Merge Racing Technologies
Adjustable Leak Jet Kit
Carbs need tuning. Every bike is different, and a lot of times carbs need adjustment from track to track. Lately I've found that the fuel screw isn't always cutting it for getting me the top-notch performance out of a bike. Engine performance is getting better and better, so when something is just a bit off, I notice it. But I've found an easy way to tune a whole new side of the carb that had been a true pain in the rear until now.
When you turn the throttle on modern four-strokes, the carburetor's accelerator pump shoots gas into the intake tract. The pump squirt makes up for the lean condition created by the slide opening and the delay in the fuel starting to get sucked up through the jets. This squirt is controlled by a bleed jet inside the bowl of the carb. The bigger the bleed jet (that lets fuel escape back into the float bowl), the less fuel is forced into the intake tract. Changing this jet requires taking off the bowl, and we all know what a pain that can be on current bikes. The Merge Racing Adjustable Leak Jet Kit replaces the diaphragm cover of the accelerator pump and allows a screwdriver adjustment of the bleed, and therefore the pump squirt.
Installation is simple once you get the carburetor off the bike. There are detailed instructions on drilling a new hole in the bowl with a (both are provided) guide plate and drill bit. On all the bikes we tried it on there was plenty of clearance for the part and access to the adjuster was simple with a long, flat screwdriver. The instructions also have a good tuning guide and a pretty decent explanation of guidelines for four-stroke jetting.
In use the part does exactly what it claims to do and is a great tool for dialing out a bog or hesitation you might have when nailing the throttle. It works better on some bikes than others; typically the more jetting issues a bike has, the better the part works. It's excellent for cleaning up the bog riders might get with opening the throttle, but we also found it as a way to add or reduce the amount of snap at low rpm. The more closed the adjuster, the more bark the bike had. And for a number of our KTM bikes (that come stock with the bleed jet plugged), the Merge piece was the best tuning tool we've tried for cleaning up the jetting. At $150 and with an installation that isn't quite bolt-on, the Merge ALJ kit will be more attractive to those who are tool-savvy, but it works as advertised. -Jimmy Lewis