^^^^^***this***^^^^^
Corey is amazing and I live and die by his product, I wonder if you should try one of Dustin’s beautifully crafted 2-1 intakes (I believe he has a sale on right now) and; sell one of the SmartCarbs (I would buy it). What is diameter of your exhaust? I have found that stock header pipes work the best for all around riding, you could get some beautiful Cone Engineering stainless megaphones from Dustin at Beck built fab (member on here) at the same time to create some back pressure. It sounds like a loss of intake vacuum due to exhaust reversions so as well as putting the o2 back on you could add a vacuum gauge.
Love your build!
Sorry it took so long to get back to this, but life got in the way most of the summer. I jumped back on the project in September, after speaking with the folks that supplied the Vape ignition. IMO, it still felt JUST like a rev limiter/ignition problem, but they suggested that the 2-into1 header I'd gotten might be the cause of my problems. I went back to the stock exhaust, and after going with the next leaner size main jet on the SmartCarbs I could rev to redline, though it wasn't ideal. I used to have to stop rolling on the throttle to prevent over-revving, but now I had to wrestle it to redline. My thoughts about the header issue were that either the header length (Mike's XS), the collector inlet/outlet sizes (Cone Engineering, and sized using an exhaust calculator program), or the muffler backpressure (Lossa Engineering) were causing the exhaust pulses to possibly stack up at the collector at higher revs, preventing the cylinders from scavenging properly.
I threw a hail Mary, and went with a designed system, end-to-end, from Delkevic. Not hideously expensive, and I thought they'd likely designed this to just bolt on and work (hah!), with possibly some minor re-jetting needed. With the Delkevic, the bike pulls from 1,300 to 5,000 RPM harder than it ever has. I had to hold on tight, which is exactly what I wanted from day 1 with this project - lighter, stronger, faster, better. Sadly, it hits a brick wall at 5k, and IT WILL NOT GO ABOVE 5k. It starts great, the low end and midrange are the best ever, but high end is non-existent.
I'm thinking about trying the torque inserts to give me some more backpressure, as the Delkevic pipe diameters are quite a bit larger than stock, the Delkevic collector outlet is huge compared to the Cone Engineering outlet, and the muffler clearly has nearly no backpressure. I can't use the O2 sensor with these headers, as I'm unwilling to drill them and weld in bungs for the O2 sensor until I'm sure I'll be keeping them, so verifying mixtures at various revs isn't possible.
With the Delkevic system I tried going back to the original main jets (one size richer), thinking maybe the header had leaned out the mixture, but that only made a slight difference in the low end and midrange. Here in NM, the first road I ride on to get anywhere has a 75mph speed limit, and the bike won't go much above 55mph (though it gets there really fast).
Any thoughts you have would be appreciated.
