I suspect you are right as I don't recall popping the last time I used the bike for trail use, but it is really bad this time around. I have the carb torn apart and suspect a good rebuild (including a couple parts I found missing!) will fix most of the issue. All the same, I sprung for the extra ACV parts while ordering and still want to drill out the ports and give it a go. So, can anyone measure the ports for me? How about the brass insert?
I'm a tellin ya, you don't wanna do it......
You will create a 'kooky zone' right above closed throttle which you can't fix.
The ACV works off of manifold pressure when the throttle is closed, creating a 'rich' condition to compensate for an extremely lean pilot, and richer main air jet, on the stock WR.
When you crack the throttle, the valve 'futters' or goes partial open, creating a mess.
If you disable the ACV (break off the pin or use a full cover gasket) and put in the correct pilot, and change the Main Air Jet to 100, you now have a YZ Carb body (mol).
If you replace the plastic hot start nut with an aluminum one, clean and polish the hot start and cavity, add a little anti-sieze, and lube the cable with THICK lube (like chain lube, that won't let water in), you will probably solve all of your decel popping.
The problem with the ACV on the WR is that once you get the motor uncorked and breathing properly (like a stock YZ), that nebulous throttle repsonse is gone, and you notice every little picadillo in the jetting, making the ACV an actual problem in the jetting.....and so you have to finish the uncorking by disabling the ACV, changing the needle, main, pilot, Main air jet, and correct the fuel screw adjustment......in other words, a stock YZ carb.
I have had (3) WR's and have tried everything that I know of to get the best performance out of the carb, the the BEST performance is no ACV, and closer to YZ jetting.
My WR is actually has a YZ head and cam, so all my jetting is the same as CA delivered YZ circa 2007.