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Discussion Starter #1 (Edited)
After very extensive dyno testing on the KTM SX and XC ATV model we developed a way to ELIMINATE the dreadful bog that we all have experienced on our machines.

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 #42 or 45 leak jets performed better.

#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 #40 pilot jet is too small. To fix this we simply replaced it with a either a 42 or #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 not correct 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 06 and newer TRX 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 or 1/4" inside 5/15 outside dementions



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 me the entire carb, we charge $125 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 $115! Parts included,



Fast64Ranchero
 

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Discussion Starter #3
wow you guys are amazing.. not only the dyno runs and stuff but doin a whole set up for the carb
Thanks, we try and do our best to help everyone out, and learn something along the way,
 

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Discussion Starter #6
We just want it to be fine tuned before we post it for the XC, right now I still have a slight bog at real low rpm's, I think some more drilling to the squirter will fix it, :D DJH knows his stuff and prob. already knows how far to drill it out, but he also makes money doing it so, I'll do my own research..... that way we can all stay friends
 

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time to get the number drills out ;)
 

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Awesome Walt...I know where my 41mm is going when i get home...it comes off a CRF450R and I know for a fact that the Acc pump spray is weak and the hole too small thats why it was dying after jumping and getting back on the throttle...

I'll just pay you and Driver a extra to dial it in on your 570 Quad...
 

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Discussion Starter #9
Awesome Walt...I know where my 41mm is going when i get home...it comes off a CRF450R and I know for a fact that the Acc pump spray is weak and the hole too small thats why it was dying after jumping and getting back on the throttle...

I'll just pay you and Driver a extra to dial it in on your 570 Quad...
Send it, we'll see what we can do for you....
 

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Hey Walt,
Been trying to get a hold of you but haven't heard back. Not sure if your inbox is full. Please PM me back when you have a chance. Really would like to send you my carb withing the next week.
Thanks
Andrew
 

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maybe i'm asking for too much,but does anyone who has done this have some pictures with the steps or guide lines of this procedure?
i want to try it for my self and a little bit of assistence/advice would be nice................and sometimes pictures speak better then a 1000 words
 

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stiko you are the man
can you explain this also?(pictures of the hole it self would be great)


#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.
 

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stiko,
i have a old yfz 450 carb laying around and i saw that he has the hole with the leak jet installed(it has a 50 jet,will install a 45)
i will try fitting it to the ktm carb(from what i saw it matches the ktm carb)

do you have any knowledge,will this work?

ps: pictures are of the bowl from the yfz
IMG_20140220_193539.jpg IMG_20140220_193545.jpg IMG_20140220_193549.jpg IMG_20140220_193602.jpg
 

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Yea should be fine just check on the rubber diaphragm on the bottom for damage. Also compare it with the ktm diaphragm it may have a longer/shorter post on it to give a different ap volume. The ktm one will swap straight in if in doubt.
 
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