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Discussion Starter · #1 ·
I've been tinkering with my SMC for a while now and it has a high idle once it's warmed up. I've got it to idle when cold at like 1900 RPM, but once she's hot and I come to a stop light she races at like 3000 ~ 3100 RPM's. Is this normal? Mods include full Akra system, KTM hard parts air box lid, SAS and throttle stop removed, and JD jet kit. I'm using the blue needle, 170 main, 45 pilot, needle on the 4th position from the top, and A/F mixture screw 1 3/4 turns out. Am I running too lean? I'm in MN and just above sea level. Doesn't matter if it's 70 degrees or 96 degrees like it was today. Bike only has 3,400 miles. Otherwise starts and runs just fine, no complaints. Any ideas? Thanks!
 

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Well the blue needle is for winter time and would only cause the bike to be richer. So, I don't think it's the JD kit. IIRC the full akra system suggesting a 178 main but every one I've ever asked about it says a 170 or 172 is about right. You might try a 172-4 but I doubt the main jet would be causing that drastic of an idle issue.

What do you have for a pilot jet? Stock is a 45. JD is supposed to be very good with questions like this. Call or email and tell 'em you situation. OR Seek out a dyno tuner who knows carbs.

I'd be pulling and cleaning the carb and maybe playing with a different pilot jet depending on what JD suggests.

No, definitely not normal!
 

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Sounds like an air leak and or the Hot start button is open... :coffee:
 

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Discussion Starter · #5 ·
The PO installed the JD jet kit, so I don't have any spare jets. I've turned the idle adjusting black knob about all the way down. I've had the carb off and cleaned a couple times. Hot start button is closed. I was thinking air leak or trying a larger pilot like 48. Thanks for any input. Guess I might be pulling the carb off again and inspecting.
 

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Ok, something to note here. The boot on the motor side of Carb has 2 different sizes. If you switched this you may be getting an air leak there?
 

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Was just going to make a thread but saw this. Just picked up a 06 625 yesterday, doing the exact same thing. After riding idle is very high, starts no problem runs no problem, except when you crack the throttle the idle stays high for about 10 seconds then backs down. Throttle seems crisp not sticking. Only mod done is previous owner put in a air/fuel mixture screw. He did say that he loosened the carb boot and turned the carb, screwed it in then turned the carb back, so possibly leaking air? Let me know what you come up with and ill do the same, Im pretty inexperienced with jetting though, but i got a great deal on the bike which looks brand new knowing that theres just somethin goin on with this carb jetting. Any help/suggestions is appreciated.
 

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K the deal is the previous owner added a aftermarket fuel mixture screw. When we pulled it out it was missing a very small washer underneath the o-ring (above the spring). put in the small washer (took fuel mixture screw to local shop my friend works at, we used a washer out of an 86 kawasaki bayou quad, probably alot of other options) and re-installed fuel mixture screw. Also the idle knob was binding up and after pulling off the cover on right side of carb you could see it was in a high position. To fix this we undid the bolt holding the knob to the carb straightened the cable and broke it free by turning it to a lower possition. It now works smoothly where it was bolted before. Fuel screw turned out 1 3/4 turns from all the way in bike runs mint. The idle knob wouldnt turn because the spring was so compressed it was binding up. The issue without the small washer on the fuel mixture screw seems to be there wasnt enough pressure on the o-ring. Maybe this will help you. Ps i didnt completely remove the carb to do this.
 

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Discussion Starter · #9 ·
Well glad yours is working better. I tried testing for vacuum leaks by spraying carb cleaner around the base gasket, carb inlet and outlets with the bike running. Figuring if it bogged down from carb cleaner, it was getting in somewhere. But never found anything. Checked and adjusted the TPS sensor. It was out of spec, got that dialed in, bike actually runs better and throttle response is crisp. But still has a high idle. Disconnect the TPS and it idles just fine, like 1800 RPM. TPS plugged in it idles 3000+ RPM. I guess I'm gonna take the carb back off and clean everything good. Maybe the TPS is faulty? Never heard of such an issue. There is a large discussion on here about disconnecting the TPS. I would rather leave it connected based on what I've read. I runs better and had better throttle response with it plugged in. Just when it was unplugged it idled at a lower RPM. I'm gonna go ride it now and see what I find.
 

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Glad you guys are getting things sorted. What about pinched/traped cable?
 

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I was under the impression that disconnecting the tps was better, but havent done it yet? You wont believe this i found this just insanely unlikely so had to update. That small washer on my fuel mixture screw was obviously lost by the previous owner right...I watched him ride the bike down the street and back, i rode the bike for 30 kms down trails up north. Then it sat in back of my truck for a 600km drive home. Then we tore it apart realizing the problem and like i said got another washer and rode it around my neighborhood. Honest to god i just had my bike mechanic friend and two other friends witness me pick the original washer off the back wheel of the bike while i was just looking over the rims talking about how they need to be black. Somehow its been stuck to the back wheel where the guy obviously dropped it, who knows when, for who knows how many kms. I think i should go buy a lottery ticket? Sorry i do not have a clue if a faulty tps is your problem, sounds like its likely though.
 

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Discussion Starter · #12 ·
Anyone know what the TPS should Ohm out to? I would like to know if mine is bad or not. Bike actually idles at 1500 RPM after I shut the choke off on start up. Once I warm it up to 160 degrees plus she idles at 3300 RPMS! We adjusted the TPS as per KTM manual. 0.88 volts throttle closed, and 3.88 volts wide open throttle. A new sensor is like $180 through KTM parts. It idles normal with TPS disconnected, but lags on throttle response.
 

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I have the same issue with mine, it has just started since last fall- it's not constant though, some days it does it, some days it does not, and even within one day some stop lights it wants to idle wicked high and 30 mins later when i stop, it's perfectly normal. When the engine is hot, the idle screw does not like to turn either so sometimes i just shut the bike off at lights so its not revving like crazy. I have all the normal mods sas removal full akro, jetted etc. sounds like i need to pull my carb apart and look for missing springs and washers etc- damn, and i just put it all back together!:rant:
 

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Discussion Starter · #14 ·
sounds like i need to pull my carb apart and look for missing springs and washers etc- damn, and i just put it all back together!:rant:
Any update? My buddy and I were trying to Ohm the TPS again tonight. But as per the KTM service manual, it's within spec. As far as I can tell, the TPS is operating just fine. So I went ahead and pulled the carb out, started inspecting. I pulled the air/fuel mixture screw out. Spring and washer still intact, but I lost or dropped the o-ring. I dropped the spring and washer, found those, but never found the O-ring. So I'm off to find a new O-ring for the A/F screw tomorrow to see if that fixes the problem. My idle adjusting knob was also hard to turn and binding. I loosened it all the way up, and it's no longer binding. I will have to re-adjust it once it's back together and running. Hope this helps.
My mechanic buddy makes a good point. Why would it idle fine with the TPS disconnected? Maybe with it disconnected it retards the timing enough to mask the problem?
 

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Nope, only update is that i have about 250 miles on it since replacing the rocker arm roller, cam bearings and rebuilding the water pump....and it's still running, so i must have done it right! :bannana:
200 of those miles were today and not once did it idle strangely :headscrat. at this point i just want to ride it since its been sitting for 3 weeks. If the idle thing comes back, i'll tackle it from there. Is your idle consistently weird every time it gets warm, or does it just happen randomly like mine?
 

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Discussion Starter · #16 ·
I put in a 180 main jet and 48 pilot jet to richen it up. Cured the idle problem. Replaced the spark plug. The previous one was too white, thus I realized too lean. But I pulled the plug after a short ride today. Still white. TPS is plugged in and now it idles perfect. But I got the dreaded 45 mph surging. I'm just about at wits end. Still too lean?
 
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