found a black no 4 nylon washer and a white no 4 nylon washer, they were both identical except in color and both were about 1/2 the height of the stock washer. I used the white one. While there I also picked up 4 no 4 brass washers as 4 together were the same height as the stock washer. So I have these to play with if the white nylon washer doesn't work for me long term.
6. I drilled the brass plug with a very small bit and chucked it in my drill with only 1/8" sticking out and drilled a small hole that a 2-1/2 drywall screw could bite into. It took me three screws before it came out. I only used one screw per attempt to ensure I had a good bite into the brass since all this is happening at the tip of the screw. I also filed the tip down a little to avoid having it bottom out on the delicate air mix screw. Not having a dent puller, I simply latched some vise grips onto the screw stuck in the plug and use a hammer and large screw driver against the face of the vise grips and sent the vise grips with the screw attached and brass plug attached flying away from the carb that was still mounted in the vise.
Note: I did compare these metric no 3 and 5 screws to computer case screws but the thread looked finer on the stock screws so instead of using computer case screws, I just bought replacements at Ace.
Thank you all for sharing your experience and making this job relatively easy for me.