It's posted in the SX thread but here you go
After very extensive dyno testing on the KTM SX ATV model we developed a way to
ELIMINATE the dreadful bog that we all have experienced on our machines. We are actively working on the XC, and should have information out on it shortly
WARNING:
USE THIS INFORMATION AT YOUR OWN
RISK; WE AREN'T RESPONSIBLE FOR ERRORS IF YOU DECIDE TO PERFORM THESE MODIFICATIONS YOURSELF. THIS INFORMATION IS SOLELY PROVIDED AS A GUIDE.
PROCEED WITH EXTREME CAUTION!!!
#1 Leak Jet Installation
To address the lack of adjustability of the accelerator pump we drilled & tapped the bowl for a leak jet. The leak jet allows us to address how far & long the accelerator pump squirts. We found that a #40 leak jet performed the best.
#2 Increase Accelerator Pump Squirt Nozzle Diameter
The next modification we made was to drill the accelerator pump squirt nozzle larger. From the factory the accelerator pump nozzle has a 0.013" opening. We found that by carefully drilling it to 0.016" (approximately 23% larger) it helped make the accelerator pump easier to tune and much more effective.
#3 Replace OEM Pilot Jet
From the factory the #42 pilot jet is too small. To fix this we simply replaced it with a #45 pilot jet. This corrected the some minor idling issues especially when the engine is cold. This is very simple and easy to do.
#4 Replace OEM Needle
The factory needle's taper is too narrow at the tip which creates a lean issue from 3/4 throttle to wide open throttle (WOT) as well as the incorrect main jet being used. To cure this we replaced the needle with a needle found in the Honda HRC kit; it allowed us then to install the correct main jet.
#5 Install O-ring
Add the O-ring mod to the accelerator pump O-Ring size.number is 010
Drilling the leak jet & squirt nozzle are NOT recommended unless you have experience in dealing with 0.001" tolerances. Not to mention the drill bits are typically special order items.
If you send us the entire carb, we charge $100 to drill/tap the bowl for a leak jet & drill the squirt nozzle (return domestic shipping included). Active subscribing (paid) members to KTMATVHQ.com only pay $85! Parts included,
I am in the process of getting some bowls & squirt nozzles ready to go so I can offer them as a "kit" with or without a core charge. Unfortunately, I don't have any kit pricing available right now.
Fast64Ranchero & Driver311
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Any progress on the xc carb yet? Also-on the sx- with the new needle installed are you going leaner or richer on the main and by how much??
