The larger filter had a huge effect. It was very difficult to get the thing to run correctly. I spent a very long time grooming the S&S carb with the stock replacement K&N flat-panel filter, and it wasn’t easy. So, I figured that with a bit of effort I should be able to dial it in. Lot’s of luck with that. This tuning job was a real handful.
I could tell right away that the thing made a whole bunch more power, but it ran terrible. Waaaaay too lean at first. I started with a #60 main jet and ended up with a #68. The pilot jet and the two air-bleeds were all over the place. Get it cleaned up down low and it wouldn’t run up top. Get the top squared away and you could hardly ride the thing on surface streets. The accelerator pump was also a headache.
I eventually got the thing pretty close, but a lot rougher around the edges than it was before the filter mod. The WOT performance is absolutely killer. It runs from 4K to 7K in 2.65 seconds, and it’s scary how quick it blows past 8K . Glad those RD springs are in there. Loads & loads of mid-range torque. Starts great. Idles good. Part throttle operation is acceptable but it ain’t gonna win any awards in the “seamlessly smooth” category.
I was truly amazed at how much the filter affected performance. It begs the question; how well would the stock DR cam have run with this filter? I plan to do a separate post on the filter setup. Seems to me that it has the potential to make significantly more horsepower, regardless of the carburetor. I also suspect that a more forgiving mixer like the stock Mikuni or a VM would not present such difficult tuning issues.
So, the 340b cam with RD valve springs seems to be hackin it. Oh! BTW, it’s loud.