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DesmoStucky

KTM 525 EXC - Carb Tuning

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Also a good idea to use ultra copper on the exhaust pipe joints to make sure you don't have any air leaks there.  

And one last thing that is very critical.  When you put the carb in, the air boot has a small cut out in it for the idle circuit.  You can align it by twisting the carb.  Use a small mirror to ensure its in the right place by shining a flashlight into the air boot with the filter out and hold a compact mirror in there.

Here is my ktm talk post on that from 2009

http://ktmtalk.com/showthread.php?323511-RFS-carb-boot-trick-(just-thought-I'd-share)&highlight=carb+alignment

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8 hours ago, Wierdrider said:

I think stock main jet is supposed to be 178(?), mine is 180. 

Stock pilot is 46(?), mine is 48. 

Yours seems a little leen on main and rich on pilot?

I thought stock pilot was 42, but I could be wrong. I have a 48, so I put that in there and took out the 50. I also put a 178 in as the main. 

3 hours ago, Spaugh said:

you need to take a can of carb cleaner and clean all the passages.  check the accelerator pump diaphragm.  then put the jets and needle settings that JD recommended for your riding conditions.  Fix the breather hose although it should not be an issue if the others were ok.  And lastly set the air/fuel screw 1.5 turns out and then get the bike hot and set the idle.  That should be a good start.  Those carbs aren't pickey at all.  Once you have it running ok, you should never have to mess with it again.

I went through the whole carb and liberally applied carb cleaner to all passages. JD recommends the 170 main, which is what I had in there before. Perhaps my pilot was too large or also JD recommends a 172 with a "free flowing exhaust". I think I'll give the 178 a try, and then bump it down to the 172 if I don't have any luck. Thanks for all the help!

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3 hours ago, Spaugh said:

Also a good idea to use ultra copper on the exhaust pipe joints to make sure you don't have any air leaks there.  

And one last thing that is very critical.  When you put the carb in, the air boot has a small cut out in it for the idle circuit.  You can align it by twisting the carb.  Use a small mirror to ensure its in the right place by shining a flashlight into the air boot with the filter out and hold a compact mirror in there.

Here is my ktm talk post on that from 2009

http://ktmtalk.com/showthread.php?323511-RFS-carb-boot-trick-(just-thought-I'd-share)&highlight=carb+alignment

Oh, and I definitely checked that the air boot idle passages are correctly aligned. Good call!

I'll give it a test ride tomorrow and report back. If I'm unsuccessful I'll shoot you a PM Spaugh. I don't think I have much more free time to tinker with it; I'd rather spend that time riding. 

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Sounds like you already crossed your Ts and dotted the i.  If you have issues at idle, changing the main isn't going to matter.  Just use the recommended JD settings, they are really good on those bikes.  

 

It really sounds like you are on the right track with the carb.  But I have to wonder if maybe a valve is out of adjustment or the timing chain is off a tooth or something if it just won't run right.  I would have to ride it to see what is going on I guess.  Hard to describe "running bad" problems through the web.  

 

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I had a problem with my 525 years ago after taking the carb apart.  This will sound dumb but I put the plate on the slide in upside down and it took a while before I finally figured it out.  It is item 21 in the diagram Robert posted up.  Check that out.  The flat side goes down like the diagram shows.

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11 minutes ago, mctrails said:

I had a problem with my 525 years ago after taking the carb apart.  This will sound dumb but I put the plate on the slide in upside down and it took a while before I finally figured it out.  It is item 21 in the diagram Robert posted up.  Check that out.  The flat side goes down like the diagram shows.

I put the plate upside down on my old Husky TE450; it took me months to figure that one out. Luckily the KTM is correct.

44 minutes ago, Spaugh said:

Sounds like you already crossed your Ts and dotted the i.  If you have issues at idle, changing the main isn't going to matter.  Just use the recommended JD settings, they are really good on those bikes.  

 

It really sounds like you are on the right track with the carb.  But I have to wonder if maybe a valve is out of adjustment or the timing chain is off a tooth or something if it just won't run right.  I would have to ride it to see what is going on I guess.  Hard to describe "running bad" problems through the web.  

 

I adjusted the valves today and only one of my exhausts was a bit tight; all others were fine.

Based on the 178 main, 48 pilot, clip 5th spot down on the JD red needle, and 2 turns on the fuel screw the bike is running MUCH better. It seems a bit rich, but it is much improved. I think the 48 pilot really helped, and I might be able to go down one more size. The bike will bog if you goose it off idle, but I'm not sure if it bogs anymore than normal. In normal riding I'm not goosing it off idle anyway, so I can probably live with it.

I took a short video of how it is running now, which I'll post up in a bit. Thanks again for all the help guys :drinks:

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Good news the 525 off idle should be very crisp no bog. Atleast mine was when jetted correctly think you still need a little tweaking but sounds like on the right track

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Depending on the year of your 525, JD has a little cap/hat that limits the travel on the accelerator diaphragm. It is designed to eliminate that bog when you crack the throttle. Give em a call and ask if you have the one that uses it. They are extremely helpful with diagnosing carb issues if you have their kit installed.

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3 minutes ago, vanjoosten said:

Depending on the year of your 525, JD has a little cap/hat that limits the travel on the accelerator diaphragm. It is designed to eliminate that bog when you crack the throttle. Give em a call and ask if you have the one that uses it. They are extremely helpful with diagnosing carb issues if you have their kit installed.

I have the JD cap added to the AP diaphragm. I was trying to figure out what to call that and the best I could come up with was "ap condom thing". Only deviation with the accelerator pump is I no longer have the o-ring mod, but it is safety wired.

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So below is a quick video after I made today's changes. The bike is running okay at roughly sea level. I still think it is too rich; it has fairly pronounced backfire on decel. I'm worried once I get up in elevation a bit it will run even poorer. Think I should go down on the main? I think I may buy a 172 and try it out, and maybe also go down to a 46 on the pilot. Anyone else running a JD kit on their 525 here in SD?

 

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That sounds about right. My 525 doesn't have a kill switch installed and when I'm working on the bike in the garage I will kill the bike with a quick flick of the throttle. This doesn't happen when riding.

 

CiD

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No kidding. All this time you were just a little over a mile from my house. I'm on Mobley St. I don't have a KTM and hate carburetors so haven't followed your thread. 

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14 hours ago, DesmoStucky said:

Based on the 178 main, 48 pilot, clip 5th spot down on the JD red needle, and 2 turns on the fuel screw the bike is running MUCH better.

Having the clip in the lower notches on the needle will make the bike rich off idle and at low to mid range.  If you think it is too rich try raising the clip position on the needle a couple of notches and see if that helps.

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On June 24, 2016 at 9:35 AM, Wierdrider said:

I think stock main jet is supposed to be 178(?), mine is 180. 

Stock pilot is 46(?), mine is 48. 

Yours seems a little leen on main and rich on pilot?

Stock ktm's come with a very lean needle and use a very rich main jet to compensate.  All to pass green sticky emissions. Hence the 180 stock main. With the JD needle 170 should be fine. 50 pilot seems a little rich but shouldn't cause any huge issues. I had a 48 pilot, a 168 main and a JD red needle in my '07 450exc. I don't recall what clip groove it was in but 4 or 5 seems in the ballpark. If it's at 5 I'd try it at 4. The popping out the exhaust is because it's lean. That's usually the pilot jet but if the needle setting is lean on the bottom that will affect it too. The other cause for exhaust popping is a leak in the exhaust. Don't be too worried as KTM' s, particularly RFS motors, are notorious for it due to the crappy exhaust flange connection design. The other thing I would check is that the accel pump is working. Take the carb off with fuel in the bowl. Actuate the throttle by rotating the throttle pulley. You should see a stream of fuel from the pump injection tube at the bottom of the throttle bore. Tuning these beasts on a stand is really difficult. Go out and ride it. Like CID says they are a different animal when riding vs in the garage. 

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hello everyone I'm at my wits end in trying to tune my 525 exc FCR carb can someone suggest a local shop that'll tune or i can send it in to rebuild ? call or text works 619,,,six six five, 0664 

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I just rebuilt one and have no idea what I’m doing but did a lot of reading. Did you thoroughly take it apart (including mid body section!), clean every single hole (this carb has a LOT of them), and replace all gaskets including the round “pressure” gasket on the slide, Then jd jetting kit, float level, then in theory it purrs?  I wasn’t much help with a shop to send it to sorry, or probably anything else :)

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