Essential, yes. It would cause the same affect. Drill the hole bigger and you get a faster vaccum to lift the slide. Change the spring to a softer one and it gives the same affect without drilling the hole out.

When I did the DJ kit for the 09' models on a 06' model. I was surprized about the softness and how short the DJ spring is. But after doing the DJ re-jetting, it was well worth it.

 

And please understand that I'm not suggesting that using the spring instead of drilling the slide on those kits with the spring provided is better or worse. Just trying to figure out the differences between the kits and their application. I guess one could say that drilling the slide is rather permanent compared to the spring replacement...you always have the OEM spring in a drawer if needed...but I don't know of any instance where one would ever want to go back to using an undrilled slide or sticking the OEM spring back into the carb. Sounds like 6-of-one-half-dozen-of-another kind of deal. At least the spring setup keeps someone from using the wrong drill bit size or drilling in the wrong place. The spring would be less intimidating to most folks. I wonder what would happen if you did both?...stalling or studdering when whacking the throttle open...or similar?

 

I went ahead with the 250SF kit and followed breakdown pics and install from here

http://www.hmfengineering.com/forums...ead.php?t=1617

These were extremely helpful! I had a problem with a screw that holds the throttle cables and ended up threading it. Left it on and took out the airbox hose to lift out the carb.

Been having trouble fitting the FMF header with the Two Brothers Slip on. Im going to the muffler shop today to try and get the header pipe opened up a bit. Should I use stock little clamp thats on the stock header or a new one? Should high temp silicone
sealant always be used?

 

I always use a small amount of high temp RTV silicone on both ends of the header. Any leaks in the exhaust will cause the bike to pop on deceleration.